[Cardioinhibitory carotid sinus hypersensitivity in subjects with symptomatic sinus dysfunction].

Cardioinhibitory carotid sinus hypersensitivity is present in about one third of patients affected by sinus dysfunction. Aim of the study was to evaluate whether carotid sinus hypersensitivity is related to a well defined (intrinsic or extrinsic) sinus node damage. Fifty-four patients with ecg signs of sinus dysfunction underwent an electrophysiological study and carotid sinus massage. Spontaneous heart rate and corrected sinus node recovery time were measured in basal condition, after adrenergic blockade (propranolol 0.2 mg/Kg i.v.) and after autonomic blockade (propranolol 0.2 mg/Kg i.v. plus atropine 0.04 mg/Kg i.v.). The association between sinus dysfunction and cardioinhibitory carotid sinus hypersensitivity was found in 18/54 pt. (16 men, 2 women; mean age +/- 1 SD 63.6 +/- 14.5 years). The remaining 36 patients (19 men, 17 women; mean age +/- 1 SD 65.8 +/- 9.8 years), affected by sinus dysfunction alone, were used as controls. No electrophysiological differences between the two groups were found; particularly, an abnormal intrinsic heart rate (according to Jose values) or an abnormal intrinsic corrected sinus node recovery time (greater than 385 msec.) were present in 83% of the patients in both groups. Among sinus dysfunction clinical features, heart rate, presence of spontaneous syncope, sino-atrial block or sinus arrest and organic heart disease were similar in the two groups while the percentage of patients with spontaneous atrial tachyarrhythmias (bradi-tachy syndrome) was significantly smaller (11% vs 44%; p less than 0.01) in carotid sinus hypersensitivity group. In conclusion, in sinus dysfunction patients, the presence of carotid sinus hypersensitivity cannot be used as a criterion to differentiate a subgroup with peculiar clinical and electrophysiological sinus node characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)