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

Background Radio frequency catheter ablation (RFCA) targeting the left ventricular postero septum (LVPS) and posterior papillary muscle (PPM) terminates or prevents ventricular fibrillation (VF) in rabbit and dog hearts. However, whether the mechanism of VF maintenance is reentry or focal Purkinje firing is unclear. Methods and Results In the present study the effects of RFCA (endocardial ablation of PPM+LVPS in 7 dogs and 7 swine), left ventricular anterolateral wall ablation (LVAL in 7 dogs), and the cut-and-sew operation (CSO: along the left ventricular posterior wall (LVPW) beside PPM in 7 swine) on VF inducibility were compared. (1) VF inducibility was decreased from 100±0% to 21.9±31.2% (p<0.0001) by PPM+LVPS endocardial ablation, but not by LVAL ablation in dogs. (2) LVPW CSO reduced VF inducibility (100±0% to 43.6±9.5%, p<0.0001) in swine. (3) In contrast to the canine Purkinje network, which is mostly localized to the subendocardium, the swine Purkinje network extends to the subepicardial layer with a higher density (p<0.001). Conclusion Both PPM+LVPS ablation (Purkinje destruction) in dogs and LVPW CSO (blocking reentry) in swine reduce VF inducibility, suggesting that in both species focal firing from the Purkinje network and reentry around the PPM contributes to the maintenance of VF. (Circ J 2008; 72: 1185-1192).