Prospective randomized trials on pacing mode: what have we learned?

Retrospective studies and observational clinical data on pacemaker mode selection indicate that physiologic pacing is associated with better clinical outcomes and reduced mortality when compared with single-chamber ventricular pacing. Methodologic flaws in such studies, especially in respect of selection bias, have cast doubt upon the validity of the results and have mandated the performance of randomized, prospective studies of pacemaker-mode prescription. Evidence available to date suggests that atrial-based pacing may confer improved quality of life and a reduction in the incidence of chronic atrial fibrillation and thromboembolic events in sinus node disease. Physiologic pacing modes have, to date, not demonstrated benefit with congestive heart failure or patient longevity. The results of ongoing, large prospective trials of mode prescription in patients with AV block and sinus node disease are needed before any change from current guidelines can be recommended.