背景:微血管功能的最佳指标应针对微血管区室。然而,冠状动脉血流储备(CFR),尽管被广泛用于诊断冠状动脉微血管功能障碍(CMD),受心外膜和微血管阻力的影响。相反,微血管阻力储备(MRR)调整血流储备分数(FFR),因此理论上与心外膜阻力无关。
目的:我们检验了MRR,与CFR不同,不受心外膜阻力增加的影响,因此是更具体的微血管功能指标。
方法:在16名接受近端左前降支支架置入术的患者中,我们创造了四个等级的人工狭窄(没有狭窄,温和,中度,和严重)使用冠状动脉血管成形术球囊在支架内充气到不同程度。对于每个狭窄等级,我们使用连续热稀释(每次64次测量)计算CFR和MRR,以评估它们对心外膜阻力变化的反应.
结果:球囊扩张分级导致平均FFR显著依次下降(无狭窄:0.82±0.05;轻度:0.72±0.04;中度:0.61±0.05;重度:0.48±0.09,p<0.001)。这转化为平均高血冠状动脉流量的线性下降(无狭窄:170.5±66.8ml/min;轻度:149.8±58.8ml/min;中度:124.4±53.0ml/min;严重:94.0±45.2ml/min,p<0.001)。随着狭窄程度的增加,CFR呈线性下降(无狭窄:2.5±0.9;轻度:2.2±0.8;中度:1.8±0.7;重度:1.4±0.6),对应于FFR下降0.1的下降0.3(p<0.001)。相比之下,MRR在所有狭窄等级中均表现出可忽略不计的下降(无狭窄:3.0±1.0;轻度:3.0±1.0;中度:2.9±1.0;重度:2.8±1.0),对应于FFR下降0.1的仅0.05的下降(p<0.001)。
结论:MRR,与CFR不同,受心外膜阻力的影响最小,因此应考虑更具体的微血管功能指标。这表明MRR还可以可靠地评估患有严重心外膜疾病的患者的微血管功能。
BACKGROUND: The optimal index of microvascular function should be specific for the microvascular compartment. Yet, coronary flow reserve (CFR), despite being widely used to diagnose coronary microvascular dysfunction (CMD), is influenced by both epicardial and microvascular resistance. Conversely, microvascular resistance reserve (MRR) adjusts for fractional flow reserve (FFR), and thus is theoretically independent of epicardial resistance.
OBJECTIVE: We tested the hypothesis that MRR, unlike CFR, is not influenced by increasing epicardial resistance, and thus is a more specific index of microvascular function.
METHODS: In a cohort of 16 patients that had undergone proximal left anterior descending artery stenting, we created four grades of artificial stenosis (no stenosis, mild, moderate, and severe) using a coronary angioplasty balloon inflated to different degrees within the stent. For each stenosis grade, we calculated CFR and MRR using continuous thermodilution (64 measurements of each) in order to assess their response to changing epicardial resistance.
RESULTS: Graded balloon inflation resulted in a significant sequential decrease in mean FFR (no stenosis: 0.82 ±0.05; mild: 0.72 ±0.04; moderate: 0.61 ±0.05; severe: 0.48 ±0.09, p<0.001). This translated into a linear decrease in mean hyperaemic coronary flow (no stenosis: 170.5 ±66.8 ml/min; mild: 149.8 ±58.8 ml/min; moderate: 124.4 ±53.0 ml/min; severe: 94.0 ±45.2 ml/min, p<0.001). CFR exhibited a marked linear decrease with increasing stenosis (no stenosis: 2.5 ±0.9; mild: 2.2 ±0.8; moderate: 1.8 ±0.7; severe: 1.4 ±0.6), corresponding to a decrease of 0.3 for a decrease in FFR of 0.1 (p<0.001). In contrast, MRR exhibited a negligible decrease across all stenosis grades (no stenosis: 3.0 ±1.0; mild: 3.0 ±1.0; moderate: 2.9 ±1.0; severe: 2.8 ±1.0), corresponding to a decrease of just 0.05 for a decrease in FFR of 0.1 (p<0.001).
CONCLUSIONS: MRR, unlike CFR, is minimally influenced by epicardial resistance, and thus should be considered the more specific index of microvascular function. This suggests that MRR can also reliably evaluate microvascular function in patients with significant epicardial disease.