Perfusion Defects Have Larger Prognostic Impact in People with Diabetes

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Among patients with even minimal perfusion defects on quantitative single-photon emission computerized tomography (SPECT), the impact on risk of major adverse cardiovascular events (MACE) is significantly higher in those with diabetes, reports a study in Diabetes Care.

Data were drawn from the international, observational REgistry of Fast Myocardial Perfusion Imaging with NExt generation SPECT (REFINE SPECT) study. In that study, patients with known or suspected coronary artery disease underwent quantitative myocardial perfusion imaging using cadmium zinc telluride cameras. From the overall study population of more than 20,000 participants, the researchers identified propensity score–matched groups of 2951 patients with or without diabetes.

Total perfusion defect (TPD) was classified as no deficit (0%), very minimal (0% to less than 1%), minimal (1% to less than 5%), mild (5% to less than 10%), and moderate to severe (greater than 10%). Associations between TPD category and risk of MACE—a composite of death from any cause, myocardial infarction, unstable angina, or late revascularization—were compared for those with diabetes and those without diabetes.

Even after matching, patients with diabetes had a higher rate of moderate to severe TPD: 7.6% versus 5.8%. Median follow-up was 4.6 years in the diabetic group and 4.7 years in the nondiabetic group. The overall rate of MACE was 16% in the patients with diabetes compared to 10% in matched patients without diabetes.

Across TPD categories, there was a significant interaction between diabetes and the risk of MACE. Risk increased progressively with each increasing TPD category, but the increases were consistently greater in those with diabetes. The difference was greatest at a TPD of greater than 10%: annualized MACE rate was 9.4% for patients with diabetes versus 3.9% for those without. For diabetic patients with a TPD of 0.5% to 3.0%, future MACE risk was the same as for nondiabetic patients with a TPD of 8% to 11%.

On Cox regression analysis, TPD was significantly associated with MACE risk, as were patient age and sex, body mass index, family history of coronary artery disease, and stress test type. In the group with no deficit (TPD of 0%), there was no difference in MACE risk between the diabetic and nondiabetic groups. However, for patients with a TPD of greater than 0%, risk was higher for those with diabetes: hazard ratio 1.70. Hazard ratios for diabetic versus nondiabetic patients were 1.68 at a TPD of 0% to less than 1%, 1.45 at a TPD of 1% to less than 5%, 1.56 at a TPD of 5% to less than 10%, and 2.35 at a TPD of greater than 10%.

Diabetes is associated with more rapid progression and a worse prognosis of cardiovascular disease. Visually assessed SPECT myocardial perfusion imaging is reported to have prognostic value in people with diabetes. The present study provides new information on the prognostic significance of quantitative SPECT defects assessed using next-generation fast myocardial perfusion imaging.

The results show that at every level of TPD greater than 0%, the risk of MACE is greater in patients with diabetes, compared to matched nondiabetic controls. The difference is such that diabetic patients with “minimal” ischemia have the same 5-year MACE risk as nondiabetic patients with “significant” ischemia. The authors note the high prevalence of mild stress perfusion myocardial abnormalities in their study: over half of patients had TPD above 0% but under 5%, the usual cutoff for an abnormal result [Han D, et al. Myocardial ischemic burden and differences in prognosis among patients with and without diabetes: results from the multicenter international REFINE SPECT Registry. 2019; DOI: 10.2337/dc19-1360].