Impact of Catheter-Tissue Contact Force on Lesion Size During Right Ventricular Outflow Tract Ablation in a Swine Model
Radiofrequency catheter ablation (RFCA) has become a widely accepted and effective non-pharmacological treatment for patients with idiopathic ventricular arrhythmias (VAs), including frequent premature ventricular contractions and ventricular tachycardia. The right ventricular outflow tract (RVOT) is one of the most common sites for ablation in such cases. However, despite its effectiveness, studies have shown that 7% to 20% of RVOT ablation procedures fail to achieve acute success or result in subsequent recurrences. One of the critical factors influencing the success of ablation procedures is the catheter-tissue contact force (CF), which has been shown to significantly impact lesion size and, consequently, the effectiveness of the ablation. However, excessive CF can lead to severe complications, such as cardiac tamponade and steam pops. This study aimed to evaluate the impact of CF on lesion size during RVOT ablation in a swine model, using a novel CF-sensing ablation catheter.
The study was conducted using twelve Guangxi Bama miniature male pigs, weighing between 40 and 50 kg. These pigs were selected because their heart size and hemodynamic conditions are comparable to those of a normal human adult. After general anesthesia was administered, a ThermoCool SmartTouch contact-sensing ablation catheter was introduced into the RVOT via the femoral vein under the guidance of the CARTO 3 electroanatomic mapping system. The animals were randomly divided into four groups based on different CF levels: group A (3–9 g), group B (10–19 g), group C (20–29 g), and group D (30–39 g). Radiofrequency ablations were performed at three points in the free wall and septum of the RVOT in power control mode at 30 W for 30 seconds, with a saline irrigation rate maintained at 17 mL/min. At the end of the procedures, the maximum depth, surface diameter, and lesion volume were measured and recorded.
A total of 72 ablation lesions were created in the RVOT of the 12 pigs. The results showed a strong correlation between CF and lesion size. In the free wall, the maximum depth, surface diameter, and lesion volume were significantly correlated with CF (b = 0.105, b = 0.162, and b = 3.355, respectively, P < 0.001). Similarly, in the septum, these parameters also showed a strong correlation with CF (b = 0.093, b = 0.150, and b = 3.712, respectively, P < 0.001). The study also found that the regional ventricular bipolar voltage amplitude, unipolar voltage amplitude, and impedance were weakly positively associated with CF (b = 0.065, b = 0.125, and b = 1.054, respectively, P < 0.001).
One of the critical findings of the study was the incidence of steam pops, which occurred only when the CF exceeded 20 g. The incidence of steam pops was significantly different among the four groups (free wall: F = 7.3, P = 0.032; septum: F = 10.5, P = 0.009). The average CF value when steam pops occurred was 30.8 ± 4.5 g in the free wall and 31.5 ± 5.2 g in the septum, with no significant difference between these values (t = –0.249, P = 0.808). Additionally, trans-mural lesions were observed when the CF exceeded 10 g in the free wall, while no trans-mural lesions were observed in the septum, even when the CF reached 30 g.
The study also evaluated the relationship between CF and local ventricular voltage amplitude and impedance. Linear regression analysis showed that the ventricular bipolar voltage amplitude, unipolar voltage amplitude, and impedance values obtained from the distal electrodes of the catheters were positively correlated with the CF value. However, the correlation coefficients were low, indicating that these indicators are not reliable predictors of real-time CF. This finding is consistent with previous studies, which have shown that indirect indicators, such as local voltage amplitude, temperature, and impedance, are not sufficiently reliable to reflect the real-time contact condition between the catheter and myocardial tissue.
The results of this study have important implications for clinical practice. The CF is a leading predictive factor for lesion size in RVOT ablation. Maintaining the CF value between 3 and 10 g appears to be reasonable and effective for creating the necessary lesion size while reducing the risk of complications, such as steam pops and perforations. However, when ablating the septum of the RVOT, where the origin of VAs is often located deep under the endocardium, increasing the CF from 10 to 20 g may be necessary. Nonetheless, CF levels greater than 20 g should be avoided to minimize the risk of complications.
The study also highlighted the limitations of using indirect indicators to assess CF during ablation procedures. Although high ventricular voltage can predict good contact conditions, it cannot exclude the possibility of excessive CF. Therefore, the clinical application value of predicting real-time CF based on local ventricular voltage amplitude before ablation is limited. The direct measurement of CF using CF-sensing catheters remains the most reliable method for ensuring optimal contact conditions during ablation.
The findings of this study are consistent with previous research on the impact of CF on lesion size during ablation procedures. For example, Shah et al. found that lesion size correlates linearly with the measured CF-time integral, and constant contact produces the largest lesions. Similarly, Matia Frances et al. showed that CFs of at least 20 g are required to achieve trans-mural lesions. Di Biase et al. also found that contact pressure between 20 and 30 g and a power setting of 40 W appear to achieve trans-murality while preserving safety.
In conclusion, this study demonstrates that CF is a critical determinant of lesion size during RVOT ablation. Maintaining the CF value between 3 and 10 g is reasonable and effective for creating the necessary lesion size while reducing the risk of complications. However, when ablating the septum of the RVOT, increasing the CF to 10–20 g may be necessary. Operators should pay close attention to real-time CF changes and avoid CF levels greater than 20 g to minimize the risk of complications, such as steam pops and perforations. Further research is needed to validate these findings in human patients and to explore the optimal CF range for different ablation sites and conditions.
doi.org/10.1097/CM9.0000000000000859
Was this helpful?
0 / 0