Contact force and force-time integral in atrial radiofrequency ablation predict transmurality of lesions

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

We prospectively studied consecutive 512 RF applications from atrial fibrillation ablation procedures. A force-sensing ablation catheter (Tacticath(®), Endosense) was used to continuously measure CF and force-time integral (FTI) during each RF application. Distal bipolar EGM was analysed before, during, and after each RF application. Depending on initial EGM morphology, transmurality of lesions was defined by: (i) disappearance of the positivity after RF when there was QR morphology, (ii) diminution >75% of the positivity when there was QRS morphology, or (iii) disappearance of the R' positivity when there was RSR' morphology. Electrogram criteria were validated by electrophysiologists blinded to force measurements. Force-time integral was higher in TL than in non-transmural lesions (NTLs): 652 ± 248 vs. 212 ± 140 gs (P < 0.001). Mean CF per RF pulse was higher in TL than in NTL: 26.3 ± 12.5 vs. 11.3 ± 10.3 g (P < 0.001). The best cut-off to predict TL was an FTI ≥ 392 gs [sensitivity 0.89, specificity (Sp) 0.93, positive predictive value (PPV) 0.98, and negative predictive value 0.67] and a higher FTI (>700 gs) warrants transmurality of RF atrial lesions (100% Sp and PPV).

Contact force and FTI during RF are correlated with TL. During RF delivery, a target FTI > 392 gs can be used as an endpoint.