Fragmented QRS complex as a predictor of exercise‐related sudden cardiac death
Sudden cardiac death (SCD) is by definition an unexpected event from a cardiac cause within a certain short time period after the onset of symptoms and is often the first manifestation of the underlying cardiac disease accounting for significant share of years of potential life lost. In the United States, SCD accounts for around 200,000 deaths yearly and in a recent study the age‐specific incidence of SCD was 4.2 per 1,000 person‐years in the general population.1 A physically active lifestyle hinders the progression of atherosclerosis and reduces the risk of cardiac events and all‐cause mortality.3 However, physical exercise (PE) transiently increases the risk of SCD and this finding is most prominent among the least‐fit and during strenuous activity.3 Even if the incidence of exercise‐related SCD or sudden cardiac arrest is relatively low in the general population,6 it would be important to identify in advance the subjects with an increased risk for such an event to counsel the subjects or patients individually about the potential risks of strenuous exercise. Research to identify abnormalities in the 12‐lead electrocardiogram (ECG) related to SCD has advanced rapidly during the past twenty years. It is hoped that this new information would give rise to tools of risk stratification of SCD. Several ECG abnormalities are linked to an increased risk of SCD, including high resting heart rate, prolonged QRS duration, fragmentation of the QRS complex, malignant forms of early repolarization, prolongation of the QT interval, prolongation of the T‐peak to T‐end (TpTe) interval, and various T‐wave abnormalities.8 In this study, we wanted to investigate if any of these markers of standard 12‐lead ECG are specifically related to exercise‐induced SCD in the general population.