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

Abstract

Abstract-Goal: Our aim was to compare the different methods of modeling the effect of circulating blood flow on the thermal lesion dimensions created by radiofrequency cardiac ablation and on the maximum blood temperature. Methods: Computational models were built to study the temperature distributions and lesion dimensions created by a non-irrigated electrode by two radiofrequency energy delivery protocols (constant voltage and constant temperature) under high and low blood flow conditions. Four methods of modeling the effect of circulating blood flow on lesion dimensions and temperature distribution were compared. Three of them considered convective coefficients at the electrode-blood and tissue-blood interfaces to model blood flow: 1) without including blood as a part of the domain; 2) constant electrical conductivity of blood; and 3) temperature-dependent electrical conductivity of blood (+2%/ºC). Method 4) included blood motion and was considered to be a reference method for comparison purposes. Results: Only Method 4 provided a realistic blood temperature distribution. The other three methods predicted lesion depth values similar to those of the reference method (differences smaller than 1 mm), regardless of ablation mode and blood flow conditions. Conclusion: Considering the aspects of lesion size and maximum temperature reached in blood and tissue, Method 2 seems to be the most suitable alternative to Method 4 in order to reduce the computational complexity. Significance: Our findings could have an important implication in future studies of RF cardiac ablation, in particular, in choosing the most suitable method to model the thermal effect of circulating blood.

Can Fat Deposition After Myocardial Infarction Alter the Performance of RF Catheter Ablation of Scar‐Related Ventricular Tachycardia?: Results from a Computer Modeling Study

“…Next, we examined through additional computer simulations as to how certain alterations in the spatial distribution of the 3 tissue types could influence lesion geometry. The lesion geometry was assessed by means of the 50 ºC isotherm . In comparison, we also simulated a control case in which the ventricular wall comprised exclusively viable myocardium.…”

Computational Model for Prediction the Occurrence of Steam Pops during Irrigated Radiofrequency Catheter Ablation

“…The advection term in Equation (1) represents the heat loss due to blood flow. The velocity field u (m/s) is governed by the incompressible Navier-Stokes Equations [7]. At RF frequencies (≈500 kHz) and over the distance of interest, the biological medium can be considered almost totally resistive, and a quasi-static approach can therefore be used to solve the electrical problem, which allows calculating the value of q [6].…”

A computational model of open-irrigated electrode for endocardial RF catheter ablation

“…We used the parameters for a Table 1. Thermal and electrical characteristics of the elements employed in the numerical models (data from [17]): σ: electric conductivity; k: thermal conductivity; ρ: density; c: specific heat. standard PI controller K p = 4.78, K i = 3.39.…”

“…The thermal lesions are identified by the 50°C isotherm contour as in previous studies [14][15][16][17]25], which is usually considered to reasonably represent the isotherm of irreversible myocardial injury in hyperthermic ablation. The thermal lesions are determined by their characteristic dimensions (see Fig 1) [3,7,8,22,26]: maximum depth (D), maximum width (MW), depth at the maximum width (DW), and surface width (SW).…”

“…Computer modeling has been used in numerous studies on RFCA [11][12][13][14][15][16][17]. This approach allows to study different issues involved in RFCA in an efficient and reliable way, as opposed to ex vivo-in vitro and in vivo setups, which are time-consuming and lack reproducibility due to the several variables involved.…”