Atrial pacing for sick sinus syndrome.

Atrial pacing is the most physiological way to pace patients with sinus node disease, as it provides both AV synchrony and a normal ventricular activation pattern. Long-term studies comparing atrial and ventricular pacing imply that atrial pacing results in fewer cardiac complications and, possibly, reduced mortality. Ventricular pacing should thus, if possible, be avoided in patients with sinus node disease. The potential risk of impending high-grade AV block during atrial pacing is low, with an annual incidence around 1% if patients are selected appropriately. Approximately 40-50% of patients with sinus node disease show signs of chronotropic incompetence during physical exercise, and are thus candidates for atrial rate responsive pacing. A preoperative evaluation of candidates for atrial pacing should include long-term Holter/telemetry, exercise test, carotid sinus stimulation, and an electrophysiological study excluding significant AV conduction disturbances.