CARDIOVASCULAR AUTONOMIC REFLEXES IN BRAIN INFARCTION

Background and Purpose Increased sympathetic activity is associated with cardiovascular complications in stroke, but the role of the parasympathetic nervous system has not been carefully outlined. In the present study our purpose was to assess quantitatively autonomic cardiovascular disturbances in brain infarction by measuring cardiovascular autonomic reflexes. Methods We studied the autonomic regulation of cardiovascular functions prospectively in 40 patients with brain infarction (acute phase, 1 month, and 6 months) and in 55 healthy control subjects by recording heart rate and blood pressure responses to normal and deep breathing, the Valsalva maneuver, tilting, and isometric work. Results In the acute phase, heart rate responses to normal breathing, deep breathing, the Valsalva maneuver, and tilting were significantly (P<.05) impaired in both hemispheric and brain stem infarctions, thus indicating hypofunction of the parasympathetic nervous system. At 1 month heart rate responses to normal breathing (brain stem, P<.05), the Valsalva maneuver (brain stem, P<.01), and tilting (hemispheric, P<.05) were still significantly lower than those of the control subjects, but at 6 months significant suppression of the response was found only in tilting (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, which may be involved in cardiovascular and other known manifestations of autonomic failure associated with stroke.