Primary prevention with the implantable cardioverter-defibrillator in high-risk long-QT syndrome patients

AIMS: Prospective data regarding the role of implantable cardioverter-defibrillator (ICD) for the primary prevention of sudden cardiac death in patients with long QT syndrome (LQTS) is scarce. Herein, we explore the prospective Rochester LQTS ICD registry to assess the risk for appropriate shock in primary prevention in a real-world setting. METHODS AND RESULTS: We studied 212 LQTS patients that had ICD implantation for primary prevention. Best-subsets proportional-hazards regression analysis was used to identify clinical variables that were associated with the first appropriate shock. Conditional models of Prentice, Williams, and Peterson were utilized for the analysis of recurrent appropriate shocks. During a median follow-up of 9.2 ± 4.9 years, there were 42 patients who experienced at least one appropriate shock and the cumulative probability of appropriate shock at 8 years was 22%. QTc ≥ 550 ms [hazard ratio (HR) 3.94, confidence interval (CI) 2.08-7.46; P < 0.001) and prior syncope on β-blockers (HR 1.92, CI 1.01-3.65; P = 0.047) were associated with increased risk of appropriate shock. History of syncope while on β-blocker treatment (HR 1.87, CI 1.28-2.72; P = 0.001), QTc 500-549 ms (HR 1.68, CI 1.10-2.81; P = 0.048), and QTc ≥ 550 ms (HR 3.66, CI 2.34-5.72; P < 0.001) were associated with increased risk for recurrent appropriate shocks, while β-blockers were not protective (HR 1.03, CI 0.63-1.68, P = 0.917). LQT2 (HR 2.10, CI 1.22-3.61; P = 0.008) and multiple mutations (HR 2.87, CI 1.49-5.53; P = 0.002) were associated with higher risk for recurrent shocks as compared with LQT1. CONCLUSION: In this prospective ICD registry, we identified clinical and genetic variables that were associated appropriate shock risk. These data can be used for risk stratification in high-risk patients evaluated for primary prevention with ICD.