Impact of repeated and combined very high-power and high-power short-duration radiofrequency ablation protocols on lesion size in a porcine ex-vivo model

Background

High-power, short-duration (HP-SD) and very high-power, short-duration (vHP-SD) ablation are established RF protocols in electrophysiology. Although lesion formation has been studied for each protocol separately, clinical procedures sometimes require repeated vHP-SD applications or sequential use of both protocols to achieve transmural, continuous lesions. The effects of repeated vHP-SD applications on lesion depth and width remain insufficiently characterized, and evidence on lesion formation when HP-SD and vHP-SD are applied sequentially at the same site is limited. This study investigates lesion characteristics after repeated vHP-SD applications and after sequential HP-SD and vHP-SD ablation at the same location across different contact force levels in a porcine ex vivo model.

Methods

RF ablations were performed on porcine ventricular myocardium in a circulating saline bath using an irrigated, temperature-controlled catheter. Two protocols were evaluated: vHP-SD (90 W, 4 s) and HP-SD (50 W, 15 s). Two experimental series were conducted. In Series A, one, two, or three consecutive vHP-SD applications were delivered at the same site with constant contact force (CF) of 15 g. In Series B, lesions were created using vHP-SD, HP-SD, or sequential vHP-SD + HP-SD at the same site with CF levels of 0, 5, 10, 15, 20, 25, and 30 g. Lesion depth and maximum diameter were assessed macroscopically.

Results

Series A included 60 lesions (n = 20 per application count). Lesion depth increased significantly and clinically between successive applications (1×: 3.1 ± 0.6 mm; 2×: 4.1 ± 0.6 mm; 3×: 4.9 ± 0.7 mm; p < 0.001). Maximum diameter also increased (1×: 7.7 ± 0.7 mm; 2×: 8.1 ± 0.7 mm; 3×: 9.0 ± 0.7 mm; p = 0.042).

Series B comprised 420 lesions (140 per protocol). Across all CF levels, sequential vHP-SD + HP-SD produced the largest lesions (depth: 0 g: 3.4 ± 0.6 mm to 30 g: 5.2 ± 0.4 mm; diameter: 0 g: 7.2 ± 0.8 mm to 30 g: 10.8 ± 0.6 mm), followed by HP-SD alone (depth: 0 g: 3.3 ± 0.3 mm to 30 g: 4.8 ± 0.6 mm; diameter: 0 g: 6.8 ± 0.5 mm to 30 g: 9.5 ± 1.5 mm), and then vHP-SD alone (depth: 0 g: 2.4 ± 0.2 mm to 30 g: 3.2 ± 0.5 mm; diameter: 0 g: 6.1 ± 0.3 mm to 30 g: 7.4 ± 1.0 mm; all p < 0.001, see Figure 1).

Conclusion

Repeated vHP-SD applications result in clinically relevant incremental increases in lesion depth and diameter. Sequential vHP-SD + HP-SD ablation produces significantly larger lesions than vHP-SD alone but does not yield clinically meaningful increases compared with HP-SD alone.