Stable Angina & Chronic Coronary Disease
A Step 2 CK high-yield lesson on stable angina/chronic coronary disease covering supply–demand pathophysiology, the typical-angina criteria and pretest probability, the stress-testing decision tree, a chest-pain differential table (stable/unstable angina, NSTEMI, STEMI, vasospastic), and the split between symptom-relief and event-reducing therapy (COURAGE/ISCHEMIA and CABG survival indications).
Pathophysiology: a supply–demand problem
Stable angina is the clinical face of chronic coronary disease (CCD). A fixed atherosclerotic plaque narrows a coronary lumen (typically flow-limiting during exertion once diameter stenosis is >70%; a left main lesion is significant at ≥50%), so flow is adequate at rest but cannot rise to meet increased myocardial O₂ demand during exertion or emotional stress. The result is transient subendocardial ischemia — the subendocardium is the last region perfused and the first to become ischemic — with chest discomfort that resolves once demand falls.
Myocardial O₂ demand is set by three levers: heart rate, contractility, and wall stress (preload + afterload). This is exactly why antianginals that lower these variables — beta-blockers, calcium-channel blockers, nitrates — relieve pain.
"Stable" means the pattern (frequency, provoking threshold, duration) has been unchanged for weeks and the plaque is not actively rupturing — the key distinction from acute coronary syndrome (ACS). Because the ischemia is demand-driven and subendocardial, the resting ECG is frequently normal and troponin stays negative.
- Typical angina = 3/3 features: (1) substernal, (2) provoked by exertion/emotion, (3) relieved by rest or nitroglycerin (usually resolves in <5 min, and <20 min).
- Atypical = 2/3; noncardiac = ≤1/3. These features set the pretest probability (age, sex, pain character).
- Discomfort is pressure/heaviness, may radiate to jaw or left arm; Levine sign = clenched fist held over the sternum.
- Anginal equivalents (dyspnea, fatigue) are common in women, the elderly, and diabetics.
- A normal resting ECG does NOT exclude CAD.
- Rest pain >20 min, a crescendo pattern, or a positive troponin → think ACS, not stable angina.
- Determinants of O₂ demand: heart rate · contractility · wall stress (preload + afterload).
Diagnosis: choosing the right stress test
Start with a resting 12-lead ECG and labs, then estimate pretest probability from age, sex, and pain character. For a stable patient with intermediate probability, the next best step is stress testing — not immediate angiography. Pick the modality with two questions:
- Can the patient exercise?
- Is the baseline ECG interpretable?
- Yes to both → exercise treadmill ECG (positive = ≥1 mm horizontal or downsloping ST depression).
- ECG uninterpretable (LBBB, ventricular paced rhythm, LVH with strain, digoxin effect, WPW, resting ST depression) → add imaging (stress echo or myocardial perfusion imaging). *With LBBB or a paced rhythm, use a vasodilator perfusion study* to avoid false septal defects.
- Cannot exercise → pharmacologic stress: a vasodilator (regadenoson, adenosine, dipyridamole) with perfusion imaging, or dobutamine stress echo.
Coronary CT angiography is a reasonable first-line test in low-to-intermediate-risk patients (2021 AHA/ACC Chest Pain guideline). Invasive coronary angiography — the anatomic gold standard — is reserved for high-risk stress findings or refractory symptoms.
Vignette: A 58-year-old man with hypertension and a 30-pack-year smoking history reports 3 months of retrosternal "pressure" that appears after climbing two flights of stairs and resolves within a few minutes of rest. The pattern is unchanged. Exam and the resting ECG are normal; troponin is negative.
- Diagnosis: stable angina (chronic coronary disease) — 3/3 typical features.
- Next best step: exercise treadmill ECG (he can exercise and the baseline ECG is interpretable).
- If instead his baseline ECG showed LBBB → vasodilator myocardial perfusion imaging (exercise ECG is uninterpretable; vasodilator avoids false septal defects).
- If the pain now occurred at rest, lasted 30 min, or troponin rose → treat as ACS: serial troponins/ECGs, antiplatelet + anticoagulation, cardiology. Do not send to a routine outpatient stress test.
Chest-pain syndromes side by side
| Entity | Classic clue / ECG | Troponin | Treatment |
|---|---|---|---|
| Stable angina | Exertional, relieved by rest/NTG; ST depression only with stress | Negative | Risk-factor Rx + antianginal; SL NTG |
| Unstable angina | Rest or crescendo pain; ST depression / T-wave inversion | Negative | Admit; ACS therapy (antiplatelet + anticoag) |
| NSTEMI | Rest pain; ST depression / T inversion | Elevated | ACS therapy ± early invasive strategy |
| STEMI | Rest pain; ST elevation | Elevated | Emergent reperfusion (primary PCI) |
| Prinzmetal (vasospastic) | Rest pain, often a younger smoker; transient ST elevation | Usually negative | CCB + nitrates; avoid nonselective beta-blockers & triptans |
The classic board framework for the event-reducing side of chronic coronary disease:
- A — Antiplatelet (aspirin 81 mg) + Antianginal + ACE inhibitor (if diabetes, HTN, CKD, or EF ≤40%)
- B — Beta-blocker + Blood-pressure control
- C — Cholesterol (high-intensity statin) + Cigarette cessation
- D — Diet + Diabetes control
- E — Exercise + Education
- Two separate goals — keep the drug lists apart.
- Symptom relief: a beta-blocker is first-line for angina (preferred when there is prior MI or reduced EF); a dihydropyridine CCB (e.g., amlodipine) or a long-acting nitrate is an acceptable alternative or add-on; ranolazine as add-on. Sublingual nitroglycerin aborts acute episodes.
- Event reduction / mortality: aspirin, high-intensity statin, ACE-I/ARB (when indicated), smoking cessation. A beta-blocker adds a mortality benefit specifically after MI and in reduced EF (not proven to reduce events in stable angina without these).
- Do NOT combine verapamil/diltiazem with a beta-blocker → bradycardia / AV block.
- Nitrate contraindications: a PDE5 inhibitor within 24 h (sildenafil/vardenafil) / 48 h (tadalafil), plus RV infarction, severe aortic stenosis, and HOCM.
- PCI relieves symptoms but does NOT reduce death/MI in stable CAD (COURAGE, ISCHEMIA).
- CABG improves survival in left main disease (≥50%), 3-vessel disease (especially reduced EF or diabetes), or 2-vessel disease involving the proximal LAD.
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