Types of Ventricular Fibrillation:

Abstract

Editorial CommentVentricular fibrillation (VF) has been considered to be caused by totally disorganized electrical activity, 1 but evidence accumulating for over half a century suggests different degrees and types of organization exist during VF. As VF continues, it progresses through different stages. Wiggers divided this time course into four stages based on high-speed cinematography 1,2 while Huang et al. divided it into five stages based on electrical activation mapping. 3 In addition to changes in VF over time, the Cedar Sinai-UCLA group has reported two distinct types of VF. [4][5][6] In type I VF, the activation rate is rapid, reentry is uncommon and short lived, and activation wavefronts follow constantly changing pathways with little repetition. Although the conduction velocity (CV) restitution curve is flat and the action potential duration (APD) restitution curve determined by pacing is steep, the authors believe this steep APD restitution curve is responsible for conduction block during type I VF. In type II VF, the activation rate is slower and many of the activation fronts are large and follow similar pathways. Whereas the APD restitution slope is flat, excitability is reduced and the CV restitution curve is broad. The authors believe this broad CV restitution is responsible for conduction block in type II VF.The same authors state that type I VF is consistent with VF Maintenance by wandering wavelets, whereas type II VF is consistent with VF maintenance by a mother rotor. 5 They also reported that the two types of VF can occur at different times in the same heart, either through reducing excitability by giving a high dose of the drug D600, which causes type II VF in a heart that exhibited type I VF before the drug, 4 or through changes in VF over time with the first two of Wiggers' stages representing type I VF and the later stages type II VF. 5 In this issue of the Journal, the same group reports that both types of VF can coexist simultaneously in different regions of the same heart. 6 They performed optical mapping in isolated, perfused rabbit hearts in which a region of ischemia was created by coronary occlusion. The ischemic zone was identified by shortening of the APD, whereas the APD was normal or lengthened in the nonischemic zone. These investigators found that type I VF was present in the nonischemic zone, whereas type II VF was present simultaneously in the ischemic zone. They reported that, after occlusion, the slope of the APD restitution curve decreased in the ischemic region consistent with type II VF, whereas the slope increased in the nonischemic region, consistent with type I VF. They also found that the incidence of conduction block was increased in all portions of the mapped myocardium after occlusion, i.e., in the ischemic zone, in the nonischemic zone, and in the border zone encompassing the boundary between these two zones. Based on these findings, the authors concluded that changes in both the ischemic and the nonischemic zones are proarrhythmic and that these two zones play ...

Endocardial Activation Drives Activation Patterns During Long-Duration Ventricular Fibrillation and Defibrillation

“…21 He proposed 4 stages to VF based on the mechanical motion of the heart: 1) Stage I, which consists of 3-6 undulatory contractions and lasting < 1 second, 2) Stage II, lasting 15-40 seconds, which is the convulsive incoordination stage, 3) Stage III, lasting 2-3 minutes, which was the tremulous incoordination phase and was characterized by progressively smaller, independently contracting areas, and finally 4) Stage IV, which was atonic fibrillation, with little to no contractile motion. Other studies have characterized VF into two, 22 four, 6 five, 4 or more 23 patterns of activation based on electrical wavefront parameters, but Wiggers stages of VF has been the most enduring characterization of VF activation patterns. The analysis conducted in this study is fundamentally different in that the patterns of VF activation are based on endocardial activation sequences that are not detectable in the midwall, epicardium, or from the body surface.…”

Spatiotemporal Relationship Between Intracellular Ca 2+ Dynamics and Wave Fragmentation During Ventricular Fibrillation in Isolated Blood-Perfused Pig Hearts

“…Lack of WB incidence statistics in the report by Omichi et al 14 prevents us from testing this assumption. However, the diversity of the dynamics of electrical waves during VF under different experimental conditions is clearly recognized nowadays 18,26,27 leading to a possibility that Ca i dynamics during VF may also depend on even subtle differences in the experimental conditions. Thus we should emphasize that the results presented here are specific to VF electrically induced in the intact, normoxemic, blood-perfused porcine heart.…”

Activation Patterns of Purkinje Fibers During Long-Duration Ventricular Fibrillation in an Isolated Canine Heart Model

“…1,2 Although several theories exist as to the cause of induction and maintenance of ventricular fibrillation (VF), [3][4][5] the role of Purkinje fibers (PFs) in this process remains unknown. Human data demonstrate that PF potentials may be viable targets for ablation during ventricular tachycardia and VF, which implies a critical role in these arrhythmias.…”