Relations between contact force, bipolar voltage amplitude, and mapping point distance from the left atrial surfaces of 3D ultrasound- and merged 3D CT-derived images: Implication for atrial fibrillation mapping and ablation.

BACKGROUND: Catheter tip-derived contact force (CF) and 3-dimensional (3D) maps are key to mapping and ablation of atrial fibrillation. OBJECTIVE: This study sought to determine the relation between CF and 3D map surfaces. METHODS: We conducted a validation study of Carto-based 3D ultrasound (3D-US) and 3D-US merged with computed tomography (3D-Merge-CT) left atrium/pulmonary vein images. Under fluoroscopic guidance, 1361 mapping points (20 patients) with CFs and electrogram information were randomly acquired around the PVs. RESULTS: CF correlated weakly with the distance of mapping points from the 3D-Merge-CT (r = 0.27; P < .001) and 3D-US (r = 0.22; P < .001) surfaces but not with bipolar voltage (r = -0.01; P = .2400). Low CF (0-4 g) yielded points close to the 3D-US surface; moderate (5-9 g) and high CFs (10-20 g) generated points beyond the surface (0.1 ± 3.9, 1.4 ± 3.4, and 2.3 ± 3.4 mm; P < .05 for each). Low, moderate, and high CFs yielded points below, close to, and beyond the 3D-Merge-CT surface (-1.2 ± 3.7, 0.4 ± 3.0, and 1.0 ± 2.9 mm; P < .05 for each). CONCLUSION: Poor correlation between CF and the distance of mapping points from the 3D map surfaces and electrogram information shows the limitation of 3D mapping and electrogram information for predicting good contact. In addition, mapping seems to require far less CF than ablation requires.