MPI SPECT and GSPECT in type 2 diabetes mellitus patient: Combined perfusion and functional imaging for cardiovascular risk stratification

Cardiovascular disease is the leading cause of morbidity and mortality in patients with type 2 diabetes mellitus (T2DM). Early detection of subclinical coronary and myocardial injury is therefore essential to reduce future cardiovascular events. MPI SPECT and its gated form (GSPECT MPI) provide simultaneous assessment of three-dimensional tracer distribution and functional/mechanical cardiac parameters, enabling detection of ischemia, viable myocardium, left-ventricular remodeling, systolic and diastolic dysfunction, and mechanical dyssynchrony often before symptoms arise. Across diverse cohorts, abnormal perfusion on SPECT consistently identifies T2DM patients at substantially higher risk of major adverse cardiovascular events (MACE), whereas normal perfusion generally corresponds to low short- to mid-term event rates. GSPECT-derived metrics including post-stress LVEF and change in LVEF, EDV/ESV, transient ischemic dilation (TID), lung-to-heart ratio, peak filling rate (PFR), and phase-dispersion measures frequently provide independent, incremental prognostic information and can refine risk assessment even when perfusion is preserved. Clinically actionable patterns (abnormal MPI, marked post-stress LVEF decline, elevated TID or lung-to-heart ratio, reduced PFR, and pronounced phase dispersion) should prompt intensified risk-factor modification, closer surveillance, and, when appropriate, anatomic coronary evaluation. Methodological heterogeneity in stress protocols, gating parameters, reconstruction algorithms, and analysis software limits the adoption of universal thresholds and underscores the need for methodological standardization and local validation. This narrative review aims to synthesize current evidence on SPECT MPI and GSPECT applications in T2DM to inform risk-tailored, targeted use of these modalities for early detection and personalized management of subclinical cardiovascular disease.