Current status of sensor-modulated rate-adaptive cardiac pacing.

In one third of patients requiring permanent cardiac pacing, sinoatrial response to exercise is inadequate. This has led to the development of a number of nonatrial sensors capable of increasing stimulation rate in response to metabolic demand. Initial sensor-modulated pacemakers were designed for use in the ventricle. This review was undertaken to compare ventricular rate-adaptive pacing with dual chamber and nonrate-adaptive atrial modes. Rate-adaptive ventricular pacing is primarily indicated in patients with complete heart block and nonfunctional atria in whom increased rates are not associated with the development of myocardial ischemia or retrograde conduction. A responsive atrium remains the best measure of metabolic demand, and devices capable of maintaining atrioventricular (AV) sequencing provide superior hemodynamic performance at usual activity levels. In addition, preserved AV relations reduce the incidence of new atrial fibrillation and stroke. Newer devices combining the advantages of atrial and nonatrial rate modulation with the preservation of AV synchrony will best utilize the developing sensor technologies.