Importance of Nitric Oxide for Cerebral Circulation in Fetal Tachyarrhythmia

为探讨快速左房起搏对胎儿循环的影响，我们制作了胎儿室上性快速心律失常模型，测定了胎羊主动脉压、中心静脉压和左右心室输出量。在母体麻醉下，打开子宫，在局部麻醉下，通过颈部切口将导管插入胎儿上级腔静脉和升主动脉。然后通过左胸廓切开术将起搏电极导线缝合到胎儿左心耳上。通过经子宫途径使用超声心动图估计心室输出量。在无起搏（对照）和起搏频率为200、300、350和400/min时观察胎儿血流动力学。当左心房起搏频率为300/min或更高时，主动脉压降低，当左心房起搏频率为350/min或更高时，中心静脉压升高。以350次/min或更高频率起搏左心房时，左心室和右心室输出量均减少。在此左房快速性心律失常模型中，当以300/min起搏左心房时，最初证实胎儿循环衰竭。在胎儿心动过速期间，给予Nomega-nitro-L-arginine methyl ester（L-NAME）可降低胎儿脑血流。NO对心动过速胎儿脑循环是必需的。

To evaluate the hemodynamic effect of rapid left atrial pacing on fetal circulation, we made a fetal supraventricular tachyarrhythmia model and measured the aortic pressure, central venous pressure, and left and right ventricular output in fetal lambs. Under maternal anesthesia, the uterus was opened, and under local anesthesia, catheters were inserted into the fetal superior vena cava and ascending aorta through a neck incision. Pacing leads were then sutured onto the fetal left atrial appendage via left thoracotomy. Ventricular output was estimated using an echocardiography by a transuterine approach. Fetal hemodynamics were observed without pacing (control), and at the pacing rates of 200, 300, 350, and 400/min. The aortic pressure decreased when the left atrium was paced at 300/min or more and central venous pressure increased when the left atrium was paced at 350/min or more. The left and right ventricular output decreased when the left atrium was paced at 350/min or more. Fetal circulatory failure was initially confirmed when the left atrium was paced at 300/min in this left atrial tachyarrhythmia model.During fetal tachycardia, administration of Nomega-nitro-L-arginine methyl ester (L-NAME) decreased fetal cerebral blood flow. NO is essential for fetal cerebral circulation in tachycardia.