Myocardial flow reserve and resting contractility modulate the impact of contractile reserve in patients undergoing rubidum-82 positron emission tomography.

Although ejection fraction reserve (EFR) harbors prognostic value in patients undergoing positron emission tomography (PET) myocardial perfusion imaging (MPI), whether resting EF and myocardial flow reserve (MFR) modulate its prognostic value 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 of EFR with the primary outcome across the spectrum of resting EF and MFR. Restricted cubic splines were used to allow non-linearity. The 50th percentile of EFR served as the reference, with the 25th and 75th percentiles representing low and high EFR. The analysis included 7,737 consecutive patients among whom 463 deaths and 821 HF hospitalizations occurred over a median follow-up of 554 days. A low EFR was associated with a 25% greater risk of the primary outcome (HR: 1.25; 95% CI: 1.16 to 1.35). The association was stronger at higher values of resting EF (HR at EFs of 40% and 70%: 0.99 and 1.21 respectively) and MFR (HR at MFRs of 1 and 3: 1.06 and 1.27 respectively). Similarly, a high EFR carried a protective association that was more pronounced at a higher resting EF and MFR. The prognostic implications of contractile reserve, as measured by EFR, are most pronounced in patients with a higher resting EF and MFR.