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

目前尚不清楚心室颤动（VF）时小波传播模式在结构不同的组织之间是如何变化的。我们假设室间隔组织的结构复杂性影响心室内可重入小波的维持。方法和结果：采用计算机成像系统（2毫米分辨率），连续窗120毫秒，对分离的、融合的犬右心室（RV）游离壁（n=9）、室间隔（n=5）和左心室（LV）游离壁（n=6）进行心内膜激活模式分析。每个组织样本被逐步切割以减少组织质量，直到VF终止。在基线时，小波在间隔处比在左室和左室自由壁处出现更多（P=0.004），并且间隔内的VF显示的周期长度比在右室和左室自由壁处显示的短（P=0.017）。随着组织质量的减小，各区域的VF依次变得更有组织，小波数减少，VF周期长度延长。单个和“数字8”固定的、可重入的小波通常在左室自由壁组织质量减少后被绘制，很少在左室自由壁被绘制，但在间隔中未被观察到。与左室和左室自由壁相比，维持室间隔室颤所需的临界质量更少（P=0.0006）。大体解剖和组织学检查表明，中隔的组织结构比左室和左室自由壁更为复杂。结论：室间隔和心室游离壁的VF激活模式随着组织质量的逐渐减少而不同。室间隔组织结构的复杂性影响心室纤维性颤动的维持。

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.