Importance of Nitric Oxide for Cerebral Circulation in Fetal Tachyarrhythmia

为了评价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性心律失常模型，测量了胎羔主动脉压、中心静脉压和左、右室输出量。在母体麻醉下切开子宫，在局部麻醉下，通过颈部切开将导管插入胎儿的上腔静脉和升主动脉。起搏导线经左胸切开缝合于胎儿左心耳。用超声心动图通过经腹膜腔入路估计心输出量。观察未起搏(对照组)、以200、300、350和400次/分钟起搏的胎儿血流动力学。左房起搏速度在300次/min或以上时，主动脉压降低，中心静脉压升高。当左心房以350次/分钟或更快的速度起搏时，左、右室心输出量减少。在这个左房性快速性心律失常模型中，当左心房以300min的速度起搏时，最初确认胎儿循环衰竭。在胎儿心动过速期间，给予诺米伽-硝基-L-精氨酸甲酯(L-NAME)减少了胎儿的脑血流量。在心动过速时，NO对胎儿脑循环是必不可少的。

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.