Aim: In experimental studies, nonexcitatory electrical stimulation delivered at the time of absolute myocardial refractoriness resulted in cardiac contractility modulation (CCM) with improved systolic function. This study reports the initial experience with CCM in patients with chronic heart failure.
Methods and results: Twenty-five patients, 23 males, with a mean age of 62+/-9 years and drug-refractory NYHA class III heart failure were assigned to CCM-generator implantation. The underlying heart disease was idiopathic dilated cardiomyopathy in 12 patients and coronary heart disease in 13 patients. Acute efficacy of CCM with 7.73-V stimuli delivered via two right ventricular leads was evaluated by measuring the time derivative of left ventricular pressure (dP/dt). After implantation, the CCM generator was activated for 3 h daily over 8 weeks. In 23/25 patients the CCM system was implanted successfully. Heart failure significantly improved from NYHA class III to class II in 15 patients and to class I in 4 patients (p < 0.000001), left ventricular ejection fraction improved from 22+/-7% to 28+/-8% (p = 0.0002), and the Minnesota Living with Heart Failure Score improved from 43+/-22 to 25+/-18 (p = 0.001). The 6-min walk test increased from 411+/-86 to 465+/-81 m (p= 0.02). Nine patients (39%) had intermittent sensations associated with CCM delivery. There were two (8%) non-device-related deaths during follow-up.
Conclusions: These preliminary data indicate that CCM by delivery of intermittent nonexcitatory electrical stimuli is a promising technique for improving ventricular systolic function and symptoms in patients with drug-refractory NYHA class III heart failure.