In vivo contact force analysis and correlation with tissue impedance during left atrial mapping and catheter ablation of atrial fibrillation.

BACKGROUND The aim of this study was to evaluate in vivo contact force (CF) and the correlation of CF with impedance during left atrial 3-dimensional electroanatomical mapping and ablation. METHODS AND RESULTS CF during point-by-point left atrial mapping was assessed in 30 patients undergoing atrial fibrillation ablation. Operators were blinded to the real-time CF data. Data were analyzed according to 11 predefined areas in the left atrial and 6 segments around the ipsilateral pulmonary veins. A total of 3475 mapping and 878 ablation points were analyzed. Median CF during mapping was 14.0g (6.5-26.2; q1-q3), ranging from 5.1g at the ridge to 29.8g at the roof. Median CF at the ridge and mitral isthmus were 5.1g and 6.9g, respectively. Extremely high CF ≥100g was noted in 24 points (0.7%). Median CFs during ablation around the right and left pulmonary veins were 22.8g (12.6-37.9; q1-q3) and 12.3g (6.9-30.2; q1-q3), respectively. The lowest median CFs were recorded at the anterior-superior and anterior-inferior segments of the left pulmonary veins (7.2g and 7.9g). Impedance values during mapping and impedance fall during ablation correlated with the applied CF (R(2)=0.16; P<0.001 and R(2)=0.04; P<0.001) although there was significant overlap. CONCLUSIONS Excessively high and low CF values can be observed during left atrial mapping and ablation. The low CF obtained at the mitral isthmus and anterior segments of the left pulmonary veins may explain why reconnection after ablation occurs more frequently at these sites. CF and impedance do correlate; however, the impedance for a given CF ranges widely, limiting its use in clinical practice.