During radiofrequency (RF) ablation procedures, lesion volume is highly dependent on contact force (CF). It has recently been shown that bipolar electrogram (EGM) recording predict lesions’ transmurality. We hypothesized that there is a correlation between CF and EGM criteria of transmural lesion during RF.

We prospectively studied all 524 RF applications in 8 ablation procedures for atrial fibrillation (7) and atrial flutter (1). A force sensing 3.5mm-tip ablation catheter (Tacticath^®, Endosense) was used to continuously measure CF and force-time integral (FTI) during each RF application. Distal bipolar EGM was analyzed before, during, and after each RF application. Depending on initial EGM morphology, transmurality was defined by 1) disappearance of the positivity after RF when there is QR morphology, 2) diminution >75% of the positivity when there is QRS morphology and 3) disappearance of the R’ positivity when there is RSR’ morphology. Two electrophysiologists blinded to force measurements validated each EGM criteria.

Mean FTI was higher in EGM-defined transmural lesions (ETL) than in EGM-defined non-transmural lesions (ENTL): 652±248 gs vs. 212±139 gs (p<0.0001). Mean CF per RF pulse was higher in ETL than in ENTL: 26.2±12.5 g vs. 11.2±10.3 g (p<0.0001). Mean duration of RF application was higher in ETL than in ENTL: 28.6±13.5 s vs. 21.8±10.8 (p<0.0001). There was an inverse correlation between mean delay of ETL criteria occurrence during RF and mean CF (r=-0.31, p=<0.0001). An FTI >392 gs was best predictive of transmurality (Se=0.89, Sp=0.93, AUC=0.95), and an FTI>700 gs always resulted in a transmural lesion on EFM criteria (Sp=100%, PPV=100%).

CF and FTI during RF are correlated with transmurality of atrial lesions during ablation and a minimum FTI of 392 gs should always be aimed during RF delivery in order to obtain transmural lesions.