Benefits of the advances in cardiac pacemaker technology.

Pacemaker technology has expanded rapidly in the last thirty years. Each phase of development has been marked by both improvements in clinical benefit and disadvantageous interactions of physiology and technology. Each phase of development has led to smaller, more reliable devices with greater programmability. Advances in generator technology and battery design have increased longevity of devices. The first devices used asynchronous pacing which had a significant effect in reducing the mortality of surgically induced complete heart block. Ventricular demand pacemakers overcame the problems of asynchronous competitive pacing, but exposed the pacemaker syndrome. Atrioventricular sequential pacing restored atrioventricular synchrony, resulting in hemodynamic improvement, but created the phenomenon of pacemaker-mediated tachycardia. Alternative dual chamber modes and algorithms have largely resolved this. Adaptive-rate devices have been of benefit to patients with chronotropic incompetence, and are now incorporating an increasing variety of biosensors. Almost all the problems of pacing have been overcome, but the increasing complexity of pacemaker technology is now a major limitation to its proper use.