Nonexcitatory, cardiac contractility modulation electrical impulses: Feasibility study for advanced heart failure in patients with normal QRS duration

BACKGROUND Cardiac contractility modulation signals are associated with acutely improved hemodynamics, but chronic clinical impact is not defined. OBJECTIVES The purpose of this randomized, double-blind, pilot study was to determine the feasibility of safety and effectively delivering cardiac contractility modulation signals in patients with heart failure. METHODS Forty-nine subjects with ejection fraction <35%, normal QRS duration (105 +/- 15 ms), and New York Heart Association (NYHA) class III or IV heart failure despite medical therapy received a cardiac contractility modulation pulse generator. Patients were randomized to have their devices programmed to deliver cardiac contractility modulation signals (n = 25, treatment group) or to remain off (n = 24, control group) for 6 months. Evaluations included NYHA class, 6-minute walk, cardiopulmonary stress test, Minnesota Living with Heart Failure Questionnaire, and Hotter monitoring. RESULTS Although most baseline features were balanced between groups, ejection fraction (31.4% +/- 7.4% vs 24.9% +/- 6.5%, P =.003), end-diastolic dimension (52.1 +/- 21.4 mm vs 62.5 +/- 6.2 mm,P =.01), peak VO2 (16.0 +/- 2.9 mL O-2/kg/min vs 14.3 +/- 2.8 mL O-2/kg/min, P =.02), and anaerobic threshold (12.3 +/- 2.5 mL O-2/kg/min vs 10.6 +/- 2.4 mL O-2/kg/min, P =.01) were worse in the treatment group than in the control group. Nevertheless, one death occurred in the control group, and more patients in the treatment group were free of hospitatization for any cause at 6 months (84% vs 62%). No change in ectopy was observed. Compared with baseline, 6-minute walk (13.4 m), peak VO2 (0.2 mL O-2/kg/min), and anaerobic threshold (0.8 mL O-2/kg/min) increased more in the treatment group than in control. None of these differences were statistically significant (small sample size). NYHA and Minnesota Living with Heart Failure Questionnaire changed similarly in the two groups. CONCLUSION Despite a sicker population in the treatment group, no specific safety concerns emerged with chronic cardiac contractility modulation signal administration. Further study is required to definitively define the safety and efficacy of cardiac contractility modulation signals.