Early repolarization: normalization of the electrocardiogram with exercise as a clinically useful diagnostic feature.

BACKGROUND

Early repolarization is a normal ECG variant which may resemble various pathologic conditions including acute myocardial infarction/injury and pericarditis. Some electrocardiographers believe early repolarization resolves with exercise-induced increases in heart rate. The purpose of this study was to evaluate qualitatively and quantitatively this phenomenon.

METHODS

From among 3,000 consecutive patients referred for evaluation of ischemic heart disease by exercise treadmill testing, 25 patients with early repolarization and no risk factors for cardiovascular disease (Group I), 28 patients with early repolarization and risk factors for cardiovascular disease (Group IIA), and 28 matched control patients (Group IIB) were identified and evaluated retrospectively. Group II patients also underwent radionuclide stress imaging. All study patients had otherwise normal ECGs and a negative history of cardiovascular disease.

RESULTS

In patients with early repolarization, diagnostic ST elevation was most frequently evident in ECG lead V4. We found that the ECG normalized progressively, beginning almost immediately with the onset of exercise, and typically returned completely to the isoelectric baseline at an average heart rate of approximately 106 beats per minute. In patients with otherwise normal ECGs and no history of cardiovascular disease, early repolarization was a strong predictor of a negative exercise treadmill test and only infrequently was associated with a positive radionuclide imaging study. Early repolarization was found in virtually all demographic groups with respect to age, race, and gender except for a disproportionate infrequency in white females.

CONCLUSION

A progressive decrease in ST segment elevation and normalization of the ECG with mild exercise was a predictable response in patients who have early repolarization with otherwise normal ECGs and no history of cardiovascular disease. This phenomenon may be clinically useful as a bedside diagnostic tool in evaluating patients who present with early repolarization, otherwise normal ECGs, and negative cardiac history, in which the diagnosis of acute myocardial infarction/injury or pericarditis is being considered. These findings warrant formal evaluation in a prospective clinical trial.