Cardiac arrhythmias after chronic embolization of the sinus node artery: alterations in parasympathetic pacemaker control.

Embolization of the sinus node artery was accomplished in dogs by injecting rapidly hardening vinyl latex into the sinus node artery. Embolization immediately shifted the pacemaker to a junctional focus; however, with time postoperatively, the pacemaker shifted to an atrial site. Variable episodes of pacemaker failure, sinoatrial block, junctional rhythm, wandering atrial pacemaker and idioventricular escape rhythms were commonly observed on Holter monitor in isolation but only rarely when the dog was in the laboratory. Severe bradycardia (38.9 +/- 3.7 beats/min) was the predominant rhythm by 3-6 months postoperatively. In addition, these same dogs had a greater overall increase in heart rate after atropine than normal dogs (17.5 +/- 13.5 vs 116.6 +/- 15.9 beats/min above control; p less than 0.02). Responses to vagal stimulation in this group were abnormal, as long periods of asystole and bradycardia were observed after stimulation was terminated. These data suggest an alteration in parasympathetic pacemaker control after chronic embolization of the sinus node artery.