Does contractility modulation have a role in the treatment of heart failure?

Cardiac resynchronization therapy (CRT) is an established therapy for patients with systolic dysfunction, QRS duration greater than 120 ms, and New York Heart Association (NYHA) class III or IV symptoms. However, most patients with heart failure have QRS duration below 120 ms and 30% or more of CRT recipients are nonresponders. Cardiac contractility modulation (CCM) signals are nonexcitatory electrical impulses applied during the absolute refractory period that are intended to enhance contractile strength independent of QRS duration. Myocardial biopsy studies suggest that modulation of protein phosphorylation and gene expression underlie the mechanisms by which CCM exerts its effects. Two prospective randomized studies have investigated the impact of CCM on exercise tolerance and quality of life in patients with chronic heart failure. These studies have included predominantly patients with NYHA class III heart failure with QRS duration below 130 ms. This review summarizes results of these clinical studies and outlines additional studies underway to further clarify the role of CCM in the treatment of heart failure.