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. Programming considerations to tailor the rate drop algorithm when two different physiological responses are triggered by carotid sinus massage are discussed. The importance of careful clinical assessment to detect all appropriate physiological responses as well as new pacing algorithms is depicted.