Long QT syndrome (LQTS) is a condition where delayed heart electrical activity leads to prolonged QT intervals on an ECG, increasing the risk of arrhythmias, such as torsades de pointes and sudden cardiac death (SCD).1,2 It is often linked to mutations in heart ion channel genes, such as KCNQ1, KCNH2, and SCN5A.3 Although rare, affecting one in 2,000 people, LQTS is concerning in young, healthy individuals, particularly athletes at risk during exercise or stress.4,5
Intense training in athletes can lead to reversible QT prolongation due to cardiovascular adaptations, such as bradycardia and increased vagal tone.6,7 Unlike congenital LQTS, exercise-induced long QT resolves with detraining, making its distinction critical.8
Detraining – temporary cessation of training – normalizes QT intervals, helping differentiate exercise-induced long QT from congenital LQTS.9 This avoids unnecessary treatments, such as β-blockers or ICDs, and allows athletes to resume sports activity.
This study explores exercise-induced long QT, its reversibility, and detraining as a diagnostic tool, aiming to improve diagnostic accuracy, athlete safety, and management protocols.
Methods
Search Strategy
A search was conducted from November 2, 2024 to November 14, 2024 using the following databases: PubMed, ScienceDirect, Google Scholar, SpringerLink, and Cochrane. A manual search was also performed on the included articles to identify any relevant studies that may not have been captured in the electronic search. The keywords used were “exercise” OR “sport” AND “long QT” AND “detraining.” Boolean operators (AND and OR) were applied to combine the keywords effectively.
Eligibility Criteria
The inclusion criteria for this review encompassed studies investigating exercise-induced long QT and its potential reversibility through detraining in human subjects of all age groups. Only articles published in English were considered, ensuring accessibility to a broad range of relevant research. The study designs eligible for inclusion were randomized controlled trials, cohort studies, and case report/case series/case presentation.
Data Extraction and Quality Analysis
This review was conducted in accordance with the PRISMA Extension for Scoping Reviews guidelines. The three authors independently evaluated the eligibility and validity of the included articles to reduce bias and ensure the reliability of the review process. Data extraction was systematically performed by the same researchers. Discrepancies were resolved through discussion.
Results
Study Selection
A total of 505 articles were initially retrieved. After removing duplicates, 463 articles remained. Following the first screening by title and abstract, 53 full-text articles were retained for eligibility assessment. Ultimately, six articles were identified as eligible and fully included in the analysis for this review (Figure 1).8,10–14
Athlete Classification
Supplementary Table 1 summarizes the athlete classification of the included studies, which predominantly focused on young male athletes, ranging from adolescents to young adults, actively engaged in high-intensity cardiovascular endurance sports, such as running, swimming, cycling, and military training. These athletes were selected for the studies due to the identification of prolonged QT intervals during pre-participation screenings or routine training assessments. For example, Dagradi et al. reported that 81% of the participants were competitive athletes, with the remainder being recreational athletes.8 Similarly, Pagani et al. specifically included military athletes involved in strenuous training, with some performing intense swimming and running routines of up to 35 miles/week, while Roagna et al. focused on competitive basketball players with heavy training loads.11,12
These athletes were chosen for their involvement in sports that demand sustained cardiovascular effort, which can lead to exercise-induced adaptations in the heart. These adaptations, such as bradycardia and increased vagal tone, contribute to prolonged QT intervals.15 The studies highlighted the importance of careful assessment of prolonged QT intervals in this population, as these adaptations can mimic pathological conditions, such as congenital LQTS. The identification of prolonged QT during pre-participation screenings emphasizes the need for clinicians to differentiate between benign exercise-induced changes and pathological QT prolongation.
Genetic Testing and Family History
Genetic testing was a key component of the studies to evaluate for congenital LQTS, which is caused by mutations in specific ion channel genes, such as KCNQ1, KCNH2, and SCN5A (Supplementary Table 2).1,16 Across the studies, the majority of athletes tested negative for pathogenic mutations, indicating that their QT prolongation was likely unrelated to genetic mutations commonly associated with congenital LQTS. However, it is important to note that negative genetic testing does not definitively exclude congenital LQTS, as current genetic panels may not capture all pathogenic variants. For instance, Dagradi et al. found that 42.3% of athletes with reversible QT prolongation tested negative for LQTS-associated mutations.8 Similarly, Pagani et al. reported that three athletes with reversible QT prolongation tested negative for genetic mutations.11 While these findings suggest that the QT prolongation observed in these athletes was likely exercise-induced rather than genetically inherited, the absence of genetic mutations alone does not fully exclude an inherited basis for LQTS.
Family history was also assessed in all studies to determine any inherited predisposition to arrhythmias or SCDs, both of which are characteristic features of congenital LQTS.8,17 Interestingly, none of the athletes in the studies with reversible QT prolongation had a positive family history of LQTS or SCD. However, the absence of a family history does not confirm the absence of inherited susceptibility, as underreporting or incomplete family health records may lead to misclassification. While the lack of familial linkage may suggest that exercise-induced long QT is more likely a functional and reversible adaptation rather than a chronic inherited condition, further investigation and long-term follow-up are needed to better understand the arrhythmic risks in these athletes.
Additional Examinations
To further investigate the nature of the QT prolongation observed in the athletes, several additional examinations were performed across the studies (Supplementary Table 3). One of the primary methods used was transthoracic echocardiography, which helps assess the structural health of the heart. The results from these echocardiograms largely demonstrated that the athletes had normal cardiac structure and function, reinforcing the idea that the QT prolongation observed was likely functional, rather than caused by any underlying heart disease. For instance, Pagani et al. found that two of the three athletes in their study had no structural abnormalities, while one athlete showed mild left ventricular and atrial enlargement.11 Similarly, Roagna et al. reported normal left ventricular ejection fraction (62%) and global longitudinal strain in athletes, with further improvements in electromechanical dispersion parameters after a period of detraining. These findings support the conclusion that exercise-induced long QT is not associated with structural heart issues, but rather a temporary and reversible adaptation to intense training.12
In addition to echocardiography, some studies incorporated dynamic assessments to evaluate how the QT interval behaves under various conditions. For example, Viskin et al. used a quick standing test, which initially revealed significantly abnormal QT stretching in one athlete.13 However, after detraining, the QT interval improved, further supporting the notion that the QT prolongation was not congenital, but rather, linked to the physical stresses of exercise. Bains et al. conducted epinephrine or isoproterenol testing, and in some cases, misinterpretation of the results despite following standard protocols contributed to the overestimation of the QT interval and subsequent misdiagnosis of LQTS. It is important to note that these pharmacological agents do not inherently cause overestimation if QT intervals are measured according to accepted standards.10 These tests highlight the potential for overdiagnosis of LQTS, emphasizing the importance of distinguishing exercise-induced long QT from true congenital LQTS.
Finally, exercise stress tests and Holter monitoring were used in some studies to observe QT dynamics during exercise and monitor QT variability over time.18 Exercise stress tests revealed that QT prolongation can occur during intense physical activity, but typically normalizes at rest. Holter monitoring further confirmed that these fluctuations during daily activities or stress were functional adaptations to intense training, not signs of structural cardiac issues.
Detraining Protocol
Detraining protocols, lasting 1–6 months depending on the study, were used to evaluate the reversibility of QT prolongation. By ceasing physical activity for a set period, researchers observed whether QT intervals returned to baseline, suggesting the prolongation was a transient, exercise-induced adaptation rather than congenital LQTS. Supplementary Tables 4 and 5 describe the detraining protocol and results in detail.
For instance, Dagradi et al. implemented a 3–6-month detraining period. This led to a significant shortening of QTc intervals, from 492 ± 37 ms at baseline to 423 ± 25 ms after the detraining period.8 Additionally, the Schwartz score dropped substantially, further supporting the notion that the QT prolongation was not congenital.19 Similarly, Pagani et al. found that three military athletes who followed a 1–3-month detraining protocol experienced corrected QT interval (QTc) normalization and resolution of any associated symptoms.11
Roagna et al. used a 6-month detraining period, during which both QTc prolongation and T-wave morphological abnormalities were resolved completely. Follow-up assessments conducted at 3 and 6 months confirmed sustained improvements, with QTc values normalizing to 401 ms on a resting ECG. This highlights the effectiveness of a longer detraining period in athletes, and further suggests that exercise-induced long QT is reversible.12
Similarly, Viskin et al. reported a partial QTc shortening after 4 months of detraining, and Napolitano et al. documented complete normalization of cardiac repolarization after 5 months of detraining. These findings underscore the reversible nature of QT prolongation in athletes and the role of detraining as a critical diagnostic tool to differentiate exercise-induced changes from congenital LQTS.13,14
Although most studies did not detail the individual components of the Schwartz score, they reported total scores to estimate the probability of congenital LQTS. The score incorporates clinical factors, such as QTc duration, syncope, and family history. For instance, the study by Dagradi et al. documented a reduction in total Schwartz score from 3.0 ± 1.2 to 0.06 ± 0.24 following detraining.8 Despite the lack of granular data, the consistent decline in total scores supports the role of detraining as an effective tool for differentiating exercise-induced long QT from congenital LQTS.
In some cases, β-blockers were prescribed to manage the prolonged QTc intervals in athletes. However, these medications were discontinued after detraining once the QT intervals normalized, as seen in studies by Bains et al. and Pagani et al.10,11 The cessation of β-blockers did not lead to any further arrhythmic events, reinforcing that the QT prolongation was most likely due to the effects of intense training rather than an inherent arrhythmic condition.
Discussion
This study sheds light on exercise-induced long QT, an often overlooked and misdiagnosed condition in athletes. Unlike congenital LQTS, this study reveals that QT prolongation in some athletes results from physiological adaptations to high-intensity endurance training and is reversible with detraining. However, reversibility alone does not confirm benignity, as the potential for recurrence and arrhythmic risk upon retraining remains uncertain. This raises concerns regarding the long-term safety of athletes returning to high-intensity sports without continuous monitoring. Furthermore, negative genetic testing does not confirm the absence of inherited/congenital LQTS, as current genetic panels may not capture all pathogenic variants. Similarly, the absence of a reported family history does not rule out inherited susceptibility, underscoring the need for comprehensive assessment beyond these factors.
Differentiation Between Exercise-induced Long QT and Congenital LQTS
This study highlights that exercise-induced long QT is distinct from congenital LQTS. While congenital LQTS is caused by genetic mutations and leads to permanent electrical abnormalities in the heart,20 exercise-induced long QT occurs as a temporary adaptation to high-intensity endurance training.8,11 The difference between congenital LQTS and exercise-induced long QT lies in the reversibility of QT interval prolongation. In those with exercise-induced long QT, the prolonged QT interval would return to normal levels with detraining, unlike in congenital LQTS, where a reduction may be visible, but not all the way to normal levels.8
Athletes with exercise-induced long QT tested negative for LQTS-related genetic mutations. Moreover, they had no family history of SCDs or inherited arrhythmias, which are common signs of congenital LQTS.10,21 The absence of a family history or genetic mutations does not definitively eliminate the possibility of an inherited risk for LQTS, due to the possibility of incomplete family health records, underreporting, and unknown or untested genetic mutations that could be relevant. This distinction is crucial, because congenital LQTS usually requires lifelong management with β-blockers or even ICDs.22 In contrast, exercise-induced long QT is temporary and does not require such aggressive treatments.23 By accurately distinguishing between the two conditions, clinicians can avoid unnecessary interventions and alleviate the psychological distress that may come from a misdiagnosis.
From a physiological standpoint, vagal tone and bradycardia are likely responsible for the prolonged QT intervals observed in these individuals.15 Additionally, adrenergic surges during intense exercise can momentarily affect ion channel behavior, mimicking the repolarization abnormalities typically seen in congenital LQTS.5,18,24 However, unlike congenital LQTS, which is driven by permanent genetic changes, these adaptations are functional and resolve once the athlete ceases intense physical training.
The reversibility of QT prolongation following detraining in some athletes suggests that this phenomenon may represent a functional adaptation rather than a congenital disorder.8,11,25 However, it remains unclear whether these athletes can safely resume competitive activity, as there are no prospective follow-up data assessing clinical endpoints, such as arrhythmias or SCD. While available evidence indicates that QT intervals often normalize after detraining, it cannot be definitively concluded that all affected athletes are free of underlying genetic predisposition, given that not all mutations are known or routinely tested, and family history may be incomplete or underreported. Importantly, acquired QT prolongation has been associated with arrhythmic risk. Therefore, the available data should not be interpreted as providing reassurance of a benign course. Instead, these findings highlight the need for further investigation to clarify the long-term implications of exercise-induced long QT.
One plausible mechanism in exercise-induced long QT in the athlete population is the activation of stretch-activated ion channels.26 The opening of these stretch-activated ion channels could lead to the influx or outflux of various ions in the intracellular space, implicating the phases of cardiac action potential.27 Stretch-activated ion channels were categorized by their ion selectivity, resulting in potassium selective channels and non-selective cation channels. Potassium selective channels help potassium ions to move outward from the cell, leading to faster repolarization or even hyperpolarization, potentially shortening the cardiac action potential. In regard to exercise-induced long QT, the role of non-selective cation channels is more plausible due to its role in the influx of various cations other than potassium, including sodium and calcium ions, which favor depolarization. The activation of these non-selective cation channels could prolong the second phase in cardiac action potentials, which involves calcium ions, which would explain the prolonged QT interval.28 The overexpression or mutations associated with these potential non-selective cation channels, such as Piezo1, Piezo2, and TRP channels, must be considered as one possible cause.
These findings have crucial implications for diagnosing and managing athletes with prolonged QT intervals, which may help prevent unnecessary restrictions and treatments.
Demonstration of Reversibility with Detraining
This review highlights that exercise-induced long QT is reversible with detraining, as evidenced by significant shortening of QTc intervals and near-zero Schwartz scores, distinguishing it from congenital LQTS, where prolongation persists without treatment.8,9,11 This reversibility has important clinical implications, offering a noninvasive way to potentially rule out congenital LQTS in athletes. If detraining normalizes the QT interval, it suggests an adaptive response to training rather than a pathological condition, avoiding unnecessary interventions, such as β-blockers or ICDs.22 The underlying mechanisms include reduced vagal tone, normalized adrenergic signaling, and regression of cardiac remodeling, all of which contribute to improved repolarization.15,24,29
Practical Implications for Athletes and Sports Medicine
Available data do not support a definitive reduction in SCD risk following detraining, nor do they establish safety upon return to high-intensity sports. Instead, current evidence highlights the need for individualized monitoring. Athletes with exercise-induced long QT should undergo periodic ECG evaluations, and return-to-play decisions should be made on a case-by-case basis, rather than assuming safety based on QT interval normalization alone.
Bradycardia, commonly observed in highly trained athletes, may further contribute to QT prolongation by extending ventricular repolarization. While these physiological adaptations may not be inherently pathological, they warrant close observation, especially in athletes with borderline QT intervals or those with a family history of SCDs or arrhythmic events.
The occurrence of ventricular arrhythmias or other adverse cardiac events were not observed during follow-up in the studies included. This could be explained by the relatively short duration of follow-up conducted and the scarcity of cases documented on this condition. In some patients, re-prolongation of the QT interval occurs during return to play in competitive sports, and in other patients, the QT interval remains normal with relatively lower intensity activities compared with before, demonstrating a possible dose-dependent relationship. As we know, increased QT interval is correlated with increased risk in ventricular arrhythmias. Even though the benign nature of this condition cannot be ascertained at this point, monitoring the athlete’s response to exercise after detraining would be wise, considering the risk associated.
Pre-participation Screening Considerations
Pre-participation cardiovascular screening is critical for identifying prolonged QT intervals, but clinicians must interpret QTc intervals in athletes carefully, taking into account their training status, autonomic tone, and exercise history. Serial ECG evaluations, including 12-lead ECGs at rest, during exercise (stress tests), and postexercise recovery, are essential for monitoring dynamic changes in the QT interval. While prolonged QTc intervals traditionally led to immediate disqualification from competitive sports, emerging evidence suggests that a subset of athletes exhibit reversible QT prolongation. Instead of automatic exclusion, these individuals should be reclassified into a monitored athlete population, allowing continued participation under close surveillance. This approach ensures that athletes who do not have congenital LQTS are not unnecessarily restricted while maintaining patient safety through structured follow-up protocols.
For athletes with borderline or prolonged QTc intervals, a detraining protocol involving 4–6 weeks of exercise cessation followed by follow-up ECG assessments can help determine whether QT prolongation is exercise-induced. If QT intervals normalize after detraining, continued participation may be considered with periodic ECG monitoring. However, persistent QT prolongation, especially in the presence of concerning clinical features, such as a positive family history or syncope, warrants further evaluation, including genetic testing and risk stratification using tools, such as the Schwartz score.
Recommendations for Clinical Practice
Clinicians should avoid premature diagnoses of congenital LQTS by recognizing that some cases of QT prolongation in athletes are reversible and related to physiological adaptations rather than genetic mutations. However, the distinction between benign and potentially arrhythmic QT prolongation remains unclear, necessitating careful assessment and follow-up. While detraining can be a useful diagnostic tool, it does not guarantee long-term safety. Athletes with exercise-induced long QT should undergo periodic ECG evaluations to monitor for recurrence or the emergence of arrhythmic risks. Increased awareness and education among healthcare providers, athletes, and coaches are essential to ensuring that QT prolongation is correctly identified and managed with appropriate caution.
Limitations
This study provides valuable insights, but has limitations. Variability in detraining protocols across studies may have influenced QT interval normalization, highlighting the need for standardized protocols in future research. Small sample sizes limit the generalizability of the findings, emphasizing the importance of larger, more diverse studies. While no pathogenic genetic mutations were identified, undetected or novel variants could still play a role, warranting the use of advanced genetic and electrophysiological tools in future research. Additionally, the lack of long-term data raises questions about the recurrence of QT prolongation and arrhythmic risks upon retraining, highlighting the need for follow-up studies to ensure the long-term safety of returning athletes.
While our findings observed a higher prevalence of QT prolongation among male athletes compared with female athletes, this must be interpreted with caution due to a methodological limitation: the lack of a female sample base. If the overall athlete cohort was predominantly men (e.g. due to underrepresentation of women in competitive sports or sampling bias), the higher absolute number of affected men could simply reflect the underlying sex distribution of the study population. Thus, we cannot conclusively state that men are more prone to exercise-induced long QT. Future studies should ensure balanced enrollment and explicitly analyze sex-specific incidence rates to clarify whether observed differences are attributed to sex.
Another notable limitation of this review is the absence of a standardized baseline definition for what constitutes a ‘heavy’ workload or ‘intense’ athletic activity. The included studies used these terms inconsistently, often without objective quantification or uniform criteria. This variability reflects the heterogeneity in study designs, participant characteristics, and training regimens, thereby complicating cross-study comparisons and synthesis of findings. The lack of standardized metrics for exercise intensity diminishes the external validity of the results, and limits their applicability across diverse athletic populations and sporting contexts.
An important limitation of the present review pertains to the incomplete application of standardized provocative stress testing protocols, such as epinephrine infusion, isoproterenol administration, or orthostatic challenge at both baseline (during peak training periods) and following the detraining phase. The absence of such assessments at multiple time points precludes a comprehensive evaluation of the dynamic QT interval behavior under sympathetic stimulation across physiologically distinct states. Given that provocative testing is instrumental in differentiating congenital LQTS or exercise-induced long QT, its omission post-detraining restricts the interpretive validity of QT normalization and limits the ability to definitively attribute reversibility to training cessation alone. Future prospective studies should incorporate serial provocative testing as part of a standardized diagnostic algorithm to more accurately delineate the temporal electrophysiological responses and to strengthen causal inferences regarding the benign nature of exercise-induced long QT.
Future Research Perspectives
Larger prospective studies are essential to validate these findings and refine clinical guidelines for managing QT prolongation in athletes. Future research should prioritize standardizing detraining protocols to ensure consistent assessments, exploring molecular and electrophysiological mechanisms using advanced imaging and genetic tools, and identifying biomarkers for risk stratification. Longitudinal studies tracking athletes as they return to high-intensity training are also crucial to monitor QT stability and evaluate the long-term risk of arrhythmic events.
Conclusion
By examining detraining protocols as a diagnostic tool, this study offers a practical strategy to potentially differentiate exercise-induced long QT and congenital LQTS. However, these findings should be interpreted cautiously, as reversibility does not inherently indicate a lack of risk. The recurrence of QT prolongation upon retraining suggests that some athletes may remain vulnerable to arrhythmias despite initial ECG normalization. Future studies should include longer follow-up and arrhythmic event monitoring to ensure safe return-to-play guidelines for affected individuals.