Contact Geometry Affects Lesion Formation in Radio-Frequency Cardiac Catheter Ablation

Abstract

One factor which may be important for determining proper lesion creation during atrial ablation is catheter-endocardial contact. Little information is available that relates geometric contact, depth and angle, to ablation lesion formation. We present an electrothermal computer model of ablation that calculated lesion volume and temperature development over time. The Pennes bioheat equation was coupled to a quasistatic electrical problem to investigate the effect of catheter penetration depth, as well as incident catheter angle as may occur in practice. Biological experiments were performed to verify the modelling of electrical phenomena. Results show that for deeply penetrating tips, acute catheter angles reduced the rate of temperature buildup, allowing larger lesions to form before temperatures elevated excessively. It was also found that greater penetration did not lead to greater transmurality of lesions. We conclude that catheter contact angle plays a significant role in lesion formation, and the time course must be considered. This is clinically relevant because proper identification and prediction of geometric contact variables could improve ablation efficacy.

Towards patient-specific modelling of lesion formation during radiofrequency catheter ablation for atrial fibrillation

“…The appropriate values for A and ΔE were found at this point to ensure that damaged tissue with Ω(t) ≥ 1 corresponded to 323.15K tissue temperatures and ablation times between 30s and 60s. Thus, the model parameters and outcomes on test simulations in atrial slabs were in agreement with previous studies [7,8]. Note that this model did not include cooling effects from the blood flow in the atria, and also kept the electrical conductivity of the tissue constant throughout.…”

“…Firstly, the propagation of heat throughout the tissue due to the ablation catheter was computed by solving the modified Pennes bioheat equation in the following form [7,8]:…”

“…Further to this, the tissue geometries were initialised with a uniform temperature of 310.15K and uniform potential of 0V. The catheter was modelled based on a 7-french geometry (2.33 mm diameter), matching both clinical standards and previous studies [7,8]. The catheter was modelled as perpendicular to the endocardial tissue surface, which produced radially symmetric ablation and heat propagation patterns.…”

“…The simulated procedures were relatively quick (~30 minutes), although the fully transmural lesions were achieved at an inevitable price of wide lesions in regions of high AWT. While the model had its limitations, it did demonstrate the viability of patient-specific evaluation of RFCA procedures, which could provide useful information for the clinic and ultimately lead to the improved clinical treatment of AF.Limitations of the model include disregarding cooling effects by the blood in the atria, which may lead to a decrease of the lesion formation times [14], as well as the use of one specific catheter geometry [7,8]. A study by Gallagher et al [7] has suggested that changing the catheter depth and angle would vary the ratio of the lesion depth to the lesion width.…”

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

“…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.…”