Pulsed Field Ablation Index-Guided Ablation for Lesion Formation: Impact of Contact Force and Number of Applications in the Ventricular Model

Abstract

Background: The effect of contact force (CF) on lesion formation is not clear during pulsed field ablation (PFA). The aim of this study was to evaluate the impact of CF, PFA, and their interplay through the PFA index (PF index) formula on the ventricular lesion size in swine.

Methods: PFA was delivered through the CF-sensing OMNYPULSE catheter. Predefined PFA applications (×3, ×6, ×9, and ×12) were delivered maintaining low (5-25 g), high (26-50 g), and very high (51-80 g) CFs. First, PFA lesions were evaluated on necropsy in 11 swine to investigate the impact of CF/PFA-and their integration in the PF index equation-on lesion size (study characterization). Then, 3 different PF index thresholds-300, 450, and 600-were tested in 6 swine to appraise the PF index accuracy to predict the ventricular lesion depth (study validation).

Results: In the study characterization data set, 111 PFA lesions were analyzed. CF was 32±17 g. The average lesion depth and width were 3.5±1.2 and 12.0±3.5 mm, respectively. More than CF and PFA dose alone, it was their combined effect to impact lesion depth through an asymptotically increasing relationship. Likewise, not only was the PF index related to lesion depth in the study validation data set (r²=0.66; P<0.001) but it also provided a prediction accuracy of the observed depth of ±2 mm in 69/73 lesions (95%).

Conclusions: CF and PFA applications play a key role in lesion formation during PFA. Further studies are required to evaluate the best PFA ablation settings to achieve transmural lesions.

Keywords: catheter ablation; electroporation; heart ventricles; swine.

Figure 1.

The OMNYPLUSE catheter. Top, The OMNYPULSE catheter. The OMNYPULSE is a multielectrode, contact force (CF)–sensing catheter with a distally located spherical cage that is 12 mm in diameter. The catheter has a deflectable tip designed to facilitate electrophysiological mapping of the heart and to transmit pulsed field ablation energy up to 12 electrodes along the catheter tip for ablation purposes. The catheter shaft measures 7.5F and is deployed through a 10F guiding sheath. The OMNYPULSE catheter has CF-sensing technology and incorporates magnetic-based navigation technology allowing the CARTO 3 system to display the location and orientation of the catheter. Images courtesy of ©Biosense Webster, Inc. All rights reserved.

Figure 2.

Study characterization data set. Impact of contact force (CF) and pulsed field ablation (PFA) on the lesion depth. A significant increase in the lesion size was recorded from very-low-dose PFA (×3) to high-dose PFA (×12) provided that CF >5 g was warranted.

Figure 3.

Study characterization data set. Impact of contact force (CF) >5 g and pulsed field ablation (PFA) dose on lesion size: histological analysis. Once a good catheter-tissue contact was achieved (CF >5 g), a progressively higher PFA dose was associated with deeper lesions (A) and increasing width up to 9 applications at which it plateaus. (B). The histological sections were consistent with this observation (C–F). In fact, when the system was toggled from ×3 to ×12 PFA dose, despite a slight increase in the lesion width, the average lesion depth nearly doubled. Images courtesy of © Biosense Webster, Inc. All rights reserved.

Figure 4.

Study validation data set: relationship between contact force (CF) and pulsed field ablation index (PF index). PF index and CF were linearly related for each attained PF index value.

Figure 5.

Study validation data set: correlation between lesion depth and pulsed field ablation index (PF index). A, The attained PF index values were plotted against the observed lesion depth on histology. The 2 variables were linearly related, and >60% of the variation of the lesion depth was explained by the variation of the PF index parameter (r²=0.6644). Furthermore, when the actual lesion depth was plotted against the expected lesion depth, or PF index/100, it was clear that the actual lesion depth on histology was predicted by the PF index values attained during ablation with a prediction accuracy of ±2 mm.

Figure 6.

The histological correlation between pulsed field ablation index (PF index, PFI) and the ventricular lesion depth. As reported in 2 different specimens, the PF index was clearly correlated with the average ventricular lesion depth. For instance, a PF index of 298 (A) and 527 (B) was associated with a mean ventricular lesion depth of 2.98 (A) and 4.92 (B) mm, respectively, thus providing invaluable insights on the prediction of the lesion depth through the PF index value. Images courtesy of © Biosense Webster, Inc. All rights reserved.