USMLE/COMLEX 2 - Myocardial Infarctions

Here are key facts for USMLE Step 2 CK & COMLEX-USA Level 2 from the Myocardial Infarctions: Diagnosis & Treatment tutorial, focusing on clinical management and treatment decision-making that are essential for these exams. See the tutorial notes for further details and relevant links.

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1. Demographic patterns: Myocardial infarction incidence after age 35, from highest to lowest: Black males > Black females > White males > White females. 2. Gender differences: Timing of first MI tends to be earlier in men than women by about 10 years, possibly related to risk factors like smoking and hyperlipidemia. 3. Mortality trends: Although mortality has declined overall, rates are higher in women than male peers, especially for young and/or minority women. 4. Key modifiable risk factors: Dyslipidemia, diabetes mellitus, hypertension, smoking (including e-cigarettes), obesity, psychosocial stress, alcohol consumption, poor diet. 5. Awareness challenges: Many people, especially women, are unaware of risk factors and symptoms—a significant obstacle to prevention and treatment. 1. Definition: Myocardial infarction is defined as myocardial injury with ischemia. 2. Typical symptom pattern: Chest pain (angina) variably described as dull, sharp, squeezing, pressure, or simply discomfort, often radiating to arms, neck, jaw, or back. 3. Atypical presentations: Not all patients experience angina—absence of chest pain and/or young age often leads to missed or delayed diagnosis. 4. Symptom timeline:

• Prodromal symptoms: Days, weeks, or months prior to heart attack
• Acute symptoms: Experienced at the time of the event
• Silent MI: No noticeable symptoms

5. Associated symptoms: Gastrointestinal issues (nausea, vomiting, indigestion), extreme fatigue, headaches, dizziness, lightheadedness, shortness of breath (dyspnea), anxiety, or sense of impending doom. 1. ECG timing: Should be administered as soon as possible when MI is suspected and re-administered frequently to observe the evolution of the infarction. 2. ECG interpretation: Distinguishes between ST-segment elevated (STEMI) or Non-ST elevated (NSTEMI) myocardial infarctions, influencing treatment strategies. 3. ECG localization: Different lead changes indicate specific infarct locations:

• Lateral infarction: Leads I and aVL; left circumflex artery
• Apical infarctions: Leads V5 and V6; 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 additional leads V3R through V6R
• Posterolateral infarctions: Requires additional posterior leads V7-V9; right coronary or left circumflex artery

4. Cardiac biomarkers: Key to diagnosis, especially cardiac troponin, helping distinguish between NSTEMI and unstable angina. 5. Biomarker patterns: Cardiac troponin I and CK-MB both peak within 24 hours of the MI and fall to normal levels over time. 1. Time sensitivity: Treatment should begin as soon as possible, ideally before hospital arrival, to reduce the extent of myocardial necrosis. 2. Pre-hospital treatment:

• Oxygen administration when saturation is less than 90%
• Aspirin for antiplatelet effects
• Nitrates for chest pain (morphine is an option if nitrates are ineffective)

3. Reperfusion strategies: Vary by severity but generally include percutaneous coronary intervention (angioplasty), coronary bypass grafting, or fibrinolytic drugs. 4. Treatment by MI type:

• STEMI: Emergency PCI recommended; if unavailable, fibrinolytic drugs must be given ASAP
• NSTEMI: Unstable, complicated cases require immediate PCI/CABG; uncomplicated cases may wait longer and may not require revascularization
• Fibrinolytic drugs generally not recommended for NSTEMI as potential risks outweigh benefits

5. Medication protocol:

• Antiplatelets (aspirin, clopidogrel, others)
• Anticoagulation drugs (unfractionated or low molecular weight heparin)
• Beta-blockers (or calcium-channel blockers)
• Statins
• ACE inhibitors

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1. Anterior infarction: Changes in leads V3 and V4; associated with blockages in the left anterior descending artery. 2. Anterior septal infarction: Changes in leads V1 and V2; associated with blockages in the proximal left anterior descending artery. 3. Lateral infarction: Changes in leads I and aVL; often the result of blockage in the left circumflex artery. 4. Inferior infarction: Changes in leads II, aVF, and III; associated with blockages in the right coronary artery, or less frequently, the left circumflex artery. 5. Apical infarction: Changes in leads V5 and V6; often associated with blockages in the left circumflex or right coronary arteries. 1. Mortality variation: Rates are higher in women than men, especially for young and/or minority women. 2. MI as heart failure precursor: Myocardial infarction is an important cause of heart failure, which is itself a significant cause of death. 3. Smoking risk: Includes possible risk from daily use of e-cigarettes. 4. Dietary factors: Poor diet, particularly those low in fruits and vegetables, increases risk. 5. Awareness gap: Unawareness of risk factors and symptoms represents a significant obstacle to prevention and treatment. 1. Prodromal timeline: Symptoms may appear days, weeks, or even months prior to the heart attack. 2. Sleep disturbances: Many patients report sleep problems, particularly during the prodromal period. 3. Pain radiation patterns: Some patients experience pain in arms, neck, jaw, or back, which may radiate from the chest. 4. Psychological symptoms: Patients may feel unaccountably anxious or experience a sense of impending doom prior to and during the heart attack. 5. Diagnosis challenges: Absence of chest pain and/or young age of a patient often leads to missed or delayed diagnosis, associated with worse outcomes. 1. STEMI management: Patients with STEMI should receive emergency PCI; if unavailable, fibrinolytic drugs must be given as soon as possible. 2. NSTEMI approach: Unstable, complicated NSTEMI often requires immediate PCI or CABG; uncomplicated NSTEMI patients may wait longer, and revascularization may not be necessary. 3. Fibrinolytic considerations: Generally not recommended for NSTEMI patients because potential risks outweigh benefits. 4. Long-term management: Focuses on reducing risk factors through improved diet and exercise, as well as medications to manage hypertension and hyperlipidemia. 5. Antithrombotic strategy: Includes both antiplatelet agents (aspirin, clopidogrel) and anticoagulation drugs (heparin) in the acute setting. 1. Troponin significance: Cardiac biomarkers, especially troponin, are key to diagnosing myocardial infarction. 2. NSTEMI vs. unstable angina: Biomarker values help distinguish between these conditions, as only NSTEMI is associated with rising/falling levels of troponin. 3. Biomarker kinetics: Both cardiac troponin I and CK-MB peak within 24 hours of MI and gradually return to normal. 4. Q-wave significance: May indicate the size or location of a current MI, or may indicate a prior MI. 5. ECG evolution: Serial ECGs help observe the evolution of the infarction, providing important diagnostic and prognostic information.

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Below is information not explicitly contained within the tutorial but important for USMLE Step 2 CK & COMLEX Level 2. 1. Cardiac causes: Acute coronary syndrome, pericarditis, myocarditis, aortic dissection, Takotsubo cardiomyopathy. 2. Pulmonary causes: Pulmonary embolism, pneumonia, pneumothorax, pleuritis. 3. Gastrointestinal causes: Esophageal spasm, GERD, peptic ulcer, pancreatitis, cholecystitis. 4. Musculoskeletal causes: Costochondritis, rib fracture, thoracic muscle strain. 5. Psychiatric causes: Anxiety, panic attack, somatization disorder. 1. HEART score: Evaluates History, ECG, Age, Risk factors, and Troponin to classify chest pain risk. 2. TIMI score: Predicts 14-day risk of adverse events in patients with NSTEMI/UA. 3. GRACE score: Estimates in-hospital and 6-month mortality risk for ACS patients. 4. CRUSADE score: Estimates bleeding risk in NSTEMI patients undergoing invasive management. 5. High-risk features: Hemodynamic instability, heart failure, recurrent angina, ventricular arrhythmias, mechanical complications. 1. P2Y12 inhibitor selection: Clopidogrel vs. ticagrelor vs. prasugrel based on patient characteristics and risk. 2. Anticoagulation options: Unfractionated heparin, low molecular weight heparin, fondaparinux, or bivalirudin. 3. Early conservative vs. early invasive strategy: Decision-making for NSTEMI/UA patients based on risk factors. 4. Culprit-only vs. complete revascularization: Strategies for STEMI patients with multivessel disease. 5. Special populations management: Patients with renal dysfunction, elderly, diabetics, and those with bleeding risk. 1. Cardiac rehabilitation: Exercise prescription, risk factor modification, psychosocial support. 2. Secondary prevention medications: Optimizing GDMT (guideline-directed medical therapy). 3. Follow-up testing: Role of stress testing, echocardiography, and other imaging modalities. 4. Return to activities: Recommendations for driving, exercise, sexual activity, and work. 5. Depression screening: Recognition and management of post-MI depression, which affects outcomes.