Magnetic guidance versus manual control: comparison of radiofrequency lesion dimensions and evaluation of the effect of heart wall motion in a myocardial phantom

Abstract

Background: Magnetic navigation system (MNS) ablation was suspected to be less effective and unstable in highly mobile cardiac regions compared to radiofrequency (RF) ablations with manual control (MC). The aim of the study was to compare the (1) lesion size and (2) stability of MNS versus MC during irrigated RF ablation with and without simulated mechanical heart wall motion. Methods: In a previously validated myocardial phantom, the performance of Navistar RMT Thermocool catheter (Biosense Webster, CA, USA) guided with MNS was compared to manually controlled Navistar irrigated Thermocool catheter (Biosense Webster, CA, USA). The lesion dimensions were compared with the catheter in inferior and superior orientation, with and without 6-mm simulated wall motion. All ablations were performed with 40 W power and 30 ml/ min irrigation for 60 s. Results: A total of 60 ablations were performed. The mean lesion volumes with MNS and MC were 57.5 ± 7.1 and 58.1 ± 7.1 mm3, respectively, in the inferior catheter orientation (n = 23, p = 0.6), 62.8 ± 9.9 and 64.6 ± 7.6 mm3, respectively, in the superior catheter orientation (n = 16, p = 0.9). With 6-mm simulated wall motion, the mean lesion volumes with MNS and MC were 60.2 ± 2.7 and 42.8 ± 8.4 mm3, respectively, in the inferior catheter orientation (n = 11, p = <0.01*), 74.1 ± 5.8 and 54.2 ± 3.7 mm3, respectively, in the superior catheter orientation (n = 10, p = <0.01*). During 6-mm simulated wall motion, the MC catheter and MNS catheter moved 5.2 ± 0.1 and 0 mm, respectively, in inferior orientation and 5.5 ± 0.1 and 0 mm, respectively, in the superior orientation on the ablation surface. Conclusions: The lesion dimensions were larger with MNS compared to MC in the presence of simulated wall motion, consistent with greater catheter stability. However, similar lesion dimensions were observed in the stationary model.