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在前一章中,阐述了第三位相阻滞的概念和讨论了它在解释各种心律失常起因中的应用。并且指出,虽然这一名称在晚近才被引用,但其基本机制或不应期,在心脏生理学方面早已熟知。反之,本章讨论的第四位相阻滞的名称,是根据仅在10年前由Singer等发表的电生理学观察。Singer等报道,当浦顷野纤维发生舒张期除极时,落在电舒张期(第四位相)后期的冲动,其跨膜电位显著比复极刚完成后者为小。由于膜电位水平降低(负值减小)时产生的动作电位,其0位相除极的速率与振幅(决定传导性的二个主要
In the previous chapter, the concept of the third phase retardation was expounded and its application in explaining the causes of various arrhythmias was discussed. And pointed out that although the name has only recently been cited, but its basic mechanism or refractory period, already well-known in cardiology. Conversely, the fourth phase block discussed in this chapter is based on electrophysiological observations published only by Singer et al. 10 years ago. Singer et al. Reported that the impulses falling in the late period of the diastolic phase (fourth phase) had a significantly smaller transmembrane potential than those of the latter group, when they were exposed to diastolic depolarization. Due to the reduction of the membrane potential level (negative decrease) when the action potential generated, the zero phase of the rate and amplitude of the pole (determines the conductivity of the two main