Cardiovascular autonomic neuropathy is the most frequent clinical form of autonomous diabetic neuropathy and appears secondary to cardiac autonomous fibre involvement, actively involved in cardiac rhythm impairment. Type 2 diabetes mellitus patients can present cardiac autonomic neuropathy early in the disease. Autonomous nerve function in DM patients should be assessed as early as the diagnosis is set in order to establish the optimal therapeutic strategy. The most frequent cardio-vagal test used is heart rate variability. An abnormal heart rate variability in the presence of orthostatic arterial hypotension indicates a severe cardiac autonomic neuropathy diagnosis. The development of cardiac autonomic neuropathy is subjected to glycaemic control, duration of the disease and associated risk factors. The glycaemic control is extremely important, especially early in the disease. Therefore, a poor glycaemic control carries unfavourable long-term effects, despite an ulterior optimal control, a phenomenon named “hyperglycaemic memory”. In type 2 diabetes mellitus patients, the association of cardiac autonomic neuropathy with intensive glycaemic control increases the mortality rate, due to the fact, that, secondary to autonomous impairment, the patients do not present the typical symptoms associated with hypoglycaemia. Stratifying the cardiac autonomic neuropathy aids the clinician in assessing the morbidity and mortality risk of diabetes mellitus patients, because it is an independent risk factor for mortality, associated with silent myocardial infarctions and the risk of sudden death.
Objective: The aim of this study was to evaluate the impact of age, diabetes duration, glycaemic control, existence of cardiac autonomic neuropathy (CAN), retinopathy and of macroangiopathy on the peripheral nerve function in patients with type 2 diabetes.
Methods: One hundred forty-nine type 2 diabetes mellitus patients were assessed with peripheral motor and sensory nerve conduction tests and cardiovascular reflex tests, as well as being evaluated for retinopathy, common carotid artery intimal-media-thickness (IMT) and ankle-brachial index (ABI).
Results: The duration of diabetes has the strongest effect in the reduction of the amplitude of motor response in the peroneal nerve and of the sensory amplitude in the sural nerve. The strongest correlations were found between glycaemic control and decreasing motor amplitude in the median nerve and sensory amplitude in the sural nerve, respectively. The motor and sensory nerve action potential amplitudes were significantly affected in the group of patients with CAN. According to multivariate logistic regression analysis, duration of diabetes and presence of CAN were the most important factors that influenced the motor and sensory nerve function.
Conclusion: The presence of CAN together with diabetes duration and poor glycaemic control were associated with impaired peripheral nerve function, while macroangiopathy does not seem to be associated with the impairment of these electrophysiological parameters.