Department of Radiology, Northwestern University, Feinberg School of Medicine, 737 N Michigan, Suite 1600, Chicago, IL, 60611, USA.
Department of Radiology, Mayo Clinic, Rochester, MN, 55902, USA.
J Cardiovasc Magn Reson. 2021 Dec 6;23(1):138. doi: 10.1186/s12968-021-00828-y.
Quantitative evaluation of mitral regurgitation (MR) in hypertrophic cardiomyopathy (HCM) by cardiovascular magnetic resonance (CMR) relies on an indirect volumetric calculation. The aim of this study was to directly assess and quantify MR jets in patients with HCM using 4D flow CMR jet tracking in comparison to standard-of-care CMR indirect volumetric method.
This retrospective study included patients with HCM undergoing 4D flow CMR. By the indirect volumetric method from CMR, MR volume was quantified as left ventricular stroke volume minus forward aortic volume. By 4D flow CMR direct jet tracking, multiplanar reformatted planes were positioned in the peak velocity of the MR jet during systole to calculate through-plane regurgitant flow. MR severity was collected for agreement analysis from a clinical echocardiograms performed within 1 month of CMR. Inter-method and inter-observer agreement were assessed by intraclass correlation coefficient (ICC), Bland-Altman analysis, and Cohen's kappa.
Thirty-seven patients with HCM were included. Direct jet tracking demonstrated good inter-method agreement of MR volume compared to the indirect volumetric method (ICC = 0.80, p = 0.004) and fair agreement of MR severity (kappa = 0.27, p = 0.03). Direct jet tracking showed higher agreement with echocardiography (kappa = 0.35, p = 0.04) than indirect volumetric method (kappa = 0.16, p = 0.35). Inter-observer reproducibility of indirect volumetric method components revealed the lowest reproducibility in end-systolic volume (ICC = 0.69, p = 0.15). Indirect volumetric method showed good agreement of MR volume (ICC = 0.80, p = 0.003) and fair agreement of MR severity (kappa = 0.38, p < 0.001). Direct jet tracking demonstrated (1) excellent inter-observer reproducibility of MR volume (ICC = 0.97, p < 0.001) and MR severity (kappa = 0.84, p < 0.001) and (2) excellent intra-observer reproducibility of MR volume (ICC = 0.98, p < 0.001) and MR severity (kappa = 0.88, p < 0.001).
Quantifying MR and assessing MR severity by indirect volumetric method in HCM patients has limited inter-observer reproducibility. 4D flow CMR jet tracking is a potential alternative technique to directly quantify and assess MR severity with excellent inter- and intra-observer reproducibility and higher agreement with echocardiography in this population.
通过心血管磁共振（CMR）对肥厚型心肌病（HCM）患者的二尖瓣反流（MR）进行定量评估依赖于间接容积计算。本研究旨在通过 4D 流 CMR 射流跟踪直接评估和量化 HCM 患者的 MR 射流，并与标准 CMR 间接容积方法进行比较。
本回顾性研究纳入了接受 4D 流 CMR 的 HCM 患者。通过 CMR 的间接容积方法，MR 容积被量化为左心室每搏量减去主动脉前向容积。通过 4D 流 CMR 直接射流跟踪，在收缩期 MR 射流的最大速度平面上定位多平面重建平面，以计算射流的跨平面反流流量。在 CMR 后 1 个月内进行临床超声心动图检查，收集 MR 严重程度的协议分析数据。通过组内相关系数（ICC）、Bland-Altman 分析和 Cohen's kappa 评估方法间和观察者间的一致性。
共纳入 37 例 HCM 患者。直接射流跟踪法与间接容积法相比，MR 容积具有良好的方法间一致性（ICC=0.80，p=0.004）和中等程度的 MR 严重程度一致性（kappa=0.27，p=0.03）。直接射流跟踪与超声心动图（kappa=0.35，p=0.04）的一致性高于间接容积法（kappa=0.16，p=0.35）。间接容积法各组成部分的观察者间可重复性显示，收缩末期容积的可重复性最低（ICC=0.69，p=0.15）。间接容积法显示出良好的 MR 容积一致性（ICC=0.80，p=0.003）和中等程度的 MR 严重程度一致性（kappa=0.38，p<0.001）。直接射流跟踪显示（1）MR 容积（ICC=0.97，p<0.001）和 MR 严重程度（kappa=0.84，p<0.001）具有极好的观察者间可重复性，（2）MR 容积（ICC=0.98，p<0.001）和 MR 严重程度（kappa=0.88，p<0.001）具有极好的观察者内可重复性。
在 HCM 患者中，通过间接容积法定量评估和评估 MR 严重程度的方法，观察者间的可重复性有限。4D 流 CMR 射流跟踪是一种潜在的替代技术，可以直接定量评估 MR 严重程度，并具有极好的观察者间和观察者内的可重复性，与该人群的超声心动图具有更高的一致性。
