Early repolarization: electrocardiographic phenotypes associated with favorable long-term outcome.

BACKGROUND: Early repolarization (ER) in inferior/lateral leads of standard ECGs increases the risk of arrhythmic death. We tested the hypothesis that variations in the ST-segment characteristics after the ER waveforms may have prognostic importance.

METHODS AND RESULTS: ST segments after ER were classified as horizontal/descending or rapidly ascending/upsloping on the basis of observations from 2 independent samples of young healthy athletes from Finland (n=62) and the United States (n=503), where ascending type was the dominant and common form of ER. Early repolarization was present in 27/62 (44%) of the Finnish athletes and 151/503 (30%) of the US athletes, and all but 1 of the Finnish (96%) and 91/107 (85%) of US athletes had an ascending/upsloping ST variant after ER. Subsequently, ECGs from a general population of 10 864 middle-aged subjects were analyzed to assess the prognostic modulation of ER-associated risk by ST-segment variations. Subjects with ER ≥0.1 mV and horizontal/descending ST variant (n=412) had an increased hazard ratio of arrhythmic death (relative risk 1.43; 95% confidence interval 1.05 to 1.94). When modeled for higher amplitude ER (>0.2 mV) in inferior leads and horizontal/descending ST-segment variant, the hazard ratio of arrhythmic death increased to 3.14 (95% confidence interval 1.56 to 6.30). However, in subjects with ascending ST variant, the relative risk for arrhythmic death was not increased (0.89; 95% confidence interval 0.52 to 1.55).

CONCLUSIONS: ST-segment morphology variants associated with ER separates subjects with and without an increased risk of arrhythmic death in middle-aged subjects. Rapidly ascending ST segments after the J-point, the dominant ST pattern in healthy athletes, seems to be a benign variant of ER.