Key result
Exercise QTc parameters show no association with all-time arrhythmic events in long QT syndrome.
Why the study?
Better risk stratification methods are needed for patients with long QT syndrome to predict arrhythmic events.
Does exercise QTc measurement correlate with arrhythmic events in patients with long QT syndrome?
Cohort (n=439)
Yes
Does exercise QTc measurement correlate with arrhythmic events in patients with long QT syndrome?
Recovery QTc and the difference between baseline and recovery QTc on treadmill stress testing do not predict arrhythmic events in patients with Long QT Syndrome.
Exercise QTc parameters should not guide arrhythmic risk stratification in LQTS; leaves open whether other stress-test metrics predict events in prospective cohorts.
Background: Major advances in the characterization and clinical management of patient with long QT syndrome (LQTS) has been achieved in the past decades. However, the quest for better risk stratification is ongoing. Objective: We aimed to identify the association between exercise QTc and arrhythmic cardiac events in patients with LQTS. Methods: In a retrospective analysis of the Canadian LQTS Registry, we evaluated the correlation between exercise QTc and all-time arrhythmic events (AE): arrhythmic syncope, aborted cardiac arrest, sudden death, ventricular arrhythmia or appropriate ICD shock. Severe AE excluded arrhythmic syncope. Exercise QTc was measured at 4-5 minutes in recovery on a treadmill stress test performed at initial diagnosis. Results: A total of 439 patients were identified including 181 probands. Genotype was reported in 310, with LQT1 in 192 and LQT2 in 79. Arrhythmia events were reported in 141 (32%) patients including arrhythmic syncope in 111, aborted cardiac arrest in 24, sudden death in 3 and ICD shock in 3. Mean6SD age, heart rate (HR), baseline and recovery QTc and the difference between recovery and baseline QTc (delta QTc) are shown in the Table. When comparing patients with No AE vs All-time AE, there was no statistically significant difference in recovery QTc or delta QTc for the overall cohort or when stratified by proband status, LQT1 or LQT2. The same lack of a correlation was observed when comparing No AE vs Severe AE. Conclusion: In a national population-based cohort of patients with LQTS, recovery QTc and the difference between baseline and recovery QTc did not correlate with AE. The lack of association between the degree of exercise QTc maladaptation and symptoms may be influenced by medical management strategies including cascade screening, lifestyle modification and medical therapy for LQT. The data from this study does not support the use of exercise QTc parameters in risk stratification for arrhythmic symptoms.
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Atallah et al. (2025) conducted a cohort in Long QT syndrome (LQTS) (n=439). Exercise QTc (recovery QTc and delta QTc) was evaluated on All-time arrhythmic events (arrhythmic syncope, aborted cardiac arrest, sudden death, ventricular arrhythmia or appropriate ICD shock). In 439 patients with long QT syndrome, exercise QTc parameters did not significantly correlate with all-time arrhythmic events, which occurred in 32% of the cohort.
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