Investigating Feed-Forward Neural Regulation of Circulation From Analysis of Spontaneous Arterial Pressure and Heart Rate Fluctuations
Legramante, Jacopo M. ; Raimondi, Gianfranco ; Massaro, Michele ; et al. ; - ASI Sponsor
Apr - 1999

journal : Circulation

Issue : 13
type: Article Journal

Abstract
Background--Analysis of spontaneous fluctuations in systolic arterial pressure (SAP) and pulse interval (PI) reveals the occurrence of sequences of consecutive beats characterized by SAP and PI changing in the same (+PI/+SAP and -PI/-SAP) or opposite (-PI/+SAP and +PI/-SAP) direction. Although the former reflects baroreflex regulatory mechanisms, the physiological meaning of -PI/+SAP and +PI/-SAP is unclear. We tested the hypothesis that -PI/+SAP and +PI/-SAP nonbaroreflex sequences represent a phenomenon modulated by the autonomic nervous system reflecting a feed-forward mechanism of cardiovascular regulation. Methods and Results--We studied anesthetized rabbits before and after (1) complete autonomic blockade (guanethidine+propranolol+atropine, n=13; CAB), (2) sympathetic blockade (guanethidine+propranolol, n=15; SB), (3) parasympathetic blockade (atropine, n=16), (4) sinoaortic denervation (n=10; SAD), and (5) controlled respiration (n=10; CR). Nonbaroreflex sequences were defined as [\>=]3 beats in which SAP and PI of the following beat changed in the opposite direction. CAB reduced the number of nonbaroreflex sequences (19.1\+/-\12.3 versus 88.7\+/-\36.6, P<0.05), as did SB (25.3\+/-\11.7 versus 84.6\+/-\23.9, P<0.001) and atropine (11.2\+/-\6.8 versus 94.1\+/-\32.4, P<0.05). SB concomitantly increased baroreflex sensitivity (1.18\+/-\0.11 versus 0.47\+/-\0.09 ms/mm Hg, P<0.01). SAD and CR did not significantly affect their occurrence. Conclusions--These results suggest that nonbaroreflex sequences represent the expression of an integrated, neurally mediated, feed-forward type of short-term cardiovascular regulation able to interact dynamically with the feedback mechanisms of baroreflex origin in the control of heart period.

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