Early repolarization: friend or foe?

Abstract

In the current issue of the Journal, Klatsky et al (1) address the possible risk of chronically having “normal” electrocardiographic (ECG) changes that may mimic the presence of an acute myocardial infarction. The authors compare the rates of hospital admissions for various conditions, and outpatient cardiovascular diagnoses, in patients with early repolarization and controls. The presence of “normal” early repolarization changes on the ECG could indeed be misinterpreted as signs of an acute thrombotic occlusion of a coronary artery, and lead to inappropriate and even potentially harmful reperfusion therapy. Of the many people who present for emergency clinical evaluation with symptoms suggesting an acute coronary syndrome, only a small proportion have the thrombotic coronary occlusion for which immediate reperfusion therapy is indicated. The current European Society of Cardiology/American College of Cardiology guidelines suggest immediate reperfusion therapy only in patients with “ST elevation or presumably new left bundle branch block” (2). However, since ST elevation in the absence of myocardial infarction is common, the diagnostic threshold for such therapy yields low specificity. In the current paper, 30% of the subjects chronically had ST elevations 3 mm. Other studies (3,4) also indicate that ST elevation above the commonly accepted threshold is not unusual, particularly in young men. Thus an individual’s age and gender should also be considered. Both female gender and older age are associated with lower amplitudes of all ECG waveforms, including the ST segment (3). The phenomenon associated with “normal” ST elevation has been termed “early repolarization” and pertains to the absence of a truly isoelectric ST segment between the QRS complex of ventricular depolarization and the T wave of repolarization. The prevalence of early repolarization may be increased when the ST-segment changes are measured late after the J point, the heart rate is accelerated or there are conditions such as left ventricular hypertrophy or fascicular or bundle branch block that prolong the ventricular depolarization process (3). The findings by Klatsky et al (1) support previous reports of a high prevalence of early repolarization in young men of African descent (5– 8), and in persons who engage regularly in “vigorous” exercise (9,10). These findings also support the benign prognosis of this condition and even show nonsignificant trends toward lower use of health care. However, this study does not provide direct information on whether inappropriate and unnecessary therapy was administered as a result of misinterpretation of the early repolarization changes in patients who were admitted for in-hospital care. Because ST elevation due to early repolarization may be interpreted as changes due to myocardial infarction, several noninvasive and practical approaches can be taken to minimize misinterpretation. This editorial considers the use of new algorithms for computerized analysis of an individual ECG; observations of the “stability” of the ST-segment changes on serial ECGs; and other nonECG manifestations of ischemia, such as regional wall motion abnormalities assessed by echocardiography and myocardial perfusion defects via radionuclide measurements or contrast echocardiography.