The role of iNOS in cerebral circulation in asphyxia

胎儿完全性房室传导阻滞常见于胶原病母亲的胎儿，与胎儿水肿或胎儿死亡有关。然而，其病理生理机制尚未完全揭示，治疗策略尚未完成。为了揭示胎儿完全性房室传导阻滞的病理生理机制，并为该疾病的治疗提供依据，我们采用冷冻消融胎儿房室结的方法建立了胎儿完全性房室传导阻滞的动物模型，然后用心外膜起搏电极对胎儿心室进行起搏。在12只胎羊中建立完全性房室传导阻滞，以60、90、120、150、180、210、240和270/min的速率起搏心室。在心室起搏前和起搏期间测量主动脉压、中心静脉压和右心室输出量。12例胎儿中有9例发生完全性房室传导阻滞。起搏频率为60、90和240/min时，收缩期主动脉压降低。起搏频率为60/min时，中心静脉压升高。起搏频率为60、90、120、180、210、240和270/min时，右心室输出量降低。起搏频率为150次/min时主动脉压最高，中心静脉压最低，完全性房室传导阻滞胎羊右心室心输出量最高。

Fetal complete atrioventricular block, which is often seen in the fetuses with collagen disease mothers, is associated with hydrops fetalis or fetal death. However, the pathophysiology has not uncovered completely and the treatment strategy has not been accomplished. To uncover the pathophysiology of fetal complete atrioventricular block and to establish suitable treatment for this condition, we created complete atrioventricular model in fetal lamb by cryoablating atrioventricular node, then we paced fetal ventricle by epicardial pacing lead. Complete atrioventricular block was created in 12 fetal lambs, and the ventricle was paced at rates of 60, 90, 120, 150, 180, 210, 240, and 270/min. The aortic pressure, central venous pressure, and right ventricular output were measured before and during ventricular pacing. Complete atrioventricular block was created in 9 out of 12 fetuses. Systolic aortic pressure was decreased at pacing rates of 60, 90, and 240/min. Central venous pressure was increased at a pacing rate of 60/min. Right ventricular output decreased at pacing rates of 60, 90, 120, 180, 210, 240, and 270/min, while no difference was found at the pacing rate of 150/min. Ventricular pacing at a rate of 150/min gave the highest aortic pressure, the lowest central venous pressure, and the highest right ventricular cardiac output in fetal lambs with complete atrioventricular block.