Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
Early Origins of Adult Health Research Group, School of Pharmacy & Medical Sciences, University of South Australia, Adelaide, SA, 5001, Australia.
J Physiol. 2020 Jul;598(13):2557-2573. doi: 10.1113/JP279054. Epub 2020 Jun 2.
The application of fetal cardiovascular magnetic resonance imaging (CMR) to assess fetal cardiovascular physiology and cardiac function through the quantification of ventricular volumes has previously been investigated, but the approach has not yet been fully validated. Ventricular output measurements calculated from heart rate and stroke volumes (SV) of the right and left ventricles measured by ventricular volumetry (VV) exhibited a high level of agreement with phase-contrast (PC) blood flow measurements in the main pulmonary artery and ascending aorta, respectively. Ejection fraction of the right ventricle, which is lower than that of the left ventricle in postnatal subjects, was similar to the left ventricular ejection fraction in the fetus; probably due to the different loading conditions present in the fetal circulation. This study provides evidence to support the reliability of VV in the sheep fetus, providing evidence for its use in animal models of human diseases affecting the fetal circulation.
The application of ventricular volumetry (VV) by cardiovascular magnetic resonance imaging (CMR) in the fetus remains challenging due to the small size of the fetal heart and high heart rate. The reliability of this technique in utero has not yet been established. The aim of this study was to assess the feasibility and reliability of VV in a fetal sheep model of human pregnancy. Right and left ventricular outputs by stroke volume (SV) measured using VV were compared with 2D phase-contrast (PC) CMR measurements of blood flow in the main pulmonary artery (MPA) and ascending aorta (AAo). At 124-140 days (d) gestation, singleton bearing Merino ewes underwent CMR under general anaesthesia using fetal femoral artery catheters, implanted at 109-117d, to trigger cine steady state free precession acquisitions of ventricular short-axis stacks. The short-axis cine stacks were segmented at end-systole and end-diastole, yielding right and left ventricular SV, ejection fraction, and cardiac outputs (SV × heart rate). PC cine acquisitions of MPA and AAo were analysed to measure blood flow, which served as comparators for the right and left cardiac outputs by VV. There was good correlation and agreement between VV and PC measures of ventricular outputs with no significant bias (r = 0.926; P < 0.0001; Bias = -4.7 ± 10.5 ml min kg ; 95% limits of agreement: -15.9 to 25.2 ml min kg ). This study validates fetal VV by CMR in a large animal model of human pregnancy and provides preliminary reference values of fetal sheep right and left ventricles in late gestation.
通过心室容积定量评估胎儿心血管生理学和心功能的胎儿心血管磁共振成像（CMR）的应用已经得到了研究，但该方法尚未得到充分验证。通过心室容积测量法（VV）测量右心室和左心室的每搏量（SV）计算得出的心输出量与主肺动脉和升主动脉的相位对比（PC）血流测量值高度一致。右心室射血分数低于产后受试者的左心室射血分数，但与胎儿的左心室射血分数相似；这可能是由于胎儿循环中存在不同的负荷条件。本研究为羊胎儿 VV 的可靠性提供了证据，为其在影响胎儿循环的人类疾病的动物模型中的应用提供了依据。
由于胎儿心脏较小且心率较高，CMR 中的心室容积测量（VV）在胎儿中的应用仍然具有挑战性。该技术在子宫内的可靠性尚未确定。本研究旨在评估 VV 在人类妊娠羊胎儿模型中的可行性和可靠性。通过 VV 测量的右心室和左心室的每搏量（SV）与主肺动脉（MPA）和升主动脉（AAo）的二维相位对比（PC）CMR 血流测量进行比较。在 124-140 天（d）妊娠时，通过胎儿股动脉导管在全身麻醉下对单胎妊娠的美利奴母羊进行 CMR，该导管在 109-117 天植入，以触发心室短轴堆栈的电影稳态自由进动采集。短轴电影堆栈在收缩末期和舒张末期进行分割，得出右心室和左心室 SV、射血分数和心输出量（SV×心率）。对 MPA 和 AAo 的 PC 电影采集进行分析以测量血流，该血流作为 VV 测量的右心和左心输出量的比较器。VV 和 PC 测量的心室输出之间具有良好的相关性和一致性，且无显著偏差（r=0.926；P<0.0001；偏倚=-4.7±10.5ml min kg ；95%一致性区间：-15.9 至 25.2 ml min kg ）。本研究在人类妊娠的大型动物模型中通过 CMR 验证了胎儿 VV，为妊娠晚期绵羊胎儿的右心室和左心室提供了初步参考值。
