Step 1 Basics (USMLE)

1.06 Systolic Heart Murmurs

Cardiovascular system review for the USMLE STEP 1 Exam

• Heart murmurs are caused by turbulent blood flow in the heart

• There are 4 different types of systolic murmurs: ventricular septal defect (VSD), patent ductus arteriosus (PDA), aortic stenosis, and mitral or tricuspid regurgitation

• PDA produces a constant, machine-like murmur

• VSD produces a harsh holosystolic murmur

• Aortic stenosis produces a crescendo-decrescendo systolic ejection murmur

• Mitral and tricuspid regurgitation produce a holosystolic high pitched "blowing" murmur

• Mitral valve prolapse produces a mid-systolic click followed by a late systolic murmur

• Aortic regurgitation produces a decrescendo diastolic murmur

• Mitral stenosis produces a rumbling diastolic murmur

5.13 OCD and Related Disorders

Psych review for the USMLE Step 1 Exam

• Obsessive Compulsive Disorder (OCD): Unwanted thoughts (obsessions) and repetitive behaviors (compulsions). Treat with CBT + SSRIs/SNRIs.
• Tic Disorders: Tourette Syndrome involves multiple motor and at least one vocal tic. Treat with Habit Reversal Therapy.
• Body Dysmorphic Disorder: Preoccupation with minor flaws, treat with SSRIs and CBT.
• Trichotillomania: Hair pulling disorder, treat with Habit Reversal Training and sometimes SSRIs.
• PANDAS: Pediatric disorder after strep infection, sudden OCD-like symptoms. Treat with antibiotics, CBT, and SSRIs.

5.12 Anxiety Related Disorders

Psychiatry review for the USMLE Step 1 Exam

• Anxiety is a normal response to threats or stressors in the environment
• Anxiety disorders occur when anxiety causes significant distress or impairment in functioning
• Generalized Anxiety Disorder (GAD) involves persistent and excessive worry about various aspects of daily life for at least 6 months, accompanied by physical symptoms
• Treatment for GAD typically involves a combination of cognitive-behavioral therapy (CBT) and selective serotonin reuptake inhibitors (SSRIs)
• Panic Disorder is diagnosed in individuals who experience spontaneous panic attacks and fear future attacks
• Panic attacks are acute episodes of intense anxiety and physical symptoms
• Treatment for Panic Disorder involves CBT and SSRIs, with SSRIs being the first-line medication
• Agoraphobia is the fear of being in public places where escape may be difficult and often follows a traumatic event
• CBT and SSRIs are the recommended treatment for Agoraphobia
• Social Anxiety Disorder (Social Phobia) involves fear of scrutiny or embarrassment in social situations
• Public speaking can be a significant trigger for individuals with social anxiety disorder
• Beta blockers can be used to treat social anxiety disorder by reducing physical symptoms
• Treatment for social anxiety disorder usually involves CBT, SSRIs, or beta blockers.

5.11 Eating and Feeding Disorders

Psychiatry Review for the USMLE Step 1 Exam

• Eating Disorders:

  • Main disorders: bulimia nervosa, anorexia nervosa, and binge eating disorder.
  • Bulimia and anorexia share anxiety and compensatory behaviors.
  • Anorexia: low body weight, fear of gaining weight, treatment involves slow refeeding.
  • Bulimia: normal weight, signs of forced vomiting, treated with CBT and SSRIs.
  • Binge Eating Disorder: uncontrollable eating, negative emotions, SSRIs and CBT for treatment.

• Feeding Disorders:

  • Occur in children, not related to body image.
  • Common disorders: avoidant/restrictive food intake disorder, rumination disorder, and pica.
  • Avoidant/Restrictive Food Intake Disorder: avoidance or restriction of food intake.
  • Pica: eating non-nutritious substances, common in young children.
  • Rumination Disorder: regurgitation without associated symptoms.

5.10 Mood Disorders (Depression and Bipolar)

Psychiatry Review for the USMLE Step 1 exam

• Mood disorders are persistent disruptions in emotion, categorized into bipolar disorders and depressive disorders.
• Bipolar disorders are characterized by manic or hypomanic episodes, while depressive disorders feature periods of depression.
• Major Depressive Disorder (MDD) is characterized by feelings of sadness, guilt, worthlessness, and anhedonia lasting for at least two weeks.
• SIG E CAPS is an acronym used to remember the symptoms of depression: Sleep changes, Interest loss, Guilt, Energy loss, Concentration difficulties, Appetite changes, Psychomotor retardation, and Suicidal ideation.
• In MDD, at least 5 of the SIG E CAPS symptoms must persist for more than 2 weeks.
• Persistent Depressive Disorder (dysthymia) is a chronic, low-grade form of MDD that lasts for at least two years.
• Mania is a symptom common to all bipolar disorders, characterized by elevated or irritable mood and increased activity or energy.
• Mania lasting for at least 1 week is called a manic episode, while hypomania is a less severe form lasting longer than 4 days.
• The symptoms of mania can be remembered using the mnemonic DIG FAST: Distractibility, Irritable mood/insomnia, Grandiosity, Flight of ideas, Agitation/increased activity, Speedy thoughts/speech, and Thoughtlessness.
• Bipolar I involves manic episodes, and bipolar II involves hypomanic episodes and major depressive episodes.
• Bipolar I requires at least one manic episode, while bipolar II requires depressive episodes.
• Mood stabilizers such as lithium, valproate, carbamazepine, and lamotrigine are used to treat bipolar disorders. Litium is the best (notable exeptions however).
• Antidepressants are contraindicated for bipolar patients due to the risk of flipping into mania.
• The risk of suicide is high in bipolar patients, with 25-50% attempting suicide and 10-15% dying by suicide.
• Cyclothymia is a less common form of bipolar disorder characterized by cycling between hypomania and mild depression over many years.

5.09 Schizophrenia

Psychiatry review for the USMLE Step 1 Exam

• Epidemiology:
  • Slight male predilection (1.4:1 male to female ratio).
  • Men present between 18-25, women between 28-35.
  • Affects about 0.5% of the population.
• Symptoms:
  • Positive symptoms: hallucinations, delusions, disorganized behavior and speech.
  • Negative symptoms: flat affect, anhedonia, apathy, alogia, lack of interest in socialization.
  • Cognitive symptoms: impairments in attention, executive function, working memory.
• Diagnosis:
  • Criteria: two or more symptoms lasting over a month.
  • Schizophreniform disorder if symptoms last less than 1 month.
• Pathophysiology:
  • Excess dopamine in prefrontal cortical pathway (negative symptoms).
  • Excess dopamine in mesolimbic pathway (positive symptoms).
  • Other neurotransmitters may also play a role (especially serotonin excess).
• Treatments:
  • Antipsychotics (D2 receptor antagonists).
  • First-generation antipsychotics: haloperidol, chlorpromazine (more side effects).
  • Second-generation antipsychotics (atypical antipsychotics): aripiprazole, olanzapine, quetiapine, risperidone (lower extrapyramidal side effects, higher metabolic side effects).
• Outcomes:
  • Rule of thirds: one-third full recovery, one-third improved with mild symptoms, one-third require high-level care.

5.08 Cluster C Personality Disorders

Psychiatry review for the USMLE Step 1 Exam

• Introduction:

  • Cluster C personality disorders = anxious/worried.
  • Disorders: avoidant, obsessive-compulsive, dependent.
  • Distinguish from normal traits.

• Avoidant Personality Disorder:

  • Inhibited, introverted, anxious.
  • Fear of rejection, low self-esteem.
  • Characteristics: avoidance, preoccupation with criticism/rejection, social ineptness.
  • Treatment: Anti-anxiety drugs may help temporarily.

• Obsessive-Compulsive Personality Disorder:

  • Perfectionism, inflexibility, diligence.
  • Not OCD; need for control, not obsessions/compulsions.
  • Characteristics: details, work focus, rigidity.
  • Example: Mark, unemployed with attention to detail.

• Dependent Personality Disorder:

  • Excessive reliance on others for support/decisions.
  • Linked to early medical/psychiatric conditions.
  • Characteristics: decision-making, fear of disapproval, reliance.
  • Example: Bob, farm laborer dependent on mother.

• Conclusion:

  • Cluster C = anxiety-driven.
  • Understand characteristics, not specific diagnoses.
  • Examples show impact on lives.

5.07 Cluster B Personality Disorders

Psychiatry review for USMLE Step 1 Exam

• Cluster B personality disorders are the highest yield among all personality disorders.
• The cluster B disorders include borderline personality disorder, histrionic personality disorder, narcissistic personality disorder, and antisocial personality disorder.
• Substance abuse and comorbid mood disorders, particularly major depressive disorder (MDD), are commonly associated with cluster B disorders.
• Personality disorders are distinguished from normal personality traits by their negative impact on daily life, lack of awareness of the problem, and deviation from cultural expectations.
• Borderline personality disorder is characterized by unstable emotions, impulsivity, disturbed relationships, and potential psychotic features.
• Criteria for diagnosing borderline personality disorder include frantic efforts to avoid abandonment, unstable interpersonal relationships, identity disturbance, impulsivity, recurrent suicidal behavior, affective instability, chronic feelings of emptiness, inappropriate anger, and paranoid ideation or dissociative symptoms under stress.
• Borderline personality disorder has a high risk of suicide, especially in women, and is often treated with dialectical behavior therapy (DBT).
• Histrionic personality disorder involves excessive attention-seeking, inappropriate sexually seductive behavior, shallow emotional expression, and self-dramatization.
• Diagnostic criteria for histrionic personality disorder include discomfort when not the center of attention, sexually provocative behavior, emotional instability, attention to physical appearance, impressionistic speech, self-dramatization, and susceptibility to influence.
• Histrionic personality disorder is more common in women and is associated with the defense mechanism of regression.
• Narcissistic personality disorder is characterized by grandiosity, a need for admiration, lack of empathy, and a sense of entitlement.
• Diagnostic criteria for narcissistic personality disorder include a grandiose self-importance, fantasies of unlimited success, a belief in being unique, excessive need for admiration, sense of entitlement, exploitation of others, lack of empathy, envy, and arrogant behavior.
• Narcissistic personality disorder is exemplified by individuals who exhibit characteristics similar to a former president (not mentioned by name), including being grandiose, preoccupied with success, and envious of others.
• Antisocial personality disorder, often referred to as sociopathy, involves a disregard for others' rights, lack of remorse, criminal behavior, hostility, and manipulation.
• Antisocial personality disorder is more common in males, has a high prevalence in incarcerated individuals, and is usually preceded by childhood conduct disorder.
• Diagnostic criteria for antisocial personality disorder include failure to conform to social norms, deceitfulness, impulsivity, aggressiveness, disregard for safety, irresponsibility, and lack of remorse.

5.06 Cluster A Personality Disorders

Psychiatry review for the USMLE Step 1 Exam.

• The cluster A personality disorders include paranoid, schizoid, and schizotypal.
• These disorders are characterized by individuals who are perceived as weird, awkward, and quiet.
• Personality disorders differ from normal personality quirks based on their negative impact on daily life, lack of awareness of the problem, and deviation from cultural expectations.
• Paranoid Personality Disorder:
  • Patients are chronically suspicious and distrustful of others, without persistent fixed delusions.
  • Key characteristics include unwarranted suspicions, doubts about loyalty, reluctance to confide, reading hidden meanings, holding grudges, perceiving attacks on reputation, and suspicion of infidelity.
• Schizoid Personality Disorder:
  • Individuals prefer isolation and have difficulty forming relationships.
  • Criteria for diagnosis include a lack of interest in close relationships, solitary activities, indifference to praise or criticism, emotional coldness, and flattened affectivity.
• Schizotypal Personality Disorder:
  • Considered a less severe form of schizophrenia, with odd behavior, speech, thinking, and mild perceptual experiences.
  • Notable features include social isolation, "magical" beliefs, mild paranoia, constricted affect, and social anxiety.

5.05 Hallucinogens (Types, Intoxication, and Withdrawal)

Psychiatry review for the USME STEP 1 Exam.

• Hallucinogens are a diverse class of drugs that cause hallucinations and other symptoms.
• Common hallucinogens discussed in the podcast are LSD, marijuana, PCP, and ketamine.
• LSD activates serotonin receptors, causing visual and auditory hallucinations, time and reality distortions, mood elevation, and dilation of the pupils. No notable withdrawal symptoms.
• Marijuana acts as a depressant, stimulant, and hallucinogen. THC binds to cannabinoid receptors, increasing neurotransmitters like dopamine and serotonin. Intoxication symptoms include red eyes, anxiety, euphoria, increased appetite, dry mouth, paranoid delusions, and perceived slowed time. Mild withdrawal symptoms include irritability, depression, sleep problems, and decreased appetite. Heavy cannabis use in adolescence is linked to an increased risk of schizophrenia.
• PCP antagonizes NMDA glutamate receptors and activates dopaminergic neurons. Intoxication symptoms include increased pain threshold, agitation, hallucinations, nystagmus, ataxia, and tachycardia. No notable withdrawal symptoms.
• Ketamine is structurally similar to PCP and acts as a milder version. It causes hallucinations and dissociation and is used medically for analgesia.

5.04 Depressants (Types, Intoxication, and Withdrawal)

Psychiatry review for the USMLE Step 1 exam.

• Depressants decrease neuronal activity in the brain.
• They can work by stimulating GABAergic neurons or binding to opiate receptors.
• Common GABA-promoting depressants: alcohol, benzodiazepines, barbiturates, and inhalants.
• Opioid depressants include heroin and morphine derivatives.
• Alcohol enhances GABA receptor effects, inhibits glutamate activity, and causes intoxication symptoms such as disinhibition, slurred speech, impaired motor control, lethargy, respiratory depression, and coma.
• Alcohol withdrawal symptoms include anxiety, agitation, insomnia, nausea/vomiting, tremors, autonomic dysfunction, seizures, and can be life-threatening (delirium tremens).
• Benzodiazepines bind to the benzodiazepine receptor, enhance GABA effects, and cause intoxication symptoms similar to alcohol.
• Benzodiazepine withdrawal symptoms include anxiety, agitation, insomnia, and seizures, which are treated with a gradual tapering of the drug.
• Inhalants depress brain activity and cause symptoms such as disinhibition, paranoia, lethargy, dizziness, ataxia, slurred speech, and high doses can lead to respiratory depression and brain damage.
• Opioids bind to opioid receptors, reduce pain, improve mood, and cause intoxication symptoms like drowsiness, constricted pupils, seizures, and respiratory depression.
• Opioid overdose can be reversed with naloxone, an opioid receptor antagonist.
• Opioid withdrawal symptoms include dysphoria, anxiety, weakness, sweating, dilated pupils, and diarrhea, and can be managed with medications like methadone and buprenorphine.
• Alcohol withdrawal is an emergency and requires prompt treatment with benzodiazepines.

5.03 Stimulants (Types, Intoxication, and Withdrawal)

Psychiatry review for the USMLE Step 1 Exam.

• Stimulants increase CNS activity and activate the sympathetic nervous system.
• They can block reuptake of neurotransmitters or stimulate their release.
• Intoxication symptoms include agitation, dilated pupils, sweating, euphoria, hallucinations, and increased norepinephrine, epinephrine, dopamine, and serotonin levels.
• Prescribed stimulants: amphetamine, dextroamphetamine, and methylphenidate (used for ADHD).
• Recreational stimulants: methamphetamine, cocaine, MDMA, nicotine, and caffeine.
• Cocaine blocks reuptake of norepinephrine, epinephrine, and dopamine, and can cause hallucinations, paranoia, chest pain, and potentially cardiac death.
• Methamphetamine can cause tactile hallucinations where patients feel like bugs are crawling on their skin.
• MDMA can induce feelings of connectedness, heightened emotions, and hallucinations.
• Withdrawal from stimulants, particularly cocaine and methamphetamine, is characterized by depression, headache, malaise, fatigue, hypersomnolence, anhedonia, constricted pupils, vivid dreams, and flu-like symptoms.
• Withdrawal symptoms are opposite to the effects experienced during intoxication.

5.02 Classical and Operant Conditioning

Psychiatry review for the USMLE Step 1 Exam

• Classical Conditioning:

  • Pavlovian conditioning discovered by Ivan Pavlov, a Russian physiologist known for his experiments with dogs.
  • Learning through association.
  • Example: Conditioning dogs to respond to a noise the way they would respond to meat.
  • Involves associating an unconditioned stimulus with a new conditioned stimulus to elicit the same response.

• Process of Classical Conditioning:

• Start with a stimulus that produces a response (e.g., smelling pizza makes you hungry).
• Pair the stimulus and response with an unconditioned stimulus (e.g., receiving a text indicating pizza delivery).
• Eventually, the conditioned stimulus (the text notification) alone elicits the conditioned response (mouth watering).

• Extinction and Spontaneous Recovery in Classical Conditioning:

  • If the conditioned stimulus (text notification) is presented without the unconditioned stimulus (pizza), the conditioned response (mouth watering) will weaken and eventually extinguish.
  • Spontaneous recovery may occur, where the conditioned behavior briefly reappears after a period of extinction.

• Terms in Classical Conditioning:

  • Unconditioned stimulus (US): Triggers a response unconditionally.
  • Unconditioned response (UR): The response elicited by the unconditioned stimulus.
  • Conditioned stimulus (CS): Initially neutral stimulus that becomes associated with the unconditioned stimulus.
  • Conditioned response (CR): The response elicited by the conditioned stimulus.

• Operant Conditioning:

  • Developed by B.F. Skinner.
  • Learning occurs through rewards and punishments for behavior.
  • Three types of responses: neutral operants, reinforcers, and punishers.

• Examples of Operant Conditioning:

  • Positive reinforcement: Giving a child candy for good behavior.
  • Negative reinforcement: Taking away a child's phone until homework is done to increase desired behavior.
  • Positive punishment: Using physical force as punishment (not recommended).
  • Negative punishment: Taking away a child's phone to decrease unwanted behavior.

• Different Schedules of Reinforcement:

  • Continuous Reinforcement: Positive reinforcement every time a specific behavior occurs.
  • Fixed Ratio Reinforcement: Reinforcement after a specified number of correct responses.
  • Fixed Interval Reinforcement: Reinforcement after a fixed time interval with at least one correct response.
  • Variable Ratio Reinforcement: Reinforcement after an unpredictable number of responses.
  • Variable Interval Reinforcement: Reinforcement after an unpredictable amount of time.

• Summary:

  • Classical conditioning involves learning through association of stimuli.
  • Operant conditioning involves learning through rewards and punishments for behavior.

5.01 Ego Defenses

Psychiatry review for the USMLE Step 1 Exam

• Defense mechanisms protect the unconscious part of our personality from anxiety caused by unacceptable thoughts or feelings.
• Ego defenses are categorized into three groups: mature, neurotic, and immature.
• Immature defense mechanisms include projection, regression, denial, acting out, and splitting.
• Projection involves attributing objectionable thoughts or emotions to others.
• Regression is behaving in an age-inappropriate way to avoid tension associated with the current phase of development.
• Denial is not accepting or believing something to protect one's ego.
• Acting out involves giving in to socially inappropriate impulses to avoid anxiety.
• Splitting is viewing people as either all good or all bad, without considering the middle ground.
• Neurotic defense mechanisms include intellectualization, isolation of affect, displacement, rationalization, reaction formation, and repression.
• Intellectualization is overanalyzing situations or focusing on irrelevant details to avoid negative feelings.
• Isolation of affect is unconsciously limiting the experience of emotions associated with a stressful event.
• Displacement involves shifting emotions from one thing to another, which is deemed more acceptable.
• Rationalization is justifying one's behavior or negative feelings through rational explanations.
• Reaction formation is unconsciously acting opposite to an unacceptable impulse.
• Repression involves preventing thoughts or feelings from entering consciousness to avoid negative emotions.
• Mature defense mechanisms include humor, altruism, suppression, and sublimation.
• Humor is used to relieve anxiety and negative thoughts.
• Altruism involves performing beneficial acts for others to experience pleasure and relieve anxiety.
• Suppression is consciously blocking undesirable ideas, thoughts, or impulses.
• Sublimation is transforming anxiety or emotions into socially valued pursuits.
• Sublimation involves channeling negative emotions into productive and socially desirable actions.

4.08 Myasthenia Gravis and Lambert Eaton Syndrome

MSK/Rheumatology review for the USMLE Step 1 Exam

• Introduction:
  • Review of neuromuscular junction and its components: presynaptic part, postsynaptic part, synaptic cleft.
  • Cascade of events leading to the release of acetylcholine into the synaptic cleft.
• Myasthenia Gravis:
  • Autoimmune neuromuscular junction disease.
  • Fluctuating muscle weakness, especially ocular and eyelid weakness, distal limb weakness.
  • Antibodies target nicotinic acetylcholine receptors (n-AChR's).
  • Association with thymic hyperplasia and enlarged thymus.
  • Treatment: Acetylcholinesterase inhibitors (AChE inhibitors), immunosuppressants.
• Lambert Eaton Syndrome:
  • Autoimmune neuromuscular junction disease associated with cancer.
  • Fluctuating muscle weakness, autonomic dysfunction, decreased reflexes.
  • Antibodies target presynaptic calcium channels on nerve terminals.
  • Autonomic manifestations due to calcium channels also present in smooth muscle.
  • Around 50% of cases associated with an underlying malignancy.
  • Treatment: Immunosuppression, addressing underlying malignancy if present.

This high yeild podcast covers schizophrenia type disorders for the USMLE Step 1 exam.

I cover the following topics:

• Defining psychotic symptoms: hallucinations, delusions, and disorganized thoughts/speech
• Example of a delusional belief about a small being inside the body
• Schizophrenia spectrum disorders: schizophrenia, schizophreniform, and brief psychotic disorder
• Differentiating the disorders based on the duration of symptoms: brief (6 months)
• Progression from brief psychotic disorder to schizophreniform to schizophrenia
• Schizoaffective disorder: combination of schizophrenia and a mood disorder (MDD)
• Highlighting the importance of episodes with only schizophrenia symptoms in schizoaffective disorder
• Delusional disorder: focusing on delusions without hallucinations, disorganized thoughts/behavior, or mood disorders
• Contrasting delusions in delusional disorder with those in schizophrenia
• Litigious tendencies observed in delusional disorder cases
• Mood disorders with psychotic features: exploring MDD as an example
• Psychotic symptoms in MDD appear only during depressive episodes
• Clarifying the distinction between psychotic symptoms in MDD and schizoaffective disorder
• Summary: Understanding the different disorders and their symptom overlap.

4.07 Polymyositis and Dermatomyositis

MSK/Rheum review for the USMLE Step 1 Exam

• Polymyositis and dermatomyositis are autoimmune inflammatory myopathies.
• They are caused by abnormal activation of T cells that attack skeletal muscle and both cause proximal muscle weakness, especially of the shoulders and pelvic girdle muscles.
• Polymyositis develops when there is abnormal activation of CD8 T cells, while dermatomyositis is primarily attacked by CD4 T cells.
• Both are diagnosed through a muscle biopsy and the presence of elevated CK levels and several different autoantibodies.
• Dermatomyositis includes dermatologic manifestations, such as gottron papules, heliotrope rash, and shawl rash.
• Both are associated with MI, interstitial lung disease, and various types of cancer (dermatomyositis more so).
• Both diseases require prompt treatment with steroids and immunosuppressive agents.

4.06 Osteoarthritis vs Rheumatoid Arthritis

Rheumatology review for the USMLE Step 1 exam

• Rheumatoid arthritis and osteoarthritis both cause joint inflammation, joint pain, and can limit joint range of motion
• Osteoarthritis is a degenerative joint disease that occurs when the articular cartilage that covers the ends of bones begins to degrade and erode
• The most common joints affected by osteoarthritis are the hips and knees, and the distal interphalangeals of the hands are also commonly affected
• Osteoarthritis tends to be more asymmetric and localized, presenting as a single degenerated joint
• Rheumatoid arthritis is an inflammatory autoimmune disease that affects the joints and other parts of the body
• RA typically develops in patients who are genetically predisposed and triggered by environmental factors, such as smoking
• The two autoantibodies present in RA are rheumatoid factors and anti-cyclic citrullinated peptide (anti-CCP) antibodies
• Rheumatoid factors activate the complement system and stimulate the inflammatory response in the body.
• Anti-CCP antibodies bind citrullinated peptides and stimulate inflammation in the synovium of joints
• Rhematoid arthritis has extra-articular manifestations, the most common of which are rheumatoid nodules

4.05 Scleroderma

Rheumatology review for the USMLE Step 1 exam

• Scleroderma is a chronic autoimmune connective tissue disease that causes thickening and hardening of the skin, as well as fibrosis (excess deposition of collagen and other ECM proteins) throughout the body.
• Autoreactive immune cells activate endothelial cells, which produce large amounts of endothelin 1, leading to overactivation of fibroblasts that overexpress collagen.
• It typically affects younger women (35-50 years old) with a F:M ratio of 5:1.
• There are two distinct forms of scleroderma: diffuse (systemic) and limited, each associated with unique antibodies and clinical presentations.
• Diffuse scleroderma involves the skin and internal organs and is rapidly progressive. Skin tightens especially in the fingers, and internal organs including the lungs, kidneys, GI system, and heart can be affected. It is associated with anti-Scl-70 antibody and anti-RNA III polymerase.
• Limited scleroderma tends to only affect the skin, characterized by the mnemonic CREST: Calcinosis cutis, Raynaud phenomenon, Esophageal dysmotility, Sclerodactyly, and Telangiectasia. It is associated with anti-Centromere antibody.
• Treatment involves NSAIDs and DMARDs for musculoskeletal pain, H2 blockers or PPIs for esophageal reflux, and Ace inhibitors for scleroderma renal crisis. There is no cure for the disease.

HIGH YIELD 2: Marfan's vs Homocystinuria vs Ehlers-Danlos

High yield review for the USMLE Step 1 exam.

• Marfan's syndrome, Ehlers-danlos, and homocystinuria are three distinct diseases that affect connective tissue.
• They share similarities like tall stature, long fingers, scoliosis, high arched palate, chest wall deformities, joint hypermobility, and lens dislocation.
• Marfan's syndrome is caused by FBN1 gene mutation on chromosome 15, and it results in defective fibrillin-1. It causes aortic root dilation, and upward lens dislocation.
• Homocystinuria is caused by a defect in homocysteine breakdown, and it results in elevated levels of homocysteine, which is toxic to the body. It causes thrombosis and downward lens dislocation.
• Ehlers-Danlos syndrome is caused by a deficiency in type III collagen, and it results in hyperextensible skin, easy bruising and bleeding. It can cause vascular rupture, and it usually occurs in the arterial system.
• Patients with Marfan's syndrome present with scoliosis, long fingers and toes, and caved-in chest wall.
• Patients with homocystinuria present with developmental delay, long fingers and toes, and upward lens dislocation.
• Patients with Ehlers-Danlos syndrome present with recurrent bruising, soft hyperextensible skin, and joint hyperextensibility

4.04 Systemic Lupus Erythematosus

Rheumatology review for the USMLE Step 1 Exam

• Marfan's syndrome, Ehlers-danlos, and homocystinuria are three distinct diseases that affect connective tissue.
• They share some clinical features like tall stature, long fingers, scoliosis, high arched pallet, chest wall deformities, joint hypermobility, and lens dislocation.
• Marfans is caused by a mutation in the FBN1 gene, resulting in defective fibrillin-1, and the main complication is aortic root dilation.
• Homocystinuria is a metabolic disorder caused by a defect in homocysteine breakdown, leading to elevated levels of homocysteine, and the main complication is thrombosis.
• Ehlers-Danlos is caused by a deficiency in type III collagen, and the main complication is vascular rupture.
• Marfans has an upward lens dislocation, homocystinuria has a downward lens dislocation, and Ehlers-Danlos has hyperextensible skin and joint hyperextensibility.
• Marfans usually presents in teens, homocystinuria in children, and Ehlers-Danlos in young adults.
• Patient presentations: Marfans - scoliosis, long fingers, and caved in chest wall in a tall teen; Homocystinuria - developmental delay, long fingers, and tall stature in a child; Ehlers-Danlos - recurrent bruising, hyper extensible skin, and joint hyperextensibility in a young adult.

4.03 Large Vessel Vasculitis

Rheumatology review for the USMLE Step 1 Exam

• Vasculitis is inflammation of blood vessels
• Vasculitis is split into three groups based on the size of blood vessels affected: large, medium, and small vessel vasculitis
• Large vessel vasculitis involves inflammation of the aorta and its main branches
• Two distinct large vessel vasculitidies: temporal (or giant cell) arteritis and takayasu arteritis
• Temporal (giant cell) arteritis primarily affects older women (>60) and the branches of the common carotid arteries
• Symptoms of temporal arteritis: jaw pain (jaw claudication), headaches, tenderness along temporal artery
• Complication of temporal arteritis: blindness
• Takayasu arteritis mostly affects young Asian women (

4.02 Medium Vessel Vasculitis

Rheumatology review for the USMLE Step 1 exam.

• Vasculitis: inflammation of blood vessels, classified by the size of the blood vessels affected
• Medium vessel vasculitis affects the main visceral arteries and veins, and their initial branches
• Three types of medium vessel vasculitis are discussed: polyarteritis nodosa, Kawasaki disease (mucocutaneous lymph node syndrome), and Buerger disease (thromboangiitis obliterans)
• Polyarteritis nodosa affects middle-aged to older men and is idiopathic, but can be secondary to other diseases, including hepatitis B
• Histology findings show transmural inflammation with fibrinoid necrosis in early lesions, and string-of-beads sign in angiogram
• Symptoms include constitutional symptoms, abdominal pain and melena, and hypertension caused by damage to the renal arteries
• Kawasaki disease most commonly affects young Asian children, and is triggered by upper airway infections
• Symptoms include conjunctival injection, desquamating rash, cervical lymphadenopathy, strawberry tongue, and prolonged fever
• Kawasaki disease has a predilection for the coronary vessels, which can lead to aneurysm rupture and thrombi development
• Treatment for Kawasaki disease includes IVIG and aspirin to prevent complications

4.01 Small Vessel Vasculitis

Rheumatology review for the USMLE Step 1 exam

• Vasculitis is inflammation of blood vessels and is classified into three categories based on vessel size: large, medium, and small vessel vasculitis.
• Small vessel vasculitis affects arterioles, capillaries, and venules, leading to symptoms associated with damage to these vessels, such as palpable purpura.
• Five types of small vessel vasculitis include IgA vasculitis (Henoch-Schonlein Purpura), Granulomatosis with polyangiitis (Wegener Granulomatosis), Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome), Microscopic polyangiitis, and Behçet syndrome.
• IgA vasculitis is the most common in children, and anti-neutrophil cytoplasmic antibody + vasculitis are the most common in adults.
• IgA vasculitis is caused by the deposition of IgA immune complexes after an upper respiratory or GI tract infection, leading to palpable purpura, renal, GI, and joint involvement. It resolves on its own in a few weeks, and steroids and NSAIDs are used to reduce severity of symptoms.

HIGH YIELD 1: Top Weird Drug Reactions

Review for the USMLE Step 1 exam

The podcast discusses high yield weird drug side effects that are unexpected.

3.30 Spirochetes

Microbiology review for the USMLE Step 1 Exam

• Spirochetes are spiral or corkscrew-shaped bacteria that stain gram negative.
• They have a unique endoflagella that distinguishes them from other species of bacteria.
• The endoflagella rotates within the periplasmic space and causes the bacteria to move, acting as its own propeller.
• Borrelia burgdorferi, Treponema pallidum, and Leptospira interrogans are the three important species of spirochetes to know.
• Borrelia burgdorferi causes Lyme disease, which is spread from wildlife to ticks and then to humans.
• The deer tick, also known as ixodes scapularis, is associated with Borrelia burgdorferi, but deer are not the reservoir for the bacteria.
• Lyme disease presents in three stages: erythema migrans (bulls-eye rash), flu-like symptoms, Bell's palsy, myocarditis, transient myalgias, arthritis, and neurological symptoms like encephalopathy and peripheral neuropathy.
• Treponema pallidum causes syphilis, which presents in stages: primary (chancre), secondary (rash), latent, and tertiary (gummas, neurological symptoms).
• Leptospira interrogans causes leptospirosis (Weil's disease), which is spread from infected animal urine to humans through broken skin, mucous membranes, or ingestion.
• Leptospirosis presents with flu-like symptoms, jaundice, renal failure, and meningitis.

3.29 Mycoplasma and Ureaplasma

Microbiology review for the USMLE Step 1 Exam

• Mycoplasma and Ureaplasma are bacteria without cell walls, making them invisible to gram stain.
• They cause respiratory and genital infections and have a cell membrane containing cholesterol.
• Main species causing infections in humans include Mycoplasma pneumoniae, Mycoplasma genitalium, Mycoplasma hominis, and Ureaplasma urealyticum.
• Mycoplasma pneumoniae causes atypical pneumonia and is spread through respiratory droplets. Symptoms include non-specific fever, headache, and sore throat, and diagnosis is done through PCR. Treatment is with macrolides, tetracyclines, and fluoroquinolones.
• Mycoplasma genitalium, Mycoplasma hominis, and Ureaplasma urealyticum cause genital infections and are acquired through sexual contact. They cause dysuria, urgency, urethral discharge, and pelvic pain. Diagnosis and treatment are similar to Mycoplasma pneumoniae with PCR and tetracyclines being the preferred treatment.

3.28 Klebsiella Pneumoniae

Microbiology review for the USMLE Step 1 Exam

• Klebsiella pneumoniae is a lactose-fermenting, gram-negative bacilli that causes pneumonia and is part of the normal GI flora in humans.
• It causes infection when introduced to the respiratory tract and is commonly found in hospitals, making it a common cause of nosocomial pneumonia.
• Risk factors for klebsiella pneumonia include alcoholism and diabetes.
• Symptoms of klebsiella pneumonia include cough, fever, pleuritic chest pain, and shortness of breath, as well as rust-colored "currant jelly" sputum and cavitary lesions in the lungs.
• Klebsiella can also cause urinary tract infections, especially in hospital settings.
• Treatment typically involves antibiotics, but resistance testing may be necessary due to the bug's high antibiotic resistance

3.27 Chlamydia Species

Microbiology review for the USMLE Step 1 exam

• Chlamydia is a gram-negative bacteria that is an obligate intracellular organism.
• It has a two-part life cycle involving the reticular body (active form) and elementary body (inactive form).
• There are three main species of chlamydia that cause human infections: chlamydia trachomatis, chlamydia pneumoniae, and chlamydia psittaci.
• Chlamydia trachomatis is the most common sexually transmitted infection in the US and causes genital tract infections, lymphogranuloma venereum, pelvic inflammatory disease, and reactive arthritis.
• Treatment for chlamydia trachomatis includes azithromycin or doxycycline, and ceftriaxone is often added to cover Neisseria gonorrhoeae.
• Chlamydia trachomatis can also infect neonates during delivery, causing conjunctivitis and pneumonia.
• Chlamydia pneumoniae causes community-acquired pneumonia spread through respiratory droplets.
• Chlamydia psittaci is associated with pet birds and also causes pneumonia.

3.26 Pseudomonas Aeruginosa

Microbiology review for the USMLE Step 1 Exam

• Pseudomonas aeruginosa is an encapsulated gram-negative oxidase positive rod that causes a variety of diseases.
• It can be found in soil, hospitals, and water, and it particularly likes water.
• P. aeruginosa can enter the body through contact with water, inhalation of respiratory droplets, or by medical equipment.
• The symptoms of infections caused by P. aeruginosa are caused by the toxins it secretes, including phospholipase C, exotoxin A, and endotoxin.
• P. aeruginosa causes community-acquired infections such as hot tub folliculitis, otitis externa, lung infections in cystic fibrosis patients, osteomyelitis, and skin infections.
• It causes nosocomial infections such as ventilator-associated pneumonia and catheter-associated urinary tract infections.
• P. aeruginosa is associated with skin infections in burn victims

3.25 Proteus Species

Microbiology review for the USMLE Step 1 exam

• Proteus species are gram-negative rods that cause hospital acquired urinary tract infections
• They have swarming motility and can move quickly in a coordinated fashion across surfaces due to their numerous flagella
• They can self-elongate and secrete a sticky polysaccharide when in contact with solid surfaces, allowing for attachment and easy motility
• Proteus mirabilis and Proteus vulgaris are the two main species that cause infections in humans
• Proteus mirabilis tends to cause hospital acquired UTIs and can cling to medical devices such as catheters, where it can infect the epithelium of the urinary tract and ascend up to the kidneys
• Proteus mirabilis expresses urease, converting urea to ammonia, which can cause the formation of struvite kidney stones
• Proteus vulgaris is less common than Proteus mirabilis and tends to be more difficult to treat due to drug-resistance plasmids
• Treatment for Proteus mirabilis infection depends on the type of infection, and for uncomplicated UTIs, patients can be given bactrim, while fluoroquinolones are given for pyelonephritis.

3.24 Salmonella Species

Microbiology review for the USMLE Step 1 Exam

• Salmonella are gram-negative bacteria that cause gastrointestinal disease.
• They have flagella that enable them to move around and infect cells, and can live inside macrophages.
• There are two categories of salmonella species: typhoidal and non-typhoidal.
• Typhoidal salmonella, such as salmonella typhi, cause typhoid fever and are usually acquired through contaminated water.
• Non-typhoidal salmonella, such as salmonella enteritidis, are usually acquired through contaminated poultry or reptiles.
• Typhoidal salmonella cause high fever and a pink spotted rash, while non-typhoidal salmonella cause diarrhea, nausea, and vomiting.
• Both types of salmonella require large quantities of bacteria to make you sick, and supportive care is usually all that is required.
• Fluoroquinolones like ciprofloxacin are the go-to antibiotics for typhoidal salmonella.

3.23 Yersinia Species

Microbiology review for the USMLE Step 1 Exam

• Yersinia are gram-negative, non-motile bacteria that cause zoonotic diseases.
• Yersinia produce urease enzyme to survive in the stomach and are facultative intracellular bugs.
• Three species of yersinia causing disease in humans are Yersinia pestis, Yersinia enterocolitica, and Yersinia pseudotuberculosis.
• The Yersinia species inhibit phagocytosis, the capsule contains F1 and V proteins and the injectosome injects Yersinia outer proteins.
• Yersinia pestis spreads through fleas, causing bubonic, pneumonic, or septicemic plague with symptoms like fever, chills, and swollen lymph nodes.
• Yersinia enterocolitica is spread through contaminated food or dog feces, causing enteric infection, and symptoms like diarrhea, abdominal pain, and vomiting.
• Yersinia pseudotuberculosis causes enteric disease, similar to Y. enterocolitica, and granulomatous lesions that look like tuberculosis.
• Yersinia pestis is rare with 500 cases reported since 1970, compared to Y. enterocolitica, which causes 100,000 cases each year

3.22 Escherichia Coli (E. Coli)

Microbiology review for the USMLE Step 1 Exam

• Esherichia coli (E. coli) is a lactose-fermenting, gram-negative rod causing various diseases, ranging from mild gastroenteritis to septic shock.

• E. coli diseases can be divided into two categories: intestinal infections and extraintestinal infections (outside the GI system).

• E. coli is part of the normal flora in the human GI tract, but some strains are pathogenic.

• Four pathogenic strains of E. coli are Entertoxigenic E. coli (ETEC), Enterohemorrhagic E. coli (EHEC), Enteroinvasive E. coli (EIEC), and Enteropathogenic E. coli (EPEC).

• ETEC causes watery diarrhea and is commonly found in food and water in areas with inadequate sanitation and is the most important cause of travelers' diarrhea.

• EHEC, also called Shiga toxin-producing E. coli (STEC), causes bloody diarrhea and is associated with contaminated food (spinach, sprouts, lettuce, fruit, undercooked beef).

• Shiga toxin produced by EHEC causes cell death in the GI tract and can lead to hemolytic uremic syndrome (HUS) in about 10% of cases.

• EIEC causes dysentery-like symptoms such as abdominal pain, fever, and bloody diarrhea.

• EPEC causes diarrhea, malnutrition, and growth retardation, especially in children.

• Extraintestinal infections include urinary tract infections (UTIs), neonatal sepsis, and pneumonia (incomplete list)

2.22 Tuberculosis

Pulmonary system review for the USMLE Step 1 Exam

• Tuberculosis is caused by Mycobacterium tuberculosis bacteria and mainly affects the lungs. It is more common in developing countries, with India, Indonesia, China, Nigeria, Pakistan, and South Africa having the most TB deaths worldwide.

• TB is spread through inhaling infected aerosolized droplets, making crowded places hotspots for TB spread.

• Primary TB infection occurs when a person inhales infected droplets and the bacteria become dormant in a granuloma. Secondary TB infection occurs when the bacteria disseminate to surrounding tissues, affecting various parts of the body.

• Symptoms of active TB include night sweats, weight loss, fever, and cough (sometimes with blood). TB can present with various symptoms, making it known as the "great imitator."

• Diagnosis methods include chest X-rays, sputum acid-fast staining, and real-time nucleic acid amplification. Chest X-rays showing cavitary lesions and positive acid-fast staining are indicative of TB.

• Treatment involves a 4-drug combination of rifampin, isoniazid, pyrazinamide, and ethambutol (RIPE) for an extended period of time (2-4 months) to get rid of the infection.

2.21 Pneumonia: Lobar, Broncho, and Interstitial

Pulmonary system review for the USMLE Step 1 Exam

• Pneumonia is an infection of the lung parenchyma that deals with gas exchange
• Three classic patterns of pneumonia: lobar, bronchopneumonia, and interstitial pneumonia
• Lobar pneumonia involves a single lobe of the lung and has four stages: congestion, red hepatization, gray hepatization, and resolution
• Most commonly associated with strep pneumoniae, also caused by Legionella and Klebsiella
• Bronchopneumonia is an infection of the bronchi that leads to diffuse infection of adjacent alveoli
• Causative organisms include strep pneumoniae, klebsiella, H influenza, and staph aureus
• Interstitial pneumonia is an ongoing infection in the interstitial areas of alveolar walls
• Causative organisms tend to be different compared to other types of pneumonia and include Mycoplasma pneumoniae, Legionella, chlamydophilia bugs, Coxiella burnetti, and some viruses (influenza and RSV)
• On chest X-ray, lobar pneumonia shows haziness in a single lobe with sharp demarcation, while bronchopneumonia and interstitial pneumonia show more diffuse haziness throughout the lungs
• Interstitial pneumonia tends to be more indolent, and patients may have not so good looking lungs on chest X-ray but are up and walking around (walking pneumonia).

2.20 Pneumothorax

Pulmonary system review for the USMLE Step 1 Exam

• Pneumothorax is a collection of air outside the lung in the pleural cavity, caused by a hole in the pleurae that allows air to infiltrate and disturb normal respiratory function.
• There are three categories of causes: primary spontaneous, secondary spontaneous, and trauma.
• Trauma, such as blunt force or penetrating wounds, is the most common cause, as well as iatrogenic causes like transthoracic needle aspiration and central venous catheterization.
• Spontaneous pneumothorax occurs without any trauma and can be classified as primary (no underlying lung disease) or secondary (with underlying lung disease).
• Smoking greatly increases the risk for spontaneous pneumothorax, especially in tall men with Marfan's syndrome or Ehlers-Danlos syndrome.
• Tension pneumothorax is a more emergent and dangerous type of pneumothorax, where air enters the pleural cavity but cannot exit, causing pressure to build up and compress nearby structures like the lungs, blood vessels, and heart.

2.19 Pleural Effusions: Transudate vs Exudate

Pulmonary system review for the USMLE Step 1 Exam

• Pleural effusion is an abnormal accumulation of fluid in the pleural cavity.
• Pleural effusions can be characterized as either exudative or transudative based on the content of the extra fluid.
• Exudative effusions have high protein and lactate dehydrogenase content, while transudative effusions have low protein and lactate dehydrogenase content.
• Pleural exudates are commonly caused by lung infections, lung cancer, and inflammatory diseases.
• Pleural transudates are caused by increased hydrostatic pressures or decreased oncotic pressure within the lung capillaries that force fluid into the pleural cavity.
• Transudative effusions are not caused by inflammation, so lactate dehydrogenase content is not expected to be high.
• Proteins are too big to move between cells, so transudative effusions have low protein content.

2.18 Digital Clubbing

Pulmonary system review for the USMLE Step 1 Exam

• Digital clubbing is the enlargement of the ends of fingers and toes due to growth of connective tissue between the nail matrix and the distal portion of the digit.
• It is defined quantitatively as an increased angle between nail bed and nail plate (> 180°).
• Digital clubbing is caused by an interaction between platelets, megakaryocytes, and the growth factors platelet derived growth factor (PDGF) and vascular endothelial growth factors (VEGF).
• Diseases associated with digital clubbing include lung cancer, cystic fibrosis, idiopathic pulmonary fibrosis, bronchiectasis, and an empyema.
• Digital clubbing is usually not associated with asthma or COPD.

2.17 Pickwickian Syndrome

Pulmonary system review for the USMLE Step 1 Exam

• Pickwickian Syndrome is also called obesity hypoventilation syndrome
• Characterized by daytime hypoventilation leading to hypercapnia
• Often occurs in individuals with a BMI over 30
• Excess fat puts pressure on lungs and reduces ability to fully inflate
• Reduction in ventilatory drive may also cause hypercapnia
• Typical patient presents with obesity, daytime sleepiness, and symptoms consistent with obstructive sleep apnea
• Diagnosis confirmed by arterial blood gas
• Short term treatment with positive airway pressure therapy
• Long term treatment involves lifestyle changes to lose weight
• CPAP machine supplies positive pressure to reduce CO2 build up
• Weight loss relieves symptoms by reducing excess weight on lungs.

2.16 Sleep Apnea

Pulmonary system review for the USMLE Step 1 Exam

• Sleep apnea is the repeated severe decrease or cessation of airflow into the lungs for more than 10 seconds during sleep, which causes the person to stop breathing for more than 10 seconds while they’re sleeping.
• There are two types of sleep apnea: obstructive sleep apnea and central sleep apnea.
• Obstructive sleep apnea occurs when the airway collapses during sleep, and it is more likely to be associated with snoring, gasping, and choking.
• Central sleep apnea occurs when breathing cessations are caused by decreased central nervous system respiratory drive, and it is more likely to be associated with Cheyne-Stokes respirations.
• Sleep apnea can cause hypertension, pulmonary hypertension, cardiac arrhythmias, and even sudden death.
• The most common symptom patients will present with is daytime sleepiness, and obesity is associated with obstructive sleep apnea.
• Diagnosis relies heavily on testing, and the gold standard for diagnosis of sleep apnea is a sleep study (a laboratory polysomnography).

2.15 Pulmonary Hypertension

Pulmonary system review for the USMLE Step 1 Exam

• Pulmonary hypertension is elevated blood pressure within the pulmonary arteries at rest, defined as a mean pulmonary artery pressure above 20 mmHg.
• Primary pulmonary hypertension is high blood pressure in the pulmonary arteries that is not caused by some underlying disease, while secondary pulmonary hypertension is high blood pressure caused by an underlying condition.
• Common underlying conditions for secondary pulmonary hypertension include heart failure, chronic thromboembolic disease, lung disease, and autoimmune disease.
• Pulmonary hypertension can lead to right heart failure and eventually death.
• Treatment for pulmonary hypertension involves treating the underlying disease and using drugs such as PDE-5 inhibitors, endothelin receptor antagonists, and prostacyclin to dilate the vessels in the lungs and lower the pressure within the pulmonary vessels.

2.14 Acute Respiratory Distress Syndrome (ARDS)

Pulmonary system review for the USMLE Step 1 Exam

• Acute respiratory distress syndrome (ARDS) is an acute, diffuse, inflammatory form of lung injury that is life-threatening for patients.
• ARDS is a response from the lungs to severe injury, most commonly caused by sepsis, but can also be caused by pneumonia, trauma, drowning, toxin inhalation, and pancreatitis.
• The lung injury from sepsis causes systemic inflammation, damaging lung tissue and causing diffuse alveolar damage, reducing surfactant production and causing alveolar edema.
• Patients with ARDS will present with progressive cough, progressive dyspnea, and hypoxia, and usually deteriorate quickly, 12-24 hours after symptom onset.
• Diagnosis of ARDS is based on imaging findings of bilateral lung infiltrates seen as white-out on chest X-ray and ground glass opacities on CT, as well as a decreased Pao2/Fio2 ratio to less than 300.
• Patients with ARDS are placed on mechanical ventilation with low tidal volume and positive end expiratory pressure (PEEP) to keep the alveoli open at the end of the respiratory cycle.
• Treatment of ARDS involves addressing the underlying cause of the disease, such as sepsis or pneumonia.

2.13 Sarcoidosis

Pulmonary system review for the USMLE Step 1 Exam

• Sarcoidosis is a multisystem inflammatory disorder with non-caseating granulomas in various organs
• Most commonly affects the lungs and causes restrictive lung disease
• Classic patient is a young black female in her 20-30s, but can affect any gender or race
• Symptoms vary depending on which organs are affected, and can include uveitis, skin lesions, joint pain, and swollen lymph nodes
• Bilateral hilar lymphadenopathy is a classic chest X-ray finding
• Restrictive lung pattern on spirometry with normal FEV1/FEV ratio and decreased total lung capacity
• Bells palsy can be a rare symptom caused by inflammation of the facial nerve (CN VII) and external compression by granulomatous mass
• Non-progressive sarcoidosis doesn't need treatment, but patients with respiratory symptoms or bells palsy can be given immunosuppressants like corticosteroids or methotrexate.

3.21 H. Pylori

Microbiology review for the USMLE Step 1 exam

• Helicobacter Pylori (H. Pylori) is a gram-negative, comma-shaped bacteria that causes chronic gastritis
• Estimated that 50% of people worldwide are infected with H. Pylori; higher in developing countries, lower in developed countries
• More common in populations with lower socioeconomic status and in crowded conditions with poor hygiene
• Spread through oral-oral or fecal-oral routes
• Colonizes the antrum of the stomach
• Produces urease that converts urea into carbon dioxide and ammonia, helping it survive in the acidic environment of the stomach
• Secretes toxins that cause inflammation of the gastric epithelium and lead to gastritis and ulcer formation
• Most people with H. Pylori never have symptoms, but some may present with dyspepsia, abdominal pain, nausea, vomiting, gastritis, or peptic ulcer disease
• Duodenal ulcers often associated with H. Pylori or heavy NSAID use
• Diagnosis can be made through urea breath test, stool antigen test, or endoscopy with gastric biopsy
• Treated with a triple drug regimen of a proton pump inhibitor, clarithromycin, and amoxicillin or metronidazole (triple therapy)
  • PCAM

3.20 Vibrio Species

Microbiology review for the USMLE Step 1 Exam

• Vibrio species are gram negative comma-shaped rods with a single flagellum, allowing them to move quickly
• Two main species that cause human infections: Vibrio cholerae and Vibrio vulnificus
• Vibrio cholerae causes foodborne disease called cholera through cholera toxin secretion, spread through the fecal-oral route in developing countries
• Cholera is characterized by watery, mucinous diarrhea, if left untreated can lead to hypovolemic shock and high mortality
• Treatment involves rapid rehydration and electrolyte replacement, antibiotics may be used for severe cases
• Vibrio vulnificus causes severe skin infections acquired through exposure of open wounds in marine environments
• Symptoms include cellulitis, swelling, blister formation, ulceration, and hemorrhagic bullae

3.19 Campylobacter Jejuni

Microbiology review for the USMLE Step 1 exam

• Campylobacter jejuni is a gram-negative, comma-shaped bacteria that causes diarrheal illness
• It is the most common cause of bacterial diarrhea in the US
• It can be distinguished from other gram-negative, comma-shaped bacteria by its desired culture temperature of 42C/107F
• It is mostly acquired through consumption of raw milk, undercooked poultry, and contaminated water
• 90% of cases in the US occur during the summer months, likely due to increased grilling of poultry
• Symptoms include high fever, rigors, dizziness, body aches, diarrhea (more than 10 stools a day), abdominal cramping, and nausea
• Complications include Guillain-Barré syndrome (GBS) and reactive arthritis
• Diagnosis is typically made through a stool culture
• Treatment typically includes supportive care and replenishing fluids and electrolytes, with antibiotics (macrolides) used for more severe cases.

3.18 Bartonella Henselae

Microbiology review for the USMLE Step 1 exam

• Bartonella henselae is an intracellular gram negative rod that causes several different diseases
• Bartonella targets and lives inside specialized immune cells called CD34+ cells
• Bartonella creates a protective vacuole that protects it and helps it evade immune detection
• Bartonella henselae is a facultative intracellular bacteria
• Three different clinical syndromes associated with bartonella henselae: cat scratch disease, bacillary angiomatosis in immunocompromised patients, and bacterial endocarditis
• Cat scratch disease presents with cutaneous manifestations at the site of inoculation (warm, red, swollen, with a vesicle) and swollen lymph nodes near the site
• Bacillary angiomatosis symptoms include fever, multiple clustered red or violaceous papules or nodules on the skin and mucosa, and bone pain
• Bacterial endocarditis: Bartonella makes its way into the bloodstream and infects the inner surface of the heart
• Bartonella henselae is hard to culture from blood, usually diagnosed via serology
• Treatment depends on the clinical syndrome presented, cat scratch disease is usually self-limited and doesn’t necessarily require antibiotics, bacillary angiomatosis treated with a long 4-month course of either erythromycin or doxycycline.

3.17 Brucella Species

Microbiology review for the USMLE Step 1 exam

• Brucella species are gram-negative intracellular coccobacilli that are spread from animals to humans, causing a zoonotic infection called Brucellosis.
• B. melitensis is the most common species that causes infection in humans and is also the most virulent.
• Brucella only requires a very small dose (10-100 bacteria) to cause full-blown disease, often spread through contaminated unpasteurized milk or contact with animal carcasses.
• "Bruce Wayne's goat, Brucella Wayne, helps him SLAUGHTER bad guys"
• Symptoms include cyclical fever and chills, general malaise, headaches, joint pain, and nausea and vomiting.
• Diagnosis can be confirmed through blood cultures and PCR.
• Treatment involves antibiotics, typically doxycycline for a course of 6 weeks.
• People most at risk for infection include those who drink unpasteurized goat milk and those who work with animal carcasses, such as slaughterhouse workers.

3.16 Pasteurella Multocida

Microbiology review for the USMLE Step 1 exam

• Pasteurella multocida is a gram-negative coccobacillus that commonly causes infection following animal bites or scratches
• Classic presentation is a young male with swollen, red, and tender skin at the site of the bite or scratch
• Symptoms develop rapidly, usually within 3-48 hours after injury
• In rare cases, infection can progress to necrotizing fasciitis or bacteremia
• Diagnosis is made clinically using patient history and symptoms
• Treatment of choice is amoxicillin-clavulanate, and infections usually resolve with little complications when treated with antibiotic

3.15 Bordetella Pertussis

Microbiology review for the USMLE Step 1 exam

• Bordetella pertussis is a gram-negative bacterium that causes whooping cough
• Spread through respiratory droplets, most people are vaccinated against it
• Adheres to ciliated respiratory epithelial cells and produces toxins that cause inflammation and systemic effects
• Pertussis toxin and tracheal cytotoxin are important toxins secreted by the bacteria
• Symptoms include four stages: incubation, catarrhal, paroxysmal, and convalescent
• Infants and unvaccinated people are most commonly affected
• Treatment is mostly supportive, including oxygen, suctioning, hydration, and avoidance of respiratory irritants.

3.14 Haemophilus Influenzae

Microbiology review for the USMLE Step 1 exam

• Haemophilus influenzae is a gram negative coccobacilli that is often encapsulated, encapsulated strains are broken up into subgroups a through f, non-encapsulated strains are referred to as non-typable
• The most common pathogenic strain is type b, which causes disease in children and immunocompromised individuals, it is the strain that we vaccinate against
• The group B H. influenzae vaccine is a conjugated polysaccharide vaccine recommended as a routine childhood vaccination in the United States, provides protection against the group B strain of the bug
• H. influenzae mainly affects the extremes of age, very young children (younger than 5) and elderly adults (>65)
• In young children, it most commonly causes epiglottitis, otitis media, and meningitis, in elderly adults it is a cause of lower respiratory tract infections, especially in patients with COPD
• H flu infections in young children can be a medical emergency and requires treatment with antibiotics and intubation in some cases
• Otitis media is the most common H flu infection in children, caused by non-group B H flu, it is still the number one cause of otitis media in children

3.13 Moraxella Catarrhalis

Microbiology review for the USMLE Step 1 exam

• Moraxella Catarrhalis is a gram negative diplococcus that is part of normal upper respiratory tract flora
• Mainly causes three different types of infections: otitis media in children, lower respiratory tract infections in COPD patients, and pneumonia in elderly patients
• Otitis media is the most common bacterial infectious disease in childhood and the most common reason for which children receive antibiotics. M. catarrhalis causes about 15-20% of otitis media cases.
• Symptoms of otitis media in children include pulling or tugging at the ears, irritability, headache, disturbed or restless sleep, poor feeding, anorexia, vomiting, or diarrhea.
• In COPD patients, exacerbations are often due to bacterial and viral infections. M. catarrhalis is a bug to keep in mind and symptoms of a COPD exacerbation caused by this bug are very similar to those caused by other bacteria, including increased sputum production, sputum purulence, and dyspnea.
• Pneumonia due to M. catarrhalis is a cause of pneumonia in elderly patients, especially in elderly patients with an underlying cardiopulmonary disease like COPD.
• These infections are usually treated empirically with broad spectrum antibiotics such as 3rd generation cephalosporins and amoxicillin-clavulonic acid.

3.12 Neisseria Species

Microbiology review for the USMLE Step 1 exam

• Neisseria species are gram negative diplococci that infect and live inside neutrophils
• Two main species that cause infections in humans: Neisseria gonorrhoeae and Neisseria meningitidis
• Neisseria gonorrhoeae causes the sexually transmitted infection gonorrhea, which is the second most common STI
• Risk factor for gonorrhea is unprotected sex with an infected person
• N. gonorrhoeae uses pilli to adhere to epithelial cells and invade, causing a local skin infection at the site of inoculation
• Females: cervix is the most common site of infection, causes cervicitis, symptoms include thick yellow or green vaginal discharge, dysuria, and pelvic pain. If left untreated, it can cause PID, ectopic pregnancy, infertility, and chronic pelvic pain
• Males: urethra is the most common site of infection, symptoms include yellow-green discharge, dysuria, and painful swollen testes (less common)
• If left untreated, it can infect more proximal structures and cause prostatitis
• Diagnosis is done by swabbing the urethra or cervix and sending it for nucleic acid amplification testing
• Can also cause septic arthritis (in contrast, Chlamydia causes reactive arthritis)
• "Gonorrhea gon go to the joints"
• Treatment typically involves a cephalosporin (like ceftriaxone) and azithromycin to also cover chlamydial infection
• Conjunctival gonorrhea can occur in newborns during the birthing process, causing conjunctivitis in the eye.

3.11 Nocardia and Actinomyces (Branching Filamentous Species)

Microbiology review for the USMLE Step 1 exam

• Nocardia and Actinomyces are two gram positive bacteria that grow in filaments, resembling fungal hyphae.
• Both are associated with chronic pulmonary lesions, subcutaneous abscesses, and multiple draining sinuses.
• Both are capable of producing sulfur granules.
• Actinomyces is anaerobic and colonizes the mouth, GI, and urinary tracts. It can cause "lumpy jaw syndrome" and requires a long course of high dose penicillin.
• Nocardia is aerobic and stains weakly acid fast. It is found in the environment and typically causes cutaneous disease in immunocompetent individuals and pulmonary disease in immunocompromised individuals.
• Treatment for Nocardia typically involves a combination of antibiotics such as sulfonamides and trimethoprim-sulfamethoxazole.
• SNAP mnemonic: Sulfa for Nocardia; Actinomyces gets Penicillin.

3.10 Clostridium Species

Microbiology review for the USMLE Step 1 exam

• Clostridium species are spore-forming anaerobic gram-positive rods that secrete toxins
• Four main species: Clostridium difficile, Clostridium perfringens, Clostridium botulinum, Clostridium tetani
• Clostridium difficile: common cause of antibiotic-associated diarrhea, caused by overgrowth of C. diff in gut after taking antibiotics that do not kill it, treatment involves stopping offending antibiotic and changing to one that can kill C. diff
• Clostridium perfringens: associated with acute GI infections, usually acquired through consuming contaminated food, symptoms include abdominal pain, watery diarrhea and vomiting
• Clostridium botulinum: acquired through eating contaminated food, causes flaccid paralysis through production of botulinum toxin which disrupts synaptic signaling
• Clostridium tetani: causes tetanus, acquired through introduction of spores through breaks in skin, produces tetanus toxin which causes muscle stiffness and spasms.

3.09 Corynebacterium Diptheriae

Microbiology review for the USMLE Step 1 Exam

• Corynebacterium diphtheriae is an aerobic gram positive rod that causes diphtheria, commonly spreads through respiratory droplets
• C. diphtheriae produces an exotoxin called diphtheria toxin which can cause systemic effects by inactivating elongation factor (EF-2) via ADP-ribosylation and shutting down protein synthesis
• Diphtheria causes fever, sore throat, croup-like cough, pseudomembranous pharyngitis, severe cervical lymphadenopathy, myocarditis and cardiac arrhythmias
• Cutaneous diphtheria involves ulcerative lesions or cellulitis on the skin that can occur independently of respiratory diphtheria
• Vaccine available and there are not many cases of it in the US, tends to have an outsized effect on developing countries
• Risk factors for C. diphtheriae infection include IV drug use, homelessness, and crowded living conditions
• Treatment involves diphtheria antitoxin and penicillin or erythromycin

3.08 Bacillus Species

Microbiology review for the USMLE Step 1 exam

• Bacillus species are aerobic, sporulating, gram + rod-shaped bacteria found in nature such as soil, water, and air
• Two main species to discuss: Bacillus cereus and Bacillus anthracis
• Bacillus cereus is associated with foodborne infections and specifically with reheated rice, as spores can survive cooking and continue to grow in refrigerated rice, leading to enteritis symptoms
• Bacillus anthracis causes anthrax, most commonly contracted through contact with infected animals, particularly grazing animals such as sheep, goats, and cattle.
• There are three forms of anthrax: cutaneous anthrax, inhalation anthrax, and gastrointestinal anthrax
• Cutaneous anthrax is the most common form and results from inoculation of spores through a cut or opening in the skin
• Inhalation anthrax occurs when spores are inhaled and leads to systemic illness, mediastinal widening, septic shock, and death
• Gastrointestinal anthrax results from ingesting spores in contaminated food and leads to severe abdominal symptoms.

3.07 Listeria Monocytogenes

Microbiology review for the USMLE Step 1 exam

• Listeria monocytogenes is an intracellular, aerobic, gram-positive rod that can cause foodborne illness
• It can live inside various types of cells, including epithelial cells, macrophages, and monocytes, and spreads from cell to cell through actin polymerization
• It is most commonly found in refrigerated deli meats and unpasteurized dairy products, and can cause gastroenteritis, meningitis, and premature labor/spontaneous abortion in immunocompromised individuals, pregnant women, and older or young individuals
• It is usually treated with ampicillin, but bactrim (trimethoprim and sulfamethoxazole) can be used in cases of ampicillin allergy

3.06 Staphylococcus Species

Microbiology review for the USMLE Step 1 Exam

• Staphylococcus bacteria are gram-positive cocci that form clusters in the shape of grapes on a vine
• Three pathogenic species of staph: staph aureus, staph epidermidis, and staph saprophyticus
• Differentiation between species can be done using coagulase and novobiocin sensitivity tests
• Staph aureus is a major pathogen that causes many severe infections including toxic shock syndrome, septic arthritis, acute endocarditis, gastroenteritis, pneumonia, and staphylococcal scalded skin syndrome
• Toxic shock syndrome can be caused by tampons, soft tissue infections, post-surgical infections, and retained foreign bodies
• Staphylococcal scalded skin syndrome, or Ritter disease, is characterized by exfoliative damage to the skin and mainly affects newborns within 48 hours of birth
• Staph aureus can spread hematogenously and affect many parts of the body, particularly the heart and joints.
• Gastroenteritis caused by staph aureus is caused by consumption of exotoxins produced by the bacteria.

3.05 Streptococcus Species

Microbiology review for the USMLE Step 1 Exam.

• Streptococcus bacteria are gram positive cocci that form linear chains
• Hemolysis refers to the ability of bacteria to break down red blood cells and is classified as alpha (partial), beta (complete), or gamma (none)
• Alpha hemolytic streptococci include viridans streptococci and Streptococcus pneumoniae
• Viridans streptococci, particularly Streptococcus mutans, are common causes of dental cavities and endocarditis, while Streptococcus pneumoniae is a common cause of pneumonia
• Beta hemolytic streptococci include Group A streptococci (Streptococcus pyogenes) and Group B streptococci (Streptococcus agalactiae)
• Group A streptococci can cause strep throat, impetigo, and cellulitis, as well as more serious infections like scarlet fever and rheumatic fever
• Group B streptococci are commonly found in the vagina and rectum, and can cause infections in newborns and pregnant women, as well as urinary tract infections and pneumonia
• Gamma hemolytic streptococci include the Enterococcus species, which can cause urinary tract infections, endocarditis, and other infections, and can be resistant to some antibiotics
• Lancefield grouping refers to the presence of different types of carbohydrate antigens on the surface of streptococcus bacteria and is used in classification and identification of streptococcus species

3.04 Gram Negative Bacteria

Microbiology review for the USMLE Step 1 Exam.

• Gram negative bacteria are characterized by a thin cell wall surrounded by a lipid outer membrane
• They do not retain the violet gram stain and appear pink after staining
• Gram negative bacteria can be classified by shape: cocci, coccobacilli, bacilli, and spirals
• Gram negative cocci include Neisseria species, which can be further categorized as maltose fermenters or non maltose fermenters
• Gram negative coccobacilli include: Bordetella pertussis, Haemophilus influenzae, Pasteurella, Francisella tularensis, Brucella, and Acinetobacter
• Gram negative bacilli can be divided into lactose fermenting and non lactose fermenting categories
• Lactose fermenting gram negative bacilli include: Escherichia coli, Klebsiella, Enterobacter, Citrobacter, and Serratia
• Non lactose fermenting gram negative bacilli can be further divided into oxidase positive and oxidase negative
• Oxidase positive non lactose fermenting gram negative bacilli include Pseudomonas
• Oxidase negative non lactose fermenting gram negative bacilli include Shigella, Yersinia, and Salmonella
• Gram negative spirals can be divided into oxidase positive and oxidase negative categories
• Oxidase positive gram negative spirals include Vibrio species, Helicobacter pylori, and Campylobacter jejuni
• Oxidase negative gram negative spirals include Borrelia burgdorferi (cause of lyme disease) and Treponema pallidum (cause of syphilis)

3.03 Gram Positive Bacteria

Microbiology review for the USMLE Step 1 Exam.

• Gram positive bacteria are characterized by their ability to retain the violet stain during the gram stain procedure, due to their thick peptidoglycan cell walls
• Gram positive bacteria can be cocci (spherical) or bacilli (rod-shaped)
• Cocci can be grouped in clusters, pairs, or chains
• Gram positive cocci in pairs or chains include streptococcus (pairs or chains), enterococcus (pairs), and staphylococcus (clusters)
• Hemolysis describes the ability of a bacteria species to break down red blood cells and is categorized as alpha (partial), beta (complete), or gamma (none)
• Coagulase activity refers to the presence of an enzyme that causes blood to coagulate and is present in some staphylococcus species
• Gram positive bacilli can be aerobic (listeria, bacillus, corynebacterium) or anaerobic (clostridium)

3.02 Bacterial Toxins

Microbiology review for the USMLE Step 1 Exam.

• Bacterial toxins are harmful compounds produced by bacteria that cause damage to the host
• Exotoxins are toxins that are actively secreted by some species of gram positive and gram negative bacteria
• Examples of exotoxins include botulinum toxin, Corynebacterium diphtheriae toxin, and cholera toxin
• Endotoxins are toxins that are contained within the cell wall of gram negative bacteria and are released when the bacteria are lysed or fragmented
• Structurally, endotoxins consist of the O antigen, the core oligosaccharide, and Lipid A, with the Lipid A component being responsible for most of the toxicity
• Endotoxins are less virulent and more heat stable than exotoxins, and are usually contained in the bacteria's own genetic material rather than on a plasmid

3.01 Bacteria Basics

Microbio review for the USMLE Step 1 Exam:

• Bacteria are single-celled organisms that can cause infection
• Structural components of bacteria include: capsule, cell wall, flagella, fimbriae, plasma membrane, ribosomes, endospores, and DNA
• Capsules help bacteria evade the immune system by inhibiting phagocytes
• Flagella are tail-like appendages that allow bacteria to move, fimbriae help bacteria adhere to surfaces
• Most bacteria have a cell wall, which can be either gram positive or gram negative
• Plasma membrane is composed of proteins and phospholipids and performs various functions
• DNA is the genetic material, ribosomes are used to build proteins, some bacteria have endospores which are heat-resistant resting cells
• Bacteria can be classified by cell wall composition, morphology, metabolism, and based on their ability to grow at different temperatures and pH levels
• Gram staining is a laboratory technique used to differentiate between gram positive and gram negative bacteria
• Morphology of bacteria includes cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped)
• Metabolism of bacteria can be aerobic (uses oxygen) or anaerobic (doesn't use oxygen)
• Temperature and pH ranges at which bacteria can grow vary widely, some can grow at extreme conditions
• Pathogenic bacteria cause disease, while non-pathogenic bacteria do not
• Bacteria can be treated with antibiotics, but overuse can lead to antibiotic resistance

2.12 Idiopathic Pulmonary Fibrosis

Pulmonary system review for the USMLE Step 1 exam.

2.11 Bronchiectasis

Pulmonary system review for the USMLE Step 1 exam.

2.10 Asthma

Pulmonary system review for the USMLE Step 1 exam.

2.09 COPD

Pulmonary system review for the USMLE Step 1 exam.

2.08 Obstructive vs Restrictive Lung Diseases

Pulmonary system review for the USMLE Step 1 exam.

2.07 Pulmonary Embolism

Pulmonary system review for the USMLE Step 1 exam.

2.06 Physical Findings for Lung Diseases

Pulmonary system review for the USMLE Step 1 exam.

2.05 Rales, Wheezing, Ronchi, and Stridor

Pulmonary system review for the USMLE Step 1 exam.

2.04 Lung Volumes and Capacities

Pulmonary system review for the USMLE Step 1 exam.

2.03 Lung Elastic Recoil and Compliance

Pulmonary system review for the USMLE Step 1 exam.

2.02 Virchows Triad

Pulmonary system review for the USMLE Step 1 exam.

2.01 VQ ratio

Pulmonary system review for the USMLE Step 1 exam.

1.36 Cardiac Tumors

Cardiovascular system review for the USMLE Step 1 exam.

1.35 Myocarditis

Cardiovascular system review for the USMLE Step 1 exam.

1.34 Rheumatic Fever

Cardiovascular system review for the USMLE Step 1 exam.

1.33 Pericarditis

Cardiovascular system review for the USMLE Step 1 exam.

1.32 Bacterial Endocarditis

Cardiovascular system review for the USMLE Step 1 exam.

1.31 Cardiac Tamponade

Cardiovascular system review for the USMLE Step 1 exam.

1.30 Shock

Cardiovascular system review for the USMLE Step 1 exam.

1.29 Heart Failure

Cardiovascular system review for the USMLE Step 1 exam.

1.28 Torsades de Pointes

Cardiovascular system review for the USMLE Step 1 exam.

1.27 Wolff-Parkinson-White Syndrome

Cardiovascular system review for the USMLE Step 1 exam.

1.26 Supraventricular Tachycardia

Cardiovascular system review for the USMLE Step 1 exam.

1.25 Heart Block

Cardiovascular system review for the USMLE Step 1 exam.

1.24 SVC Syndrome

Cardiovascular system review for the USMLE Step 1 exam.

1.23 Aortic Dissection

Cardiovascular review for the USMLE Step 1 exam.

1.22 Myocardial Infarction

Cardiovascular review for the USMLE Step 1 exam.

1.21 Cardiomyopathies

Cardiovascular system review for the USMLE Step 1 exam.

1.20 Atherosclerosis

Cardiovascular system review for the USMLE Step 1 exam.

1.19 Fetal Alcohol Exposure

Cardiovascular system review for the USMLE Step 1 exam.

1.18 Coarctation of the Aorta

Cardiovascular system review for the USMLE Step 1 Exam.

1.17 Eisenmenger Syndrome

Cardiovascular system review for the USMLE Step 1 exam.

1.16 Ebstein Anomaly

Cardiovascular review for the USMLE Step 1 exam.

1.15 Atrial Septal Defect

Cardiovascular system review for the USMLE Step 1 Exam.

1.14 Transposition of the Great Vessels

Cardiovascular system review for the USMLE Step 1 exam.

1.13 Ventricular Septal Defects

Cardiovascular system review for the USMLE Step 1 Exam.

1.12 Tetralogy of Fallot

Cardiovascular system review for the USMLE Step 1 exam.

1.11 Patent Ductus Arteriosus (PDA)

Cardiovascular system review for the USMLE Step 1 exam.

• Patent ductus arteriosus (PDA) is a congenital heart defect where the ductus arteriosus, a connection between the pulmonary artery and aorta, fails to close after birth.
• PDA results in oxygenated blood being shunted into pulmonary circulation, leading to volume overload in the pulmonary circulation and eventually the left side of the heart.
• Symptoms include tachycardia, tachypnea, machine-like constant murmur, bounding pulses, respiratory distress, and pneumonia.
• Treatment options include fluid restriction, supportive care, and pharmacological interventions such as indomethacin, acetaminophen, or ibuprofen to reduce prostaglandin production and close the PDA.
• If these interventions don't work, surgical ligation may be performed to close the PDA.
• PDA is so painful to watch, you have to take NSAIDs afterwards.

1.10 Localization of MI on ECG

Cardiovascular system review for the USMLE Step 1 exam T

• Myocardial infarction (MI) can be localized by identifying changes in various ECG leads
• Anterior STEMI: ST elevation in precordial leads V3, V4, indicating occlusion of the distal left anterior descending artery (LAD)
• Lateral MI: ST elevation in leads I, aVL, aVR, and precordial leads V5, V6, caused by an occlusion of the LAD
• Septal MI: ST elevation in leads V1, V2, V3, caused by an occlusion to the LAD
• Inferior MI: ST elevation in leads II, III, aVF, caused by an occlusion of the right coronary artery (RCA)
• Posterior MI: ST elevation in V7, V8, V9, caused by an occlusion of the posterior descending artery (PDA)

1.09 Heart Sound Locations

Cardiovascular system review for the USMLE Step 1 exam.

• Heart sound locations include the aortic, pulmonic, tricuspid, and mitral positions
• Mnemonic to remember the positions: "all physicians take money" (aortic, pulmonic, tricuspid, mitral)
• Aortic position: 2nd intercostal space on the right side of the chest
• Pulmonic position: 2nd intercostal space on the left side of the chest
• Tricuspid position: 5th intercostal space on the left side of the chest
• Mitral position: 6th intercostal space on the left side of the chest at the midclavicular line
• All positions are near the midline except the mitral position

1.08 S2 Splitting

Cardiovascular system review for the USMLE Step 1 exam

• S2 splitting is a phenomenon where the closure of the aortic and pulmonic valves occur at different times, resulting in two heart sounds heard at what is normally S2.
• Four types of splitting: physiologic or normal splitting, wide splitting, fixed splitting, and paradoxical splitting.
• Physiologic splitting is normal and occurs when a person takes a deep breath and the difference between the closure of the aortic and pulmonic valves can be heard.
• Wide splitting is a symptom that is not normal and is associated with diseases that delay right ventricle emptying, such as right bundle branch block and pulmonary stenosis. It gets worse with inhalation.
  • Wide split, worsened by inhalation
• Fixed splitting is similar to wide splitting, but it is not made worse when the patient inhales. It is seen in patients with an atrial septal defect.
  • Fixed split, fixed in place
• Paradoxical splitting is a wide split that is fixed by inspiration and is caused by diseases that delay aortic valve closure, such as aortic stenosis and left bundle branch block.
  • Paradoxially fixded by inspiration

1.05a S3 vs S4 Sounds Only

Compare the S3 and S4 heart sounds directly. This podcast does not explain the physiologic difference between the sounds or the associated diseases. See the individual podasts for that information.

1.07 Diastolic Heart Murmurs

Cardiovacular system reveiw for the USMLE Step 1 exam.

• Diastolic heart murmurs occur when blood flow is turbulent during the diastolic phase of the heart
• Two diastolic murmurs discussed: aortic regurgitation and mitral stenosis
• Aortic regurgitation is caused by blood leaking backwards from the aorta into the left ventricle, resulting in a high pitched decrescendo murmur heard during diastole
• Aortic regurgitation is associated with conditions such as aortic root dilation, bacterial endocarditis, rheumatic fever, and bicuspid valve
  • "A vacuum adds suction. Aortic regurgitation diastolic decrescendo"
• Mitral stenosis involves narrowing of the mitral valve, causing an opening snap followed by a rumbling sound during diastole
• The main cause of mitral stenosis is rheumatic fever
  • "Ms snapped because her husband got strep throat from his lover. MS (mitral stenosis), snap’d (snap diastolic), strep throat (rheumatic fever)"

1.05 S4 Heart Sound.

Cardiovacular system reveiw for the USMLE Step 1 exam.

• The S4 heart sound, also called an S4 gallop or atrial gallop, is an extra sound that is heard in late diastole, just before S1
• It is caused by a stiff ventricle
• S4 is mostly pathogenic and almost never normal, unlike S3
• It is associated with diseases that cause the ventricles to stiffen like hypertrophic cardiomyopathy and diastolic heart failure
• In the case of an athlete with physiological hypertrophy of the ventricles, growth of the ventricles can be a normal response to cardiovascular conditioning and lead to them developing an S4 heart sound
• S4 can be heard best when at the apex of the heart when the patient is placed in the left lateral decubitus position

1.06 Systolic Heart Murmurs

Cardiovacular system reveiw for the USMLE Step 1 exam.

• Heart murmurs occur when blood flow is turbulent in the heart, producing a whooshing or swishing sound
• 4 different sounding systolic murmurs discussed: Ventricular septal defect, patent ductus arteriosus, aortic stenosis, and mitral/tricuspid regurgitation
• Patent ductus arteriosus is a machine-like murmur that is constant (heard during systole and diastole)
  • Patent ductus arteriosus: "People who constantly PDA deserve to be thrown in a machine"
• Ventricular septal defect produces a harsh holosystolic murmur (only heard during systole)
  • Ventricular septal defect: "Holy cow, its harsh being born with a VSD"
• Aortic stenosis produces a crescendo-decrescendo systolic ejection murmur (heard during systole)
  • Aortic stenosis: "ASS CD (insert your least favorite band here, I’ll say Nickelback)"
• Mitral and tricuspid regurgitation produces a holosystolic high pitched "blowing" murmur (heard during systole)
  • Mitral and tricuspid regurgitation: "It sucks to climb Mt regurgitation. Climbing Mt regurgitation blows."
• The location and cause of the murmur can indicate whether it is mitral or tricuspid regurgitation

1.04 S3 Heart Sound

Cardiovacular system reveiw for the USMLE Step 1 exam.

• The S3 heart sound, also called an S3 gallop or ventricular gallop, is an extra sound that occurs in early diastole during the ventricular filling phase
• It can be normal for some people and a sign of disease in others
• It is caused by a dilated or floppy ventricle and is associated with dilated or floppy ventricles.
• S3 can also be caused by increases in volume load on the ventricles
• It is commonly found in children and young adults, athletes, and people who are pregnant
• It is heard best when at the apex of the heart when the patient is placed in the left lateral decubitus position

1.03 Hemodynamics.

Cardiovacular system reveiw for the USMLE Step 1 exam.

• Hemodynamics studies blood flow through the body
• Volumetric flow rate (Q) describes the volume of material moving through space per unit time, in terms of psychiatry it is the amount of blood moving through a vessel per unit time
• Volumetric flow rate is proportional to radius to the 4th power, so when radius increases, volumetric flow rate increases
• Resistance is a measure of a blood vessel's opposition to blood flow
• Resistance is inversely proportional to radius to the 4th power, so when vessel radius is increased, resistance decreases
• For vessels in series, you can simply add the resistances of each up to get the total resistance
• For vessels in parallel, the total resistance is equal to the sum of the inverses of the resistances each vessel

1.01. Cardiac Output Equations

Cardiovascular system reveiew for the USMLE Step 1 exam.

• Equations that describe cardiac output and cardiac performance
• Cardiac output (CO) is the amount of blood volume pumped by the heart per min, typically given in L/min
• CO is equal to stroke volume (SV) times heart rate (HR)
• SV is influenced by preload, afterload, and contractility
• Pulse pressure is the difference between systolic and diastolic blood pressure (PP = SBP-DBP)
• High pulse pressure can be caused by stiffening of the major arteries
• Mean arterial pressure (MAP) is the average arterial pressure during one cardiac cycle
• MAP is equal to CO * TPR and MAP is equal to ⅔ DBP + ⅓ SBP
• Diastolic blood pressure contributes more to MAP than systolic pressure

1.01. S1, S2, and the Cardiac Cycle.

Cardiovascular system reveiew for the USMLE Step 1 exam.

• Two main heart sounds are s1 and s2, also known as "lub" and "dub"
• S1 corresponds to closure of the mitral and tricuspid valves
• S2 corresponds to closure of the aortic and pulmonic valves
• The pause between s2 and s1 is longer than the pause between s1 and s2 in a normal cardiac cycle
• Elevated heart rate can make it harder to distinguish the two sounds
• The noise produced by the valves slamming shut, like a door being slammed shut
• The Atria contracts before the ventricles, and the mitral and tricuspid valves separate the atria from the ventricles, so they shut first which produces S1
• The ventricles contract and push blood through the aortic and pulmonic valves, and These shut after this event producing S2.