2相早期后除极诱发时空湍流的抑制方法

Inhibition of the Turbulence Induced by Phase-2 Early Afterdepolarization

针对心肌细胞膜电位振荡的早期后除极(EAD)诱发的湍流,提出了恒定电场和周期电场两种湍流消除方法并对其效果进行了比较。基于LR91单细胞模型构建了一块包含400×400个细胞格点的二维组织,并通过将K+电流门控变量时常数和Ca2+电流最大电导分别增大4和2倍的方法在组织中心设置了一块由20×20个格点构成的具有EAD特征的区域。利用垂直场法诱导螺旋波斑图,并在EAD的作用下碎裂出现湍流即室颤。通过在反应扩散方程中引入电场项建立除颤模型,并引入膜电位的全局偏导数判别湍流的抑制效果。计算机仿真结果表明:恒定电场法抑制湍流的时间小于50ms,周期场法需历时200ms,但两种方法电场的实际作用时间无显著差异;尽管周期场法产生的总热能是恒定电场法的2.3倍,但周期场法一个周期产生的热能仅为恒定电场法的一半。因此,恒定电场法具有消除湍流快、总热能低的特点,但周期场法由于电场断续式地施加,更有利于减小热的持续积累对心肌的损伤。

Aiming at the myocardial cell membrane oscillation induced by phase-2 early afterdepolarization （EAD） due to voltage oscillation, two turbulence control methods based on constant and periodic electrical fields were presented and compared. A 2-dimensional tissue including 400 × 400 cells was developed based on the LR91 model. By increasing the time constant of K＋ current gating variable and the maximum conductance of Ca^2＋ current by 4 and 2 times respectively, an EAD region with 20 × 20 cells was created in the center of the tissue model. The cross field method was used to induce spiral wave, which was degraded to turbulence due to EAD. The defibrillation model was created by introducing an electric field term in the reaction- diffusion equation. The inhibition efficiency was evaluated by using an introduced global partial derivative. Computer simulation results showed that the constant and periodic electric fields required 50 ms and 200 ms to eliminate the turbulence, respectively, but their actual delivery time has no significant difference. The total thermal energy produced by the periodic field was 2.3 times that by the constant field, while the heat produced within one period by the periodic field was half of that by constant field method. Therefore, the constant electric field method is characterized by faster turbulence elimination and less thermal energy consumption, while periodic method can bring less damage to cardiac muscle because of its intermittent deliv nature.