Li Z Y, Maldonado C, Zee-Cheng C, Hiromasa S, Kupersmith J
Department of Medicine, University of Louisville, School of Medicine, KY.
Cardiovasc Res. 1992 May;26(5):543-8. doi: 10.1093/cvr/26.5.543.
Previous studies have attempted to characterise the genesis of triggered activity related to early afterdepolarisations. Little is known about their conduction behaviour. This study was designed to examine the origin and conduction behaviour of triggered activations to throw light on the pathogenesis of torsade de pointes.
Electrophysiological interactions related to triggered activations and early afterdepolarisations between papillary muscle and Purkinje fibres were studied in the guinea pig in a single chambered bath. EDTA (5 mM) in Tyrode's solution was used and microelectrodes were placed in both papillary muscle and Purkinje fibres.
During early superfusion, marked prolongation of action potential duration and early afterdepolarisations occurred in Purkinje fibres but not in papillary muscle. In addition: (1) with prolongation of action potential duration and early afterdepolarisations in Purkinje fibres, triggered activations arose during phase 2 and were conducted to papillary muscle, where they induced activations; (2) the number of papillary muscle discharges increased with the increase in Purkinje fibre action potential duration in a linear correlation; (3) severing a segment of papillary muscle from Purkinje fibres eliminated these papillary muscle activations; (4) some triggered activations did not conduct to papillary muscle; these had smaller amplitude, slower rate of depolarisation (dV/dt), more positive activation voltage, and similar peak voltages compared to conducted triggered activations; (5) a low plateau resulting from electrotonic interaction was recorded at the Purkinje fibre-papillary muscle junction; this plateau may have facilitated conduction of triggered activations.
In this preparation there was a disparity of effect on Purkinje fibre and papillary muscle. Prolongation of action potential duration and repetitive activations due to early afterdepolarisations originated in Purkinje fibres and were conducted to papillary muscle. Purkinje fibre-papillary muscle interactions are of interest in relation to torsade de pointes arrhythmias which are believed to arise from this mechanism.
以往研究试图描述与早期后去极化相关的触发活动的起源。关于它们的传导行为知之甚少。本研究旨在检查触发激活的起源和传导行为，以阐明尖端扭转型室速的发病机制。
在豚鼠的单腔浴槽中研究乳头肌和浦肯野纤维之间与触发激活和早期后去极化相关的电生理相互作用。使用含5 mM乙二胺四乙酸（EDTA）的台氏液，将微电极置于乳头肌和浦肯野纤维中。
在早期灌注期间，浦肯野纤维的动作电位持续时间明显延长且出现早期后去极化，而乳头肌未出现。此外：（1）随着浦肯野纤维动作电位持续时间延长和早期后去极化，触发激活在第2期出现并传导至乳头肌，在乳头肌诱发激活；（2）乳头肌放电次数随浦肯野纤维动作电位持续时间增加呈线性相关增加；（3）切断浦肯野纤维与乳头肌的一段连接可消除这些乳头肌激活；（4）一些触发激活未传导至乳头肌；与传导的触发激活相比，这些激活幅度较小、去极化速率（dV/dt）较慢、激活电压更正且峰值电压相似；（5）在浦肯野纤维 - 乳头肌交界处记录到由电紧张相互作用导致的低平期；该低平期可能促进了触发激活的传导。
在此制备中，对浦肯野纤维和乳头肌的影响存在差异。动作电位持续时间延长和早期后去极化引起的重复激活起源于浦肯野纤维并传导至乳头肌。浦肯野纤维 - 乳头肌相互作用与据信由此机制引发的尖端扭转型室速心律失常相关，值得关注。
