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Ischemic Heart Disease for ABIM

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Ischemic Heart Disease for the American Board of Internal Medicine Exam
Overview of Ischemic Heart Disease
Ischemic heart disease (IHD), also known as coronary artery disease (CAD), occurs when myocardial oxygen supply is insufficient to meet myocardial demand, typically due to atherosclerotic plaque build-up in coronary arteries. IHD encompasses stable angina, unstable angina, myocardial infarction, and ischemic cardiomyopathy. Risk factors include hypertension, hyperlipidemia, diabetes, smoking, and family history of early CAD.
Pathophysiology
  • Atherosclerosis: The primary mechanism of IHD. It involves lipid deposition in the intima of coronary arteries, forming atherosclerotic plaques. Plaques may calcify, narrow vessel lumen, and lead to decreased myocardial perfusion.
  • Plaque Rupture: Unstable plaques with thin fibrous caps are prone to rupture, leading to thrombus formation and partial or complete occlusion of coronary arteries.
  • Myocardial Oxygen Supply and Demand: Imbalance occurs when oxygen delivery is impaired or demand is increased, triggering ischemia.
Clinical Syndromes of Ischemic Heart Disease
Ischemia symptoms
Stable Angina
  • Definition: Predictable chest pain caused by transient myocardial ischemia, usually occurring with exertion and relieved by rest or nitroglycerin.
  • Pathophysiology: Fixed stenosis of a coronary artery limits blood flow during times of increased demand, leading to subendocardial ischemia.
  • Clinical Features:
    • Symptoms: Retrosternal chest pain or pressure, often radiating to the left arm or jaw. Lasts less than 15 minutes and resolves with rest.
    • Exacerbating Factors: Physical exertion, stress, cold exposure.
  • Diagnosis:
    • Exercise Treadmill Test (ETT): Preferred initial test in patients with a normal resting ECG who can exercise.
    • Pharmacologic Stress Testing: Used when exercise testing is contraindicated.
    • Coronary Angiography: Considered for high-risk patients or those with symptoms refractory to medical therapy.
  • Management:
    • Antianginal Medications: Beta-blockers (first-line), calcium channel blockers, and nitrates.
    • Risk Factor Modification: Control of blood pressure, lipids, and diabetes; smoking cessation.
    • Antiplatelet Therapy: Aspirin for all patients unless contraindicated.
Acute Coronary Syndromes (ACS)
ACS refers to a spectrum of conditions caused by acute myocardial ischemia, including unstable angina, NSTEMI, and STEMI.
Unstable Angina (UA) and Non-ST Segment Elevation Myocardial Infarction (NSTEMI)
  • Definition: Unstable angina presents as chest pain at rest or new-onset severe angina. NSTEMI involves myocardial injury with elevated cardiac biomarkers (e.g., troponin) without ST elevation.
  • Pathophysiology: Caused by partial coronary artery occlusion from a ruptured plaque and thrombus formation.
  • Clinical Features:
    • Symptoms: Chest pain at rest or with minimal exertion, often lasting longer than 20 minutes and less responsive to nitroglycerin.
  • Diagnosis:
    • ECG: ST depression or T-wave inversion.
    • Biomarkers: Elevated troponin indicates NSTEMI; absence of troponin elevation indicates unstable angina.
  • Management:
    • Antithrombotic Therapy: Dual antiplatelet therapy (aspirin and P2Y12 inhibitors like clopidogrel), anticoagulation with heparin.
    • Anti-Ischemic Therapy: Beta-blockers, nitrates, and calcium channel blockers.
    • Risk Stratification: TIMI or GRACE score to assess the need for invasive management.
    • Revascularization: Early invasive strategy with coronary angiography for high-risk patients.
ST Segment Elevation Myocardial Infarction (STEMI)
  • Definition: Acute myocardial infarction characterized by ST-segment elevation on ECG with myocardial injury.
  • Pathophysiology: Complete occlusion of a coronary artery due to plaque rupture and thrombus formation, causing transmural ischemia.
  • Clinical Features:
    • Symptoms: Severe, prolonged chest pain unrelieved by rest or nitroglycerin, associated with nausea, diaphoresis, and dyspnea.
  • Diagnosis:
    • ECG: ST-segment elevation in two or more contiguous leads.
    • Biomarkers: Elevated troponin confirms myocardial injury.
  • Management:
    • Reperfusion Therapy: Primary percutaneous coronary intervention (PCI) within 90 minutes is preferred. Fibrinolysis is an alternative if PCI is unavailable within 120 minutes.
    • Adjunctive Medications: Aspirin, P2Y12 inhibitors, heparin, and beta-blockers.
    • Post-STEMI Care: ACE inhibitors, beta-blockers, statins, and aldosterone antagonists in select patients to reduce recurrent events and improve outcomes.
Risk Factor Modification and Secondary Prevention
Long-term management focuses on reducing risk factors and preventing future ischemic events.
  • Lifestyle Modification: Smoking cessation, dietary changes (Mediterranean or DASH diet), regular physical activity (at least 150 minutes/week of moderate aerobic exercise).
  • Blood Pressure and Glycemic Control: Maintain BP <130/80 mm Hg and optimize glycemic control in patients with diabetes.
  • Lipid Management: High-intensity statin therapy for most patients with IHD; LDL target <70 mg/dL for those with high ASCVD risk.
  • Antiplatelet Therapy: Long-term aspirin therapy in all patients unless contraindicated. Dual antiplatelet therapy (DAPT) for at least 12 months post-PCI.
  • ACE Inhibitors or ARBs: Recommended for patients with hypertension, diabetes, heart failure, or reduced left ventricular ejection fraction (LVEF <40%).
  • Beta-Blockers: Long-term therapy for patients with prior MI or reduced LVEF.
Diagnostic Modalities
Noninvasive Testing
  • Exercise Treadmill Test (ETT): Initial test for evaluating stable angina in patients with normal ECG and ability to exercise.
  • Stress Echocardiography: Assesses wall motion abnormalities with exercise or pharmacologic stress.
  • Myocardial Perfusion Imaging (MPI): Evaluates myocardial blood flow with exercise or pharmacologic stress; useful in patients with abnormal baseline ECG.
Invasive Testing
  • Coronary Angiography: Gold standard for diagnosing coronary artery disease, particularly in high-risk patients or those with ACS. Identifies location and severity of coronary lesions, guiding revascularization decisions.
Key Points
  • Pathophysiology of IHD: Primarily due to atherosclerosis leading to myocardial ischemia.
  • Types of IHD:
    • Stable Angina: Predictable chest pain on exertion, relieved by rest or nitroglycerin.
    • Acute Coronary Syndromes:
    • Unstable Angina and NSTEMI: Chest pain at rest with partial coronary occlusion; NSTEMI shows elevated troponin.
    • STEMI: Complete coronary occlusion with ST-segment elevation on ECG.
  • Diagnostic Tests:
    • Stable Angina: Exercise Treadmill Test (ETT) or stress imaging.
    • ACS: ECG and troponin for initial diagnosis; coronary angiography for high-risk or unstable patients.
  • Management of ACS:
    • Unstable Angina/NSTEMI: Dual antiplatelet therapy, anticoagulation, and invasive management based on risk.
    • STEMI: Immediate reperfusion with primary PCI or fibrinolysis if PCI is delayed.
  • Secondary Prevention: Includes antiplatelet therapy (aspirin and/or DAPT), high-intensity statins, ACE inhibitors or ARBs, beta-blockers, and lifestyle modification.
  • Risk Factor Modification: Essential for long-term outcomes; includes blood pressure, lipid, and glycemic control, along with smoking cessation and regular exercise.

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