Dual-chamber pacing in hypertrophic cardiomyopathy.

This review focuses on recent developments in the field of pacing in hypertrophic cardiomyopathy (HCM). Regarding mechanisms of action, recent data indicates that pacing acts by inducing dysynchronous left ventricular activation, thus reducing contractility and increasing end-systolic volume. Following several positive uncontrolled studies, three randomized crossover trials, with a total of approximately 140 patients, have now confirmed that gradients are on average halved with pacing but the reduction in symptoms has been modest and maximum exercise capacity has not been improved. These studies have identified a placebo effect from pacemaker implantation in HCM and have questioned the efficacy of pacing as a symptomatic therapy for HCM. There is probably a subgroup of patients with HCM who respond to permanent dual-chamber pacing but their precise identification is not yet clear. Permanent pacing should continue to be considered as one option in the management of the patient with drug refractory, symptomatic obstructive HCM.