Haemodynamic changes during graded exercise in patients with diabetic autonomic neuropathy.

Abstract

Haemodynamic variables were measured during supine rest and during ergometer cycle exercise at two work loads (50 W and 100 W) in normal subjects (n = 7), in insulin-dependent diabetic subjects without neuropathy (n = 8), in insulin-dependent diabetic subjects with slight autonomic neuropathy (decreased beat-to-beat variation in heart rate, which is considered due to a cardiac parasympathetic defect; n = 8), and in insulin-dependent diabetic subjects with severe autonomic neuropathy, including orthostatic hypotension (n = 7). Compared with normal subjects, cardiac stroke volume was lower in the diabetic subjects with autonomic neuropathy, both at rest and during exercise (p < 0.025), whereas intermediate values were found in the diabetic subjects without neuropathy. The increase in cardiac output in response to exercise was smaller (p < 0.05) in both diabetic groups with autonomic neuropathy compared with the normal and diabetic subjects without autonomic neuropathy. The increase in hepato-splanchnic vascular resistance was smaller in the diabetic subjects with severe autonomic neuropathy than in the normal subjects and the diabetic subjects without autonomic neuropathy (p < 0.025), whereas intermediate values were found in the diabetic subjects with slight autonomic neuropathy. We conclude that, in diabetic patients with severe autonomic neuropathy, the responses of the heart and the splanchnic resistance vessels to exercise are impaired. While sympathetic neuropathy may be responsible for impaired function of splanchnic resistance vessels, both cardiac sympathetic neuropathy and diabetic cardiomyopathy may be involved in the impaired cardiac response to exercise in diabetic subjects with autonomic neuropathy.