Black-box modeling to estimate tissue temperature during radiofrequency catheter cardiac ablation: feasibility study on an agar phantom model

This is an author-created, un-copyedited versíon of an article published in Physiological Measurement. IOP Publishing Ltd is not responsíble for any errors or omissíons in this versíon of the manuscript or any versíon derived from it. The Versíon of Record is available online at http://doi.org/10.1088/0967-3334/31/4/009[EN] The aim of this work was to study linear deterministic models to predict tissue temperature during radiofrequency cardiac ablation (RFCA) by measuring magnitudes such as electrode temperature, power and impedance between active and dispersive electrodes. The concept involves autoregressive models with exogenous input (ARX), which is a particular case of the autoregressive moving average model with exogenous input (ARMAX). The values of the mode parameters were determined from a least-squares fit of experimental data. The data were obtained from radiofrequency ablations conducted on agar models with different contact pressure conditions between electrode and agar (0 and 20 g) and different flow rates around the electrode (1, 1.5 and 2 L min¿1). Half of all the ablations were chosen randomly to be used for identification (i.e. determination of model parameters) and the other half were used for model validation. The results suggest that (1) a linear model can be developed to predict tissue temperature at a depth of 4.5 mm during RF cardiac ablation by using the variables applied power, impedance and electrode temperature; (2) the best model provides a reasonably accurate estimate of tissue temperature with a 60% probability of achieving average errors better than 5 °C; (3) substantial errors (larger than 15 °C) were found only in 6.6% of cases and were associated with abnormal experiments (e.g. those involving the displacement of the ablation electrode) and (4) the impact of measuring impedance on the overall estimate is negligible (around 1 °C).This work was supported by the 'Plan Nacional de Investigacion Cientifica, Desarrollo e Innovacion Tecnologica del Ministerio de Educacion y Ciencia' of Spain (TEC200801369/ TEC) and by an R&D contract (CSIC-20060633) between Edwards Lifescience Ltd and the Spanish National Research Council (CSIC). The English revision and correction of this paper was funded by the Universidad Politecnica de Valencia, Spain. We thank L Melecio for his invaluable technical support in conducting the experiments.Blasco-Giménez, R.; Lequerica, JL.; Herrero, M.; Hornero, F.; Berjano, E. (2010). Black-box modeling to estimate tissue temperature during radiofrequency catheter cardiac ablation: feasibility study on an agar phantom model. Physiological Measurement. 31(4):581-594. https://doi.org/10.1088/0967-3334/31/4/009S581594314Hong Cao, Tungjitkusolmun, S., Young Bin Choy, Jang-Zern Tsai, Vorperian, V. R., & Webster, J. G. (2002). Using electrical impedance to predict catheter-endocardial contact during RF cardiac ablation. IEEE Transactions on Biomedical Engineering, 49(3), 247-253. doi:10.1109/10.983459Hong Cao, Vorperian, V. R., Jang-Zem Tsai, Tungjitkusolmun, S., Eung Je Woo, & Webster, J. G. (2000). Temperature measurement within myocardium during in vitro RF catheter ablation. IEEE Transactions on Biomedical Engineering, 47(11), 1518-1524. doi:10.1109/10.880104Hamner, C. E., Potter, D. D., Cho, K. R., Lutterman, A., Francischelli, D., Sundt, T. M., & Schaff, H. V. (2005). Irrigated Radiofrequency Ablation With Transmurality Feedback Reliably Produces Cox Maze Lesions In Vivo. The Annals of Thoracic Surgery, 80(6), 2263-2270. doi:10.1016/j.athoracsur.2005.06.017HARTUNG, W. M., BURTON, M. E., DEAM, A. G., WALTER, P. F., McTEAGUE, K., & LANGBERG, J. J. (1995). Estimation of Temperature During Radiofrequency Catheter Ablation Using Impedance Measurements. Pacing and Clinical Electrophysiology, 18(11), 2017-2021. doi:10.1111/j.1540-8159.1995.tb03862.xDing Sheng He, Bosnos, M., Mays, M. Z., & Marcus, F. (2003). Assessment of myocardial lesion size during in vitro radio frequency catheter ablation. IEEE Transactions on Biomedical Engineering, 50(6), 768-776. doi:10.1109/tbme.2003.812161KO, W.-C., HUANG, S. K. S., LIN, J.-L., SHAU, W.-Y., LAI, L.-P., & CHEN, P. H. (2001). New Method for Predicting Efficiency of Heating by Measuring Bioimpedance During Radiofrequency Catheter Ablation in Humans. Journal of Cardiovascular Electrophysiology, 12(7), 819-823. doi:10.1046/j.1540-8167.2001.00819.xLabonte, S. (1994). Numerical model for radio-frequency ablation of the endocardium and its experimental validation. IEEE Transactions on Biomedical Engineering, 41(2), 108-115. doi:10.1109/10.284921Lai, Y.-C., Choy, Y. B., Haemmerich, D., Vorperian, V. R., & Webster, J. G. (2004). Lesion Size Estimator of Cardiac Radiofrequency Ablation at Different Common Locations With Different Tip Temperatures. IEEE Transactions on Biomedical Engineering, 51(10), 1859-1864. doi:10.1109/tbme.2004.831529Lequerica, J. L., Berjano, E. J., Herrero, M., Melecio, L., & Hornero, F. (2008). A cooled water-irrigated intraesophageal balloon to prevent thermal injury during cardiac ablation: experimental study based on an agar phantom. Physics in Medicine and Biology, 53(4), N25-N34. doi:10.1088/0031-9155/53/4/n01Mattingly, M., Bailey, E. A., Dutton, A. W., Roemer, R. B., & Devasia, S. (1998). Reduced-order modeling for hyperthermia: an extended balanced-realization-based approach. IEEE Transactions on Biomedical Engineering, 45(9), 1154-1162. doi:10.1109/10.709559PILCHER, T. A., SANFORD, A. L., SAUL, J. P., & HAEMMERICH, D. (2006). Convective Cooling Effect on Cooled-Tip Catheter Compared to Large-Tip Catheter Radiofrequency Ablation. Pacing and Clinical Electrophysiology, 29(12), 1368-1374. doi:10.1111/j.1540-8159.2006.00549.xRodríguez, I., Lequerica, J. L., Berjano, E. J., Herrero, M., & Hornero, F. (2007). Esophageal temperature monitoring during radiofrequency catheter ablation: experimental study based on an agar phantom model. Physiological Measurement, 28(5), 453-463. doi:10.1088/0967-3334/28/5/001SCHUMACHER, B., EICK, O., WITTKAMPF, F., PEZOLD, C., TEBBENJOHANNS, J., JUNG, W., & LUDERITZ, B. (1999). 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Comparative analysis of different methods of modeling the thermal effect of circulating blood flow during RF cardiac ablation

Our aim was to compare the different methods of modeling the effect of circulating blood flow on the thermal lesion dimensions created by radio frequency (RF) cardiac ablation and on the maximum blood temperature. Computational models were built to study the temperature distributions and lesion dimensions created by a nonirrigated electrode by two RF energy delivery protocols (constant voltage and constant temperature) under high and low blood flow conditions. Four methods of modeling the effect of circulating blood flowon 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) temperaturedependent electrical conductivity of blood (+2%/°C). Method 4) included blood motion andwas considered to be a reference method for comparison purposes. 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. 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. 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

Modeling Left Atrial Flow, Energy, Blood Heating Distribution in Response to Catheter Ablation Therapy

Introduction: Atrial fibrillation (AF) is a widespread cardiac arrhythmia that commonly affects the left atrium (LA), causing it to quiver instead of contracting effectively. This behavior is triggered by abnormal electrical impulses at a specific site in the atrial wall. Catheter ablation (CA) treatment consists of isolating this driver site by burning the surrounding tissue to restore sinus rhythm (SR). However, evidence suggests that CA can concur to the formation of blood clots by promoting coagulation near the heat source and in regions with low flow velocity and blood stagnation.Methods: A patient-specific modeling workflow was created and applied to simulate thermal-fluid dynamics in two patients pre- and post-CA. Each model was personalized based on pre- and post-CA imaging datasets. The wall motion and anatomy were derived from SSFP Cine MRI data, while the trans-valvular flow was based on Doppler ultrasound data. The temperature distribution in the blood was modeled using a modified Pennes bioheat equation implemented in a finite-element based Navier-Stokes solver. Blood particles were also classified based on their residence time in the LA using a particle-tracking algorithm.Results: SR simulations showed multiple short-lived vortices with an average blood velocity of 0.2-0.22 m/s. In contrast, AF patients presented a slower vortex and stagnant flow in the LA appendage, with the average blood velocity reduced to 0.08–0.14 m/s. Restoration of SR also increased the blood kinetic energy and the viscous dissipation due to the presence of multiple vortices. Particle tracking showed a dramatic decrease in the percentage of blood remaining in the LA for longer than one cycle after CA (65.9 vs. 43.3% in patient A and 62.2 vs. 54.8% in patient B). Maximum temperatures of 76° and 58°C were observed when CA was performed near the appendage and in a pulmonary vein, respectively.Conclusion: This computational study presents novel models to elucidate relations between catheter temperature, patient-specific atrial anatomy and blood velocity, and predict how they change from SR to AF. The models can quantify blood flow in critical regions, including residence times and temperature distribution for different catheter positions, providing a basis for quantifying stroke risks

Computer modeling of radiofrequency cardiac ablation: 30 years of bioengineering research

[EN] This review begins with a rationale of the importance of theoretical, mathematical and computational models for radiofrequency (RF) catheter ablation (RFCA). We then describe the historical context in which each model was developed, its contribution to the knowledge of the physics of RFCA and its implications for clinical practice. Next, we review the computer modeling studies intended to improve our knowledge of the biophysics of RFCA and those intended to explore new technologies. We describe the most important technical details of the implementation of mathematical models, including governing equations, tissue properties, boundary conditions, etc. We discuss the utility of lumped element models, which despite their simplicity are widely used by clinical researchers to provide a physical explanation of how RF power is absorbed in different tissues. Computer model verification and validation are also discussed in the context of RFCA. The article ends with a section on the current limitations, i.e. aspects not yet included in state-of-the-art RFCA computer modeling and on future work aimed at covering the current gapsGrant RTI2018-094357-B-C21 funded by MCIN/AEI/10.13039/501100011033 (Spanish Ministerio de Ciencia, Innovación y Universidades/Agencia Estatal de Investigación)González-Suárez, A.; Pérez, JJ.; Irastorza, RM.; D Avila, A.; Berjano, E. (2022). Computer modeling of radiofrequency cardiac ablation: 30 years of bioengineering research. Computer Methods and Programs in Biomedicine. 214:1-16. https://doi.org/10.1016/j.cmpb.2021.10654611621

Could it be advantageous to tune the temperature controller during radiofrequency ablation? A feasibility study using theoretical models

Purpose: To assess whether tailoring the Kp and Ki values of a proportional-integral (PI) controller during radiofrequency (RF) cardiac ablation could be advantageous from the point of view of the dynamic behaviour of the controller, in particular, whether control action could be speeded up and larger lesions obtained. Methods: Theoretical models were built and solved by the finite element method. RF cardiac ablations were simulated with temperature controlled at 55 degrees C. Specific PI controllers were implemented with Kp and Ki parameters adapted to cases with different tissue values (specific heat, thermal conductivity and electrical conductivity) electrode-tissue contact characteristics (insertion depth, cooling effect of circulating blood) and electrode characteristics (size, location and arrangement of the temperature sensor in the electrode). Results: The lesion dimensions and T(max) remained almost unchanged when the specific PI controller was used instead of one tuned for the standard case: T(max) varied less than 1.9 degrees C, lesion width less than 0.2 mm, and lesion depth less than 0.3 mm. As expected, we did observe a direct logical relationship between the response time of each controller and the transient value of electrode temperature. Conclusion: The results suggest that a PI controller designed for a standard case (such as that described in this study), could offer benefits under different tissue conditions, electrode-tissue contact, and electrode characteristics.This work received financial support from the Spanish 'Plan Nacional de I+D+I del Ministerio de Ciencia e Innovacion' Grant no. TEC2008-01369/TEC and FEDER Project MTM2010-14909. The translation of this paper was funded by the Universitat Politecnica de Valencia, Spain. 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