Risk stratification in diabetes: Not all patients or perfusion defects are the same

Abstract

The management of cardiovascular disease in diabetes remains one of the major challenges in contemporary cardiology. In patients without symptomatic or previously documented coronary artery disease (CAD), there is a substantial concern for undetected asymptomatic ischemia and the risk for developing unheralded myocardial infarction or sudden cardiac death. When symptomatic CAD is present, there is an even greater concern, because of the potential for advanced atherosclerosis, which carries a very high risk for adverse cardiac outcomes. In epidemiological studies, it is recognized that the cardiovascular risk of diabetes is related to the duration of diabetes and whether it requires insulin for glycemic control. In clinical studies, these factors also play into the prognosis of diabetic patients with acute myocardial infarction or those undergoing coronary intervention or bypass surgery. Barmpouletos et al herein present the results of a retrospective analysis, suggesting that simple clinical features improve the risk stratification conferred by stress myocardial perfusion imaging in patients with diabetes. These results are potentially highly relevant to the interpretation of test results by nuclear cardiologists. The authors examined the outcomes of 886 diabetic patients studied in a single center for evaluation of suspected or known CAD. Their outcome analysis focused on ‘‘hard events,’’ specifically including only non-fatal myocardial infarction and cardiac death. During an average follow-up of 2.5 years, 65 patients (7.3%) suffered cardiac death and 33 (3.7%) non-fatal MI, indicating a relatively high-risk cohort overall. The study group was fairly typical of a referral population of diabetic patients with known or suspected CAD. Their average age was 61 years, their duration of diabetes averaged 13.2 years, and half were women. Unfortunately, more detailed information on their diabetes was limited because of the retrospective nature of the study. Potentially informative would have been Hgb A1C levels and the presence of microalbuminuria, renal insufficiency, and diabetic neuropathy. It is worth noting that an additional 109 patients who were not taking diabetes medications were excluded, because of the authors’ concern that they might be either non-compliant or erroneously diagnosed. This exclusion resulted in a somewhat higher proportion of insulin-treated patients (55%) than otherwise might have been anticipated. On myocardial perfusion imaging, important predictors of adverse cardiac events not surprisingly included summed stress scores (SSSs) [8 (present in 192 patients) and gated stress LV ejection fraction \40% (present in 115 patients). However, the authors found that age, insulin therapy, and diabetes duration [10 years were also independent predictors of cardiac risk. The latter two features are noteworthy in that they are easily obtained in the patient’s history and appeared to have an important role in stratifying patients, particularly those with high-risk perfusion abnormalities. Specifically, patients with SSS [8 and diabetes duration B10 years vs[10 years had significantly lower annual event rates, 4.3% vs 11%. Those with SSS[8 on oral hypoglycemic agents alone vs those on insulin also had significantly lower annual event rates, 3.9% vs 11.2%. Similar findings were seen when patients with stress LVEF \40% and diabetes duration B10 years vs [10 years were compared, with annual event rates of 4.3% vs 14%. The lowest event rates in patients with high-risk perfusion findings were in those with diabetes duration B10 years who were also on oral hypoglycemic agents alone. Although only 40 subjects (21%) of those with SSS[8 fell into this category, there were only three events so that the average annual event rate was just over 2%, rather remarkable for a group of symptomatic patients with moderate-large defects. Similar results were found for patients with an LVEF 40% who had shorter durations of diabetes and did not require insulin. Conversely, patients with high-risk perfusion abnormalities or low post-test LVEF, and both long duration From the Section of Cardiovascular Medicine, Yale University School of Medicine, New Haven, CT. Reprint requests: Lawrence H. Young, MD, Section of Cardiovascular Medicine, Yale University School of Medicine, New Haven, CT 06520; lawrence.young@yale.edu. J Nucl Cardiol 2010;17:990–2. 1071-3581/$34.00 Copyright 2010 American Society of Nuclear Cardiology. doi:10.1007/s12350-010-9306-3