Autonomic neuropathy is a serious and common complication of diabetes. In randomly selected cohorts of asymptomatic individuals with diabetes, about 20% had abnormal cardiovascular autonomic function. Reduced heart rate variation is the earliest indicator of cardiovascular autonomic neuropathy. The increased prevalence of painless myocardial infarction in diabetes has been attributed to autonomic neuropathy. Damage to autonomic nerve fibres from the myocardium of patients dying from painless myocardial infarction has recently been reported.
It has been recommended that testing of diabetic individuals for cardiovascular autonomic dysfunction should be part of their standard of care. Noninvasive tests are suitable for routine screening for autonomic dysfunction or for monitoring the progress of autonomic neuropathy. When performed in a carefully controlled manner, the following tests have been validated and shown to be reliable and reproducible: