In Vitro Cell Selectivity of Reversible and Irreversible Electroporation in Cardiac Tissue

BACKGROUND: Pulmonary vein isolation is a common catheter ablation technique used to treat atrial fibrillation originating from the pulmonary veins. However, incomplete lesion formation, pulmonary vein reconnection, and collateral damage to the phrenic nerve and esophagus can occur. Electroporation is a new modality to ablate and has the potential for permanent pulmonary vein isolation and selective efficacy on cardiac tissue; however, strong evidence of selective myocardial injury using electroporation is lacking. METHODS: Monolayers of neonatal rat ventricular cardiomyocytes, rat cortical neurons, and esophageal smooth muscle cells were stained with propidium iodide to measure shock-induced cell death. Biphasic shocks (10 ms) were delivered from line electrodes (1 mm separation). Neonatal rat ventricular cardiomyocytes were optically mapped to evaluate postelectroporation electrical conduction. RESULTS: Conduction block occurred when 50% to 80% of the cells near the electrode were killed and required 400 +/- 50 V/cm with the electrodes in contact versus 690 +/- 70 V/cm with the electrodes 1 mm above the cells (P<0.01). For 400 V/cm shocks applied in contact with cells, neonatal rat ventricular cardiomyocyte cultures yielded the highest degree of cell death (approximate to 60%) compared with rat cortical neurons (approximate to 40%) and smooth muscle cells (approximate to 20%). When the electrode was raised 1 mm, smooth muscle cells were nearly unaffected by the shock. CONCLUSIONS: Cell type alone yielded selective efficacy to electroporation without the confounding influences present in clinical studies, but electrode proximity to the target tissue remains important for efficacy. This exciting result suggests that electroporation may be a more selective modality for pulmonary vein isolation. GRAPHIC ABSTRACT: A graphic abstract is available for this article.