Duration and type of therapy for diabetes: Impact on cardiac risk stratification with stress electrocardiographic-gated SPECT myocardial perfusion imaging

Abstract

Background

Stress electrocardiogram(ECG)-gated single photon emission computed tomography (SPECT) imaging is highly effective in risk stratification of diabetic patients for adverse cardiac events. While patients with diabetes are predisposed to a more aggressive progression of vascular disease, the impact of its duration and type of therapy on risk stratification are unknown.

Methods

From the Hartford Hospital Nuclear Cardiology clinical database, 886 diabetic patients who underwent exercise or pharmacologic stress ECG-gated SPECT were identified, with complete follow-up regarding the occurrence of adverse cardiac events and information regarding the duration of diabetes and the type of therapy (insulin vs oral medication only) at the time of testing. Images were interpreted using the American College of Cardiology/ASNC standard 17-segment scoring model.

Results

Of the 886 diabetic patients, 98 (11%) suffered cardiac death or non-fatal myocardial infarction during follow-up (2.5 ± 1.6 years). A receiver operator characteristics curve demonstrated that diabetes ≥10 years in duration provided the maximal sum of sensitivity and specificity for the prediction of adverse cardiac outcomes. Multivariate analysis identified the following as independent predictors of adverse outcome: Post-stress ejection fraction (EF) <40% (P = .001), age (P = .004), insulin therapy (P = .031), diabetes duration >10 years (P = .038), summed stress score (SSS) >8 (P = .046). For patients with an SSS >8, diabetes duration and type of therapy significantly enhanced risk stratification. Similar findings emerged for patients with a post-stress EF <40%.

Conclusion

For diabetic patients undergoing stress ECG-gated SPECT myocardial perfusion imaging, disease duration and type of therapy provide independent and incremental prognostic information. Integration of these variables with this cardiovascular imaging technology significantly enhances cardiac risk stratification.

Introduction

The incidence of diabetes mellitus (DM) in the United States and throughout the world is increasing at a high rate. The Centers of Disease Control and Prevention estimated the prevalence of diagnosed and undiagnosed diabetes in the United States in 2007 to be 23.6 million people (7.8% of the population).¹ Moreover, diabetes confers a two to fourfold increase risk for the development of cardiovascular disease. Compared to non-diabetics, diabetics are predisposed to an aggressive form of vascular disease, with diffuse coronary atherosclerotic involvement and more rapid progression of the disease.²

Previous studies have demonstrated that myocardial perfusion imaging (MPI) with single photon emission computed tomography (SPECT) is a reliable modality for the detection of coronary artery disease (CAD) as well as risk stratification for adverse cardiac events. The size and severity of the perfusion abnormality is important in predicting adverse outcome.³ It has been shown that stress electrocardiogram (ECG)-gated SPECT MPI has comparable ability for the diagnosis and prognosis of CAD in diabetic and non-diabetic patients.4, 5, 6 For diabetic patients, the duration of the disease as well as the type of therapy for its management are important considerations and may affect patient outcomes.7, 8, 9, 10 To our knowledge, the prognostic contribution of these factors in relation to stress ECG-gated SPECT findings in a clinically referred patient population has not been reported. Therefore, the purpose of this study was to determine the impact of diabetes duration and type of therapy (insulin vs oral medications only) for its management on the prognostic value of stress ECG-gated SPECT MPI, regarding the subsequent occurrence of non-fatal myocardial infarction (MI) or cardiac death.