Prognostic utility of quantitative positron emission tomography in patients with prior coronary artery bypass grafting: incremental value of myocardial flow reserve and coronary vascular resistance

In patients with prior coronary artery bypass grafting (CABG), the utility of quantitative positron emission tomography (PET) perfusion parameters remains unestablished. While quantitative PET overcomes the limitations of relative perfusion imaging in multivessel coronary artery disease by assessing myocardial blood flow (MBF), its prognostic relevance is less well explored.

We sought to evaluate the prognostic value of PET-derived myocardial flow reserve (MFR) to assess epicardial coronary disease and coronary vascular resistance (CVR) for microvascular disease in CABG patients.

This retrospective study included consecutive patients undergoing Rubidium-82 PET myocardial perfusion imaging between May 2017 and November 2023. MFR was defined as stress/rest MBF, with a cut-off of 2.0 for impaired MFR. CVR was calculated as mean arterial pressure divided by stress MBF, with an optimal cut-off of 60 mmHg·min·g/mL determined by area under the curve analysis. The primary outcome was major adverse cardiovascular events (MACE), defined as a composite of all-cause mortality and nonfatal myocardial infarction. Associations were assessed using multivariable Cox proportional hazards models after adjusting for clinical variables and PET parameters.

A total of 556 patients (median age 72 years, 79% male) were included. Over a median follow-up of 676 (482–1077) days, 71 patients (12.8%) experienced MACE. Patients with impaired MFR or CVR had significantly higher MACE rates (both p<0.001) (Figure 1). Stratifying by preserved or impaired MFR and CVR revealed significant differences in MACE incidence across the four combination groups (p<0.001) (Figure 2). Both MFR (<2.0) and CVR (≥60) independently predicted MACE, with adjusted hazard ratios of 3.204 (95% CI, 1.777–5.777; p<0.001) and 2.350 (95% CI, 1.308–4.223; p=0.004), respectively.

PET-derived MFR and CVR provide independent and incremental prognostic value, enhancing risk stratification beyond conventional perfusion and function parameters in CABG patients.Figure 1Figure 2