Differential Association of PET-Derived Rest and Stress Myocardial Blood Flow with Cardiovascular Outcomes

Although there is strong evidence for the prognostic value of myocardial flow reserve (MFR), there are fewer data on the prognostic implications of its constituents: myocardial blood flow at rest (MBF_rest) and stress (MBF_stress). <b>Methods:</b> Consecutive patients undergoing ⁸²Rb PET imaging with regadenoson stress testing at a tertiary care center between August 2019 and August 2024 were included in this study. The 2 coprimary outcomes were a composite of death or heart failure (HF) hospitalization and a composite of myocardial infarction (MI) or late revascularization. Multivariable Andersen-Gill Cox models with robust variance estimators were used to incorporate recurrent events. Outcomes were modeled as a smooth function of MBF_stress and MBF_rest, with restricted cubic splines to allow nonlinearity. <b>Results:</b> The analysis included 8,131 consecutive patients (median age of 68 y; 46.1% were women; median follow-up of 520 d (interquartile range, 186-921 d), among whom 471 deaths, 828 HF hospitalizations, 164 MIs, and 429 late revascularizations occurred. After adjusting for the relevant covariates, an MFR of 2 achieved through a lower MBF_rest was associated with a significantly lower incidence of death and HF hospitalization, whereas an MFR of 2 achieved through a greater MBF_stress was associated with a significantly lower incidence of MI and late revascularization. Assessments of the partial χ² statistic, which measures the importance of predictors, similarly confirmed that MBF_rest was more important for predicting death or HF hospitalization whereas MBF_stress was more important for predicting MI or late revascularization. <b>Conclusion:</b> Measurements of absolute myocardial blood flow offer complementary prognostic value to MFR. A diminished MBF_stress may signal a greater risk of future ischemic outcomes, whereas an elevated MBF_rest may signal a greater risk of future death or HF hospitalization.