Exit block of artificial pacemaker induced by carotid sinus massage.

Failure of the pacemaker is a common complication of pacemaker therapy. Identification of the disorder responsible for the failure to pace is often difficult. An increase in myocardial threshold can result in nonconduction of the artificial impulse, particularly near the end of the life of the battery, when the output of current has started to decline. This report demonstrates such an increase in myocardial resistance which was apparent only upon massage of the carotid sinus.