Differential effect of right and left carotid sinus massage: implications for sudden rate drop pacing algorithm.

This present report describes a patient with syncope in whom asystole was triggered by right carotid sinus massage and complete atrioventricular block with slight bradycardia by left carotid sinus massage. A dual-chamber, rate-responsive, permanent pacemaker with 'sudden rate drop' algorithm was implanted. The present report underlines the pathophysiology and the clinical utility of carotid sinus massage on both sides.