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

Whether the prognostic value of resting myocardial blood flow (MBF_rest) and myocardial flow reserve (MFR) is modified by a patient’s ejection fraction (EF) has not been studied.

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 MBF_rest/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 MBF_rest 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 MBF_rest 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 MBF_rest carried a greater risk of death or HF hospitalization at constant MFRs.

The prognostic value of MBF_rest and MFR is much more apparent at higher EFs, with a high MBF_rest (and/or low MFR) identfying patients with a much higher risk than would be predicted based on their EF alone.