Department of Cardiology, Catharina Hospital, Eindhoven, the Netherlands.
Department of Cardiology, Radboud University Medical Centre, Nijmegen, the Netherlands.
JACC Cardiovasc Interv. 2023 Feb 27;16(4):470-481. doi: 10.1016/j.jcin.2022.12.012.
Microvascular resistance reserve (MRR) is a new index to assess coronary microvascular (dys)function, which can be easily measured invasively using continuous thermodilution. In contrast to coronary flow reserve (CFR), MRR is independent of epicardial coronary disease and hemodynamic variations. Its measurement is accurate, reproducible, and operator independent.
The aim of this study was to establish the range of normal values for MRR and to determine an optimal cutoff point.
In this exploratory study in 214 patients with angina and no obstructive coronary artery disease, after excluding significant epicardial disease, all physiological parameters, such as fractional flow reserve, index of microvascular resistance, CFR, absolute blood flow, absolute microvascular resistance, and MRR, were measured. On the basis of concordant positive or concordant negative results of index of microvascular resistance and CFR, subgroups of patients were defined with high probability of either normal (n = 122) or abnormal (n = 24) microcirculatory function, and MRR was studied in these groups.
Mean MRR in the "normal" group was 3.4 compared with a mean MRR of 1.9 in the "abnormal" group; these values were significantly different between the groups. MRR >2.7 ruled out coronary microvascular dysfunction (CMD) with a certainty of 96%, whereas MRR <2.1 indicated the presence of CMD with a similar high certainty of 96%.
MRR is a suitable index to distinguish the presence or absence of CMD in patients with angina and no obstructive coronary artery disease. The present data indicate that an MRR of 2.7 virtually excludes the presence of CMD, while an MRR value <2.1 confirms its presence.
微血管阻力储备（MRR）是评估冠状动脉微血管（功能）障碍的一个新指标，可以通过连续热稀释法进行微创测量。与冠状动脉血流储备（CFR）不同，MRR 不受心外膜冠状动脉疾病和血流动力学变化的影响。它的测量准确、可重复且不受操作者影响。
本研究旨在确定 MRR 的正常值范围，并确定最佳截断值。
在这项 214 例心绞痛且无阻塞性冠状动脉疾病患者的探索性研究中，排除明显的心外膜疾病后，测量了所有生理参数，如血流储备分数、微血管阻力指数、CFR、绝对血流、绝对微血管阻力和 MRR。基于微血管阻力指数和 CFR 的一致阳性或一致阴性结果，将患者分为高概率正常（n=122）或异常（n=24）微循环功能组，并对这些组进行了 MRR 研究。
“正常”组的平均 MRR 为 3.4，而“异常”组的平均 MRR 为 1.9，两组之间差异有统计学意义。MRR>2.7 排除冠状动脉微血管功能障碍（CMD）的确定性为 96%，而 MRR<2.1 则表明存在 CMD 的确定性也高达 96%。
MRR 是区分心绞痛且无阻塞性冠状动脉疾病患者是否存在 CMD 的合适指标。本研究数据表明，MRR 值为 2.7 几乎可以排除 CMD 的存在，而 MRR 值<2.1 则可确认 CMD 的存在。
