Muscle sympathetic nerve activity during isometric exercise in patients with cerebrovascular accidents.

Abstract

To define isometric exercise-induced pressor responses in patients with cerebrovascular accidents (CVAs) and to assess potential cardiovascular and sympathetic nervous system abnormalities during isometric exercise in CVA. Nonrandomized study. University laboratory setting. Eight men with CVA who had documented damage of subcortical structures and 8 sex-matched controls. A 2-minute sustained contraction of elbow flexor muscles in the unaffected side at 35% of maximal voluntary contraction (MVC; isometric exercise). Heart rate, arterial blood pressure, and muscle sympathetic nerve activity (MSNA), recorded from the peroneal nerve on the affected side. The percent changes in total MSNA, heart rate, and mean blood pressure in patients with CVA increased during isometric exercise but were attenuated compared with the controls. Total MSNA (mean burst amplitude per minute times burst rate) increased significantly in CVA and control subjects during isometric exercise by 18.7%+/-6.3% and 95.8%+/-25.2%, respectively. The attenuated pressor responses during isometric exercise in subjects with CVA relative to the controls indicated damage to subcortical structures; such damage lowered sympathetic nervous response to isometric exercise. Our findings suggest that isometric exercise at 35% of MVC does not put patients with CVA at risk for serious tachycardia or hypertension.