In univentricular (Fontan) physiology, peripheral and splanchnic vascular tone may be raised to counteract reduced cardiac output (CO) and elevated central venous pressure, and thus maintain vital organ perfusion. This could negatively affect the normal cardiovascular response to food ingestion, where mesenteric vasodilation and a concurrent rise in CO are central. We sought to elucidate this using rapid cardiovascular MRI. Thirty fasting subjects (50% controls; 40% female) ingested a standardized meal. Responses over ~50 minutes in mean arterial pressure (MAP), CO and blood flow in all major aortic branches were measured and regional vascular impedance (Z₀) calculated. Differences from baseline and between groups were assessed by repeated-measures mixed models. Compared to the control group, Fontan patients had greater fasting Z₀ of the legs and kidneys, resulting in greater systemic Z₀ and similar MAP. They further had similar blood flow to the digestive organs at baseline, despite larger variation in mesenteric resistance. Postprandially, blood flow to the legs decreased in the control group but not in patients. Increases in CO and superior mesenteric blood flow were similar in both groups but the celiac response was blunted in patients. No significant differences in MAP responses were observed. In conclusion, alterations in vascular tone to counteract adverse hemodynamics and raised hepatic afterload may blunt vasoreactivity in the legs and the celiac axis in Fontan physiology. Further study is needed to determine whether blunted celiac or mesenteric vasoreactivity is linked to deteriorating hemodynamics and poor prognosis in Fontan patients.

中文翻译：

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Fontan 生理学中心血管对食物摄入反应的综合 MRI 评估。

在单心室（Fontan）生理学中，外周和内脏血管张力可能升高，以抵消心输出量（CO）减少和中心静脉压升高，从而维持重要器官灌注。这可能会对食物摄入的正常心血管反应产生负面影响，其中肠系膜血管舒张和二氧化碳同时升高是其中的核心。我们试图利用快速心血管 MRI 来阐明这一点。三十名禁食受试者（50% 为对照；40% 为女性）摄入标准化膳食。测量约 50 分钟内所有主要主动脉分支的平均动脉压 (MAP)、CO 和血流量的反应，并计算局部血管阻抗 (Z ₀ )。通过重复测量混合模型评估与基线和组间的差异。与对照组相比，Fontan 患者腿部和肾脏的空腹 Z ₀更大，导致全身 Z ₀更大，MAP 相似。尽管肠系膜阻力差异较大，但他们在基线时消化器官的血流量也相似。餐后，对照组腿部的血流量减少，但患者则没有。两组的 CO 和肠系膜上血流量的增加相似，但患者的乳糜泻反应减弱。没有观察到 MAP 反应的显着差异。总之，改变血管张力以抵消不良血流动力学和升高的肝脏后负荷可能会减弱 Fontan 生理学中腿部和腹腔轴的血管反应性。需要进一步研究以确定腹腔或肠系膜血管反应性减弱是否与 Fontan 患者血流动力学恶化和预后不良有关。