The prevalence and clinical significance of J wave patterns in athletes.

Unusual ECG patterns (including ST elevation and notching or slurring of the terminal QRS) are extraordinarily common in young competitive athletes. Depending on the trait definition and the population studied, estimates of this J wave pattern (often referred to as early repolarization pattern) prevalence range from 20% to over 50%. 1–6 The highest estimates have been reported in elite endurance athletes including 58% of a study of marathon runners. 7 Among US intercollegiate athletes, black race, male sex, lower heart rate, and increased QRS voltage seem to be strongly associated with the presence of J-wave patterns. 8–10 Although there are many similarities in the appearance of the common J-wave patterns seen in healthy athletes and in patients studied in other settings, there are important differences. The J-wave patterns' association with arrhythmic events, as observed in SCD case–control studies and general population ascertainments, is characterized by a QRS complex with terminal notching followed by a horizontal ST segment in the inferior and lateral leads. This morphology is often referred to as the Haissaguerre pattern and further termed the Haissaguerre syndrome when applied to patients with this pattern who experience malignant idiopathic ventricular arrhythmias. In contrast, the morphology of the J-wave patterns most commonly seen in athletes is characterized by an ascending STsegment, particularly in the anterior leads. 11 This morphologic distinction appears to have an important impact on the clinical significance of the various patterns. In one study of over 500 athletes and nearly 11,000 population controls, 8 32% of athletes and only 3.8% of population controls had J-wave patterns. However, among individuals with J-wave patterns, the vast majority of athletes (97%) and a minority of population controls (28.4%) had a rapidly ascending ST segment. Whereas horizontal ST segment morphology was associated with an increased risk of arrhythmic death (hazard ratio 1.43) in the general population sample, the ascending ST segment was not. In this sense, the common ST-segment elevation pattern observed in athletes appears to be benign. A comparison of the ECG morphologies is illustrated in Fig. 1. Another important distinction is that J-wave patterns in athletes do not appear to be “fixed”, and may disappear with age and with time away from intense physical activity. In order to quantify this effect, we examined J-wave patterns in a cohort of athletes before and after a period of intense physical training. 10 At baseline, 37.2% of athletes demonstrated J-wave patterns and this increased to 52.7% after a relatively brief but intense training season. In addition, we performed pre- and post-season echocardiograms to look for structural correlates of the pattern. It is noteworthy, that J-wave patterns demonstrated no association with the adaptive cardiac remodeling (ventricular hypertrophy and dilation) that is common in athletes. The underlying mechanism of the dynamic nature of J wave patterns in athletes is not known, but it may be related to traininginduced increase in parasympathetic nervous system activity. This is suggested by the fact that J-wave patterns are associated with the resting bradycardia that develops during intense physical training. The increase in the J-wave patterns in our study was most marked in endurance-trained athletes, who also had significantly lower resting heart rates after training (J-wave pattern prevalence increased from 39.7% pre-training to 63.2% post-training in endurance athletes). 12 In the acute setting, exercise (associated with brief but marked increase in sympathetic nervous system activity) has been shown to attenuate J-wave patterns. Several studies have demonstrated normalization of ST segments during and