Significance of QT interval prolongation in youth and adolescent sports (literature review)

Introduction. Up to 42% of young athletes who die suddenly show no signs of known cardiac diseases at autopsy (such as cardiomyopathies, myocarditis, or congenital heart defects). However, molecular genetic analysis in young sudden death victims identifies mutations in genes responsible for Long QT Syndrome (LQTS) in 17–23% of cases. During comprehensive medical examinations (CME) of young athletes in Russian national teams within the FMBA of Russia system, up to 24% of athletes are disqualified from sports due to detected QT interval prolongation for further diagnosis, with the diagnosis of LQTS being confirmed in 0.24% of cases.

Objective. Analysis of diagnostic methods for LQTS in young athletes and criteria for their clearance for sports training.

Discussion. The pathogenesis of LQTS is based on genetically determined impairment of cardiac ion channel function, which causes myo- cardial electrical instability predisposing to cardiac events. Such events include Torsades de Pointes (TdP) ventricular tachycardia, syncope, cardiac arrest, and sudden cardiac death (SCD). Diagnosis of LQTS is based on the Schwartz criteria, which incorporate data from standard ECG (QTc > 450 ms), Holter monitoring (HM), stress tests, clinical presentation, and family history. A score of more than three points based on these criteria makes the diagnosis of LQTS highly probable. According to international criteria for QT interval assessment in adult athletes, the proposed upper limits of normal QTc duration are up to 470 ms for males and up to 480 ms for females. Some authors suggest that QTc val- ues up to 500 ms may be acceptable in athletes; however, according to the Schwartz criteria, this value is sufficient to confirm the diagnosis of LQTS. Bradycardia, typical of trained athletes, is another LQTS criterion in pediatric ECG assessment. Methods for QT assessment during bradycardia in young athletes are not specified. Intense training may increase QT interval duration; conversely, temporary detraining may lead to its decrease. The Schwartz criteria based on HM results include only T-wave alternans and TdP tachycardia. QT interval assessment during HM remains a subject of debate. To date, at least 17 pathogenic genes responsible for LQTS have been identified. Detection of Class IV–V pathogenic mutations is sufficient for diagnosing LQTS, regardless of QT duration. The issues of clearance/return to sport-specific training for athletes with LQTS remain controversial, being addressed differently across countries. There are known cases of athletes with LQTS who have achieved significant success in sport competitions, as well as regular occurrences of SCD in young individuals with this condition. Current Russian and international guidelines state that competitive sports are contraindicated for patients with confirmed LQTS.

Conclusions. The assessment of the QT interval in young athletes involves numerous methodological and clinical peculiarities distinct from those in non-athletic individuals. Underestimating these peculiarities can lead to over- or under-diagnosis of LQTS, thereby potentially creat- ing a life-threatening situation for the athlete. Individual risks in different categories of LQTS patients are composed of multiple components. Disqualification from sports does not eliminate the risk of cardiac events in LQTS; at the same time, the extent to which sports activity itself increases these risks remains unknown today. This underscores the relevance of actively studying and clarifying these unresolved issues in young athletes with QT interval prolongation and LQTS.

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