USMLE/COMLEX 3 - Myocardial Infarctions

Here are key facts for USMLE Step 3 & COMLEX-USA Level 3 from the Myocardial Infarctions: Diagnosis & Treatment tutorial, focusing on advanced clinical management, complex decision-making, and systems-based practice concepts that are essential for these exams. See the tutorial notes for further details and relevant links.

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1. Geographic distributions: Declining in high-income countries but rising in middle- and low-income countries. 2. Demographic patterns: Incidence after age 35, from highest to lowest: Black males > Black females > White males > White females. 3. Gender differences: MI occurs approximately 10 years earlier in men than women. 4. Mortality patterns: Higher mortality rates in women than their male peers, especially for young and/or minority women. 5. Modifiable risk factors: Dyslipidemia, diabetes mellitus, hypertension, smoking (including e-cigarettes), obesity, psychosocial stress, alcohol consumption, poor diet. 1. Definition: Myocardial infarction is defined as myocardial injury with ischemia. 2. ECG interpretation: Should be administered as soon as possible when MI is suspected, and re-administered frequently to observe the evolution of the infarction. 3. ECG localization: Identifying specific territories based on lead changes:

• Lateral infarction: Leads I and aVL; often left circumflex artery
• Apical infarctions: Leads V5 and V6; often left circumflex or right coronary arteries
• Anterior infarctions: Leads V3 and V4; left anterior descending artery
• Anterior septal infarctions: Leads V1 and V2; proximal left anterior descending artery
• Inferior infarctions: Leads II, aVF, and III; right coronary artery or left circumflex artery
• Right ventricular infarctions: Requires leads V3R-V6R
• Posterolateral infarctions: Requires leads V7-V9; right coronary or left circumflex artery

4. Biomarker interpretation: Using cardiac troponin patterns to differentiate between NSTEMI and unstable angina. 5. Recognizing atypical presentations: Women and elderly patients may present without classic chest pain. 1. Pre-hospital considerations: Early administration of oxygen (when saturation <90%), aspirin, and nitrates. 2. Reperfusion strategy selection: Based on severity of infarction:

• STEMI: Emergency PCI preferred; if unavailable, fibrinolytic drugs ASAP
• NSTEMI: Timing based on risk stratification (immediate for unstable patients, delayed for stable patients)

3. Pharmacotherapy selection:

• Antiplatelets: Aspirin, clopidogrel, or other P2Y12 inhibitors
• Anticoagulation: Unfractionated or low molecular weight heparin
• Anti-ischemic: Beta-blockers or calcium-channel blockers
• Plaque stabilization: Statins, ACE-inhibitors

4. Fibrinolytic therapy decisions: Not generally recommended for NSTEMI due to risk/benefit ratio. 5. Long-term management strategy: Focus on risk factor reduction through diet, exercise, and medications. 1. Prodromal symptoms: May occur days, weeks, or months before the actual MI. 2. Silent MI: Recognition that some patients may have no noticeable symptoms. 3. Gastrointestinal manifestations: Nausea, vomiting, and indigestion may mask cardiac symptoms. 4. Psychogenic symptoms: Anxiety or sense of impending doom may be harbingers of MI. 5. Evolution of infarction: Understanding the dynamic nature of ECG changes over time.

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1. Chest pain variations: Dull, sharp, squeezing, pressure, or simply described as discomfort. 2. Radiation patterns: Pain may radiate to arms, neck, jaw, or back. 3. Non-pain symptoms: Extreme fatigue, exhaustion, sleep disturbances (particularly during prodromal period). 4. Neurological symptoms: Headaches, dizziness, lightheadedness common. 5. Respiratory symptoms: Shortness of breath (dyspnea) may be a prominent feature. 1. Q-wave significance: May indicate size/location of current MI or evidence of prior MI. 2. ST-segment evaluation: Distinguishing between STEMI and NSTEMI guides treatment strategy. 3. Serial ECG importance: Re-administration to observe evolution of infarction patterns. 4. Lead selection: Standard 12-lead plus additional leads (V3R-V6R, V7-V9) when suspecting specific infarct locations. 5. Reciprocal changes: Understanding the significance of ST depression in reciprocal leads. 1. Troponin kinetics: Understanding the rise and fall pattern within 24 hours of MI. 2. CK-MB patterns: Complementary to troponin for timing and extent assessment. 3. Distinguishing features: Using biomarkers to differentiate between NSTEMI and unstable angina. 4. Timing considerations: Optimal sampling intervals for diagnosis and monitoring. 5. Interpretation in special populations: Renal dysfunction, elderly, or post-procedure elevation. 1. Timing imperatives: Treatment should begin as soon as possible to reduce myocardial necrosis. 2. PCI considerations: Emergency PCI typically recommended for STEMI patients. 3. Fibrinolytic selection: When immediate PCI not available, administration timing is critical. 4. Revascularization indications: Unstable/complicated NSTEMI often requires immediate intervention. 5. Risk-benefit assessment: Understanding when conservative management may be appropriate. 1. Gender differences: Women have higher mortality and often present atypically. 2. Racial/ethnic variations: Significant differences in MI incidence across populations. 3. Age-related considerations: Earlier occurrence in men vs. women by approximately 10 years. 4. Health literacy impact: Many patients, especially women, are unaware of risk factors and symptoms. 5. Socioeconomic factors: Impact on prevention, recognition, and treatment access.

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Below is information not explicitly contained within the tutorial but important for USMLE Step 3 & COMLEX Level 3. 1. MINOCA (MI with Non-Obstructive Coronary Arteries): Diagnostic approach and management differences. 2. Type 2 MI: Supply-demand mismatch management distinct from Type 1 atherothrombotic MI. 3. Mechanical complications: Early recognition and management of papillary muscle rupture, ventricular septal rupture, and free wall rupture. 4. Cardiogenic shock algorithms: Mechanical support device selection and timing. 5. Post-MI arrhythmia management: Risk stratification for sudden cardiac death, antiarrhythmic selection. 1. STEMI systems of care: Regional networks, transfer protocols, door-to-balloon time optimization. 2. Quality metrics: Monitoring and improving key performance indicators in MI management. 3. Transitions of care: Post-discharge planning, medication reconciliation, cardiac rehabilitation referral. 4. Healthcare disparities: Recognition and addressing inequities in MI care and outcomes. 5. Resource utilization: Appropriate use of diagnostic testing and interventions in different clinical scenarios. 1. Antithrombotic therapy personalization: Risk-benefit assessment for duration and intensity. 2. Bleeding risk management: Strategies for patients on dual or triple antithrombotic therapy. 3. Medication adherence optimization: Strategies to improve long-term compliance with secondary prevention. 4. Polypharmacy management: Addressing drug interactions and side effects in complex post-MI regimens. 5. Novel therapeutic approaches: Emerging evidence for anti-inflammatory and metabolic interventions. 1. Secondary prevention optimization: Risk factor modification, guideline-directed medical therapy. 2. Functional capacity assessment: Return to work evaluation, exercise prescriptions. 3. Psychosocial aspects: Depression screening and management, social support assessment. 4. Recurrent event prevention: Intensified therapy for very high-risk patients. 5. Heart failure development: Early recognition and intervention for post-MI ventricular dysfunction.