Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 Apr 20;17(1):43.
doi: 10.1186/s12938-018-0475-7.

Should Fluid Dynamics Be Included in Computer Models of RF Cardiac Ablation by Irrigated-Tip Electrodes?

Affiliations
Free PMC article

Should Fluid Dynamics Be Included in Computer Models of RF Cardiac Ablation by Irrigated-Tip Electrodes?

Ana González-Suárez et al. Biomed Eng Online. .
Free PMC article

Abstract

Background: Although accurate modeling of the thermal performance of irrigated-tip electrodes in radiofrequency cardiac ablation requires the solution of a triple coupled problem involving simultaneous electrical conduction, heat transfer, and fluid dynamics, in certain cases it is difficult to combine the software with the expertise necessary to solve these coupled problems, so that reduced models have to be considered. We here focus on a reduced model which avoids the fluid dynamics problem by setting a constant temperature at the electrode tip. Our aim was to compare the reduced and full models in terms of predicting lesion dimensions and the temperatures reached in tissue and blood.

Results: The results showed that the reduced model overestimates the lesion surface width by up to 5 mm (i.e. 70%) for any electrode insertion depth and blood flow rate. Likewise, it drastically overestimates the maximum blood temperature by more than 15 °C in all cases. However, the reduced model is able to predict lesion depth reasonably well (within 0.1 mm of the full model), and also the maximum tissue temperature (difference always less than 3 °C). These results were valid throughout the entire ablation time (60 s) and regardless of blood flow rate and electrode insertion depth (ranging from 0.5 to 1.5 mm).

Conclusions: The findings suggest that the reduced model is not able to predict either the lesion surface width or the maximum temperature reached in the blood, and so would not be suitable for the study of issues related to blood temperature, such as the incidence of thrombus formation during ablation. However, it could be used to study issues related to maximum tissue temperature, such as the steam pop phenomenon.

Keywords: Blood flow; Cardiac ablation; Computer model; Irrigated electrode; Radiofrequency ablation; Thermal modeling.

Figures

Fig. 1
Fig. 1
Geometry of the three-dimensional computational models built (not to scale). Cardiac tissue thickness (H) was 20 mm and the dimensions of cardiac chamber X and Y (Z = Y) were obtained from a convergence test. RF current flows between an active electrode and the dispersive electrode (bottom). The active electrode (7Fr, 4 mm) is a multi-hole open-irrigated electrode, which is assumed to be inserted into cardiac tissue to a depth DE. In the reduced model the saline irrigation through the small holes in the electrode tip is simply modeled by fixing a temperature condition of 40 °C on its surface, while in the full model it is modeled by an inlet velocity boundary condition Usaline at the electrode-blood interface. Thermal lesion is assessed by the 50 °C isotherm and its geometry is characterized by: maximum depth (D), maximum width (MW), depth at the maximum width (DW) and surface width (SW)
Fig. 2
Fig. 2
Boundary conditions of the models: a electrical boundary conditions, b thermal boundary conditions for the reduced model, and c thermal and velocity boundary conditions for the full model
Fig. 3
Fig. 3
Temperature distributions at 10 s (a) and 60 s (b) obtained with the full model. Solid lines are those of the lesion boundaries computed by the full model while dashed lines are those computed by the reduced model
Fig. 4
Fig. 4
Comparison of the progress of lesion depth (a), surface width (b) and maximum width (c) between the reduced (red lines) and the full (blue lines) models, for high and low blood flow rates and three electrode insertion depths (DE) (0.5, 1.0 and 1.5 mm)
Fig. 5
Fig. 5
Comparison of the progress of maximum temperatures reached in the tissue (a) and blood (b) between the reduced (red lines) and full (blue lines) models, for high and low blood flow rates and three electrode insertion depths (DE) (0.5, 1.0 and 1.5 mm)
Fig. 6
Fig. 6
Temperature distributions at 60 s (a) for the full model (black and white solid lines are those of the lesion boundaries computed by the full and reduced model, in this case multiplying by three the thermal convective coefficients. The dashed line is that computed by the reduced model using the previous thermal convective coefficients) and the comparison of progress of maximum blood temperatures (b) between the reduced (red lines) and full (blue line) models for low blood flow rate using an electrode insertion depth (DE) of 1.0 mm. The rationale for increasing the value of thermal convective coefficients at both interfaces was to try to match the lesion surface width of the reduced model with that of the full model

Similar articles

See all similar articles

References

    1. Matsudaira K, Nakagawa H, Wittkampf FH, Yamanashi WS, Imai S, Pitha JV, et al. High incidence of thrombus formation without impedance rise during radiofrequency ablation using electrode temperature control. Pacing Clin Electrophysiol. 2003;26(5):1227–1237. doi: 10.1046/j.1460-9592.2003.t01-1-00173.x. - DOI - PubMed
    1. Yokoyama K, Nakagawa H, Wittkampf FH, Pitha JV, Lazzara R, Jackman WM. Comparison of electrode cooling between internal and open irrigation in radiofrequency ablation lesion depth and incidence of thrombus and steam pop. Circulation. 2006;113(1):11–19. doi: 10.1161/CIRCULATIONAHA.105.540062. - DOI - PubMed
    1. González-Suárez A, Berjano E. Comparative analysis of different methods of modeling the thermal effect of circulating blood flow during RF cardiac ablation. IEEE Trans Biomed Eng. 2016;63(2):250–259. doi: 10.1109/TBME.2015.2451178. - DOI - PubMed
    1. González-Suárez A, Berjano E, Guerra JM, Gerardo-Giorda L. Computational modeling of open-irrigated electrodes for radiofrequency cardiac ablation including blood motion-saline flow interaction. PLoS ONE. 2016;11(3):e0150356. doi: 10.1371/journal.pone.0150356. - DOI - PMC - PubMed
    1. Pérez JJ, D’Avila A, Aryana A, Berjano E. Electrical and thermal effects of esophageal temperature probes on radiofrequency catheter ablation of atrial fibrillation: results from a computational modeling study. J Cardiovasc Electrophysiol. 2015;26(5):556–564. doi: 10.1111/jce.12630. - DOI - PubMed
Feedback