Assessment of the Vasodepressor Reflex in Carotid Sinus Syndrome

Background Assessment of the vasodepressor reflex in carotid sinus syndrome is influenced by the method of execution of the carotid sinus massage and the coexistence of the cardioinhibitory reflex. Methods and Results Carotid sinus massage reproduced spontaneous symptoms in 164 patients in the presence of hypotension or bradycardia (method of symptoms). When an asystolic pause was induced, the vasodepressor reflex was reassessed after suppression of the asystolic reflex by means of 0.02 mg/kg IV atropine. An isolated vasodepressor form was found in 32 (20%) patients, who had lowest systolic blood pressure (SBP) of 6515 mm Hg. Of these, only 21 (66%) patients had an SBP fall 50 mm Hg, which is the universally accepted cut-off value for the diagnosis of the vasodepressor form. Conversely, a lowest SBP value of 85 mm Hg (corresponding to the fifth percentile) detected 97% of vasodepressor patients, but was also present in 84% of the 132 patients with an asystolic reflex. These latter patients had both asystole 3 s (mean 7.6 +/- 2.2 s) and SBP fall to 63 +/- 22 mm Hg: in 46 (28%) patients, symptoms persisted after atropine (mixed form), in the remaining 86 (52%) patients, symptoms did not (cardioinhibitory form) persist. Conclusions The current definition of 50 mm Hg SBP fall failed to identify one third of patients with isolated vasodepressor form. A cut-off value of symptomatic SBP of 85 mm Hg seems more appropriate, but it is unable to identify cardioinhibitory forms. In asystolic forms, atropine testing is able to distinguish a cardioinhibitory form from a mixed form.