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

Abstract

Background— The roles of Purkinje fibers (PFs) and focal wave fronts, if any, in the maintenance of ventricular fibrillation (VF) are unknown. If PFs are involved in VF maintenance, it should be possible to map wave fronts propagating from PFs into the working ventricular myocardium during VF. If wave fronts ever arise focally during VF, it should be possible to map them appearing de novo. Methods and Results— Six canine hearts were isolated, and the left main coronary artery was cannulated and perfused. The left ventricular cavity was exposed, which allowed direct endocardial mapping of the anterior papillary muscle insertion. Nonperfused VF was induced, and 6 segments of data, each 5 seconds long, were analyzed during 10 minutes of VF. During 36 segments of data that were analyzed, 1018 PF or focal wave fronts of activation were identified. In 534 wave fronts, activation was mapped propagating from working ventricular myocardium to PF. In 142 wave fronts, activation was mapped propagating from PF to working ventricular myocardium. In 342 wave fronts, activation was mapped arising focally. More than 1 of these 3 patterns could occur in the same wave front. Conclusions— PFs are highly active throughout the first 10 minutes of VF. In addition to retrograde propagation from the working ventricular myocardium to PFs, antegrade propagation occurs from PFs to working ventricular myocardium, which suggests PFs are important in VF maintenance. Prior plunge needle recordings in dogs indicate activation propagates from the endocardium toward the epicardium after 1 minute of VF, which suggests that focal sites on the endocardium may represent foci and not breakthrough. If so, in addition to reentry, abnormal automaticity or triggered activity may also occur during VF.

Intramural Foci During Long Duration Fibrillation in the Pig Ventricle

“…The sparse distribution of the Purkinje fibers in the working myocardium makes it difficult to record activation pathways within them. 41 Figure 5. Filled squares represent electrodes.…”

Both Purkinje Cells and Left Ventricular Posteroseptal Reentry Contribute to the Maintenance of Ventricular Fibrillation in Open-Chest Dogs and Swine Effects of Catheter Ablation and the Ventricular Cut-and-Sew Operation

“…[16][17][18][19] Recently, Tabereaux et al demonstrated by sophisticated unipolar mapping that Purkinje activation plays an important role in the maintenance of VF in the isolated canine heart. 20 Although the Purkinje network spreads over the entire endocardial surface of the ventricles, that distributed in the area of the PPM root is readily identified as discrete and sharp Purkinje potentials. 21 The decreased Purkinje-ventricular coupling interval around the PPM 22,23 affects the electrical loading of the Purkinje cells by the neighboring myocardium, and this might facilitate automaticity or triggered activity.…”

Repetitive Endocardial Focal Discharges During Ventricular Fibrillation With Prolonged Global Ischemia in Isolated Rabbit Hearts

“…Ideker's group has reported in an isolated canine heart model with a relatively small mapped area that "repetitive endocardial focal discharges" (REFDs) were present in during VF with prolonged GI. 8 In addition, Purkinje fibers were highly active throughout the first 10 min of VF and were associated with the genesis of REFDs. 8 Whether or not REFDs also exist during VF with prolonged GI in rabbits remains unclear.…”