Prognostic value of SPECT myocardial perfusion entropy in high-risk type 2 diabetic patients

Background Single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) provides valuable prognostic value. However, the risk stratification of patients with type 2 diabetes mellitus (T2D) remains suboptimal. Objectives We hypothesised that myocardial perfusion entropy (MPE) quantified from SPECT myocardial perfusion images may provide an incremental prognostic value in T2D patients independently from the routinely performed assessment of myocardial ischemia. Methods T2D patients with very high and high cardiovascular risk were studied (n = 166, 65 ± 12 years). Ischemia (> 10% of left ventricular area) was assessed by SPECT MPI. In addition, SPECT MPI was used for the quantification of rest and stress MPE. The primary endpoint was major adverse cardiac events (MACEs) defined as cardiac death, Q-wave myocardial infarction (MI) and myocardial revascularisation > 3 months after SPECT. Results Forty-six patients underwent MACEs over a median follow-up of 4.6 years. Significant differences in stress MPE were observed between patients with and without MACEs (4.19 ± 0.46 vs. 3.93 ± 0.39; P ≤ .01). By Kaplan–Meier analysis, the risk of MACEs was significantly higher in patients with higher stress MPE (log-rank P ≤ .01). Stress MPE and ischemia were significantly associated with the risk of MACEs (hazard ratio: 2.30 and 1.12, respectively, P ≤ .01 for both) after adjustment for clinical and imaging risk factors as identified from preliminary, univariate analysis and including age, hypertension, stress test and ischemia. The incremental prognostic value of MPE over clinical risk factors was quantified using nested models showing improved AIC, reclassification (global continuous Net Reclassification Improvement [NRI]: 54, global Integrated Discrimination Improvement [IDI]: 4.6%), discrimination (change in c-statistic: 0.69 vs. 0.74). Conclusions Stress MPE provided independent and incremental prognostic information for the prediction of MACEs in diabetic patients.