CARDIOVASCULAR AUTONOMIC REFLEXES IN BRAIN INFARCTION

Background and Purpose Increased sympathetic activity is associated wi th cardiovascular complications in stroke, but the role of the parasym pathetic nervous system has not been carefully outlined. In the presen t study our purpose was to assess quantitatively autonomic cardiovascu lar disturbances in brain infarction by measuring cardiovascular auton omic reflexes. Methods We studied the autonomic regulation of cardiova scular functions prospectively in 40 patients with brain infarction (a cute phase, 1 month, and 6 months) and in 55 healthy control subjects by recording heart rate and blood pressure responses to normal and dee p breathing, the Valsalva maneuver, tilting, and isometric work. Resul ts In the acute phase, heart rate responses to normal breathing, deep breathing, the Valsalva maneuver, and tilting were significantly (P<.0 5) impaired in both hemispheric and brain stem infarctions, thus indic ating hypofunction of the parasympathetic nervous system. At 1 month h eart rate responses to normal breathing (brain stem, P<.05), the Valsa lva maneuver (brain stem, P<.01), and tilting (hemispheric, P<.05) wer e still significantly lower than those of the control subjects, but at 6 months significant suppression of the response was found only in ti lting (hemispheric, P<.05). Conclusions These findings suggest that in addition to the previously well-established sympathetic hyperfunction , brain infarction also seems to cause parasympathetic hypofunction, w hich may be involved in cardiovascular and other known manifestations of autonomic failure associated with stroke.