Bipolar ablation’s unique paradigm: Duration and power as respectively distinct primary determinants of transmurality and steam pop formation

Abstract

BACKGROUND Bipolar radiofrequency (RF) ablation strategies are increasingly used, mainly to target deep myocardial reentrant circuits responsible for ventricular tachycardia that cannot be extinguished with traditional unipolar RF ablation. Because this strategy is novel, factors that affect lesion geometry and steam pop formation require further investigation. OBJECTIVE To assess the effect of contact force, power, and time on the resulting lesion geometry and the risk of steam pop formation during bipolar RF ablation of thick myocardial tissue. METHODS A custom ex vivo bipolar ablation model was used to assess lesion formation. A combination of parallel and perpendicular configurations of ablation catheters was used to create lesions by varying force (20g, 30g, or 40g), power (30 or 40 W), and time (20, 30, 45, or 60 seconds). Lesion dimensions and the incidence of steam pops were recorded and then analyzed with binary logistic regression and multiple linear regression. RESULTS In bipolar ablation, lesion transmurality was most affected by the amount of time RF energy was applied. Durations longer than 20 seconds resulted in lesions deeper than half the tissue thickness. Steam pop formation was more frequent in thinner tissue, at longer ablation times, and at higher powers. CONCLUSION The parameters assessed in this ex vivo model could be used as guidelines for future in vivo work and clinical evaluation of interventricular septal bipolar ablation.

Perpendicular catheter orientation during papillary muscle ablation results in larger, deeper lesions

“…In terms of implementation, reportedly, catheter orientation does not specifically influence the likelihood of steam pops 22 . Therefore, the use of perpendicular orientation for PM‐ablation, as suggested in the current study, seemingly does not confer any additional procedural risk.…”

Insurance lesions: Does a second lesion make a difference?

“…5 Irrigation began with the delivery of RF energy at the start of ablation and proceeded for 5 s after ablation ended, similar to previous studies. 4 After each ablation, the tissue was allowed to cool to a baseline temperature of 37°C.…”

“…All ablations were carried out with an irrigated 8 Fr ablation catheter (Thermocool SF; Biosense Webster). The ex vivo model used here is based on previously published models 4,5 . The catheter was connected to a bag of 0.9% saline (9 g NaCl [VWR International] in 1 L diH 2 O) for irrigation through a CoolFlow irrigation system (Biosense Webster).…”

“…Ablation was supplemented with normal saline irrigation through the catheter tip at a nominal rate of 30 ml/min, which has been used in similar ablation models 5 . Irrigation began with the delivery of RF energy at the start of ablation and proceeded for 5 s after ablation ended, similar to previous studies 4 . After each ablation, the tissue was allowed to cool to a baseline temperature of 37°C.…”

“…The ex vivo model used here is based on previously published models. 4,5 The catheter was connected to a bag of 0.9% saline (9 g NaCl [VWR International] in 1 L diH 2 O) for irrigation through a CoolFlow irrigation system (Biosense Webster). The ablation catheter, once positioned, was oriented such that the catheter was perpendicular to the tissue (Figure 1B).…”