Sixty thousand electrocardiograms were analyzed for 5 years. Six hundr
ed (1%) revealed early repolarization (ER). Features of ER were compar
ed with race-, age-, and sex-matched controls (93.5% were Caucasians,
77% were males, 78.3% were younger than 50 years, and only 3.5% were o
lder than 70). Those with ER had elevated, concave, ST segments in all
electrocardiograms (1-5 my), which were located most commonly in prec
ordial leads (73%), with reciprocal ST depression (50%) in aVR, and no
tch and slur on R wave (56%). Other results included sinus bradycardia
in 22%, shorter and depressed PR interval in 38%, slightly asymmetric
al T waves in 96.7%, and U waves in 50%. Sixty patients exercised norm
alized ST segment and shortened QT interval (83%). In another 60 patie
nts, serial studies for 10 years showed disappearance of ER in 18%, an
d was seen intermittently in the rest of the patients. The authors con
clude that in these patients with ER: 1) male preponderance was found;
2) incidence in Caucasians was as common as in blacks; 3) patients of
ten were younger than 50 years; 4) sinus bradycardia was the most comm
on arrhythmia; 5) the PR interval was short and depressed; 6) the T wa
ve was slightly asymmetrical; 7) exercise normalized ST segment; 8) in
cidence and degree of ST elevation reduced as age advanced; 9) possibl
e mechanisms of ER are vagotonia, sympathetic stimulation, early repol
arization of sub-epicardium, and difference in monophasic action poten
tial observed on the endocardium and epicardium.