A 67-year-old man presents to the emergency department because of worsening chest pain for the past week. For the past 2 years, he has experienced substernal chest pressure when walking more than three blocks, which reliably resolved with rest. Over the past week, however, he has developed chest discomfort after walking only a short distance. Earlier today, he experienced a 20-minute episode of chest pressure while sitting and watching television. His medical history is significant for hypertension, hyperlipidemia, and coronary artery disease. Medications include aspirin, metoprolol, atorvastatin, and lisinopril. He has a 40-pack-year smoking history. Temperature is 36.7°C (98.1°F), blood pressure is 146/88 mm Hg, pulse is 92/min, and respiratory rate is 16/min. Physical examination is unremarkable. ECG demonstrates 1-mm horizontal ST-segment depressions in leads V4-V6. High-sensitivity troponin levels obtained at presentation and repeated 3 hours later remain within the normal range.
Which of the following is the most likely diagnosis?
The correct answer is:
E) Unstable angina
This patient has unstable angina, a form of acute coronary syndrome caused by plaque disruption and partial coronary thrombosis that results in myocardial ischemia without myocardial necrosis. The hallmark features are chest pain that is new in onset, occurs with increasing frequency or severity, occurs with less exertion than previously, or develops at rest.
Several clues point toward unstable angina. This patient previously had stable exertional symptoms but now has accelerating chest pain, decreased exercise tolerance, and an episode occurring at rest. These changes indicate a transition from chronic stable coronary disease to an acute coronary syndrome. Although his ECG demonstrates ischemic changes, his serial troponin levels remain normal, indicating that myocardial injury has not occurred.
A high-yield Step 2 distinction is that unstable angina and NSTEMI are clinically similar and often have identical symptoms and ECG findings. The key difference is the presence of elevated cardiac biomarkers in NSTEMI. When troponins remain normal despite symptoms of acute coronary ischemia, the diagnosis is unstable angina.
Recognition of unstable angina is critical because these patients are at substantial risk for progression to myocardial infarction and require urgent evaluation and management.
Answer choice A: Acute pericarditis, is incorrect.
Pericarditis typically causes sharp, pleuritic chest pain that worsens with inspiration and improves when leaning forward. Diffuse ST-segment elevation and PR depression are common ECG findings. This patient’s exertional and rest chest pressure is much more consistent with myocardial ischemia.
Answer choice B: Non-ST-elevation myocardial infarction (NSTEMI), is incorrect.
NSTEMI presents similarly to unstable angina but requires evidence of myocardial injury, demonstrated by elevated cardiac biomarkers. The normal serial troponin levels in this patient exclude NSTEMI.
Answer choice C: Stable angina, is incorrect.
Stable angina produces predictable symptoms at a consistent level of exertion over time. This patient’s symptoms have become more frequent, occur with less exertion, and now occur at rest, making stable angina unlikely.
Answer choice D: ST-elevation myocardial infarction (STEMI), is incorrect.
STEMI is characterized by acute coronary occlusion causing myocardial necrosis, typically resulting in persistent ST-segment elevation and elevated cardiac biomarkers. Neither finding is present in this patient.
Key Learning Point
Unstable angina is characterized by worsening ischemic chest pain that occurs at lower levels of exertion, increases in frequency or severity, or develops at rest. Unlike NSTEMI, cardiac biomarkers remain normal because myocardial necrosis has not occurred.
