Role of Purkinje-muscle junction in early ventricular fibrillation in a porcine model: Beyond the trigger concept.

Background: The role of the Purkinje network in triggering ventricular fibrillation (VF) has been studied; however, its involvement after onset and in early maintenance of VF is controversial.

Aim: We studied the role of the Purkinje-muscle junctions (PMJ) on epicardial-endocardial activation gradients during early VF.

Methods: In a healthy, porcine, beating-heart Langendorff model [control, n = 5; ablation, n = 5], simultaneous epicardial-endocardial dominant frequent mapping was used (224 unipolar electrograms) to calculate activation rate gradients during the onset and early phase of VF. Selective Purkinje ablation was performed using Lugol's solution, followed by VF re-induction and mapping and finally, histological evaluation.

Results: Epicardial activation rates were faster than endocardial rates for both onset and early VF. After PMJ ablation, activation rates decreased epicardially and endocardially for both onset and early VF [Epi: 9.7 ± 0.2 to 8.3 ± 0.2 Hz (p <.0001) and 10.9 ± 0.4 to 8.8 ± 0.3 Hz (p < .0001), respectively; Endo: 8.2 ± 0.3 Hz to 7.4 ± 0.2 Hz (p < .0001) and 7.0 ± 0.4 Hz to 6.6 ± 0.3 Hz (p = .0002), respectively]. In controls, epicardial-endocardial activation rate gradients during onset and early VF were 1.7 ± 0.3 Hz and 4.5 ± 0.4 Hz (p < .001), respectively. After endocardial ablation of PMJs, these gradients were reduced to 0.9 ± 0.3 Hz (onset VF, p < .001) and to 2.2 ± 0.3 Hz (early VF, p <.001). Endocardial-epicardial Purkinje fiber arborization and selective Purkinje fiber extinction after only endocardial ablation (not with epicardial ablation) was confirmed on histological analysis.

Conclusions: Beyond the trigger paradigm, PMJs determine activation rate gradients during onset and during early maintenance of VF.