A 62-year-old woman from Mumbai with a history of hypertension and hyperlipidemia presents with recurrent episodes of chest pain over the past 5 days. Each episode lasts 10–15 minutes, occurs at rest or with minimal exertion, and is relieved by sublingual nitroglycerin. She denies any chest pain in the preceding 3 months. On examination, she is hemodynamically stable with no acute distress. An ECG performed during a pain episode shows T-wave inversion in leads V2–V4. Troponin I measured at presentation is 0.02 ng/mL (normal <0.04 ng/mL). A repeat troponin 3 hours later is 0.03 ng/mL. What is the most likely diagnosis?

Explanation

## Clinical Presentation Analysis **Key Point:** This patient presents with: - **Accelerating angina pattern:** chest pain at rest or with minimal exertion over 5 days (new-onset unstable pattern) - **Dynamic ECG changes:** T-wave inversion in precordial leads during symptoms (indicates ischemia) - **Negative troponin:** both samples remain below the upper limit of normal (0.02 and 0.03 ng/mL, cutoff 0.04) - **Symptom relief with nitrates:** classic for coronary ischemia ## Differential Diagnosis | Feature | Unstable Angina | NSTEMI | Stable Angina | Vasospasm | |---------|-----------------|--------|---------------|----------| | **Troponin** | Negative | Elevated | Negative | Negative | | **ECG Changes** | ST depression / T inversion | ST depression / T inversion | Normal (at rest) | ST elevation (during spasm) | | **Pattern** | New-onset or accelerating | New-onset or accelerating | Predictable, exertional | Nocturnal, at rest | | **Pathophysiology** | Plaque rupture without necrosis | Plaque rupture with necrosis | Stable stenosis | Coronary vasoconstriction | **High-Yield:** **Unstable angina = ACS without myocardial necrosis (troponin-negative).** This patient has troponin-negative ACS with dynamic ECG changes and an accelerating symptom pattern, making unstable angina the diagnosis. ## Why NOT the Other Options? ### NSTEMI (Option A) - NSTEMI requires **elevated troponin** (>upper limit of normal) - This patient's troponin is persistently **negative** (0.02 and 0.03 ng/mL, both <0.04) - Without troponin elevation, there is no evidence of myocardial necrosis ### Stable Angina (Option C) - Stable angina is **predictable**, triggered by exertion, and relieved by rest or nitrates - This patient has **new-onset and accelerating** symptoms (unstable pattern) - Stable angina does not typically present with acute rest pain or dynamic ECG changes ### Vasospasm/Prinzmetal Angina (Option D) - Vasospasm typically presents with **ST-segment elevation** during pain episodes - This patient has **T-wave inversion** (ST depression pattern), not elevation - Vasospasm is usually nocturnal and occurs in younger patients without significant atherosclerosis - The 5-day accelerating pattern is more consistent with plaque rupture (unstable angina) than vasospasm ## Pathophysiology of Unstable Angina ```mermaid flowchart TD A[Atherosclerotic Plaque]:::outcome --> B[Plaque Rupture/Erosion]:::urgent B --> C[Platelet Aggregation & Thrombus Formation]:::urgent C --> D{Complete Occlusion?}:::decision D -->|No| E[Transient/Partial Obstruction]:::outcome E --> F[Myocardial Ischemia]:::outcome F --> G[Unstable Angina<br/>Troponin Negative]:::outcome D -->|Yes| H[Complete Occlusion]:::urgent H --> I[Myocardial Infarction<br/>Troponin Positive]:::outcome ``` **Clinical Pearl:** The distinction between unstable angina and NSTEMI hinges entirely on **troponin status**. Both have similar presentations (chest pain, ECG changes, risk factors), but only NSTEMI shows myocardial necrosis (troponin elevation). ## Management Implications **Key Point:** Unstable angina requires: 1. **Dual antiplatelet therapy:** aspirin + clopidogrel (or ticagrelor) 2. **Anticoagulation:** unfractionated heparin or enoxaparin 3. **Beta-blockers and ACE inhibitors** for symptom control and secondary prevention 4. **Coronary angiography:** to identify the culprit lesion and guide revascularization (PCI or CABG) The management is identical to NSTEMI, but the diagnosis is made on the basis of **troponin negativity**.