Lim, Bernard

Radiofrequency (RF) ablation for cardiac arrythmias is an established curative therapy. However, catheter-tip coagulum formation leading to thromboembolic stroke is a persistent problem despite heparinization. Recent studies demonstrated an up to 70% incidence of thrombus formation on the catheter tip during ablation and a 10 % incidence of thromboembolic events. Catheter tip thrombus can impede the delivery of RF energy to the tissue, resulting in reduced efficacy and longer procedure times. Here we report on a novel method to prevent coagulum formation on ablation catheters by delivering a negative charge to the catheter tip to repel negatively charged fibrinogen molecules during RF ablation. A novel circuit was built with a charge delivery unit using a 9 voltage battery to deliver a fixed offset direct current charge, placed in parallel to the RF delivery unit for negative charge placement during RF delivery. In in-vivo canine experiments (n=50) standard 6/4, 8/5 ablation catheters and catheters with abraded tips were advanced from right femoral veins into atria and ventricles under intra-cardiac echo (ICE) and biplane fluoroscopic guidance. The dogs received 1 of 2 therapies: no RF energy delivered with and without negative charge delivery, RF energy delivery with and without negative charge delivery. The presence of thrombus was identified with ICE. The catheter tips were examined also macroscopically with visual inspection and also with field emission scanning electron microscopy (FESEM). FESEM of the catheter tips showed surface coverage of fibrin clot of the catheter tip to be 90 % for non-charged catheters compared to 0 % (p< 0.01) in negatively-charged catheters. There was no significant difference in surface coverage of fibrin clot between negatively-charged catheters with the abraded tips (98.8%) and non-charged catheters with smooth tips (90.7 %, p=ns). Clot volume formed on the catheter tip decreased with increased amount of charge. Application of a negative charge did not affect the quality of the intracardiac electrograms or induce malignant ventricular arrhythmias. Negative charge delivery during RF ablation is feasible and safe and can eliminate coagulum formation, potentially reducing thromboembolic complications.