[Prognostic Value of Myocardial Flow Reserve Derived from 13N-ammonia PET in Patients with Ischemic Heart Disease in Japan].

Myocardial flow reserve (MFR) measured by 13N-ammonia PET is a well-established indicator of adverse outcomes in patients with ischemic heart disease (IHD), with a low MFR (<2.0) indicating a poor prognosis. Furthermore, MFR can be used to non-invasively diagnose ischemia with non-obstructive coronary arteries. However, most of the evidence originates from Western populations, and studies in Japan are limited to small sample sizes. Therefore, we aimed to investigate the utility of MFR for risk stratification of cardiovascular events in a Japanese cohort.Between January 2016 to December 2023, consecutive 413 Japanese patients who underwent NH3-PET because of known or suspected IHD at multiple facilities in Japan were analyzed. We evaluated myocardial blood flow (MBF) at rest and during adenosine-induced hyperemic stress, and calculated MFR from the ratio of stress to rest MBF. The patients were divided into two groups according to MFR as defined by receiver-operating characteristic (ROC) analysis. The frequency of major adverse cardiovascular events (MACE), including acute coronary syndrome, revascularization after three months, heart failure hospitalization, and all-cause mortality, was compared by Kaplan-Meier and log-rank test. For imaging and clinical parameters, hazard ratios (HR) and 95% confidence intervals (CI) were calculated using the Cox proportional hazards regression model.The ROC curve analysis of MFR for MACE showed the optimal cutoff value of 2.1. The incidence of MACE in the group with reduced MFR was significantly higher than that with preserved MFR (p < 0.0001). MFR and summed stress score were significant factors in univariate analysis. Multivariate analysis indicated that MFR was an independent prognostic factor of MACE (HR: 0.50, 95% CI: 0.36-0.70, p < 0.0001).In Japan, MFR derived from NH3-PET was also a useful prognostic factor. The cutoff value for MFR was comparable to that reported in previous studies involving patients in the West.