BackgroundFew data exist on the degree of interstitial myocardial fibrosis in patients with classical low-flow, low-gradient aortic stenosis (LFLG-AS) and its association with left ventricular flow reserve (FR) on dobutamine stress echocardiography. This study sought to evaluate the diffuse interstitial fibrosis measured by T1 mapping cardiac magnetic resonance technique in LFLG-AS patients with and without FR.MethodsProspective study including 65 consecutive patients (41 LFLG-AS [mean age, 67.1±8.4 years; 83% men] and 24 high-gradient aortic stenosis used as controls) undergoing dobutamine stress echocardiography to assess FR and cardiac magnetic resonance to determine the extracellular volume (ECV) fraction of the myocardium, indexed ECV (iECV) to body surface area and late gadolinium enhancement.ResultsInterstitial myocardial fibrosis measured by iECV was higher in patients with LFLG-AS with and without FR as compared with high-gradient aortic stenosis (35.25±9.75 versus 32.93±11.00 versus 21.19±6.47 mL/m², respectively; P<0.001). However, both ECV and iECV levels were similar between LFLG-AS patients with and without FR (P=0.950 and P=0.701, respectively). Also, FR did not correlate significantly with ECV (r=−0.16, P=0.31) or iECV (r=0.11, P=0.51). Late gadolinium enhancement mass was also similar in patients with versus without FR but lower in high-gradient aortic stenosis (13.3±10.2 versus 10.5±7.5 versus 4.8±5.9 g, respectively; P=0.018).ConclusionsPatients with LFLG-AS have higher ECV, iECV, and late gadolinium enhancement mass compared with high-gradient aortic stenosis. Moreover, among patients with LFLG-AS, the degree of myocardial fibrosis was similar in patients with versus those without FR. These findings suggest that diffuse myocardial fibrosis may not be the main factor responsible for the absence of FR in LFLG-AS patients.

中文翻译：

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经典低流量，低梯度主动脉瓣狭窄中的心肌纤维化

背景很少有关于多巴酚丁胺应力超声心动图上的经典低流量，低梯度主动脉狭窄（LFLG-AS）患者的间质心肌纤维化程度及其与左心室血流储备（FR）的关系的数据。这项研究旨在评估通过T1测绘心脏磁共振技术对患有和没有FR的LFLG-AS患者的弥漫性间质纤维化。方法前瞻性研究包括65名连续患者（41例LFLG-AS [平均年龄，67.1±8.4岁； 83％的男性]和24个高梯度主动脉瓣狭窄作为对照），接受多巴酚丁胺应力超声心动图评估FR和心脏磁共振，以确定心肌的细胞外体积（ECV）比例，将ECV（iECV）标记为体表面积并晚期late增强。² ; P <0.001）。然而，有和没有FR的LFLG-AS患者的ECV和iECV水平相似（分别为P = 0.950和P = 0.701）。此外，FR与ECV（r = -0.16，P = 0.31）或iECV（r = 0.11，P = 0.51）均不显着相关。晚期versus的增强质量在有和没有FR的患者中也相似，但在高梯度主动脉瓣狭窄中则较低（分别为13.3±10.2、10.5±7.5和4.8±5.9 g；P= 0.018）。结论与高梯度主动脉瓣狭窄相比，LFLG-AS患者的ECV，iECV和g增强末期质量更高。此外，在患有LFLG-AS的患者中，有纤维化的患者与无纤维化的患者的心肌纤维化程度相似。这些发现表明，弥漫性心肌纤维化可能不是导致LFLG-AS患者缺乏FR的主要因素。