Optimization of ventricular pacing: where should we implant the leads?

The original goal of implantable pacemakers was to prevent syncope and death due to prolonged periods of asystole from Stokes-Adams attacks and complete heart block (1). Subsequently, devices that were increasingly complex were developed to maintain atrioventricular (AV) sequential activation and to provide a better chronotropic response to exercise. Atrial based pacing (either AAI or DDD) has become standard for patients in sinus rhythm. Compared with ventricular pacing, atrial based pacing improves hemodynamic function and reduces the incidence of pacemaker syndrome, atrial fibrillation and congestive heart failure in patients with sick sinus syndrome. The effect of atrial based pacing on long term mortality is less clear (2,3). Rate responsive pacing improves functional capacity and exercise duration in subjects with chronotropic incompetence (4).