Pulmonary vasodilator therapy in Fontan patients can improve exercise tolerance. We aimed to assess the potential for non-invasive testing of acute vasodilator response using four-dimensional (D) flow MRI during oxygen inhalation.

Six patients with well-functioning Fontan circulations were prospectively recruited and underwent cardiac MRI. Ventricular anatomical imaging and 4D Flow MRI were acquired at baseline and during inhalation of oxygen. Data were compared with six age-matched healthy volunteers with 4D Flow MRI scans acquired at baseline.

All six patients tolerated the MRI scan well. The dominant ventricle had a left ventricular morphology in all cases. On 4D Flow MRI assessment, two patients (Patients 2 and 6) showed improved cardiac filling with improved preload during oxygen administration, increased mitral inflow, increased maximum E-wave kinetic energy, and decreased systolic peak kinetic energy. Patient 1 showed improved preload only. Patient 5 showed no change, and patient 3 had equivocal results. Patient 4, however, showed a decrease in preload and cardiac filling/function with oxygen.

Using oxygen as a pulmonary vasodilator to assess increased pulmonary venous return as a marker for positive acute vasodilator response would provide pre-treatment assessment in a more physiological state – the awake patient. This proof-of-concept study showed that it is well tolerated and has shown changes in some stable patients with a Fontan circulation.

Fontan 患者的肺血管扩张剂治疗可以改善运动耐量。我们的目的是评估吸氧过程中使用四维 (D) 血流 MRI 进行非侵入性测试急性血管舒张反应的潜力。

前瞻性招募了 6 名 Fontan 循环功能良好的患者，并进行了心脏 MRI 检查。在基线和吸氧期间采集心室解剖成像和 4D Flow MRI。通过基线时获得的 4D Flow MRI 扫描数据与六名年龄匹配的健康志愿者进行比较。

所有六名患者都对 MRI 扫描耐受良好。所有病例的优势心室均具有左心室形态。在 4D Flow MRI 评估中，两名患者（患者 2 和患者 6）显示心脏充盈改善，输氧期间前负荷改善，二尖瓣流入增加，最大 E 波动能增加，收缩期峰值动能降低。1 号患者仅表现出预载改善。患者 5 没有表现出任何变化，而患者 3 的结果则模棱两可。然而，4 号患者在吸氧后表现出前负荷和心脏充盈/功能下降。

使用氧气作为肺血管扩张剂来评估肺静脉回流增加，作为急性血管扩张剂阳性反应的标志，将在更生理的状态（清醒的患者）下提供治疗前评估。这项概念验证研究表明，它具有良好的耐受性，并且在一些具有 Fontan 循环的稳定患者中显示出变化。