Assessment of far-field capture in a 3D box-scar lesion: A depth-dependent analysis in the swine right ventricle
R Kato, M Takigawa, M Honda, G Nitta, M Negishi, R Tateishi, J Yamaguchi, I Kawamura, K Goto, K Ihara, T Nishimura, S Tao, S Miyazaki, H Watanabe, T SasanoAbstract
Background
In a previous atrial study, far-field capture was evaluated in a two-dimensional (2D) transmural box-scar lesion created in the right atrium. Far-field capture was not observed when pacing was performed more than 6 mm away from viable myocardium. Building on these findings, the present ventricular study was designed to evaluate depth-related far-field capture in a three-dimensional (3D) setting. To eliminate lateral far-field effects, box lesions with diameters ≥12 mm were created so that pacing from the lesion center reflected only depth-dependent capture.
Purpose
To quantify the relationship between pacing threshold and lesion depth in a 3D ventricular model allowing only depth-related far-field capture.
Methods
Fourteen swine underwent right ventricular septal radiofrequency ablation. Box lesions were created at 50 W, with a constant ablation duration within each box, while the duration was varied among boxes to achieve different lesion depths, maintaining a short-axis diameter ≥12 mm. Pacing thresholds were determined at the lesion center. After heart explantation, lesion depth, short-axis, and long-axis diameters were measured macroscopically. The relationship between pacing threshold and lesion depth was analyzed using linear regression after logarithmic transformation of thresholds. Cases with no capture at 20 mA were handled by assigning 21 mA (upper-limit substitution).
Results
Twenty-eight lesions from 14 swine were analyzed. Lesion depth was 3.3 mm [2.5–4.5 mm], long-axis 19.0 mm [16.0–20.3 mm], and short-axis 16.9 mm [12.7–19.1 mm]. Pacing threshold showed a positive correlation with lesion depth (R² = 0.82, p < 0.001). Each 1-mm increase in lesion depth was associated with a 1.7-fold increase in pacing threshold (95% CI 1.54–1.87). "Based on inverse regression, pacing thresholds of 2.5 mA, 4 mA, and 6 mA corresponded to lesion depths of 2.0 mm (95% CI 1.5–2.4 mm), 2.8 mm (95% CI 2.5–3.1 mm), and 3.6 mm (95% CI 3.3–3.9 mm), respectively.
Conclusion
Pacing threshold increased proportionally with lesion depth in the ventricle. Under conditions that eliminate lateral far-field effects, this quantitative model provides a practical reference to interpret pacing responses after ventricular ablation.