Cardiology
META ANALYSIS
● Meta-analysis
Microvascular Resistance Reserve Predicts CAD Outcomes: HR 0.75 per Unit Increase
JACC. Cardiovascular interventions
Published March 27, 2026
Gallinoro Emanuele, De Bruyne Bernard, Pijls Nico, Belmonte Marta, Paolisso Pasquale, Di Lenarda Fra…
PubMed ↗
DOI ↗
This meta-analysis evaluated the prognostic value of microvascular resistance reserve (MRR) in coronary artery disease (CAD) by analyzing five prospective studies with a total of 3,186 participants. The study aimed to determine the association between MRR and major adverse cardiovascular events (MACE). The primary endpoint was the hazard ratio (HR) for adverse cardiovascular outcomes per unit increase in MRR. Results indicated that a higher MRR significantly reduced the risk of adverse events (HR: 0.75; 95% CI: 0.64-0.88), with substantial heterogeneity (I² = 80.9%). When MRR was dichotomized, low MRR was associated with a more than two-fold increased risk for MACE (HR: 2.39; 95% CI: 1.66-3.43). Subgroup analyses revealed a stronger prognostic effect in patients with ST-segment elevation myocardial infarction (STEMI) compared to those with stable CAD (HR: 0.46 vs. 0.86; P for interaction < 0.0001). No specific safety or adverse events were reported in relation to MRR measurement. Clinically, these findings suggest that MRR is a robust, independent predictor of cardiovascular outcomes, particularly in acute coronary syndrome. A threshold of MRR ≥ 3 was identified as optimal for sensitivity and rule-out performance, indicating its potential utility in invasive physiological assessments for risk stratification.
AI Accuracy Review: 9/10
· Auto-published
This study focuses on coronary artery disease (CAD), a condition where the blood vessels that supply the heart become narrowed or blocked. Researchers looked at a new way to measure heart health called microvascular resistance reserve (MRR). They reviewed several studies to see how MRR relates to serious heart problems. They found that higher MRR levels are associated with a lower risk of major heart events, while lower levels significantly increase that risk. This means that MRR could be a useful tool for doctors to assess heart health, especially in patients with acute conditions like heart attacks. For patients, this could mean that knowing your MRR might help doctors better understand your heart health and risks. However, more research is needed to confirm these findings and to see how MRR can be used in everyday medical practice.
What this means for you: Higher levels of a new heart measure may lower your risk of serious heart problems.
View Original Abstract ↓
BACKGROUND: Microvascular resistance reserve (MRR) is a novel index for evaluating coronary microvascular function independently of epicardial disease. Its prognostic significance in coronary artery disease (CAD) remains uncertain.
OBJECTIVES: The aim of this study was to assess the association between MRR and adverse cardiovascular outcomes across various CAD presentations.
METHODS: A systematic review and meta-analysis was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. MEDLINE and Embase were searched from January 2019 to January 2025 for prospective studies reporting HRs for major adverse cardiovascular events in relation to MRR. Risk for bias was assessed using the Quality in Prognosis Studies tool. Pooled HRs were calculated using a random-effects model; heterogeneity was evaluated using the I statistic.
RESULTS: Five studies (n = 3,186) were included. Higher MRR was significantly associated with lower risk for adverse events (HR per unit increase: 0.75; 95% CI: 0.64-0.88; I = 80.9%). When dichotomized, low MRR conferred a more than 2-fold increased risk for major adverse cardiovascular events (HR: 2.39; 95% CI: 1.66-3.43). Subgroup analysis showed a stronger prognostic effect for ST-segment elevation myocardial infarction (HR: 0.46) vs stable CAD (HR: 0.86; P for interaction < 0.0001). Threshold analysis identified MRR ≥ 3 as optimal for sensitivity (58.9%) and rule-out performance, while lower thresholds improved specificity.
CONCLUSIONS: MRR is a robust, independent predictor of cardiovascular outcomes of both acute and chronic CAD. Its prognostic impact is particularly pronounced for acute coronary syndrome. A threshold of 3 provides the best prognostic balance, supporting its integration into invasive physiological assessment for risk stratification.