Postural hypotension enhanced by exercise in patients with chronic autonomic failure.

The effect of supine exercise on blood pressure (BP), measured while recumbent and after head-up postural change, was investigated in three groups with marked postural hypotension due to chronic autonomic failure: 15 with associated neurological impairment (Shy-Drager syndrome, SDS, multiple system atrophy); 15 with pure autonomic failure (PAF) and two with a deficiency of the enzyme dopamine beta hydroxylase (DBH deficiency). Fifteen normal subjects were controls. In controls, exercise increased supine BP, and there was no postural fall before or after exercise. In SDS and PAF, however, exercise produced a substantial fall in BP, which was greater in PAF. In both groups, BP fell to a lower level on standing after than before exercise. In DBH deficiency, there was little change in BP with exercise, but BP fell to a lower level on standing after exercise. In all three groups with autonomic failure, there were more symptoms of postural hypotension on standing after exercise. The influence of exercise on both supine and postural BP, therefore, should be considered in the clinical and laboratory assessment of autonomic dysfunction.