A 62-year-old woman from Mumbai with a 10-year history of hypertension presents with intermittent chest pain occurring at rest over the past 2 days. The pain is substernal, lasts 15–20 minutes, and is relieved by sublingual nitroglycerin. She denies any chest pain at present. Vital signs are stable. Physical examination is unremarkable. ECG shows T-wave inversion in leads V2–V4 with normal ST segments. Troponin I is negative (<0.04 ng/mL). She has no prior history of myocardial infarction. What is the most likely diagnosis?

Explanation

## Clinical Presentation Analysis **Key Point:** This patient presents with **Unstable Angina (UA)**, characterized by: - New-onset angina at rest (within 2 days) - Angina of increasing frequency/severity - Angina with prolonged duration (15–20 minutes) - **Negative troponin** (no myocardial necrosis) - **Abnormal ECG** (T-wave inversion — indicates ischemia) ## Diagnostic Criteria: ACS Spectrum | Feature | Unstable Angina | NSTEMI | STEMI | |---------|-----------------|--------|-------| | **Symptoms** | Ischemic chest pain | Ischemic chest pain | Ischemic chest pain | | **Troponin** | Negative | Positive | Positive | | **ECG** | ST depression, T-wave inversion, or normal | ST depression, T-wave inversion | ST elevation ≥1 mm (≥2 contiguous leads) | | **Pathophysiology** | Plaque rupture without transmural necrosis | Plaque rupture with partial transmural necrosis | Plaque rupture with complete transmural necrosis | **High-Yield:** The **critical distinguishing feature** between unstable angina and NSTEMI is **troponin status**: - **Negative troponin + ischemic ECG changes = Unstable Angina** - **Positive troponin + ischemic ECG changes = NSTEMI** Both are acute coronary syndromes (ACS) and require aggressive antiplatelet, anticoagulant, and anti-ischemic therapy. ## Why NOT the Other Options? **Stable Angina:** This patient has **new-onset** angina at rest, which is unstable by definition. Stable angina is predictable, occurs with exertion, and is relieved by rest or nitrates. Rest angina is a hallmark of instability. **Prinzmetal Angina (Vasospasm):** While vasospastic angina can present with rest pain and T-wave changes, it typically: - Occurs at a fixed time of day (often early morning) - Is associated with **ST elevation** (not depression or isolated T-wave inversion) - Occurs in younger patients without significant atherosclerotic disease - Responds dramatically to calcium channel blockers This patient's presentation (older, hypertensive, rest pain with T-wave inversion) is more consistent with atherosclerotic plaque rupture (UA) than vasospasm. ## Management of Unstable Angina ```mermaid flowchart TD A[Unstable Angina diagnosed]:::outcome --> B[Risk stratification]:::decision B -->|High-risk| C[Dual antiplatelet therapy]:::action C --> D[Anticoagulation LMWH/UFH]:::action D --> E[Beta-blockers, ACE-I, statins]:::action E --> F[Coronary angiography within 24-72 hrs]:::action F --> G{Significant CAD?}:::decision G -->|Yes| H[PCI or CABG]:::action G -->|No| I[Medical management + risk factor modification]:::action B -->|Low-risk| J[Conservative management + stress test]:::action ``` **Clinical Pearl:** Unstable angina and NSTEMI are managed identically (dual antiplatelet therapy, anticoagulation, early invasive strategy) because both represent acute plaque rupture. The troponin distinction is prognostic (NSTEMI has worse outcomes) but does not change the acute management strategy. **Key Point:** T-wave inversion in the absence of positive troponin indicates ischemia without necrosis — the hallmark of unstable angina. [cite:Harrison 21e Ch 297]