Electrophysiologic findings in carotid sinus massage.

Thirty patients with carotid sinus syndrome were electrophysiologically studied. In 14 patients carotid sinus massage was performed during atrial and ventricular stimulation, and the conduction times were measured. The AH-time was prolonged by more than 120 ms in 6 patients (20%); the HV-time was prolonged in 6 patients by more than 55 ms (20%); 5 patients had bundle branch block (16.7%); The sinus node recovery time was prolonged in 7 out of 27 patients (26%). Ten patients (33%) did not have additional electrophysiologic abnormalities. There was a predominance of carotid sinus syndrome on the right side. During carotid sinus massage there was a significant increase of the AH-time, but there were no significant changes of the HV-time or the width of the QRS-complexes. Twenty-one patients developed an atrial asystole and 9 patients an atrial bradycardia and an additional AV-block. There was a longer AH-time and a longer prolongation of the AH-time in the patients who developed an AV-block. Twelve out of 14 patients (85.7%) developed an AV-block during carotid sinus massage and atrial pacing. During ventricular pacing 5 of 14 patients (35.7%) revealed a complete retrograde block before carotid sinus massage and 5 of the remaining 9 patients developed a total retrograde block during carotid sinus massage. Consequently, in 71.4% of the patients with carotid sinus syndrome complete retrograde conduction block and atrial asystole can be expected during attacks of ventricular asystole and simultaneous ventricular pacing. In conclusion, there is a high incidence of additional disturbances of the sinus node function and AV-conduction in patients with carotid sinus syndrome. AAI pacemakers are contraindicated due to the common development of additional AV-block during carotid sinus massage. Physiologic pacing might contribute to better hemodynamics, particularly in patients with the mixed type of carotid sinus syndrome.