Effect of recent randomized trials on current pacing practice.

The most common indication for a permanent pacemaker is symptomatic bradycardia. An atrial-based pacemaker (dual-chamber or atrial) usually is preferred, except in patients with chronic atrial fibrillation. Several prospective, randomized trials recently have been completed to evaluate new indications for permanent pacemakers. A dual-chamber pacemaker with an optimal atrioventricular interval can reduce the left ventricular outflow tract gradient by >50% in patients with hypertrophic cardiomyopathy. This has been associated with symptomatic improvement in the majority of patients, but an important placebo effect appears likely. Pacing also has been evaluated in patients with medically refractory dilated cardiomyopathy. Despite encouraging initial studies, routine implantation of a permanent pacemaker in dilated cardiomyopathy is not indicated. In patients with cardioinhibitory or mixed vasovagal syncope and carotid sinus hypersensitivity, implantation of a pacemaker markedly decreases syncopal episodes. Pacemaker therapy is clearly indicated in patients with atrial fibrillation associated with symptomatic bradycardia, and exciting new data on the use of pacing to prevent atrial fibrillation appear promising. The best pacing modality for this indication may be dual-site atrial pacing. Finally, permanent pacemakers play an important role in the treatment of symptomatic long QT syndrome, usually in combination with beta-blockers.