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Updated: Jul 26, 2025
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Published on: March 22, 2024
Microvascular resistance reserve: diagnostic and prognostic performance in the ILIAS registry
Coen K M Boerhout1, Joo Myung Lee2, Guus A de Waard1
1Heart Center, Amsterdam UMC, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
Aims:
The microvascular resistance reserve (MRR) was introduced as a means to characterize the vasodilator reserve capacity of the coronary microcirculation while accounting for the influence of concomitant epicardial disease and the impact of administration of potent vasodilators on aortic pressure. This study aimed to evaluate the diagnostic and prognostic performance of MRR.
Methods And Results:
A total of 1481 patients with stable symptoms and a clinical indication for coronary angiography were included from the global ILIAS Registry. MRR was derived as a function of the coronary flow reserve (CFR) divided by the fractional flow reserve (FFR) and corrected for driving pressure. The median MRR was 2.97 [Q1-Q3: 2.32-3.86] and the overall relationship between MRR and CFR was good [correlation coefficient (Rs) = 0.88, P < 0.005]. The difference between CFR and MRR increased with decreasing FFR [coefficient of determination (R2) = 0.34; Coef.-2.88, 95% confidence interval (CI): -3.05--2.73; P < 0.005]. MRR was independently associated with major adverse cardiac events (MACE) at 5-year follow-up [hazard ratio (HR) 0.78; 95% CI 0.63-0.95; P = 0.024] and with target vessel failure (TVF) at 5-year follow-up (HR 0.83; 95% CI 0.76-0.97; P = 0.047). The optimal cut-off value of MRR was 3.0. Based on this cut-off value, only abnormal MRR was significantly associated with MACE and TVF at 5-year follow-up in vessels with functionally significant epicardial disease (FFR <0.75).
Conclusion:
MRR seems a robust indicator of the microvascular vasodilator reserve capacity. Moreover, in line with its theoretical background, this study suggests a diagnostic advantage of MRR over other indices of vasodilatory capacity in patients with hemodynamically significant epicardial coronary artery disease.
Insights
Microvascular resistance reserve (MRR) effectively assesses coronary microcirculation vasodilator capacity. Abnormal MRR predicts major adverse cardiac events and target vessel failure in patients with significant coronary artery disease.
Area of Science:
- Cardiology
- Vascular Biology
- Diagnostic Imaging
Background:
- The microvascular resistance reserve (MRR) quantifies coronary microcirculation vasodilator capacity, accounting for epicardial disease and aortic pressure.
- Evaluating MRR's diagnostic and prognostic performance is crucial for understanding coronary artery disease.
Purpose of the Study:
- To evaluate the diagnostic and prognostic performance of MRR.
- To assess MRR's utility in patients with stable symptoms and coronary angiography indications.
Main Methods:
- 1481 patients from the ILIAS Registry with stable symptoms and coronary angiography indication were analyzed.
- MRR was calculated as coronary flow reserve (CFR) divided by fractional flow reserve (FFR), corrected for driving pressure.
- 5-year follow-up data was used to assess major adverse cardiac events (MACE) and target vessel failure (TVF).
Main Results:
- The median MRR was 2.97, with a good correlation between MRR and CFR (Rs = 0.88).
- MRR was independently associated with MACE (HR 0.78) and TVF (HR 0.83) at 5-year follow-up.
- An optimal MRR cut-off of 3.0 identified patients with abnormal MRR significantly associated with MACE and TVF in cases of significant epicardial disease (FFR <0.75).
Conclusions:
- MRR is a robust indicator of microvascular vasodilator reserve capacity.
- MRR demonstrates a diagnostic advantage over other indices in patients with significant epicardial coronary artery disease.
- Abnormal MRR is a significant predictor of adverse cardiac events in specific patient subgroups.
