Outcome by Sex in Patients With Long QT Syndrome With an Implantable Cardioverter Defibrillator

Background Sex differences in outcome have been reported in patients with congenital long QT syndrome. We aimed to report on the incidence of time-dependent life-threatening events in male and female patients with long QT syndrome with an implantable cardioverter defibrillator (ICD). Methods and Results A total of 60 patients with long QT syndrome received an ICD for primary or secondary prevention indications. Life-threatening events were evaluated from the date of ICD implant and included ICD shocks for ventricular tachycardia, ventricular fibrillation, or death. ICDs were implanted in 219 women (mean age 38±13 years), 46 girls (12±5 years), 55 men (43±17 years), and 40 boys (11±4 years). Mean follow-up post-ICD implantation was 14±6 years for females and 12±6 years for males. At 15 years of follow-up, the cumulative probability of life-threatening events was 27% in females and 34% in males (log-rank P=0.26 for the overall difference). In the multivariable Cox model, sex was not associated with significant differences in risk first appropriate ICD shock (hazard ratio, 0.83 female versus male; 95% CI, 0.52-1.34; P=0.47). Results were similar when stratified by age and by genotype: long QT syndrome type 1 (LQT1), long QT syndrome type 2 (LQT2), and long QT syndrome type 3 (LQT3). Incidence of inappropriate ICD shocks was higher in males versus females (4.2 versus 2.7 episodes per 100 patient-years; P=0.018), predominantly attributed to atrial fibrillation. The first shock did not terminate ventricular tachycardia/ventricular fibrillation in 48% of females and 62% of males (P=0.25). Conclusions In patients with long QT syndrome with an ICD, the risk and rate of life-threatening events did not significantly differ between males and females regardless of ICD indications or genotype. In a substantial proportion of patients with long QT syndrome, first shock did not terminate ventricular tachycardia/ventricular fibrillation.