Early repolarization and short QT interval in healthy subjects

BACKGROUND An early repolarization (ER) pattern is common in ECGs from patients with ventricular fibrillation (VF). These patients with ER have shorter QT intervals. Morphological variants of the ER pattern also have been associated with idiopathic VF, but their prevalence in healthy subjects is unclear. OBJECTIVE The purpose of this study was to study the prevalence of ER and its morphological variants, and its association with the QTc interval in healthy subjects. METHODS Digital ECGs from 1886 healthy subjects from Phase I clinical trials were analyzed by a central ECG laboratory. RESULTS ER, defined as J-point elevation >= 0.1 mV in >= 2 contiguous leads, was present in 514 subjects (27.3%), of whom 505 (98.2%) were males. The prevalence of ER declined progressively with increasing age. ER pattern was seen in lateral leads (I, aVL, V-4-V-6) in 26.1%, in inferior (II, III, aVF) or inferolateral leads in 8%, and was global in 1.9%. The terminal portion of the QRS complex was notched in 43.1% and slurred in 56.9%. Notching was common in inferior/lateral leads, and slurring was common in anterior leads. A non-ascending ST segment was seen in 71% of ECGs with a notched pattern but in only 12.3% of ECGs with a slurred pattern. The ER group had slower heart rates (9.3 +/- 13.3 bpm [mean difference +/- SD], P < .001) and shorter QTc intervals (QTcB = 20.2 +/- 25.6 ms, QTcF = 11.0 +/- 21.9 ms; P < .001). Four subjects in each group had a short QT interval (QTcF <350 ms). CONCLUSION ER and all of its variants are common in healthy young males with slower heart rates and slightly shorter QTc intervals. A short QT interval (QTcF <350 ms) is rare.