[Cardiac autonomic neuropathy in the diabetic patient]

The importance of cardiac autonomic neuropathy (CAN) derives from its remarkable frequency and its clinical impact. The clinical features are postural hypotension and resting tachycardia, these abnormalities may be overlooked in a high number of patients asymptomatic. Although rarely life threatening, CAN causes considerable morbidity, which can be ameliorated by its identification and appropriate treatment. Circulatory reflexes were studied in 48 diabetic patients and 14 normal control subjects. Twenty-six of the diabetic patients had normal response. The remaining 22 had evidence of neuropathy and abnormal cardiac response during these tests. Only one patient had postural syncope but he had severe orthostatic hypotension. The others remained asymptomatic. All the control subjects had normal reflexes. Beat-to-beat variation with deep breathing (sinus arrhythmia), carotid body massage and mental stress, were important for the detection of CAN (86, 90 and 90% sensitivity respectively). The Valsalva maneuver and sinus arrhythmia showed 82 and 92% of specificity for the diagnosis of CAN. Our findings suggest that CAN in diabetic patients can be detected by these relatively simple test. We propose a rational approach to the diagnosis. Our method is applicable as a clinical routine examination for cardiac neuropathy.