CAD Overview and Pathophysiology

Jun 17, 2025

Overview

This lecture covers coronary artery disease (CAD), including its pathophysiology, risk factors, clinical presentations, complications, diagnosis, and treatment strategies.

Coronary Anatomy & Key Vessels

  • Four main coronary arteries: Posterior Descending Artery (PDA), Right Coronary Artery (RCA), Left Anterior Descending (LAD), and Left Circumflex (LCX).
  • LAD is the most critical artery, supplying the septum and anterior wall of the left ventricle.

Pathophysiology of CAD

  • CAD is mainly caused by atherosclerosis, where fatty plaques narrow coronary arteries.
  • Risk factors: Smoking, Advanced age (men >45, women >55), Diabetes, high LDL/low HDL cholesterol, Hypertension, and Family history ("SAD CHF").
  • Plaques can be stable (covered by fibrous cap) or unstable (prone to rupture and thrombosis).

Clinical Presentation

  • Stable angina: Chest pain with exertion, relieved by rest, due to fixed lumen narrowing.
  • Acute coronary syndrome (ACS): Includes unstable angina, NSTEMI, and STEMI, often due to plaque rupture and thrombus formation.
  • Unstable angina/NSTEMI: Chest pain at rest, increased frequency/intensity, possible T-wave inversion or ST depression.
  • STEMI: Persistent chest pain, ST elevation on ECG, complete artery occlusion, transmural infarction.

Complications of Myocardial Infarction

  • Arrhythmias (esp. first 24 hours): V-tach, V-fib, AV block (RCA occlusion).
  • Acute heart failure: Loss of contractility (esp. LAD), decreased ejection fraction, hypotension, pulmonary edema, cardiogenic shock.
  • Pericarditis: Pleuritic, positional chest pain, friction rub; fibrinous (1-3 days) or Dressler's (≈2 weeks post-MI).
  • Mechanical complications: Ventricular septal defect (new murmur, right heart failure), papillary muscle rupture (acute mitral regurgitation, left heart failure), free wall rupture (tamponade), pseudoaneurysm (thromboembolic risk).

Diagnosis

  • First test for chest pain: ECG; look for ST changes or T wave inversions.
  • Cardiac biomarkers (troponin) help distinguish unstable angina (normal) from NSTEMI/STEMI (elevated).
  • Localize STEMI on ECG:
    • Anterior (V1-V4, LAD)
    • Inferior (II, III, aVF, RCA)
    • Lateral (I, aVL, V5, V6, LCX)
    • Posterior (ST depression V1-V3, positive V7-V9, PDA)
  • Echocardiogram: Correlate wall motion abnormalities with vascular territories.
  • Coronary angiogram: Definitive diagnosis and therapy for occlusions.
  • Stress testing (exercise/pharmacologic): Diagnose stable CAD in low-risk, pain-free patients.

Treatment Overview

  • Stable CAD: Aspirin, beta-blockers, nitrates (short and long acting), statins, add calcium channel blockers or ranolazine if needed.
  • Revascularization (PCI or CABG) for high-risk lesions or refractory symptoms; PCI if <3 vessels and normal EF, CABG if left main/3+ vessels or low EF.
  • After stenting: Dual antiplatelet therapy (aspirin + clopidogrel/ticagrelor) for 1 year.
  • ACS (unstable angina/NSTEMI): Aspirin + clopidogrel + heparin; revascularize if TIMI score >3, cardiogenic shock, or refractory angina.
  • STEMI: Aspirin, clopidogrel, heparin, rapid PCI; give TPA if PCI unavailable, then transfer.
  • Post-MI: Initiate ACE inhibitors or ARBs to prevent ventricular remodeling if tolerated.

Key Terms & Definitions

  • Atherosclerosis — Build-up of fatty plaques inside artery walls, causing narrowing.
  • Stable Angina — Exertional chest pain relieved by rest, due to fixed coronary stenosis.
  • Unstable Angina — Chest pain at rest or with minimal exertion, no myocardial necrosis.
  • NSTEMI — Non-ST elevation myocardial infarction; subendocardial infarct with positive troponins.
  • STEMI — ST-segment elevation myocardial infarction; transmural infarct, ST elevation on ECG.
  • Cardiogenic Shock — Inadequate tissue perfusion from cardiac failure leading to hypotension.
  • Pericarditis — Inflammation of pericardium, often with pleuritic, positional pain and friction rub.
  • PCI — Percutaneous coronary intervention; catheter-based stent placement.
  • CABG — Coronary artery bypass graft surgery.

Action Items / Next Steps

  • Review coronary anatomy and major risk factors.
  • Memorize ECG changes and vessel localization for MI types.
  • Study MI complications and their timeframes.
  • Practice diagnostic algorithms for chest pain.
  • Complete assigned readings on CAD pathophysiology and management.

Full transcript