Vagal role and pacemaker indication in hypersensitive carotid sinus reflex.

The effect of carotid sinus pressure (CSP) on sinus rate was studied in 24 patients with sinoatrial pauses below 3 sec (control) and 23 patients with sinoatrial pauses above 3 sec (hypersensitive carotid sinus reflex equal to (HCSR). For registration of P waves, intraatrial electrograms were used. CSP was applied several times before and after atropine. Patients with HCSR showed inconstant response to CSP. The maximal result was considered diagnostic. No difference in the lengths of sinoatrial pauses was found between patients without dizziness or syncopes in the presence of HCSR and patients with dizziness that proved clinically to be based on the existence of HCSR. It was concluded that CSP-induced asystole can serve neither as a differential diagnostic criterion nor as an indication for pacemaker application. Sick sinus syndrome, and thereby dysfunction of the sinus node, were excluded by rapid atrial stimulation. Patients with HCSR showed overall higher age, slower resting heart rate before and after atropine and less atropine response during CSP compared to control. Hypersensitivity of the carotid sinus reflex was interpreted as a part of the physiological augmentation of vagal tone in elderly people.