Computer simulations of consecutive radiofrequency pulses applied at the same point during cardiac catheter ablation: Implications for lesion size and risk of overheating

Computer simulation-based nanothermal field and tissue damage analysis for cardiac tumor ablation

Radiofrequency ablation is a nominally invasive technique to eradicate cancerous or non-cancerous cells by heating. However, it is still hampered to acquire a successful cell destruction process due to inappropriate RF intensities that will not entirely obliterate tumorous tissues, causing in treatment failure. In this study, we are acquainted with a nanoassisted RF ablation procedure of cardiac tumor to provide better outcomes for long-term survival rate without any recurrences. A three-dimensional thermo-electric energy model is employed to investigate nanothermal field and ablation efficiency into the left atrium tumor. The cell death model is adopted to quantify the degree of tissue injury while injecting the Fe3O4 nanoparticles concentrations up to 20% into the target tissue. The results reveal that when nanothermal field extents as a function of tissue depth (10 mm) from the electrode tip, the increasing thermal rates were approximately 0.54362%, 3.17039%, and 7.27397% for the particle concentration levels of 7%, 10%, and 15% compared with no-particle case. In the 7% Fe3O4 nanoparticles, 100% fractional damage index is achieved after ablation time of 18 s whereas tissue annihilation approach proceeds longer to complete for no-particle case. The outcomes indicate that injecting nanoparticles may lessen ablation time in surgeries and prevent damage to adjacent healthy tissue.

Atrioesophageal Fistula Rates Before and After Adoption of Active Esophageal Cooling During Atrial Fibrillation Ablation

BACKGROUND

Active esophageal cooling reduces the incidence of endoscopically identified severe esophageal lesions during radiofrequency (RF) catheter ablation of the left atrium for the treatment of atrial fibrillation. A formal analysis of the atrioesophageal fistula (AEF) rate with active esophageal cooling has not previously been performed.

OBJECTIVES

The authors aimed to compare AEF rates before and after the adoption of active esophageal cooling.

METHODS

This institutional review board (IRB)-approved study was a prospective analysis of retrospective data, designed before collecting and analyzing the real-world data. The number of AEFs occurring in equivalent time frames before and after adoption of cooling using a dedicated esophageal cooling device (ensoETM, Attune Medical) were quantified across 25 prespecified hospital systems. AEF rates were then compared using generalized estimating equations robust to cluster correlation.

RESULTS

A total of 14,224 patients received active esophageal cooling during RF ablation across the 25 hospital systems, which included a total of 30 separate hospitals. In the time frames before adoption of active cooling, a total of 10,962 patients received primarily luminal esophageal temperature (LET) monitoring during their RF ablations. In the preadoption cohort, a total of 16 AEFs occurred, for an AEF rate of 0.146%, in line with other published estimates for procedures using LET monitoring. In the postadoption cohort, no AEFs were found in the prespecified sites, yielding an AEF rate of 0% (P < 0.0001).

CONCLUSIONS

Adoption of active esophageal cooling during RF ablation of the left atrium for the treatment of atrial fibrillation was associated with a significant reduction in AEF rate.

Effects of Pulsed Radiofrequency Source on Cardiac Ablation

Heart arrhythmia is caused by abnormal electrical conduction through the myocardium, which in some cases, can be treated with heat. One of the challenges is to reduce temperature peaks-by still guaranteeing an efficient treatment where desired-to avoid any healthy tissue damage or any electrical issues within the device employed. A solution might be employing pulsed heat, in which thermal dose is given to the tissue with a variation in time. In this work, pulsed heat is used to modulate induced temperature fields during radiofrequency cardiac ablation. A three-dimensional model of the myocardium, catheter and blood flow is developed. Porous media, heat conduction and Navier-Stokes equations are, respectively, employed for each of the investigated domains. For the electric field, solved via Laplace equation, it is assumed that the electrode is at a fixed voltage. Pulsed heating effects are considered with a cosine time-variable pulsed function for the fixed voltage by constraining the product between this variable and time. Different dimensionless frequencies are considered and applied for different blood flow velocity and sustained voltages. Results are presented for different pulsed conditions to establish if a reasonable ablation zone, known from the obtained temperature profiles, can be obtained without any undesired temperature peaks.

How far the zone of heat-induced transient block extends beyond the lesion during RF catheter cardiac ablation

PURPOSE

While radiofrequency catheter ablation (RFCA) creates a lesion consisting of the tissue points subjected to lethal heating, the sublethal heating (SH) undergone by the surrounding tissue can cause transient electrophysiological block. The size of the zone of heat-induced transient block (HiTB) has not been quantified to date. Our objective was to use computer modeling to provide an initial estimate.

METHODS AND MATERIALS

We used previous experimental data together with the Arrhenius damage index (Ω) to fix the Ω values that delineate this zone: a lower limit of 0.1-0.4 and upper limit of 1.0 (lesion boundary). An RFCA computer model was used with different power-duration settings, catheter positions and electrode insertion depths, together with dispersion of the tissue's electrical and thermal characteristics.

RESULTS

The HiTB zone extends in depth to a minimum and maximum distance of 0.5 mm and 2 mm beyond the lesion limit, respectively, while its maximum width varies with the energy delivered, extending to a minimum of 0.6 mm and a maximum of 2.5 mm beyond the lesion, reaching 3.5 mm when high energy settings are used (25 W-20s, 500 J). The dispersion of the tissue's thermal and electrical characteristics affects the size of the HiTB zone by ±0.3 mm in depth and ±0.5 mm in maximum width.

CONCLUSIONS

Our results suggest that the size of the zone of heat-induced transient block during RFCA could extend beyond the lesion limit by a maximum of 2 mm in depth and approximately 2.5 mm in width.

Active esophageal cooling during radiofrequency ablation of the left atrium: data review and update

INTRODUCTION

Radiofrequency (RF) ablation of the left atrium of the heart is increasingly used to treat atrial fibrillation (AF). Unfortunately, inadvertent thermal injury to the esophagus can occur during this procedure, potentially creating an atrioesophageal fistula (AEF) which is 80% fatal. The ensoETM (Attune Medical, Chicago, IL), is an esophageal cooling device that has been shown to reduce thermal injury to the esophagus during RF ablation.

AREAS COVERED

This review summarizes growing evidence related to active esophageal cooling during RF ablation for the treatment of AF. The review presents data demonstrating improved outcomes related to patient safety and procedural efficiency and suggests directions for future research.

EXPERT OPINION

The use of active esophageal cooling during RF ablation reduces esophageal injury, reduces or eliminates fluoroscopy requirements, reduces procedure duration and post-operative pain, and increases long-term freedom from arrhythmia. These effects in turn increase patient same-day discharge rates, decrease operator cognitive load, and reduce cost. These findings are likely to further accelerate the adoption of active esophageal cooling.