Cardiovascular autonomic neuropathy (CAN) is a common but frequently overlooked complication of diabetes, which can lead to a diverse spectrum of disabling clinical manifestations ranging from mild exercise intolerance to sudden cardiac death. Although traditionally diagnosed using indirect cardiovascular reflex tests, new direct scintigraphic imaging techniques have demonstrated that a cardiac "dysinnervation" can occur early in the course of diabetes, which may have considerable implications for myocardial stability and function. Indeed recent studies have demonstrated that cardiovascular sympathetic tone may be altered very early in the cause of diabetes, and can be associated with altered myocardial blood flow regulation and impaired left ventricular (LV) function. Although convincing evidence has yet to be generated that any therapeutic intervention is capable of reversing CAN complicating diabetes once established, the development and progression of CAN has recently been shown to be sensitive to the simultaneous management of multiple cardiovascular risk factors. This chapter will review the clinical importance of CAN in diabetes, with a particular focus on its impact on the heart.
Key Words: Cardiac; diabetes; neuropathy; imaging; scintigraphy; autonomic. INTRODUCTION
Diabetes is reaching epidemic proportions in many parts of the world with the number of subjects with diabetes expected to double during the next 30 years (1). In concert with the rising prevalence of diabetes, the impact of its chronic complications is expected to have a major impact on health care resources utilization during the same time period. Cardiovascular autonomic neuropathy (CAN) is a common but frequently overlooked complication of diabetes, which can lead to a diverse spectrum of clinical manifestations ranging from impairment of exercise tolerance to sudden cardiac death (2). New scinti-graphic imaging techniques have demonstrated that cardiac dysinnervation can occur early in the course of diabetes and is often asymptomatic, but can rapidly progress with poor metabolic control and result in a complex array of clinical outcomes (3). Although the impact of cardiac dysinnervation on myocardial stability and function remains unclear and somewhat controversial, recent data have highlighted its role in the development of altered myocardial blood flow regulation, impaired left ventricular (LV) function, and potentially in the development of diabetic cardiomyopathy (4-6). Although the sensitivity
From: Contemporary Diabetes: Diabetic Neuropathy: Clinical Management, Second Edition Edited by: A. Veves and R. Malik © Humana Press Inc., Totowa, NJ
of CAN to intensified glycemic control has been inconsistent, the simultaneous management of multiple cardiovascular risk factors in subjects with diabetes appears to have salutary effects in halting its development and progression (7). This chapter will consider the clinical importance of CAN complicating diabetes, with a particular focus on its impact on the heart.
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