Vigorous Exercise in Patients With Hypertrophic Cardiomyopathy.

Importance: Whether vigorous intensity exercise is associated with an increase in risk of ventricular arrhythmias in individuals with hypertrophic cardiomyopathy (HCM) is unknown. Objective: To determine whether engagement in vigorous exercise is associated with increased risk for ventricular arrhythmias and/or mortality in individuals with HCM. The a priori hypothesis was that participants engaging in vigorous activity were not more likely to have an arrhythmic event or die than those who reported nonvigorous activity. Design, Setting, and Participants: This was an investigator-initiated, prospective cohort study. Participants were enrolled from May 18, 2015, to April 25, 2019, with completion in February 28, 2022. Participants were categorized according to self-reported levels of physical activity: sedentary, moderate, or vigorous-intensity exercise. This was a multicenter, observational registry with recruitment at 42 high-volume HCM centers in the US and internationally; patients could also self-enroll through the central site. Individuals aged 8 to 60 years diagnosed with HCM or genotype positive without left ventricular hypertrophy (phenotype negative) without conditions precluding exercise were enrolled. Exposures: Amount and intensity of physical activity. Main Outcomes and Measures: The primary prespecified composite end point included death, resuscitated sudden cardiac arrest, arrhythmic syncope, and appropriate shock from an implantable cardioverter defibrillator. All outcome events were adjudicated by an events committee blinded to the patient's exercise category. Results: Among the 1660 total participants (mean [SD] age, 39 [15] years; 996 male [60%]), 252 (15%) were classified as sedentary, and 709 (43%) participated in moderate exercise. Among the 699 individuals (42%) who participated in vigorous-intensity exercise, 259 (37%) participated competitively. A total of 77 individuals (4.6%) reached the composite end point. These individuals included 44 (4.6%) of those classified as nonvigorous and 33 (4.7%) of those classified as vigorous, with corresponding rates of 15.3 and 15.9 per 1000 person-years, respectively. In multivariate Cox regression analysis of the primary composite end point, individuals engaging in vigorous exercise did not experience a higher rate of events compared with the nonvigorous group with an adjusted hazard ratio of 1.01. The upper 95% 1-sided confidence level was 1.48, which was below the prespecified boundary of 1.5 for noninferiority. Conclusions and Relevance: Results of this cohort study suggest that among individuals with HCM or those who are genotype positive/phenotype negative and are treated in experienced centers, those exercising vigorously did not experience a higher rate of death or life-threatening arrhythmias than those exercising moderately or those who were sedentary. These data may inform discussion between the patient and their expert clinician around exercise participation.

Clinical Significance of Early Repolarization in Long QT Syndrome.

OBJECTIVES: This study sought to determine the prevalence of early repolarization pattern (ERP) within a large cohort of patients with long QT syndrome (LQTS) and examine the correlation and clinical significance of ERP with symptomatic status and subsequent risk of breakthrough cardiac events (BCEs). BACKGROUND: The electrocardiographic ERP is associated with an increased risk of arrhythmic events and sudden cardiac death. METHODS: ERP was defined as an end-QRS notch or slur on the downslope of a prominent R-wave with a J point ≥0.1 mV in 2 or more contiguous leads of the 12-lead electrocardiogram, excluding V1 to V3. A patient was considered previously symptomatic if they had a suspected LQTS-triggered cardiac event prior to diagnosis. BCEs were defined as LQTS-attributable syncope/seizures, aborted cardiac arrest, appropriate ventricular fibrillation-terminating implantable cardioverter-defibrillator shocks, and sudden cardiac death following diagnosis and institution of a LQTS-directed treatment program. RESULTS: In this study, 528 patients (57% female) with genotype-confirmed LQTS (283 with LQT1, 193 with LQT2, and 52 with LQT3) were reviewed from which 2,618 electrocardiograms were analyzed over a median follow-up of 6.7 (interquartile range, 3.6 to 10 years) years. Eighty-two (15.5%; female 51%) patients were identified as having ERP; 40 (50%) of these ERP-positive patients showed persistent ERP. One hundred twenty-four patients (23.5%) were classified as previously symptomatic LQTS and 39 (7.2%) experienced a subsequent BCE. ERP was not associated with either symptomatic status (p = 0.62) or BCE (p = 0.61). CONCLUSIONS: Although ERP is common in LQTS, this extensive study suggests that the presence of concomitant ERP does not correlate with either those with a history of LQTS-triggered events prior to diagnosis or those with subsequent BCEs from their treated LQTS substrate.