心室肌细胞数学模型短期记忆特性的研究

Short-term Memory Study of the Ventricular Mathematical Model

心室颤动(简称室颤)是心血管系统疾病的主要死因。由于心肌细胞固有电生理异质性和其动力学因素的影响,给室颤发生机制的正确认识带来了许多困难。其中,心脏短期记忆现象的存在使利用恢复曲线斜率作为唯一标准的判断方法失效。因此,研究和揭示心脏固有的短期记忆特性及其在室颤发生中的作用具有重要意义。利用向下扫描刺激模式研究三种最常用的心肌细胞数学模型的动力学和局部S1S2恢复曲线,判断模型的记忆特性。并利用刺激周期突变的方法研究了模型记忆的衰变过程。结果表明,动作电位时程的频率依赖性与S1刺激的周期有关,S1的周期越小,不同时间间隔的S2刺激下动作电位时程的差异越大。除Luo-Rudy1991模型外,Luo-Rudy1994和Noble1991模型均可部分反映心肌的记忆特性,其记忆的消失基本遵循指数衰减的规律。因此,在计算机定量电生理研究中,可选用这两种模型研究心脏短期记忆现象及其与室颤的关系。

Ventricular fibrillation （VF） is the main cause of sudden death in cardiovascular diseases. The effects of electrophysiological heterogeneity and dynamic factors bring a lot of difficulties in understanding and revealing the mechanisms of VF. Cardiac short-term memory is one of the factors that make invalidation of restitution curve slope as the criteria for transition from ventricular tachycardia to VF. Therefore,investigation of inherent properties of short-term memory and its role in VF has great significance. In this paper we took advantage of the perturbed downsweep protocol to measure dynamic and local S1S2 restitution curves on three widely used mathematical models to reveal their memory property. And by making abrupt change of the stimulation cycle length,we examined the attenuation process of the memory. The results showed：the rate-dependent action potendial duration（APD） is related with S1 pacing. The APD difference under different S2 cycle length is more pronounced with short S1 cycle length. Except the Luo-Rudy 1991 model,the Luo-Rudy 1994 and Noble 1991 models can at least reflect some of the short-term memory. And the memory attenuated in exponential way. Therefore,in quantitative electrophysiological study,these two models can be used in the future for investigating the characteristics of the short-term memory and its contribution to VF.