The prognostic significance of rate pressure product corrected myocardial flow reserve

Background: It is unknown whether myocardial flow reserve (MFR) corrected for rate pressure product (RPP) can risk stratify events when added to uncorrected MFR. In this study, we evaluated the relationship between concordant vs discordant corrected and uncorrected MFR and incident outcomes. Methods: Consecutive patients referred for clinically indicated positron emission tomography were enrolled in a prospective registry. MFR was calculated as the ratio of stress to rest myocardial blood flow and corrected for RPP (MFRcorr). Concordant MFR groups were defined as MFR ≥2-MFRcorr ≥2 and MFR <2-MFRcorr <2, while discordant MFR groups were defined as MFR ≥2-MFRcorr <2 and MFR <2-MFRcorr ≥2. The primary outcome was a composite of myocardial infarction, late revascularization and death. Results: The study population included 4564 patients, mean (SD) age 66 (12) years, 56% females, 60% White and 24% Black. Compared with patients with MFR ≥2-MFRcorr ≥2, there was an increase in risk of the primary outcome in those with MFR ≥2-MFRcorr <2 [hazard ratio (95% confidence interval)]: 1.59 (.98, 2.57; P = .061), MFR <2-MFRcorr ≥2:2.16 (1.50, 3.11; P < .001) and MFR <2-MFRcorr <2:2.91 (2.13, 3.98; P < .001). Conclusions: MFR <2 is associated with a higher risk of cardiovascular outcomes and death even if corrected MFR is ≥2.