后负荷急性增高在诱发家兔室性心律失常中的作用

无论在迷走神经完整或切断后,急性缩窄麻醉家兔的胸主动脉使血压升高时约半数能诱发少量室性早搏等。但在迷走神经切断后它们潜伏期较短,且可被心得安所阻断.当缩窄胸主动脉或静脉滴注苯肾上腺素使血压预先升高(未出现心律失常)时,可明显增加刺激下丘脑室旁核诱发的室性早搏次数。这在迷走神经切断后更为明显,而且血压预先升得越高,刺激下丘脑越易诱发较多的室性早搏。结果提示,心脏后负荷的急性增高不仅本身可能诱发少数室性早搏,而且可明显增加诱发神经源性心律失常的敏感性。后负荷增高的这种影响可能受迷走神经活动的保护。

EFFECTS OF ACUTE INCREASES IN AFTERLOAD ON GENESIS OF VENTRICULAR ARRHYTHMIAS IN RABBITS

Experiments were performed in 30 anaesthetized rabbits. A few ventricular arrhythmias, mainly ventricular premature beats or bigeminy, were often induced by the abrupt elevation of arterial blood pressure (BP) resulting from the occlusion of thoracic aorta before or after vagotomy. The 'latent period producing the arrhythmias after vagotomy was shorter than in intact condition, and the higher th& BP was raised, the higher incidence of the arrhythmias emerged. Intravenous injection of propranolol(1.5mg/kg) could completely prevent the occurrence of the arrhythmias.Neurogenic ventricular arrhythmias induced by stimulating the paraven-tricular nucleus (PV ) of the hypothalamus occured easier-during the control BP liad been raised to a stable height ( but -no arrhythmias emerging ) by the occlusion of aorta or intravenous infusion of phenylephrine ( 50mg/ 500ml, 0.5-3.7ml/min ) before -the stimulation. The higher the control BP raised by phenylephrine was,the easier the arrhythmias by stimulating PV complementally emerged. In addition, the vagotomy facilitated genesis of the arrhythmias induced by the occlusion of aorta and stimulating PV comp-lementally.These results suggest that the ibrupt elevation in afterload can do evoke a few ventricular arrhythmias due to. direct effects on the heart, and help to raise the sensitivity of the neurogenic arrhythmias, that the effects of increasing afterload might be decreased by raised vagal outflow in intact condition and be prevented by prdpranolol.