USMLE Guide: Stable Angina

Introduction

This USMLE guide provides an overview of stable angina, a common condition encountered in clinical practice. It covers the definition, etiology, clinical presentation, diagnostic approach, and management of stable angina.

Definition

Stable angina, also known as angina pectoris, is a clinical syndrome characterized by chest pain or discomfort due to myocardial ischemia, typically precipitated by physical exertion or emotional stress and relieved by rest or nitroglycerin.

Etiology

Stable angina is primarily caused by coronary artery disease (CAD), which leads to the narrowing or obstruction of the coronary arteries supplying the heart muscle. CAD is commonly caused by atherosclerosis, a buildup of cholesterol plaques within the arterial walls.

Clinical Presentation

The typical presentation of stable angina includes:

• Chest pain or discomfort, often described as a pressure, squeezing, or heaviness
• Pain may radiate to the left arm, jaw, neck, or back
• Precipitating factors: physical exertion, emotional stress, cold weather, heavy meals
• Pain relief: rest or administration of nitroglycerin
• Stable symptoms over time, occurring with predictable patterns

Diagnostic Approach

The diagnostic workup for stable angina involves several components:

History and Physical Examination

• Detailed history of presenting symptoms, including pain characteristics, duration, and precipitating factors
• Identification of risk factors for CAD (e.g., smoking, hypertension, diabetes, dyslipidemia)
• physical examination to assess for signs of CAD (e.g., abnormal heart sounds, carotid bruits)

Electrocardiogram (ECG)

• Resting ECG to evaluate for ST-segment changes, T-wave inversions, or Q waves suggestive of myocardial ischemia or previous infarction
• Exercise stress testing to induce and assess the presence of ischemic changes during physical exertion

Cardiac Biomarkers

• Measurement of cardiac troponin levels to assess for myocardial injury or infarction
• Elevated troponin may indicate unstable angina or acute coronary syndrome, rather than stable angina

Imaging

• Coronary angiography (invasive) to visualize coronary artery anatomy and identify any significant stenosis or occlusion
• Non-invasive imaging techniques, such as stress echocardiography or nuclear myocardial perfusion imaging, may be used to assess myocardial ischemia and viability

Management

The management of stable angina aims to relieve symptoms, prevent or reduce future cardiovascular events, and improve quality of life. It involves both lifestyle modifications and pharmacotherapy:

Lifestyle Modifications

• Smoking cessation and avoidance of secondhand smoke
• Regular physical activity and exercise within individual capacity
• Healthy diet low in saturated fats, cholesterol, and sodium
• Weight management and control of comorbid conditions (e.g., hypertension, diabetes)

Pharmacotherapy

• antiplatelet agents (e.g., aspirin, clopidogrel) to reduce the risk of thrombosis and future cardiovascular events
• Beta-blockers or calcium channel blockers to decrease myocardial oxygen demand
• Nitroglycerin for acute symptom relief and prophylactic use
• Statins to lower cholesterol levels and stabilize atherosclerotic plaques
• ACE inhibitors or ARBs in patients with concomitant hypertension or left ventricular dysfunction

Invasive Procedures

• Percutaneous coronary intervention (PCI) with stent placement to relieve significant coronary artery stenosis
• Coronary artery bypass graft (CABG) surgery for complex or extensive CAD not amenable to PCI

Conclusion

Stable angina is a common manifestation of coronary artery disease and is characterized by chest pain or discomfort with predictable patterns. The diagnostic approach involves a thorough history, physical examination, ECG, cardiac biomarkers, and imaging. Management includes lifestyle modifications, pharmacotherapy, and potentially invasive procedures. Understanding the pathophysiology, clinical presentation, and management of stable angina is crucial for medical students preparing for the USMLE examination.