The prognostic interplay between PET-derived resting myocardial blood flow and left ventricular ejection fraction

AIMS: Whether the prognostic value of resting myocardial blood flow (MBFrest) and myocardial flow reserve (MFR) is modified by a patient's ejection fraction (EF) has not been studied. METHODS AND RESULTS: Consecutive patients undergoing stress/rest MPI using Rb-82 PET between 2019 and 2024 were included. The primary outcome was a composite of death and heart failure (HF) hospitalizations. Multivariable Andersen-Gill Cox models were used to assess the association with the primary outcome, adjusting for traditional risk factors and other PET parameters. Restricted cubic splines were used to allow non-linearity. The 50th percentile of MBFrest/MFR served as the reference, with the 25th and 75th percentiles representing low and high comparators respectively. A total of 8089 patients with a median follow-up of 519 days (IQR: 186-916 days), among whom 466 deaths and 819 HF hospitalizations ocurred. Both high MBFrest and low MFR were associated with an increased risk of the primary outcome (HRs of 1.39 95% CI: 1.18-1.63 and 1.70 95% CI: 1.41-2.04, respectively). There was a significant interaction with EF for both variables (P < 0.001), with greater prognostic value at higher EFs. At EFs of 40%, 50%, 60%, 70% the HRs for high vs. low MBFrest were 1.24, 1.61, 1.97, and 2.46, respectively and for low vs. high MFR were 1.57, 2.06, 2.59, and 3.13, respectively. Across the spectrum of EF, a higher MBFrest carried a greater risk of death or HF hospitalization at constant MFRs. CONCLUSION: The prognostic value of MBFrest and MFR is much more apparent at higher EFs, with a high MBFrest (and/or low MFR) identfying patients with a much higher risk than would be predicted based on their EF alone.