Nonhomogeneous force application during typical flutter ablation explains local difficulties in lesion creation

Abstract

Introduction – The current scientific literature suggests similar or even better catheter contact on caval regions of the cavo-tricuspid isthmus (CTI) compared to the more medial or annular part. Yet CTI ablation can be challenging owing to instability at the inferior vena cava (IVC) edge. No study specifically addressed the issue of catheter-tissue contact on caval/mid/annular regions of the CTI. Methods – Twenty-seven patients (22 men, 67±12 years) underwent typical atrial flutter ablation with a contact force (CF) sensing catheter (Tacticath 75, Abott) and were prospectively included. Operators aimed at optimizing CF for all RF pulses. The product of CF, time (force-time integral; FTI) and delivered power (FTPI) has been proposed as an estimate of lesion size. In a subset of 8 consecutive pts, electrograms (EGM) of all RF lesions were analyzed. Annular CTI was defined as sites showing both atrial and ventricular near-field bipolar EGM. Mid CTI sites had only atrial near field bipolar EGM on both distal and proximal dipoles (or distal only in case of superior-to-inferior approach). Caval sites had near-field bipolar EGM only in distal dipole, while the proximal one was inferiorly located. Results – Complete persistent (at 30 min) CTI block was obtained in all patients. A steerable sheath was used in 12 pts (44%). Procedure duration was 93±30 min, RF delivery time 10±6 min, fluoroscopy time 14±8 min. Mean CF was 15.8±5.9 g. CF was significantly lower (11.1±9.7 g) at the caval CTI than at mid CTI (19.9±11.8 g) and annular CTI (20±12.2 g; p=0.001). CF and FTI were higher during sinus rhythm than during Fl (23.2±15.3 vs 18.5±15.4 g, p=0.04 and 677±432 vs 532±357 gs, p=0.03). Use of a sheath improved mean CF (24.4±12.5 vs 18.4±14.9 g, p=0.01) but this was not significant at caval sites (17.5±11.4 vs 12.6±10.7 g, p=0.31). Conclusion – Applied forces are significantly lower at the IVC edge during CTI ablation. This supports the use of a steerable sheath in challenging cases.