Screening asymptomatic patients with type 2 diabetes: The debates persist

Journal of Nuclear Cardiology, Sep 2015

George A. Beller, Jamieson M. Bourque

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Screening asymptomatic patients with type 2 diabetes: The debates persist

Received Aug Screening asymptomatic patients with type 2 diabetes: The debates persist George A. Beller 0 1 Jamieson M. Bourque 0 MHS 0 1 0 Reprint requests: Jamieson M. Bourque MD, MHS, Division of Cardi- ovascular Medicine, Department of Medicine, University of Virginia Health System , Charlottesville, VA 1 Cardiovascular Division, Department of Medicine, University of Virginia Health System , Charlottesville, VA - During the past decade considerable discussion and debate pertaining to the clinical value and cost-effectiveness of imaging asymptomatic patients with Type 2 diabetes to detect functionally important coronary artery disease (CAD) have transpired. The controversy continues with two articles published in this issue of the Journal of Nuclear Cardiology. Petretta et al1 take the ‘‘Pro’’ position, whereas, Gibbons2 takes the ‘‘Con’’ position in this ongoing debate. These authors cite recent published clinical research studies to bolster their points of view. The rationale for screening Type 2 diabetic patients for CAD stems from data indicating that CAD is the leading cause of mortality in these patients, accounting for 65% to 70% of deaths.3 Furthermore, these data showed that diabetes was associated with a 2 to 4 fold increased prevalence of CAD, and an increased risk of dying from CAD, compared to nondiabetic patients.4,5 Other data supported the notion that patients with diabetes without a prior myocardial infarction (MI) had the same risk of coronary events as patients without diabetes and a prior MI.6 This led to the concept of diabetes as a coronary risk equivalent, which required more aggressive primary prevention measures such as statin therapy to reduce LDL cholesterol to below 100 mg/dl. Since stress perfusion imaging was successful in separating high and low risk subsets of symptomatic patients, it was thought that if diabetes is a CAD equivalent, should not asymptomatic diabetic patients also undergo imaging to detect CAD and improve outcomes? The concept of CAD risk equivalency has been recently questioned following the report of a meta-analysis7 comprising more than 45,000 patients followed for a mean of 13.4 years. This analysis showed, contrary to the existing paradigm, that patients with diabetes and no prior MI had actually a 43% lower risk of future CAD events compared with patients without diabetes and a prior MI. This finding and the observation that one-third of asymptomatic diabetic patients have no evidence of coronary atherosclerosis by CTA or CAC scoring8 have led to movement away from considering Type 2 diabetes as a CAD equivalent. It should be noted that published studies reporting the percentage of asymptomatic Type 2 diabetic patients that have significant CAD have patient populations with substantial differences in clinical risk profiles. Some of these diabetic patient populations, despite being asymptomatic at the time of imaging, have a significant number of patients with either known CAD, peripheral vascular disease, renal disease, or an abnormal resting ECG. These may have been symptomatic in the past and even may have had a prior MI or revascularization. For example, in the Mayo Clinic cohort of asymptomatic diabetic patients, 50% were referred for preoperative risk assessment, 43% had ECG Q-waves and 28% had peripheral vascular disease.9 In contrast, other asymptomatic patient cohorts in published studies were at lower clinical risk, with no prior history of CAD, no prior symptoms consistent with CAD, and a normal resting electrocardiogram. An example of this type of population is the DIAD study10 which excluded patients with a history of CAD or those with an abnormal resting ECG. Both types of asymptomatic diabetic patient cohorts are included in screening studies, although the probability of detecting CAD, and determining an increased risk for future cardiac events, are higher in the former. This should be kept in mind when reviewing reports either supporting or negating the concept of screening for CAD in diabetic patients. Other issues regarding the value of screening raised by Dr. Gibbons in his argument against routine screening of asymptomatic patients is whether it provides incremental prognostic information to traditional CAD risk factors, and whether it will lead to changes in treatment that improves outcomes compared to standard guideline medical therapy and other primary prevention measures (e.g., invasive strategies for silent ischemia, even greater reduction of LDL cholesterol, etc.). To our knowledge, these benefits of screening have not yet been demonstrated. Certainly, knowledge of presence of occult coronary atherosclerosis or significant CAD found by screening might lead to better compliance with medical therapy, and better outcomes. This also has not been definitively demonstrated. It has been observed that the prevalence of high-risk CAD and ischemia on stress imaging in diabetic patients may be decreasing, presumably because of b (...truncated)


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George A. Beller, Jamieson M. Bourque. Screening asymptomatic patients with type 2 diabetes: The debates persist, Journal of Nuclear Cardiology, 2015, pp. 1233-1236, Volume 22, Issue 6, DOI: 10.1007/s12350-015-0283-4