Determinants of carotid sinus hypersensitivity in patients with suspected reflex syncope

To elucidate the pathophysiology of the carotid sinus reflex in a large cohort of patients with suspected reflex syncope.

We reviewed an electronic database of patients with suspected reflex syncope who underwent carotid sinus massage. The diagnostic protocol included both right and left massage, in supine and upright positions, followed by tilt testing.

The cohort included 2249 patients (52% male), median age 73 years. The conventional abnormality threshold of a maximum RR interval ≥ 3000 ms was present in 14.7% of patients and of a systolic blood pressure fall > 50 mmHg in 14.3% of patients. Abnormal responses occurred more frequently on the right side than the left side, and more during upright than supine testing. A second abnormal test occurred more often ipsilaterally. The extent of the maximum RR interval elicited by massage was independent of the baseline RR interval, whereas the difference in systolic blood pressure fall increased markedly with higher baseline values. The occurrence and severity of cardioinhibition and vasodepression increased with age, beginning at 40 years. Abnormal RR intervals and blood pressure drops were observed more frequently in men than in women. Additionally, there was only a limited correlation between positive responses to carotid massage and tilt testing concerning asystole and blood pressure reduction.

Age, sex and initial systolic blood pressure strongly influence response to carotid sinus massage. Abnormal responses did not correlate with positive tilt test results, possibly as a result of opposing effects of age and sex on carotid sinus hypersensitivity and vasovagal syncope.