Dynamic ST-Segment Abnormality.

A 37-year-old man came to the emergency department because of several days of intermittent chest pain. An electrocardiogram (ECG) showed sinus rhythm, left atrial and left ventricular enlargement, and an early repolarization pattern. A second ECG recorded 10 minutes later was strikingly different, with ST-segment elevation and large upright T waves in the anterior precordial leads, interpreted as evidence of an ST-segment elevation myocardial infarction, and the cardiac catheterization team was activated. Closer inspection of the ECG, however, disclosed that the changes were because of intermittent ventricular pre-excitation of the Wolff-Parkinson-White type, and no electrocardiographic, echocardiographic, or serum markers of myocardial infarction were found.