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.
Keywords: female; implantable cardioverter defibrillator; life threatening events; long QT syndrome; sex.