BACKGROUND Coronary microvascular disease (CMVD) is associated with adverse cardiovascular outcomes. However, there is no reliable and noninvasive quantitative diagnostic method available for CMVD. The use of a pressure wire to measure the index of microcirculatory resistance (IMR) is possible, but it has inevitable practical restrictions. We hypothesized that computation of the quantitative flow ratio could be used to predict CMVD with symptoms of ischemia and no obstructive coronary artery disease (INOCA). METHODS We retrospectively assessed the diagnostic efficiency of the quantitative flow ratio‑derived index of microcirculatory resistance (QMR) in 103 vessels from 66 patients and compared it with invasive IMR using the thermodilution technique. RESULTS Patients were divided into the CMVD group (41/66, 62.1%) and non-CMVD group (25/66, 37.9%). Pressure-wire IMR measurements were made in 103 coronary vessels, including 44 left descending arteries (LADs), 18 left circumflex arteries (LCXs) and 41 right coronary arteries (RCAs). ROC curve analysis showed a good diagnostic performance of QMR for all arteries (area under the curve=0.820, 95% confidence interval 0.736-0.904, p<0.001) in predicting microcirculatory function. The optimal cut-off for QMR to predict microcirculatory function was 266 (sensitivity: 82.9%, specificity: 72.6%, and diagnostic accuracy: 76.7%). CONCLUSION QMR is a promising tool for the assessment of coronary microcirculation. The assessment of the IMR without the use of a pressure wire may enable more rapid, convenient, and cost-effective assessment of coronary microvascular function.

中文翻译：

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定量流量比衍生的微循环阻力指数作为识别缺血且无阻塞性冠状动脉疾病（INOCA）患者微循环功能的新工具。

背景冠状动脉微血管疾病（CMVD）与不良心血管结局相关。然而，目前尚无可靠且无创的CMVD定量诊断方法。使用压力丝测量微循环阻力（IMR）指数是可能的，但它不可避免地存在实际限制。我们假设定量流量比的计算可用于预测有缺血症状且无阻塞性冠状动脉疾病 (INOCA) 的 CMVD。方法 我们回顾性评估了 66 名患者的 103 条血管中定量流量比衍生的微循环阻力指数 (QMR) 的诊断效率，并将其与使用热稀释技术的侵入性 IMR 进行了比较。结果患者分为CMVD组（41/66，62.1%）和非CMVD组（25/66，37.9%）。在 103 条冠状动脉中进行了压力线 IMR 测量，其中包括 44 条左降动脉 (LAD)、18 条左回旋动脉 (LCX) 和 41 条右冠状动脉 (RCA)。ROC曲线分析显示QMR对所有动脉在预测微循环功能方面具有良好的诊断性能（曲线下面积=0.820，95%置信区间0.736-0.904，p<0.001）。QMR 预测微循环功能的最佳截止值为 266（敏感性：82.9%，特异性：72.6%，诊断准确性：76.7%）。结论 QMR 是评估冠状动脉微循环的一种有前途的工具。不使用压力线评估 IMR 可以更快速、方便且经济有效地评估冠状动脉微血管功能。