IJCS | Volume 32, Nº4, July/August 2019

392 Lampert Sports participation for athletes with ICDs Int J Cardiovasc Sci. 2019;32(4):391-395 Review Article known. Restriction from sports, for any reason, has been shown to decrease both physical and emotional quality of life for athletes. 9 For many adolescents with ICDs, restriction from sports was the biggest factor impacting their quality of life. 10 Further, a 2006 retrospective survey of Heart Rhythm Society physician-members, 11 suggested that many ICD patients were participating in sports, despite the consensus recommendations, and and the survey respondents did not describe adverse events. While survey results are limited by selection and recall bias, these results suggested that a prospective registry of athletes with ICDs was feasible, ethical, and necessary. Feasible, as many ICD patients were participating in sports. Ethical, as study participants were already practicing sports and were not asked to perform activities of which safety was unknown. Necessary, as if the risks were as high as hypothesized, those participating needed to know, while if the risks were not so high, others might choose to participate. Based on the preliminary results provided by this survey, the ICD Sports Safety Registry, a multinational, prospective, observational registry, was established to identify and quantify risks associated with sports participation for ICD patients. The ICD sports registry In this study, of which two-year results were published in 2013 and four-year results in 2017, 12,13 440 athletes with ICDs, aged 10-60 years, 2/3 males, 46% with a history of ventricular arrhythmia (secondary prevention) who had chosen to continue competing in sports higher than Class “IA” regarding static/dynamic intensity, were prospectively followed. Participants were contacted regularly during the follow-up, and ICD records obtained, and rhythms adjudicated for shocks received at any time. The most common cardiac diagnoses were LQTS, HCM, and CAD, and the most common sports, running, soccer, and basketball. Among the twenty athletes participating at the university interscholastic level, diagnoses were similar, and the sports included soccer, basketball, lacrosse, and others. 14 Over a median follow-up of 44 months, there were no occurrences of the primary endpoints—no failures of the ICD to defibrillate or externally resuscitated arrests, and no injuries due to syncopal arrhythmia or loss of control following shock. The 95% confidence interval for the occurrence of adverse events based on 376 participants followed for at least 2 years was 0% to 0.9% and based on 167 participants followed for at least 4 years, it was 0% to 2.2%. Many participants received shocks, with forty-six (10%) receiving appropriate shocks (for VT/ VF) during competition or practice, a rate of 3 per 100 person-years. Whilemore athletes received shocks during some formof physical activity than during rest, there was no difference between competition/practice and other physical activities. 13 In this population, older athletes were more likely to receive shocks during sports than those under 18 years old. While the ICD Registry demonstrated that it is safe for many athletes with ICDs to continue competing, whether ventricular arrhythmias requiring shock for termination are more common in competitive athletes is yet to be determined. A subanalysis of the ICD Registry which compared the primary population with a subpopulation of intensive recreational athletes enrolled in Europe 15 (and not described in the papers focused on competitive athletes) suggested that arrhythmias with physical activitywere more common in those competing. However, there were differences between the European and US athletes. In the general population, the “paradox of exercise” is well-described. 16 While overall, sudden death is less common in those who exercise vigorously, the risk of an event is higher during exercise. While often considered a “paradox”, this is likely explained by the role of the autonomic nervous system in arrhythmogenesis. Catecholamines are known to promote arrhythmias. 17 For well-conditioned individuals, catecholamines will be at the highest levels when they are vigorously exercising. Whether a similar “paradox of exercise” exists in the most common genetic cardiovascular diseases in the athlete-ICD population, is unknown. An ongoing observational study, the “Exercise in Genetic Cardiovascular Disease” (NIH # R01 HL125918-01) is currently enrolling individuals with HCM and LQTS (in two parallel studies, Lifestyle and Exercise in HCM (LIVE-HCM) and Lifestyle and Exercise in LQTS (LIVE- LQTS) at all levels of exercise, both with and without ICDs, to determine whether arrhythmic endpoints are more or less frequent in patients who exercise when compared to those who do not (http://www.livehcm. org/ and http://livelqts.org/) . The impact of shocks on quality of life was not measured in the ICD Sports Registry. ICD shocks decrease quality of life, as shown in many studies. 18 However, while about one-third of those athletes who received shocks during sports stopped playing one or