Mortality in Diabetic Patients with Cardiovascular Autonomic Neuropathy

Cardiovascular autonomic diabetic neuropathy (CADN) may carry an increased risk of mortality. However, in previous studies the prognosis of patients with CADN seemed to be influenced by life‐threatening macro‐ and microvascular complications which had already been present at the start of the study period. Between 1981 and 1983, 1015 diabetic patients have been examined for CADN (abnormal heart rate variation at rest and during deep respiration) at the Diabetes Research Institute, Düsseldorf. Thirty‐five patients (28 with Type 1 diabetes, 7 with Type 2 diabetes) with CADN have been retrospectively recruited and reviewed 8 years later and compared with 35 patients without CADN who were matched for sex, age, and duration of diabetes. Exclusion criteria for entry into the study included severe micro‐ or macrovascular complications, such as proliferative retinopathy, proteinuria or symptomatic coronary artery disease. During the 8‐year observation period, 8 patients with CADN and 1 patient without CADN died. The survival rate estimates steadily declined in patients with CADN over the whole period studied. The 8‐year survival rate estimate in patients with CADN was 77 % compared with 97 % in those with normal autonomic function (p < 0.05). Deaths were mainly due to macrovascular diseases (n = 3) and sudden unexpected deaths (n = 3). One patient with CADN died after an episode of severe hypoglycaemia. Among the deceased patients, coefficient of variation of R‐R intervals during deep breathing was significantly reduced when compared with those who survived (1.04 ± 0.5 % vs 1.87 ± 1.0 %; p < 0.05), and symptoms of autonomic neuropathy (orthostatic hypotension, gastroparesis, gustatory sweating) were more frequent (7/8 vs 10/27 patients). The mean QTc interval was not different between the groups. These results suggest a relatively poor prognosis of patients with CADN in the absence of clinically detectable micro‐ and macrovascular complications.