## Investigation of Choice for Suspected Stable Angina ### Clinical Context The patient presents with classic exertional angina: chest pain on effort that resolves with rest. The resting ECG is normal, which is typical in stable angina between episodes. Before starting antianginal drugs, objective evidence of inducible ischemia is needed. ### Why Exercise Stress Test (Treadmill ECG) is Correct **Key Point:** Exercise stress test is the first-line non-invasive investigation for suspected stable angina in patients with normal resting ECG and intermediate pretest probability. **High-Yield:** The stress test serves dual purposes: 1. **Diagnostic** — reproduces symptoms and demonstrates ST-segment depression (≥1 mm in 2 contiguous leads) indicating ischemia 2. **Prognostic** — assesses exercise capacity, time to symptom onset, and severity of inducible ischemia **Clinical Pearl:** A positive stress test (ST depression + anginal symptoms) confirms the diagnosis and guides intensity of antianginal therapy. The test is non-invasive, cost-effective, and widely available in India. ### When to Proceed to Coronary Angiography Angiography is reserved for: - High-risk stress test results (early ST depression, hemodynamic instability) - Diagnostic uncertainty after stress testing - Consideration for revascularization (PCI/CABG) - Recurrent symptoms despite optimal medical therapy ### Diagnostic Accuracy | Investigation | Sensitivity | Specificity | Use | | --- | --- | --- | --- | | Exercise ECG | 65–70% | 70–75% | First-line in normal resting ECG | | Coronary angiography | 95%+ | 95%+ | Gold standard but invasive; reserved for high-risk/refractory cases | | Echocardiography (resting) | Low | Moderate | Assesses LV function; not diagnostic for ischemia | | Chest X-ray | N/A | N/A | Excludes pulmonary causes; not diagnostic for CAD |
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