Cardiac contractility modulation therapy in advanced systolic heart failure.

Cardiac contractility modulation (CCM) is the application of nonexcitatory electrical signals to the myocardium, during the absolute refractory period of the action potential, to elicit a positive inotropic effect without increasing myocardial oxygen consumption. These effects are independent of QRS duration; consequently, CCM device therapy might benefit symptomatic patients with reduced left ventricular ejection fraction who are not candidates for cardiac resynchronization therapy. Preclinical studies have demonstrated a rapid positive inotropic effect of CCM, which seems to be mediated by modulation of cardiomyocyte Ca(2+) fluxes and alterations in the phosphorylation of cardiac phospholamban. In vivo translational and clinical studies that utilized double biphasic voltage pulses to the right ventricular aspect of the interventricular septum have demonstrated positive global effects on cardiac reverse remodelling and contractility. Long-term application of CCM seems to improve patients' exercise tolerance and quality of life. These benefits are apparently accomplished with an acceptable safety profile; however, to date, no data have demonstrated reductions in hospitalizations for heart failure or mortality. CCM is currently available in Europe and ongoing studies are attempting to identify the ideal target population and accumulate additional outcome data.