A 62-year-old woman from Mumbai with a history of hypertension and smoking presents to the emergency department with 2 episodes of chest pain over the past 6 hours, each lasting 15–20 minutes and relieved by rest. The most recent episode occurred 30 minutes ago. She denies dyspnea or diaphoresis. Vital signs are stable: BP 135/88 mmHg, HR 78 bpm. Physical examination is unremarkable. 12-lead ECG shows T-wave inversion in leads V2–V4. Troponin I measured at presentation is <0.01 ng/mL (normal). Repeat troponin 3 hours later is also <0.01 ng/mL. What is the most likely diagnosis?

Explanation

## Clinical Presentation Analysis ### Key Features of This Case 1. **Recurrent chest pain at rest** (2 episodes in 6 hours, each 15–20 minutes) 2. **T-wave inversion** on ECG (anterior leads V2–V4) — indicates ischemia 3. **Negative troponins** at presentation and 3 hours (serial troponins remain <0.01 ng/mL) 4. **Stable vital signs** and minimal symptoms (no diaphoresis) ## Differential Diagnosis: ACS Spectrum | Feature | Stable Angina | Unstable Angina | NSTEMI | |---------|---------------|-----------------|--------| | **Chest pain pattern** | Predictable, exertional | New onset or at rest; increasing frequency/severity | Prolonged, at rest | | **Troponin** | Negative | **Negative** | **Positive** | | **ECG changes** | Normal or old changes | ST depression, T-wave inversion | ST depression, T-wave inversion | | **Pathophysiology** | Fixed stenosis | Plaque rupture without necrosis | Plaque rupture **with myocardial necrosis** | **High-Yield:** The **defining feature** of unstable angina is **troponin-negative ACS with dynamic ischemic ECG changes**. This patient fits perfectly: T-wave inversion (ischemia) but no troponin elevation (no necrosis). ## Why This Is Unstable Angina **Key Point:** Unstable angina represents **acute coronary syndrome without myocardial necrosis**. It is diagnosed when: 1. Clinical features of ACS are present (chest pain, recurrent episodes, pain at rest) 2. ECG shows ischemic changes (ST depression, T-wave inversion) 3. Cardiac biomarkers (troponin, myoglobin, CK-MB) remain **negative** **Clinical Pearl:** T-wave inversion in anterior leads (V2–V4) suggests anterior wall ischemia from left anterior descending (LAD) artery disease. The absence of troponin elevation indicates that ischemia has not yet progressed to irreversible myocardial necrosis. **Mnemonic: UA = ACS without Troponin = Unstable Angina** - **A**cute coronary syndrome (yes — recurrent chest pain, ECG changes) - **C**ardiac biomarkers (negative — troponin <0.01) - **S**yndrome (yes — fits ACS pattern) ## Management Implications **High-Yield:** Unstable angina requires: 1. **Dual antiplatelet therapy** (aspirin + P2Y12 inhibitor) 2. **Anticoagulation** (unfractionated heparin or LMWH) 3. **Early invasive strategy** (coronary angiography within 24 hours) 4. **Beta-blockers, ACE inhibitors, statins** for secondary prevention Unlike NSTEMI, unstable angina does NOT show myocardial necrosis, but it carries significant risk of progression to MI and requires urgent coronary angiography to identify and treat the culprit lesion.