Long-term incidence and efficacy of appropriate therapy in subcutaneous and transvenous implantable cardioverter-defibrillators: A secondary analysis of the PRAETORIAN-XL trial

Background Previous secondary analyses of the PRAETORIAN trial showed no differences in all appropriate therapy (shocks and antitachycardia pacing (ATP)) rates or first-shock efficacy between subcutaneous (S-ICD) and transvenous ICDs (TV-ICD) during 4.1 years of follow-up. However, ICD therapy is intended to provide lifelong protection, and data on the incidence and efficacy of appropriate therapy during long-term follow-up are lacking. The PRAETORIAN-XL trial extends follow-up by an additional 4 years to evaluate long-term appropriate therapy rates and first-shock efficacy. We hypothesize that S-ICD and TV-ICD demonstrate comparable performance during extended follow-up of more than 8 years. Purpose To compare the long-term incidence and efficacy of appropriate therapy in patients with S-ICD and TV-ICD, a secondary analysis of the PRAETORIAN-XL trial. Methods This is a secondary analysis of the PRAETORIAN-XL trial. From 39 centers in Europe and the United States, patients with a class I or IIa indication for implantable cardioverter-defibrillator (ICD) without the need for cardiac pacing were enrolled and randomized between March 2011 and January 2017. Patients were followed for an additional 4 years after the follow-up period of the PRAETORIAN trial. Appropriate therapy was defined as ATP or ICD shock for ventricular fibrillation (VF) or ventricular tachycardia (VT), and electrical storm was defined as 3 or more VF or VT episodes within 24 hours. Only appropriate therapies adjudicated with electrograms were analyzed, and analyses were performed according to a modified intention-to-treat principle. Results A total of 849 patients were randomized to the S-ICD group (n=426) and the TV-ICD group (n=423). During a median 7.3 (interquartile: 3.8-8.7) years follow-up, there was no difference in appropriate therapy rate between the S-ICD group and the TV-ICD group (116 and 103 patients, respectively; 8-year Kaplan-Meier estimated cumulative incidence: 31.7% vs. 29.8%; p=0.293) (Figure 1, 2). During follow-up, there is a linear annual increase in new patients receiving appropriate therapy (S-ICD: 2.6-8.6 per 100 patient-years, and TV-ICD: 3.1-6.8 per 100 patient-years). The first shock efficacy was similar between the S-ICD groups and the TV-ICD group (92.4% vs. 92.7%; p=0.888). The first ATP terminated 54.4% of monomorphic VTs (160/294), however, 9.9% of VT were accelerated and 0.7% of VT were converted to VF after ATP delivery (Figure 1). In total, 22 electrical storms occurred in 16 patients in the S-ICD group, and 24 electrical storms occurred in 20 patients in the TV-ICD group (p=0.482). Conclusions During long-term follow-up, there were no differences in the rate of appropriate therapy and first shock efficacy between S-ICD and TV-ICD. There is a linear increase in new patients receiving appropriate therapy over the years, emphasizing the long-term benefit of ICD therapy with the current guidelines.Figure 1.The details of the therapiesFigure 2.