Cardiovascular disease (CVD) is the leading cause of mortality and morbidity among patients with type 1 and type 2 diabetes. Adults with diabetes have heart disease death rates two to four times higher than adults without diabetes.1 According to the Centers for Disease Control and Prevention, the prevalence of diabetes has increased from 4.9% in 1990 to 6.9% in 1999 and 7.8% in 2007. The increase in the number of cases of diabetes has closely paralleled the changes in the incidence of obesity and the aging of the population.
The complications of diabetes have a considerable impact on patient survival and quality of life, especially with respect to CVD. Several forms of CVD have increased in diabetes. The overall prevalence of coronary artery disease (CAD) has been estimated to be as high as 55% in diabetic patients vs. <4% in the general population. Diabetes mellitus has added another new dimension to the usual risk factors of CAD.2 Approximately up to 25% of patients referred for either percutaneous or surgical revascularization procedures have diabetes. Because CAD risk can be modified by intervention, it is important not to underestimate the impact of diabetes in the development of CAD, as these patients may benefit by appropriate screening and aggressive intervention.
CAD in diabetics, in addition to the more frequent occurrence, has some important characteristics. Myocardial ischemia is frequently silent or asymptomatic in these patients3 and vascular disease is more diffuse and accelerated.2 Furthermore, the outcome of diabetic patients after a cardiac event is worse than in comparable non-diabetic patients. Following acute myocardial infarction (MI), both in-hospital and 1-year mortality are twice that of non-diabetic patients with or without primary coronary intervention.4
Patients with type 2 diabetes usually have other associated risk factors such as hypertension or hyperlipidemia. Diabetic patients with hyperlipidemia have significantly higher event rates than non-diabetic patients at the same cholesterol levels. This further increases their cardiovascular risk. Diabetic women have increased risk of cardiovascular death up to 7.5 times that of women without diabetes and they lose the premenopausal protection seen in their healthy counterparts.5,6 Diabetic patients suffering from MI have a higher chance of dying from their event or from subsequent heart failure. Thrombolytic therapy may be less beneficial in diabetic patients7 and surgical and percutaneous revascularization is associated with greater long-term mortality in diabetic patients.8
The increased incidence of CVD as well as worse prognosis for diabetic patients makes early diagnosis of CAD and risk stratification essential to improve the prognosis in this high-risk population. This chapter will discuss the evaluation of CAD in diabetic patients with emphasis on non-invasive imaging.
DIAGNOSIS OF CAD IN DIABETIC PATIENTS
Diabetes has been established as an important risk factor for CAD. The American Diabetes Association (ADA) recommends assessment for CVD risk factors (dyslipidemia, hypertension, smoking, positive family history of premature CAD, and presence of micro- or macroalbuminuria) ...