Huhta Heikki, Junno Juulia, Haapsamo Mervi, Erkinaro Tiina, Ohtonen Pasi, Davis Lowell E, Hohimer A Roger, Acharya Ganesh, Rasanen Juha
Department of Obstetrics and Gynecology, University of Oulu, Oulu, Finland.
Department of Anesthesiology and Surgery, Oulu University Hospital, Oulu, Finland.
Exp Physiol. 2018 Jan 1;103(1):58-67. doi: 10.1113/EP086500. Epub 2017 Dec 3.
What is the central question of this study? The fetal aortic isthmus has an important physiological role, allowing communication between the left and right ventricular outputs, which are arranged in parallel. Can the aortic isthmus provide unrestrictive communication between the left and right ventricular circulations during occlusion of the ascending aorta? What is the main finding and its importance? During occlusion of the ascending aorta, fetal carotid artery perfusion pressure fell significantly, showing that the aortic isthmus failed to redirect blood flow and pressure from the ductus arteriosus to the aortic arch. This suggests that the aortic isthmus cannot provide unrestrictive communication between left and right ventricular circulations. The fetal aortic isthmus (AoI) allows communication between left (LV) and right ventricular (RV) outputs and represents an arterial watershed between the brachiocephalic (brain) and subdiaphragmatic (placenta) circulations. To understand the capability of the AoI to maintain the balance between the upper and lower body circulations, we performed a complete occlusion of the fetal ascending aorta in nine chronically instrumented sheep at near term gestation. We hypothesized that the occlusion would significantly decrease LV output and concomitantly increase RV output in order to maintain adequate systemic cardiac output and perfusion pressure to the fetal brain circulation through retrograde filling of the AoI. Fetal cardiac function and haemodynamics were assessed by pulsed and tissue Doppler at baseline, 15 and 60 min after occlusion of the ascending aorta and 15 min after occlusion was released. Carotid artery and jugular vein pressures were monitored. Occlusion of the ascending aorta increased (P < 0.002) RV output from [mean (SD)] 684 (369) to 907 (414) ml min and decreased (P < 0.0001) LV output from 440 (136) to 40 (16) ml min . Combined cardiac output decreased (P < 0.02) from 1125 (494) to 946 (417) ml min . During occlusion, carotid artery mean pressure decreased from 32 (7) to 12 (7) mmHg (P < 0.0001). Systemic venous pressure was unaffected. Left ventricular systolic and diastolic function deteriorated during occlusion. Right ventricular systolic function improved, while diastolic dysfunction developed. Fetal carotid artery perfusion pressure decreased significantly during occlusion of the ascending aorta, demonstrating that AoI failed to redirect blood flow and pressure from the ductus arteriosus to the aortic arch. Our finding suggests that at near term gestation the aortic AoI cannot provide unrestrictive communication between LV and RV circulations.
本研究的核心问题是什么？胎儿主动脉峡部具有重要的生理作用，使并行排列的左右心室输出之间能够进行血液流通。在升主动脉闭塞期间，主动脉峡部能否在左右心室循环之间提供无阻碍的血液流通？主要发现及其重要性是什么？在升主动脉闭塞期间，胎儿颈动脉灌注压显著下降，表明主动脉峡部未能将动脉导管的血流和压力重新导向主动脉弓。这表明主动脉峡部无法在左右心室循环之间提供无阻碍的血液流通。胎儿主动脉峡部（AoI）使左心室（LV）和右心室（RV）输出之间能够进行血液流通，并且是头臂（脑）循环和膈下（胎盘）循环之间的一个动脉分水岭。为了了解AoI维持上下体循环平衡的能力，我们在接近足月妊娠的9只长期植入仪器的绵羊身上对胎儿升主动脉进行了完全闭塞。我们假设闭塞会显著降低左心室输出，同时增加右心室输出，以便通过AoI的逆行充盈维持足够的全身心输出量和胎儿脑循环的灌注压。在升主动脉闭塞前、闭塞后15分钟和60分钟以及闭塞解除后15分钟，通过脉冲和组织多普勒评估胎儿心脏功能和血流动力学。监测颈动脉和颈静脉压力。升主动脉闭塞使右心室输出从[平均（标准差）]684（369）毫升/分钟增加到907（414）毫升/分钟（P<0.002），左心室输出从440（136）毫升/分钟减少到40（16）毫升/分钟（P<0.0001）。联合心输出量从1125（494）毫升/分钟减少到946（417）毫升/分钟（P<0.02）。在闭塞期间，颈动脉平均压从32（7）毫米汞柱降至12（7）毫米汞柱（P<0.0001）。全身静脉压未受影响。闭塞期间左心室收缩和舒张功能恶化。右心室收缩功能改善，而舒张功能障碍出现。在升主动脉闭塞期间，胎儿颈动脉灌注压显著下降，表明AoI未能将动脉导管的血流和压力重新导向主动脉弓。我们的发现表明，在接近足月妊娠时，主动脉峡部不能在左心室和右心室循环之间提供无阻碍的血液流通。
