The value of cardiovascular autonomic function tests: 10 years experience in diabetes

Five simple, noninvasive cardiovascular reflex tests have been used to assess autonomic function in one center over the past 10 yr. Seven hundred seventy-four diabetic subjects were tested for diagnostic and research purposes. In 543 subjects completing all five tests, abnormalities of heart rate tests occurred in 40%, while abnormal blood pressure tests occurred in less than 20%. Their results were grouped as normal (39%), early (15%), definite (18%), and severe (22%) involvement. Six percent had an atypical pattern of results. Two hundred thirty-seven diabetic subjects had the tests repeated greater than or equal to 3 mo apart: 26% worsened, 71% were unchanged, and only 3% improved. The worsening followed a sequential pattern with first heart rate and later additional blood pressure abnormalities. Comparison between a single test (heart rate response to deep breathing) and the full battery in 360 subjects showed that one test alone does not distinguish the degree or severity of autonomic damage. These tests provide a useful framework to assess autonomic neuropathy simply, quickly, and noninvasively.