Which diagnosis is characterized by substernal chest pain with ST-segment elevations >1 mm in more than two contiguous leads and evidence of myocardial necrosis?

• A. ST-elevation myocardial infarction
• B. Non-ST-segment elevation myocardial infarction
• C. Unstable angina
• D. Aortic dissection

Answer: (D)

ST-elevation myocardial infarction. When chest pain is substernal and the ECG shows ST-segment elevations greater than 1 mm in two or more contiguous leads, it indicates acute transmural injury from a complete coronary occlusion. The presence of myocardial necrosis is shown by positive cardiac biomarkers (for example, troponin or CK-MB), confirming infarction rather than ischemia alone. This classic combination distinguishes STEMI from other causes of chest pain: unstable angina and NSTEMI may have chest pain and biomarker changes, but they do not produce widespread ST elevations in multiple contiguous leads; aortic dissection often presents with very different symptoms and ECG findings.