Mechanism of Ventricular Fibrillation witli[ Critical Mass Hypothesis : Computer Simulation and Experimental Mapping Analyses

目前尚不清楚室颤(VF)过程中的子波传播模式在结构不同的组织之间是如何变化的。方法和结果：采用计算机标测系统(2 mm分辨率)，连续120ms，分析了犬右室(RV)游离壁(n=9)、室间隔(n=5)和左室(LV)游离壁(n=6)在VF过程中的心内膜激活模式。每个组织样本被逐步切割以减少组织质量，直到室颤终止。基线时间隔波数多于右室和左室游离壁(P=0.004)，室间隔VF波长短于右室和左室游离壁(P=0.017)。随着组织质量的减少，VF在各区域逐渐变得更有组织：子波数目减少，VF周期长度延长。在右室游离壁和LV游离壁的组织质量减少后，单个和“8”字形固定的折返波经常被定位，但它们在间隔中没有被观察到。室间隔内维持室性心动过速所需的临界质量低于右室和左室游离壁(P=0.0006)。大体解剖和组织学检查显示，室间隔的组织结构比右室和左室游离壁的组织结构更为复杂。结论：室间隔和左室游离壁的VF激活模式不同，组织质量逐渐减少。室间隔组织结构的复杂性影响了心室纤颤的维持。

It is unclear how the patterns of wavelet propagation during ventricular fibrillation (VF) vary between structurally different tissues. We hypothesized that the structural complexities of the septal tissue influence the maintenance of reentrant wavelets in the ventricle.Methods and Results : Endocardial activation patterns during VF were analyzed in the isolated, per fused canine right ventricular (RV) free wall (n=9), interventricular septum (n=5), and left ventricular (LV) free wall (n=6) using a computerized mapping system (2-mm resolution) with 120-ms consecutive windows. Each tissue sample was cut progressively to reduce the tissue mass until the VF was terminated. More wavelets were seen in the septa than in the RV and LV free walls at baseline (P=0.004), and VF in the septa displayed a shorter cycle length than in the RV and LV free walls (P=0.017). As the tissue mass decreased, VF became successively more organized in all regions : the number of wavelets decreased and the cycle length of VF lengthened. Single and "figure-eight" stationary, reentrant wavelets were often mapped after tissue mass reduction in the RV free walls and rarely in the LV free walls, but they were not observed in the septa. Less critical mass was required to maintain VF in the septa than in the RV and LV free walls (P=0.0006). Gross anatomic and histologic examinations indicated that the tissue structure of the septa is more complex than that of the RV and LV free walls.Conclusion : VF activation patterns with progressive reduction of tissue mass differ for the septum and the ventricular free walls. The structural complexities of the septal tissue influence the maintenance of fibrillation in the ventricle.