Effects of Contact Force-Guided Radiofrequency Current Application on Lesion Size and Coronary Arteries in Developing Porcine Myocardium

Objectives: Catheter contact force (CF) monitoring has been shown to be a major determinant of lesion quality in radiofrequency (RF) catheter ablation thereby improving efficacy of RF catheter ablation in adult patients. The value of CF monitoring in pediatric patients undergoing RF ablation has not been studied yet. This animal study was conducted to assess the impact of CF monitoring on RF lesion size in small piglets as a model of pediatric RF ablation.

Methods: RF catheter ablation with continuous CF monitoring was performed in 12 piglets (median body weight 18.5 kg) using a 7F TactiCath Quartz RF ablation catheter (Abbott, Abbott Park, Illinois, United States). A total of seven lesions were induced in each of the animals (atrial myocardium n = 2, AV annulus n = 3, ventricular myocardium n = 2) with low (10–20 g) or high (40–60 g) CF. Conventional RF energy was delivered with a target temperature of 65°C at 30 W for 30 seconds. Coronary angiography was performed prior and immediately after RF application and was repeated after 48 hours prior to removal of the hearts. Lesions with surrounding myocardium were excised, fixated, and stained. Lesion volumes were assessed by exact microscopic planimetry.

Results: A total of 80 lesions could be identified in the explanted hearts. Median (interquartile range [IQR]) atrial lesion size was 35.4 (27.8–75) mm³, AV annulus lesion size was 69.2 (IQR 45.3–116.7) mm³, and ventricular lesion had a volume of 116.1 (79.9–160.9) mm³. No differences in lesion volumes were found between lesions performed with high and low CFs. In addition, there was no correlation between lesion volume and mean CF, force time integral or lesion size index. After ablation at the AV annulus, 8/32 (25%) of lesions (low CF n = 4, high CF n = 4) extended to the coronary arteries on histologic examination.

Conclusion: There was no correlation between catheter CF and lesion volume in young piglets after RF application. These findings are in contrast to previous studies on CF in AF ablation and might be attributed to the fact that ablation catheter was used without irrigated tip in the present study and RF energy therefore might be lost by convection resulting in comparatively small lesions. Transmural extension of the RF lesions to coronary arteries was frequently noted in small individuals. It is therefore possible that less CF than used in adult hearts during RF ablation is advisable in the immature hearts of pediatric patients.