Evaluation of sinus and atrioventricular nodes function in patients with vasovagal syncope

Evaluation of sinus and atrioventricular nodes function as a potential factor responsible for prolonged bradycardia, asystole, or both in patients with cardioinhibitory and non-cardioinhibitory vasovagal syncope (VVS). The study included 258 patients (mean age = 47.7 +/- 17.2 years; range 18-62; 147 females) with a history of VVS. They were divided among four groups, according to results of head-up tilt test (HUTT).

All patients underwent standard HUTT, carotid sinus massage (CSM), and rapid transesophageal atrial pacing for evaluation of total sinus node recovery time (SNRT), and corrected sinus node recovery time (CNRT), resting and intrinsic heart rate (IHR), and Wenckebach point (WP). Values of SNRT > 1,500 ms, CNRT > 525 ms, WP < 130 bpm, and CSM-induced pause >3 seconds were considered abnormal.

SNRT, CNRT, and WP before and after pharmacological blockade, resting heart rate, and IHR did not differ significantly among the study groups. The prevalence of mild sinus node dysfunction (SND), decreased value of WP, and cardioinhibitory carotid sinus hypersensitivity was similar among all study groups.

The prevalence of mild SND, abnormal atrioventricular conduction, and carotid sinus hypersensitivity (CSH) was similar among patients with VVS regardless of the type of vasovagal reaction. SND and CSH do not seem to play an important role in the pathogenesis of cardioinhibitory vasovagal reaction.