Prevalence and Predictors of Ischemia and Outcomes in Outpatients With Diabetes Mellitus Referred for Single-Photon Emission Computed Tomography Myocardial Perfusion Imaging

Abstract

Background— The prevalence of ischemia and its prediction of events are unclear in outpatients with diabetes mellitus in the modern era of intensive medical management. We sought to identify the prevalence of ischemia, subsequent cardiac events, and impact of sex, stress type, and symptom status on these findings in a cohort of stable outpatients with diabetes mellitus referred for single-photon emission computed tomography myocardial perfusion imaging (MPI). Methods and Results— The study cohort included 575 consecutive outpatients with diabetes mellitus who underwent quantitative, gated single-photon emission computed tomography MPI. Clinical information, stress MPI variables, and cardiac events were prospectively collected and analyzed. The study population was at intermediate risk of coronary artery disease or had known coronary artery disease (40.3%); 29% of patients were asymptomatic at the time of stress testing. Scintigraphic ischemia and significant (≥10%) left ventricular ischemia were present in 126 patients (21.9%) and 29 patients (5.0%), respectively, and <1% of patients had early revascularization. The risk of ischemia was increased >2-fold by male sex ( P <0.001), but was not impacted by pharmacological stress ( P =0.15) or presence of symptoms ( P =0.89). During a median 4.4 years follow-up, the rate of cardiac death/nonfatal myocardial infarction was moderate at 2.6%/y (cardiac death 0.8%/y) in the total cohort, but was 5.7%/y in those with ischemia ( P <0.001). Pharmacological stress predicted a higher cardiac event rate ( P <0.001) but symptoms did not ( P =0.55). Conclusions— This cohort of stable outpatients with diabetes mellitus referred for single-photon emission computed tomography had low rates of significant ischemia and early revascularization; an initially low cardiac event rate increased after 2 years. Independent predictors of cardiac death/nonfatal myocardial infarction were known coronary artery disease, pharmacological stress, and MPI ischemia. Nearly one third of those with events had a normal MPI, indicating a need for improved risk stratification.