Cerebral hemodynamics in carotid sinus syndrome and atrioventricular block

Carotid sinus syndrome (CSS) is a cause of syncope due to exaggerated baror eceptor-mediated cardioinhibiiory/vasodepressive reflexes. We sought to det ermine if cerebral hemodynamics and regulation were specifically altered in these patients by comparison with pure asystole without vasodepression in patients with atrioventricular block (AVB), Mean blood flow velocity (trans cranial Doppler sonography) and mean arterial blood pressure (Finapres) wer e recorded during cardioinhibition induced by carotid massage in patients w ith CSS (n = 14, 75 +/- SD 8 years) and asystole induced by temporary pacem aker inhibition in patients with complete AVE (n = 10, 69 +/- 11 years), Ce rebrovascular resistance was estimated by the arterial pressure/cerebral fl ow velocity ratio, and dynamic cerebral autoregulatory responses were deter mined by the rate of regulation and autoregulatory index. Asystole and card ioinhibition each induced a decrease in arterial pressure (CSS 55 +/- 9% vs AVE 40 +/- 14%, p <0.05) and cerebral flow velocity (CSS 66 +/- 19% vs AVE 69 +/- 14%, p = NS), with an initial transient increase in cerebrovascular resistance (CSS 102 +/- 136% vs AVE 128 +/- 92%, p = NS) followed by a dec rease (CSS 38 +/- 12%, AVB 29 +/- 13%, p = NS), The rate of regulation and autoregulatory index were higher with AVE (0.43 +/- 0.20 and 8.5 +/- 1.1 se cond(-1)) than CSS (0.20 +/- 0.12 and 4.8 +/- 1.3 second(-1), respectively, p <0.01 and p <0.001 vs AVE). During asystole and vasodepression, cerebral hypoperfusion in CSS is normally compensated for by cerebral autoregulatio n. The lower rate of regulation in CSS compared with AVE likely results fro m persistent peripheral vasodepression triggered by carotid massage. (C) 20 00 by Excerpta Medico, Inc.