Department of Engineering, Durham University, Durham, DH1 3LE, United Kingdom of Great Britain and Northern Ireland.
Physiol Meas. 2020 Apr 16;41(3):035007. doi: 10.1088/1361-6579/ab7d77.
In healthy adults, the right atrium (RA) serves as a reservoir for the systemic flow return from the superior vena cava (SVC) and inferior vena cava (IVC), preparing the two flows to be transferred to the right ventricle (RV) and pulmonary circulation. This study aims to quantify the haemodynamics of the RA and the associated SVC and IVC inflows, which have not been fully understood to date.
Eighteen adults with structurally normal hearts underwent 4D flow magnetic resonance imaging. The cardiac cycle was resolved to 20 temporal phases with a spatial resolution of 3 × 3 × 3 mm. Analysis included objective visualisation of the flow structures in the RA identified by three different vortex identification criteria, kinetic energy (KE), enstrophy and dissipation. KE and helicity flux were also assessed in both caval veins.
Vortex identification methods confirmed that in the majority of participants the blood flow from the caval veins filling the RA during ventricular systole is not chaotic, but rather forms an organised pattern of a single coherent forward turning vortex structure. Thirteen participants displayed a single vortex flow structure, four showed multiple vortices and one had a helical flow pattern without a clear vortex structure. A strong positive correlation exists between the flow KE and enstrophy density.
This suggests that flow energy in the RA is mainly rotational, part of which is convected by the highly helical SVC and IVC inflows. Multiple vortices tend to be associated with higher dissipation rates in the central RA region due to turbulence. The rotational nature of the flow in the RA maintains KE better than non-rotational flow. RA flow characteristics are highly related to the helicity content in the caval veins, as well as the KE flux intensity. Lower caval helicity or IVC KE flux dominance tends to favour single vortex formation while the opposite tends to lead to multiple vortices or the rare helical flow patterns. Atria lacking single vortex flow are inclined to have a larger energy input from atrial contraction.
在健康成年人中，右心房（RA）是来自上腔静脉（SVC）和下腔静脉（IVC）的全身血流回流的储液器，为将这两种血流转移到右心室（RV）和肺循环做准备。本研究旨在量化 RA 和相关 SVC 和 IVC 流入的血液动力学，迄今为止，这方面尚未被充分了解。
18 名结构正常的成年人接受了 4D 流动磁共振成像。心脏周期被解析为 20 个时间相位，空间分辨率为 3×3×3mm。分析包括通过三种不同的涡旋识别标准、动能（KE）、旋度和耗散来对 RA 中的流结构进行客观可视化。还评估了两条腔静脉中的 KE 和螺旋通量。
涡旋识别方法证实，在大多数参与者中，心室收缩时从腔静脉流入 RA 的血流不是混沌的，而是形成单个向前旋转涡旋结构的有序模式。13 名参与者显示出单个涡旋流结构，4 名参与者显示出多个涡旋，1 名参与者显示出无明显涡旋结构的螺旋流模式。血流 KE 和旋度密度之间存在很强的正相关。
这表明 RA 中的流能量主要是旋转的，其中一部分是由高度螺旋的 SVC 和 IVC 流入来对流的。由于湍流，多个涡旋往往与中央 RA 区域的较高耗散率相关。RA 中的流的旋转性质比非旋转流更好地保持 KE。RA 流特征与腔静脉中的螺旋含量以及 KE 通量强度密切相关。较低的腔静脉螺旋性或 IVC KE 通量优势往往有利于单个涡旋的形成，而相反的情况则倾向于导致多个涡旋或罕见的螺旋流模式。缺乏单个涡旋流的心房往往更容易从心房收缩中获得更大的能量输入。
