Screening for Coronary Artery Disease in Asymptomatic Diabetic Patients
Screening for Coronary Artery Disease in Asymptomatic Diabetic Patients
European Cardiovascular Disease 2007
Published: June 2007
Published: June 2007
Diabetes is an important risk factor for coronary artery disease (CAD) as reflected by the four-fold greater incidence of CAD in diabetic patients compared with the general population.1 Cardiovascular death is the most common cause of mortality in the type 2 diabetic population and, once diagnosed with CAD, patients with diabetes have a considerably poorer prognosis than their non-diabetic counterparts. Accordingly, early detection of CAD in patients with diabetes may be of paramount importance and could improve outcome substantially. However, a complicating issue is the silent progression of CAD in patients with diabetes. Consequently, the disease is frequently already in an advanced state when it becomes clinically manifest.2 In addition, recent studies have indicated that conventional coronary risk factors are of limited value for detection of CAD in asymptomatic type 2 diabetes patients.3,4 These observations have raised the question of whether or not asymptomatic patients with diabetes should be screened for CAD.
Issues in Screening
To determine whether or not it is appropriate to screen asymptomatic individuals, several questions should be addressed. First, the prevalence of CAD in the population should be high enough to justify testing for the disease. A relatively low prevalence will result in a relatively high percentage of false-positive test results, leading to unnecessary further testing. On the other hand, if the prevalence is too high, testing will not be effective and will result in a high number of false-negative results. Second, the proposed test should have sufficient accuracy and should allow accurate distinction between low-risk and high-risk patients. In addition, the proposed screening strategy should be cost-effective. Finally, the test results should have consequences for individual patient management and should lead to improved outcome.
The Prevalence of Coronary Artery Disease
To date, data on the prevalence of CAD in patients with diabetes are still limited and only a small number of studies have prospectively addressed this clinical question. Recently, results from the Detection of Silent Myocardial Ischaemia in Asymptomatic Diabetics (DIAD) study were published.4 In this study by Wackers et al., the prevalence of silent ischaemia was evaluated in 522 asymptomatic patients with two or more risk factors, using gated technetium-99m sestamibi single photon emission computed tomography (SPECT) imaging. The authors noted a relatively high percentage (22%) of abnormal myocardial perfusion studies. Moreover, in 40% of patients with abnormal SPECT, the perfusion defect involved more than 5% of the left ventricular myocardial tissue. The fact that conventional risk factor assessment was not predictive of abnormalities during SPECT imaging was of particular interest. Zellweger et al. studied 1,737 patients with diabetes, of whom 826 were asymptomatic – a prevalence of 39% abnormal SPECT studies was observed.5 Considerably higher values of abnormal studies were reported by Sconamiglio and colleagues, who evaluated myocardial perfusion with myocardial contrast echocardiography in 1,899 asymptomatic diabetic patients.3 Overall, the prevalence of abnormal studies was 60%, and this percentage was comparable between patients with or without three or more risk factors. Thus, the current literature shows a wide variation in the prevalence of silent ischaemia, which could be (partially) attributed to differences in patient characteristics, study design and inclusion criteria.
References:
- http://www.diabetes.org/diabetes-statistics/prevalence.jsp. Accessed 28 August 2006.
- Nesto RW, Phillips RT, Kett KG, et al., Angina and exertional myocardial ischemia in diabetic and nondiabetic patients: assessment by exercise thallium scintigraphy, Ann Intern Med, 1988;108:170–75.
- Scognamiglio R, Negut C, Ramondo A, et al., Detection of coronary artery disease in asymptomatic patients with type 2 diabetes mellitus, J Am Coll Cardiol, 2006;47:65–71.
- Wackers FJ, Young LH, Inzucchi SE, et al., Detection of silent myocardial ischemia in asymptomatic diabetic subjects: the DIAD study, Diab Care, 2004;27:1954–61.
- Zellweger MJ, Hachamovitch R, Kang X, et al., Prognostic relevance of symptoms versus objective evidence of coronary artery disease in diabetic patients, Eur Heart J, 2004;25: 543–50.
- Rajagopalan N, Miller TD, Hodge DO, et al., Identifying highrisk asymptomatic diabetic patients who are candidates for screening stress single-photon emission computed tomography imaging, J Am Coll Cardiol, 2005;45:43–9.
- De Lorenzo A, Lima RS, Siqueira-Filho AG, et al., Prevalence and prognostic value of perfusion defects detected by stress technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography in asymptomatic patients with diabetes mellitus and no known coronary artery disease, Am J Cardiol, 2002;90:827–32.
- Anand DV, Lim E, Lahiri A, et al., The role of non-invasive imaging in the risk stratification of asymptomatic diabetic subjects, Eur Heart J, 2006;27:905–12.
- Anand DV, Lim E, Hopkins D, et al., Risk stratification in uncomplicated type 2 diabetes: prospective evaluation of the combined use of coronary artery calcium imaging and selective myocardial perfusion scintigraphy, Eur Heart J, 2006;27: 713–21.
- Scholte AJ, Bax JJ, Wackers FJ, Screening of asymptomatic patients with type 2 diabetes mellitus for silent coronary artery disease: combined use of stress myocardial perfusion imaging and coronary calcium scoring, J Nucl Cardiol, 2006;13:11–18.
- Sorajja P, Chareonthaitawee P, Rajagopalan N, et al., Improved survival in asymptomatic diabetic patients with high-risk SPECT imaging treated with coronary artery bypass grafting, Circulation, 2006;112:I311–16.
