Diffuse Perfusion Impairment Versus Global Myocardial Flow Reserve and Focal Perfusion Impairments in Patients Undergoing ⁸² Rb-PET Imaging

BACKGROUND: Although global myocardial flow reserve (MFR) is a powerful prognostic factor, it may overlook segmental abnormalities and does not differentiate focal from diffuse perfusion impairments. Therefore, we sought to assess whether integrated MFR provides incremental prognostic value beyond global MFR. METHODS: Consecutive patients undergoing positron emission tomography myocardial perfusion imaging between 2019 and 2025 were included. For each patient, global MFR and the proportion of the myocardium with diffuse and focal integrated MFR impairment were quantified. The primary outcome was the total burden of death, myocardial infarction, and heart failure hospitalization. Multivariable Andersen-Gill Cox models with robust variance estimators were used to estimate hazard ratios (HRs). Restricted cubic splines were used to account for potential nonlinearity. RESULTS: for interaction <0.001). At ejection fractions of 40%, 50%, 60%, and 70%, the HRs per interquartile range for greater diffuse impairment were 1.43, 1.97, 2.49, and 3.02, respectively. CONCLUSIONS: Diffuse impairments in myocardial perfusion are associated with poorer outcomes compared with focal impairments and are more informative than global MFR. Diffuse impairments may be more prognostic in patients with a preserved ejection fraction.