End QRS notching or slurring in the electrocardiogram: influence on the definition of "early repolarization".

p i J a To the Editor: The transition from the QRS complex to the ST-segment on the 12-lead electrocardiogram (ECG) has been conventionally termed the ST junction (STj). Occasionally, the terminal portion of the QRS complex manifests a notch or slur when transiting into the ST-segment. This has been described as a normal variant in healthy individuals (1) in whom STj is very often elevated. The term “early repolarization” has been used to describe the latter phenomenon with or without end QRS notching or slurring (2). Until recently, end QRS notching or slurring has generally been considered benign. However, Haïssaguerre et al. (3) reported a higher frequency of the early repolarization pattern in 206 survivors of idiopathic ventricular fibrillation compared with 412 healthy controls matched for age, sex, race, and level of physical activity. More recently, a “horizontal” ST-segment with or without STj elevation, but with end QRS notching or slurring, has been shown to have an important prognostic role (4,5). Although numerous studies have investigated the benign and athological significance of end QRS slurring or notching, there re many inconsistencies in definitions. The goal of our study was o explore the prevalence and demographic characteristics of QRS nd notching or slurring and of associated STj amplitude in an pparently healthy white population. ECG recordings were obtained from 1,496 adults as previously escribed (6). There were 859 males and 637 females, with a mean age of 37.4 12.6 years (range 18 to 82 years) overall (39.2 12.1 years [range 18 to 82 years] for males and 35.1 12.9 years [range 18 to 71 years] for females). ECGs were analyzed with the widely used University of Glasgow ECG Analysis Program (7). Average beats were calculated automatically and reviewed manually. STj amplitude was measured in the inferior limb (II, III, and aVF),