Diabetic Cardiovascular Autonomic Neuropathy
One of the most overlooked of all serious complications of diabetes is cardiovascular autonomic neuropathy (CAN),1–3 which encompasses damage to the autonomic nerve fibers that innervate the heart and blood vessels, resulting in abnormalities in heart rate control and vascular dynamics.4
The present report discusses the clinical manifestations (eg, resting tachycardia, orthostasis, exercise intolerance, intraoperative cardiovascular liability, silent myocardial infarction [MI], and increased risk of mortality) in the presence of CAN. It also demonstrates that autonomic dysfunction can affect daily activities of individuals with diabetes and may invoke potentially life-threatening outcomes. Advances in technology, built on decades of research and clinical testing, now make it possible to objectively identify early stages of CAN with the use of careful measurement of autonomic function and to provide therapeutic choices that are based on symptom control and that might abrogate the underlying disorder.
Epidemiology of CAN
Little information exists as to frequency of CAN in representative diabetic populations. This is further complicated by the differences in the methodology used and the lack of standardization. Fifteen studies using different end points report prevalence rates of 1% to 90%.1 The heterogenous methodology makes it difficult to compare epidemiology across different studies. CAN may be present at diagnosis, and prevalence increases with age, duration of diabetes, and poor glycemic control. CAN also cosegregates with distal symmetric polyneuropathy, microangiopathy, and macroangiopathy. Age, diabetes, obesity, and smoking are risk factors for reduced heart rate variability (HRV)5 in type 2 diabetes. Thus, there may be selectivity and sex-related differences among the various cardiovascular risk factors as to their influence on autonomic dysfunction.6 HbA1c, hypertension, distal symmetrical polyneuropathy, retinopathy, and exposure to hyperglycemia were shown to be risk factors for developing CAN in type 1 diabetes.7
Clinical Manifestations of CAN
Whereas abnormalities in HRV are early findings of CAN, resting tachycardia …