Safety, Performance, and Efficacy of Cardiac Contractility Modulation Delivered by the 2-Lead Optimizer Smart System: The FIX-HF-5C2 Study

Background: Prior studies of cardiac contractility modulation (CCM) employed a 3-lead Optimizer system. A new 2-lead system eliminated the need for an atrial lead. This study tested the safety and effectiveness of this 2-lead system compared with the 3-lead system. Methods: Patients with New York Heart Association III/IVa symptoms despite medical therapy, left ventricular ejection fraction 25% to 45%, and not eligible for cardiac resynchronization therapy could participate. All subjects received an Optimizer 2-lead implant. The primary end point was the estimated difference in the change of peak VO₂ from baseline to 24 weeks between FIX-HF-5C2 (2-lead system) subjects relative to control subjects from the prior FIX-HF-5C (3-lead system) study. Changes in New York Heart Association were a secondary end point. The primary safety end point was a comparison of device-related adverse events between FIX-HF-5C2 and FIX-HF-5C subjects. Results: Sixty subjects, 88% male, 66±9 years old with left ventricular ejection fraction 34±6% were included. Baseline characteristics were similar between FIX-HF-5C and FIX-HF-5C2 subjects except that 15% of FIX-HF-5C2 subjects had permanent atrial fibrillation versus 0% in FIX-HF-5C. CCM delivery did not differ significantly between 2- and 3-lead systems (19 892±3472 versus 19 583±4998 CCM signals/day, CI of difference [-1228 to 1847]). The change of peak VO₂ from baseline to 24 weeks was 1.72 (95% Bayesian credible interval, 1.02-2.42) mL/kg per minute greater in the 2-lead device group versus controls. 83.1% of 2-lead subjects compared with 42.7% of controls experienced ≥1 class New York Heart Association improvement (P<0.001). There were decreased Optimizer-related adverse events with the 2-lead system compared with the 3-lead system (0% versus 8%; P=0.03). Conclusions: The 2-lead system effectively delivers comparable amount of CCM signals (including in subjects with atrial fibrillation) as the 3-lead system, is equally safe and improves peak VO₂ and New York Heart Association. Device-related adverse effects are less with the 2-lead system. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03339310.