Revista Española De Cardiología

Francisco J. Chorro, Francisca Pelechano, Isabel Trapero, Xavier Ibañez-Catalá, Luis Such-Miquel, Álvaro Tormos, Juan Guerrero, Joaquín Cánoves, Luis Mainar, José Millet, Antonio Alberola, and Luis Such

Rev Esp Cardiol. 2012;65(2):143–151 (Español) (English)

The aim of this study was to analyze the effects of a radiofrequency-induced linear lesion during ventricular fibrillation and the capacity to capture myocardium through high-frequency pacing.

Ventricular fibrillation (VF) was recorded in 22 isolated perfused rabbit hearts using multiple epicardial electrodes.The activation maps were analyzed upon applying trains of stimuli at 3 different frequencies close to that of the arrhythmia, in three situations: a) at baseline; b) after radio-frequency (RF) ablation to induce a lesion of the left ventricular free wall (length=10 [1]mm), and c) after lengthening the lesion (length=23 [2]mm). Following the lesion, the regularity of the recorded signals decreased and significant variations in the direction of the activation fronts were observed. On lengthening the lesion, there was a slight increase in the episodes with at least 3 consecutive captures when pacing at cycles 10% longer than the arrhythmia (baseline: 0.6 [0.7]; initial lesion: 1 [1] no significant differences; lengthened lesion: 3 [2.8]; P<.001), while a decrease was observed in those obtained upon pacing at cycles 10% shorter than the arrhythmia.

The authors conclude that:

1.  The RF-induced lesion increases the heterogeneity of myocardial activation during VF and modifies arrival of the activation fronts in the adjacent zones.

2.  High-frequency pacing during VF produces occasional captures during at least 3 consecutive stimuli.

3.  The lengthened lesion slightly increases capture capacity when using cycles slightly longer than the VF.

Comments

Within the current controversy over the basic mechanisms responsible for VF, the authors analyze the effects of a RF-induced linear lesion during VF and the capacity to capture myocardium through high-frequency pacing.  This is a very interesting basic research study, because although transcatheter RF-ablation is widely used in the treatment of all kinds of arrhythmias (AF among them), its effects on AF have not been extensively investigated. The results obtained may be of use in guiding future research on myocardial capture during VF using programmed stimulation procedures.

As the authors themselves point out, the study has certain limitations. The features of the model used enabled the analysis of VF and the effects of the lesions without interference from metabolic deterioration that accompanies the onset of VF, although the analysis of the results is restricted to situations similar to the initial moments of the arrhythmia when it occurs in a clinical setting.