Exercise-induced QTc prolongation and implications for military service members: a case series

Abstract: Exercise is often seen as a voluntary activity with physical and mental health benefits. However, for military service members exercise is a required component of military service to ensure service members are prepared to meet the physical demands of their missions.1 The prevalence of corrected QT interval (QTc) prolongation among highly athletic individuals has been shown to be elevated over the general population.2–4 An international consensus statement has set the prolonged QTc cut-off as 470 ms for male athletes and as 480 ms for female athletes, but they acknowledge that 1 electrocardiogram (ECG) with a prolonged QTc warrants further evaluation, such as repeat ECG, consideration of per sonal and family history, and in some cases additional cardiac or genetic testing, before a diagnosis of long QT syndrome (LQTS) is made.5 The importance of a follow-up evaluation for QTc prolongation was further demonstrated by a recent study from Dagradi and colleagues,6 which identified a group of athletes with an acquired form of exercise-induced long QT (LQT). Individuals with exercise-induced LQT presented with QTc prolongation but showed a significant reduction in their QTc after a 3- to 6-month detraining period compared to individuals with genotypically or clinically confirmed LQTS.6 A separate case report of a young female athlete observed this same pattern of QTc normalization following a 4-month detraining period.7 Cases of exercise-induced LQT have also been noted to contribute to the misdiagnosis of LQTS.8 Herein we report 3 additional cases of exercise-induced LQT among military service members who underwent extensive cardiac evaluations with a period of exercise cessation. Given that military service members are required to be highly active, this population may be at an elevated risk for exercise-induced LQT. Distinguishing between this acquired form of QTc prolongation and congenital LQTS is important, as there are military-specific repercussions that could arise from an inappropriate diagnosis of LQTS.