Microvascular complications and cardiac autonomic dysfunction in patients with diabetes mellitus type 1

BACKGROUND: The presence of cardiac autonomic neuropathy (CAN) in patients with diabetes mellitus (DM) is associated with increased mortality and chronic microvascular complications of diabetes. OBJECTIVE: To investigate a possible association between specific findings of CAN during exercise testing (ET) and nephropathy and retinopathy in patients with type 1 DM. METHODS: We conducted a cross-sectional study of 84 patients with type 1 DM. All patients underwent clinical laboratory evaluation and performed ET, and those who presented findings suggesting myocardial ischemia were excluded from data analysis (n = 3). The assessment of microvascular complications (retinopathy and nephropathy) was performed in the sample. RESULTS: Patients with nephropathy and those with retinopathy achieved a lower heart rate (HR) at peak exercise (HR max) and smaller increase in HR in relation to rest (Peak ΔHR) compared with those without these complications. These patients also had a smaller reduction in HR in the second and 4th minutes after the end of the test (ΔHR recovery 2 and 4 minutes). After performing a multivariate analysis with control for possible confounding factors, the ΔHR recovery in two and four minutes, maximum HR and Peak ΔHR remained significantly associated with retinopathy; and ΔHR recovery in the second and 4th minutes remained associated with the presence of nephropathy. CONCLUSION: The ET can be considered an additional tool for early detection of CAN and to identify patients at increased risk for microvascular complications of diabetes.