Cardiovascular autonomic neuropathy in patients with diabetes mellitus.

Cardiovascular autonomic neuropathy associated with diabetes mellitus is caused by an impairment of the autonomic system. The prevalence of this condition ranges from 20% to 65%, depending on the duration of the diabetes mellitus. Clinically, the autonomic function disorder is associated with resting tachycardia, exercise intolerance, orthostatic hypotension, intraoperative cardiovascular instability, silent myocardial ischemia and increased mortality. For the diagnosis, the integrity of the parasympathetic and sympathetic nervous system is assessed. Parasympathetic activity is examined by measuring heart rate variability in response to deep breathing, standing and the Valsalva manoeuvre. Sympathetic integrity is examined by measuring blood pressure in response to standing and isometric exercise. The treatment includes the metabolic control of diabetes mellitus and of the cardiovascular risk factors. Treating symptoms such as orthostatic hypotension requires special attention.