Chronic safety and performance of the extravascular ICD: results from the global EV ICD Pivotal study

Abstract

Abstract Background Implantable cardioverter defibrillators (ICDs) prevent sudden cardiac death in patients at high risk for ventricular arrhythmias, but conventional systems carry a risk of transvenous (TV) lead-related complications. The novel extravascular ICD (EV ICD) may reduce some of these complications, while offering anti-tachycardia pacing (ATP), pause prevention pacing, and a device of similar size and projected battery longevity as a TV ICD, by placing a lead substernally. The EV ICD Pivotal study demonstrated EV ICD safety and performance for termination of ventricular arrythmias at 6 months. Longer-term performance is unknown. Purpose To report the chronic safety and performance of the EV ICD system. Methods The extravascular implantable cardioverter defibrillator (EV ICD) Pivotal study was a prospective, international, single-arm, premarket clinical study. Patients with a class I or IIa indication for a single-chamber ICD per ESC or ACC/AHA/HRS guidelines were enrolled. Freedom from major system- and/or procedure-related complications at 18 mo was evaluated, as well as conversion of arrhythmias by anti-tachycardia pacing (ATP) or shock through all available follow up. Rates of ATP success were evaluated using the generalized estimating equation (GEE) and simple proportions. Results Implantation was attempted in 316 patients: 74.7% male, age 53.8±13.1 years, 82% primary prevention, left ventricular ejection fraction of 38.9%±15.4%, and New York Heart Association Class I (23.4%) or II/III (65.5%). Of 299 implanted patients (average follow up 16.2±7.2 mo), 19 experienced 80 spontaneous, appropriately treated arrhythmic episodes: 37 treated by ATP, 15 by ATP and shock, and 28 by shock alone with a Kaplan-Meier (KM) estimated 6.8% of patients experiencing appropriate therapy by 18 mo (Figure). Of discrete episodes treated with shock, 21/21 (100%) were successfully terminated. ATP was delivered in 12 patients, successfully treating 35/52 episodes (67.3%; GEE adjusted 59.0%). Inappropriate shocks occurred in 35 patients through all follow up, with a rate of 10.2% at 1 year. The KM estimate of freedom from major EV ICD system-or procedure-related complications rate through 18 mo was 91.9% (95% CI: 88.2% to 94.4%). The most common event was lead dislodgment (10 events in 9 patients) identified 0 to 120 days post-implant, predominantly due to anchoring technique. Conclusion The safety and effectiveness of a novel EV ICD system with a substernal lead extends through chronic follow up. Shocks were avoided in nearly half of all spontaneous episodes because of the availability of ATP.Figure