Impaired myocardial flow reserve from 82-rubidium positron emission tomography predicts survival benefit from revascularization: a multicenter registry study
Authors: Toftholm M , Kim Wadt Hansen K W H , Signe Hoejstrup S H , Louise Hougesen Bjerking L H B , Soeren Galatius S G , Kirsten Bouchelouche K B , Lars Jakobsen L J , Evald Hoej Christiansen E H C , Lisbeth Marner L M , Ulrik Talleruphuus U T , Eva Irene Bossano Prescott E I B P 
Published: November 2023

Abstract

Background
The identification of patients that may accrue prognostic benefit from revascularization is complex. Myocardial perfusion imaging (MPI) using 82-rubidium positron emission tomography (82Rb-PET) provides information on myocardial perfusion defects, calcium-score, left ventricular ejection fraction (LVEF), and myocardial flow reserve (MFR).

Purpose
To examine if MFR assessed by 82-Rb PET MPI identifies subgroups that benefit from revascularization.

Methods
We included 7462 all-comers suspected of coronary artery disease undergoing 82-Rb-PET MPI at three high-volume nuclear centers in Denmark between January 1, 2018, and August 20, 2020. Patients with reversible perfusion defects &lt;5%, eGFR &lt;30 mL/min/1.73m2, receiving dialysis, left ventricular ejection fraction &lt;35%, and those that died within 90 days of their index 82Rb-PET MPI were excluded.
Revascularization was defined as percutaneous coronary intervention (PCI) or coronary artery bypass-graft surgery (CABG) within 90 days of MPI. Patients were followed for major adverse cardiac events (MACE), a composite of all-cause death, acute coronary syndromes, ischemic stroke, or heart failure, and all-cause mortality until July 9, 2022. We analyzed each outcome according to revascularization and MFR (&lt;2 vs. ≥2) using the Kaplan-Meier estimator and proportional hazards Cox regressions adjusted for patient and 82Rb-PET characteristics, including any perfusion defects, using inverse probability weighting.

Results
A total of 1805 patients were included (mean age 69 (SD 10.6), 29.8% females, 27% diabetes), of whom 902 (50%) had MFR &lt;2. The median follow-up was 35.9 months. A total of 480 were revascularized. 58 experienced a MACE; 36 died.
Revascularization was associated with a significantly lower risk of all-cause mortality and MACE among patients with MFR&lt;2, whereas there was no survival benefit from revascularization among those with normal MFR (figure 1).
After adjustment, HR for revascularization for MACE in the MFR&lt;2 group was 0.51 (95%CI 0.33-0.78) versus 1.19 (95%CI 0.64-2.20) in the MFR&gt;=2 group (p for interaction 0.042) and for All-cause mortality 0.48 (95%CI 0.30-0.77) in the MFR&lt;2 group versus 1.01 (95%CI 0.43-2.39) in the MFR&gt;=2 group (p for interaction 0.28). Results were independent of the extent of reversible perfusion defect, consistent across several subgroups, and independent of the mode of revascularization (CABG or PCI), figure 2.

Conclusion
In this observational study, revascularization was associated with improved prognosis, specifically among patients with impaired MFR, whereas among patients with normal MFR, there was no prognostic benefit. Impaired MFR may identify patients with prognostic benefit from revascularization. This novel hypothesis should be tested in a randomized controlled trial.Kaplan MeierForest plot