动作电位动态变化对螺旋波演化行为的影响

Effects of dynamic change of action potential on evolution behavior of spiral wave

在心脏病患者的心脏中观察到心室不同部位的心肌细胞动作电位时长(APD)恢复曲线陡峭程度差别很大,而陡峭的APD恢复曲线既可以在某些情况下导致螺旋波破碎和心室纤维性颤动,也可能在另一些情况下不导致螺旋波破碎,螺旋波动力学行为与陡峭的APD恢复曲线的关系仍未完全清楚,因此需要深入研究.本文采用二维可激发介质元胞自动机模型,研究陡峭程度不同的APD恢复曲线下螺旋波的动力学行为,数值模拟结果表明:陡峭的APD恢复曲线可以使漫游螺旋波稳定,也可以促进螺旋波漫游或引起破碎,甚至使螺旋波消失,观察到在APD恢复曲线总平均斜率大于1情况下螺旋波仍维持稳定或漫游,在APD恢复曲线总平均斜率比1小很多的情况下螺旋波出现破碎;在APD恢复曲线总平均斜率大于1的情况下观察到多普勒失稳、爱克豪斯失稳和APD交替变化三种螺旋波破碎方式,其中APD交替变化导致的螺旋波破碎可在APD恢复曲线总平均斜率比1小很多的情况下发生.观察到螺旋波通过漫游出系统边界和遇到传导障碍消失.此外,还发现通过增大元胞APD有利于防止螺旋波破碎.对产生这些现象的物理机制进行解释.

It is observed in cardiac patients that the steepnesses of action potential duration(APD)restitution curve of cardiomyocytes in different regions of the ventricle are significantly different from region to region.However,the steep APD restitution curve can either lead the spiral wave to break up and set up the ventricular fibrillation in certain conditions or result in no breakup of spiral wave in other conditions.The relationship between the dynamic behavior of spiral wave and steep APD restitution curve is still not completely clear.Therefore,further research is needed.In this paper,a two-dimensional excitable medium cellular automata model is used to study the influences of the APD restitution curves with different steepnesses on the dynamic behavior of spiral wave.Numerical simulation results show that the steep APD restitution curve can stabilize the meandering spiral wave,causing the stable spiral wave to roam or break,and even to disappear.When the total average slope of APD restitution curve is greater than 1,it is observed that spiral wave may be still stable or meandering.When the total average slope of APD restitution curve is much smaller than 1,the breakup of spiral waves may occur.Three types of spiral wave breakups are observed.They are the Doppler instability,Eckhaus instability,and APD alternation.The Doppler instability and Eckhaus instability are related to the total average slope of APD restitution curve greater than 1,and the spiral wave breakup caused by APD alternans may occur when the total average slope of APD restitution curve is much smaller than 1.When the total average slope of APD restitution curve is greater than 1,the phenomena that spiral waves disappear by meandering out of the system boundary and conduction barriers are observed.In addition,we also find that increasing cellular APD is beneficial to preventing spiral wave from breaking up.The physical mechanisms behind those phenomena are heuristically analyzed.