Radiofrequency cardiac ablation with catheters placed on opposing sides of the ventricular wall: Computer modelling comparing bipolar and unipolar modes

Abstract

Koruth, J.; Berjano, E. (2014). Radiofrequency cardiac ablation with catheters placed on opposing sides of the ventricular wall: Computer modelling comparing bipolar and unipolar modes. International Journal of Hyperthermia. 30 (6) Materials and methods:We built computational models to study the temperature distributions and lesion dimensions created by BM and UM on IVS and VFW during RFA. Two different UM types were considered: sequential (SEUM) and simultaneous (SIUM). The effect of ventricular wall thickness, catheter misalignment, epicardial fat, and presence of air in the epicardial space were also studied.Results: As regards IVS ablation, BM created transmural and symmetrical lesions for wall thicknesses up to 15 mm. SEUM and SIUM were not able to create transmural lesions with IVS thicknesses ≥ 12.5 and 15 mm, respectively. Lesions were asymmetrical only with SEUM. For VFW ablation, BM also created transmural lesions for wall thicknesses up to 15 mm. However, with SEUM and SIUM transmurality was obtained for VFW thicknesses ≤ 7.5 and 12.5 mm, respectively. With the three modes VFW lesions were always asymmetrical. In the scenario with air or a fat tissue layer on the epicardial side, only SIUM was capable of creating transmural lesions. Overall, BM was superior to UM in IVS and VFW ablation when the catheters were not aligned. Conclusions:Our findings suggest that BM is more effective than UM in achieving transmurality across both ventricular sites, except in the situation of the epicardial catheter tip surrounded by air or placed over a fat tissue layer.

High-power bipolar ablation for incessant ventricular tachycardia utilizing a deep midmyocardial septal circuit

“…Bipolar ablation was most useful in patients with thicker interventricular septum measuring more than 1.5 cm, with transmural lesions penetrating as deep as 2.5 cm. In a computer-generated model of the temperature distribution using this same setup for bipolar ablation, the lesion width became more narrow at the middle of the septum, with thicker tissue (>15 mm) resembling an hourglass shape 7 . The total duration of ablation in this model was 120 seconds, which is in contrast to our case in which longer lesions were applied for up to 5 minutes to allow more time for conductive heating and presumably deeper lesions.…”

Comparative Analysis of Different Methods of Modeling the Thermal Effect of Circulating Blood Flow During RF Cardiac Ablation

“…the blood is included in the domain. In this method, electrical conductivity of blood was assumed to be constant, as in previous studies [3,9,11,[13][14][15]. As in Method 1, convective boundary conditions were applied at the electrode-blood and tissue-blood interfaces to simulate cooling by the blood flow (Fig.…”

“…2b and 2c show the thermal and velocity boundary conditions. The effect of blood circulating inside the cardiac chamber was modeled by four methods which have been used in previous studies [3,5,[9][10][11][13][14][15]17,20,24]. Each case was assessed under conditions of high and low blood flow.…”

“…Some models do not consider blood as part of the model domain, and consequently the blood-tissue and blood-electrode interfaces were really model boundaries [3][4][5][6][7][8] on which an electrical boundary condition of zero current density was set. Other models consider blood as part of the domain [9][10][11][12][13][14][15][16][17][18][19][20][21], thus allowing RF current to flow through the blood. These models represent the initial value of the impedance (basal impedance) more realistically than those that do not include blood.…”

Coupled electrical-thermal model for monopolar and bipolar radiofrequency liver tumor ablation

“…Besides this monopolar RFA configuration, the use of two needles has recently been considered in a bipolar configuration for cardiac ablation studies [14]. The authors simulated in [13] a bipolar configuration for liver tumor ablation where 2 needles inject pulsed radiofrequency currents using the finite difference method.…”