Key result
Abnormal microvascular resistance reserve was associated with a significantly higher risk of major adverse cardiovascular events compared to normal MRR (RR 4.88; 95% CI 3.49-6.83).
Why the study?
Does abnormal microvascular resistance reserve (MRR) predict adverse cardiovascular outcomes in patients undergoing coronary microcirculation assessment?
Meta-Analysis (n=1,605)
Does abnormal microvascular resistance reserve (MRR) predict adverse cardiovascular outcomes in patients undergoing coronary microcirculation assessment?
Relative Risk: 4.88 (95% CI 3.49–6.83)
Abnormal microvascular resistance reserve (MRR) is a significant predictor of adverse cardiovascular outcomes, including cardiovascular death and MACE.
Introduction Microvascular resistance reserve (MRR) is a novel invasive indice for coronary microcirculation assessment, that overcomes the limitations of coronary flow reserve (CFR) and index of microcirculatory resistance (IMR), as it is independent of stenosis severity and accounts for rest and hyperemia conditions. Purpose Given its promising role in the future of coronary microvascular dysfunction assessment, we aimed to systematically review and meta-analyze available studies reporting its prognostic significance. Methods We performed a systematic search in 3 different databases (MEDLINE/PubMed, Web of Science and Scopus). After selecting all appropriate studies according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a random effect meta-analysis was performed. Results Our analysis included 5 studies and a total of 1,605 patients (453 abnormal MRR; 1152 normal MRR). Patients with abnormal MRR are at significantly higher risk for cardiovascular death [Risk Ratio (RR): 2.37; 95% Confidence Interval (CI): 1.52-3.70], major adverse cardiovascular events (RR: 4.88; 95%CI: 3.49-6.83), myocardial infarction (RR: 1.93; 95%CI: 1.53-2.42) and heart failure hospitalizations (RR: 4.83; 95%CI: 1.59-14.70), in comparison to the normal MRR cohort. However, abnormal MRR was not associated with a significantly higher risk of future revascularizations, compared to normal controls (RR: 1.29; 95%CI: 0.52-3.19). Conclusion This systematic review and meta-analysis shows the significant microcirculation-specific prognostic effect of MRR in both survival and adverse outcomes. Further data from large randomized studies, will delineate the clinical utility and prognostic effect of MRR in coronary microvascular dysfunction.
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Pyrpyris et al. (2025) conducted a meta-analysis in Coronary microvascular dysfunction (n=1,605). Abnormal microvascular resistance reserve (MRR) vs. Normal MRR was evaluated on Major adverse cardiovascular events (RR 4.88, 95% CI 3.49-6.83). Abnormal microvascular resistance reserve was associated with a significantly higher risk of major adverse cardiovascular events compared to normal MRR (RR 4.88; 95% CI 3.49-6.83).
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