4Early repolarisation in young adults: a dose-dependent relationship with physical activity

Abstract

Introduction: The early repolarisation (ER) pattern is associated with arrhythmic death in middle-aged populations. The risk is increased with ER followed by a horizontal ST segment ( horizontal-ST ER ). ER associated with a rapidly ascending ST segment ( ascending-ST ER ) has been shown to be benign. The prevalence of ER has not been documented in young adults and its significance in this group is not known. Furthermore, ER is commonly seen in athletes but underlying mechanisms are unclear. We demonstrate the prevalence of ER in a large population of young healthy adults and explore the relationship with physical activity. Methods: 6831 individuals aged ≤35 years underwent cardiac screening with a medical questionnaire and a 12-lead ECG. Type and volume of physical activity undertaken was recorded and classified by dynamic activity, based on maximal oxygen consumption (VO2max). Abnormal ECGs (n=215) and those of insufficient quality (n=40) were excluded. Therefore 6616 ECGs were assessed. ER was defined, as per accepted definitions, as ≥0.1mV J-point elevation in the inferior and/or lateral leads. All ECGs were analysed by a single observer and reported for the presence of ER (Intra-observer agreement 96%, kappa=0.9), morphology of the J-point (notched or slurred) and of the associated ST segment. Automated baseline measurements were checked manually if outside accepted normal ranges. Voltage criteria (Sokolow-Lyon) for left ventricular hypertrophy and presence of an RSR' pattern was also recorded. Results: The overall prevalence of ER was 21%. The prevalence of ascending-ST ER was 15% and of horizontal-ST ER was 6%. ER was seen in the inferior leads in 51%. The J-point was notched in 52%. ER was associated with male sex (p<0.001) although horizontal-ST ER was relatively more common in females. There was a positive correlation between the volume of exercise and the prevalence of ascending-ST ER (See fig. 1). This was more evident with more dynamic exercise types. The prevalence of horizontal-ST ER was independent of exercise. Ascending-ST ER was associated with a shorter QTc and with ECG features of physical training. Horizontal-ST ER was not associated with training features. There was a negative association between the ER and RSR' patterns (OR 0.4, p<0.001). There were no significant associations between the presence of ER and reported syncope or family history of sudden death. Conclusion: ER is common in young active individuals. Ascending-ST ER predominates and is related to physical activity. Horizontal-ST ER is independent of physical activity. The two phenotypes likely represent different underlying mechanisms. Long-term follow-up is required in this age group and future studies should aim to refine the ER phenotype by ST segment and take in to account volumes of physical activity. ![Graphic][1] Figure 1 Odds ratio of ER with increasingly volume of exercise (by quintile), corrected for age and sex. [1]: /embed/inline-graphic-1.gif