What is the most likely cause of mid-sternal pain with exertion in a patient with a history of coronary artery disease (percutaneous coronary intervention (PCI)), diabetes mellitus (treated with insulin), and hypertension?

Unstable Angina Pectoris

This patient has unstable angina pectoris (Option B), characterized by new-onset exertional chest pain that fails to resolve with rest, accompanied by ECG changes indicating acute myocardial ischemia, in the setting of established coronary artery disease.

Clinical Presentation Analysis

This patient presents with the classic triad defining unstable angina rather than stable angina:

• New-onset severe angina (CCS Class III equivalent - pain after walking only two blocks) in a patient with known CAD 1
• Pain not relieved by rest - a critical distinguishing feature from stable angina, which characteristically resolves within minutes of stopping exertion 1, 2
• ECG changes indicating acute ischemia (2-mm ST-segment depression and T-wave changes in V1-V2) 1

Why This is Unstable Angina and Not the Other Options

Excluding Stable Angina (Option C)

Stable angina is definitively ruled out because the pain does not resolve with rest 1, 2. The European Society of Cardiology explicitly defines typical angina as chest discomfort that is "relieved by rest and/or nitrates within minutes" 1, 2. This patient's pain persists despite rest, which is pathognomonic for unstable angina 1.

Additionally, stable angina presents with a predictable pattern over time, whereas this represents either new-onset severe symptoms or a change in pattern - both defining features of unstable angina 1, 3.

Excluding NSTEMI (Option D)

NSTEMI is excluded by the normal initial troponin 1. The European Society of Cardiology guidelines state that cardiac troponin T or troponin I are "very sensitive and specific markers for myocardial necrosis" and distinguish unstable angina from NSTEMI 1. While serial troponins should be obtained, the initial normal value with these clinical and ECG findings is consistent with unstable angina rather than NSTEMI.

Excluding GERD (Option A)

GERD is highly unlikely given the clear exertional trigger, radiation to neck and jaw (classic for cardiac ischemia), significant ST-segment depression on ECG, and the patient's extensive cardiac risk profile (prior PCI, diabetes, hypertension) 1, 2. The European Society of Cardiology notes that pain reproduced by palpation makes CAD less likely, but this patient has no such findings 1.

Key Diagnostic Features Supporting Unstable Angina

High-Risk Clinical Profile

• Prior PCI three years ago - establishes known CAD with high likelihood of disease progression 1
• Diabetes mellitus on insulin - major risk factor that significantly increases pretest probability of obstructive CAD and is associated with worse outcomes 1, 4, 5
• Multiple cardiovascular risk factors (hypertension, likely dyslipidemia given CAD history) 1

Characteristic Pain Pattern

The pain meets criteria for atypical angina (meets two of three typical angina characteristics): substernal location with radiation to neck/jaw, and exertional trigger, but lacks relief with rest 1, 2. The European Society of Cardiology recognizes that unstable angina commonly presents with "prolonged anginal pain at rest" or "recent destabilization of previously stable angina" 1.

ECG Findings

ST-segment depression ≥1 mm in contiguous leads (V1-V2) with T-wave changes are "the most reliable electrocardiographic indicators of unstable coronary disease" 1. These findings indicate acute myocardial ischemia and significantly elevate risk.

Clinical Implications and Risk Stratification

This patient falls into the high-risk category for unstable angina based on:

• Pain not controlled with rest 1, 3
• Significant ST-segment depression (≥1 mm) 1
• Multiple comorbidities including diabetes 1, 4
• Prior history of CAD 1

The European Society of Cardiology guidelines emphasize that unstable angina carries substantial risk, with historical studies showing acute myocardial infarction occurring in approximately 25% of patients within three months of symptom onset, though more recent data with modern therapy shows lower rates 1, 3, 6.

Critical Management Considerations

Immediate hospitalization is mandatory 1, 3. This patient requires:

• Continuous cardiac monitoring for arrhythmias 1
• Serial troponin measurements (every 3-6 hours) to definitively exclude evolving NSTEMI 1
• Aggressive antianginal therapy including nitrates, beta-blockers (with caution given diabetes), and aspirin 1, 3, 6
• Early cardiology consultation for risk stratification and consideration of coronary angiography 1

Common pitfall: Do not discharge this patient or treat as stable angina simply because the initial troponin is normal - the persistent pain despite rest and significant ECG changes mandate admission and aggressive management 1.