HYPOTENSIVE AND REGIONAL HEMODYNAMIC-EFFECTS OF EXERCISE, FASTED AND AFTER FOOD, IN HUMAN SYMPATHETIC DENERVATION

1. In human sympathetic denervation due to primary autonomic failure, food and exercise in combination may produce a cumulative blood pressu re lowering effect due to simultaneous splanchnic and skeletal muscle dilatation unopposed by corrective cardiovascular reflexes, We studied 12 patients with autonomic failure during and after 9 min of supine e xercise, when fasted and after a liquid meal, Standing blood pressure was also measured before and after exercise. 2. When fasted, blood pre ssure fell during exercise from 162 +/- 7/92 +/- 4 to 129 +/- 9/70 +/- 5 mmHg (mean arterial pressure by 22 +/- 5%), P < 0.0005, After the m eal, blood pressure fell from 159 +/- 8/88 +/- 6 to 129 +/- 6/70 +/- 4 mmHg (mean arterial pressure by 22 +/- 3%), P < 0.0001, and further d uring exercise to 123 +/- 6/61 +/- 3 mmHg (mean arterial pressure by 9 +/- 3%), P < 0.01. The stroke distance-heart rate product, an index o f cardiac output, did not change after the meal, During exercise, chan ges in the stroke distance-heart rate product were greater when fasted . 3. Resting forearm and calf vascular resistance were higher when fas ted, Calf vascular resistance fell further after exercise when fasted, Resting superior mesenteric artery vascular resistance was lower when fed; 0.19 +/- 0.02 compared with 0.32 +/- 0.06, P < 0.05, After exerc ise, superior mesenteric artery vascular resistance had risen by 82%, to 0.53 +/- 0.12, P < 0.05 (fasted) and by 47%, to 0.29 +/- 0.05, P < 0.05 (fed). 4. On standing, absolute levels of blood pressure were hig her when fasted [83 +/- 7/52 +/- 7 compared with 71 +/- 2/41 +/- 3 (fe d), each P < 0.05]. Subjects were more symptomatic on standing post-ex ercise when fed, 5, In human sympathetic denervation, exercise in the fed state lowered blood pressure further than when fasted and worsened symptoms of postural hypotension.