A computational comparison of radiofrequency and pulsed field ablation in terms of lesion morphology in the cardiac chamber

Myocardial injury and inflammation following pulsed-field ablation and very high-power short-duration ablation for atrial fibrillation

INTRODUCTION

Pulmonary vein isolation (PVI) using radiofrequency ablation (RFA) is an established treatment strategy for atrial fibrillation (AF). To improve PVI efficacy and safety, high-power short-duration (HPSD) ablation and pulsed-field ablation (PFA) were recently introduced into clinical practice. This study aimed to determine the extent of myocardial injury and systemic inflammation following PFA, HPSD, and standard RFA using established biomarkers.

METHODS

We included 179 patients with paroxysmal AF receiving first-time PVI with different ablation technologies: standard RFA (30-40 W/20-30 s, n = 52), power-controlled HPSD (70 W/5-7 s, n = 60), temperature-controlled HPSD (90 W/4 s, n = 32), and PFA (biphasic, bipolar waveform, n = 35). High-sensitivity cardiac troponin T (hs-cTnT), creatine kinase (CK), CK MB isoform (CK-MB), and white blood cell (WBC) count were determined before and after ablation.

RESULTS

Baseline characteristics were well-balanced between groups (age 63.1 ± 10.3 years, 61.5% male). Postablation hs-cTnT release was significantly higher with PFA (1469.3 ± 495.0 ng/L), HPSD-70W (1322.3 ± 510.6 ng/L), and HPSD-90W (1441.2 ± 409.9 ng/L) than with standard RFA (1045.9 ± 369.7 ng/L; p < .001). CK and CK-MB release was increased with PFA by 3.4-fold and 5.8-fold, respectively, as compared to standard RFA (p < .001). PFA was associated with the lowest elevation in WBC (Δ1.5 ± 1.5 × 109 /L), as compared to standard RFA (Δ3.8 ± 2.5 × 109 /L, p < .001), HPSD-70W (Δ2.7 ± 1.7 × 109 /L, p = .037), and HPSD-90W (Δ3.6 ± 2.5 × 109 /L, p < .001).

CONCLUSION

Among the four investigated ablation technologies, PFA was associated with the highest myocardial injury and the lowest inflammatory reaction.

Cardiac blood vessels and irreversible electroporation: findings from pulsed field ablation

The clinical use of irreversible electroporation in invasive cardiac laboratories, termed pulsed field ablation (PFA), is gaining early enthusiasm among electrophysiologists for the management of both atrial and ventricular arrhythmogenic substrates. Though electroporation is regularly employed in other branches of science and medicine, concerns regarding the acute and permanent vascular effects of PFA remain. This comprehensive review aims to summarize the preclinical and adult clinical data published to date on PFA's effects on pulmonary veins and coronary arteries. These data will be contrasted with the incidences of iatrogenic pulmonary vein stenosis and coronary artery injury secondary to thermal cardiac ablation modalities, namely radiofrequency energy, laser energy, and liquid nitrogen-based cryoablation.

Atrial Fibrillation Ablation: Current Practice and Future Perspectives

Catheter ablation to perform pulmonary vein isolation (PVI) is established as a mainstay in rhythm control of atrial fibrillation (AF). The aim of this review is to provide an overview of current practice and future perspectives in AF ablation. The main clinical benefit of AF ablation is the reduction of arrhythmia-related symptoms and improvement of quality of life. Catheter ablation of AF is recommended, in general, as a second-line therapy for patients with symptomatic paroxysmal or persistent AF, who have failed or are intolerant to pharmacological therapy. In selected patients with heart failure and reduced left-ventricular fraction, catheter ablation was proven to reduce all-cause mortality. Also, optimal management of comorbidities can reduce AF recurrence after AF ablation; therefore, multimodal risk assessment and therapy are mandatory. To date, the primary ablation tool in widespread use is still single-tip catheter radiofrequency (RF) based ablation. Additionally, balloon-based pulmonary vein isolation (PVI) has gained prominence, especially due to its user-friendly nature and established safety and efficacy profile. So far, the cryoballoon (CB) is the most studied single-shot device. CB-based PVI is characterized by high efficiency, convincing success rates, and a beneficial safety profile. Recently, CB-PVI as a first-line therapy for AF was shown to be superior to pharmacological treatment in terms of efficacy and was shown to reduce progression from paroxysmal to persistent AF. In this context, CB-based PVI gains more and more importance as a first-line treatment choice. Non-thermal energy sources, namely pulsed-field ablation (PFA), have garnered attention due to their cardioselectivity. Although initially applied via a basket-like ablation tool, recent developments allow for point-by-point ablation, particularly with the advent of a novel lattice tip catheter.

How intramyocardial fat can alter the electric field distribution during Pulsed Field Ablation (PFA): Qualitative findings from computer modeling

Even though the preliminary experimental data suggests that cardiac Pulsed Field Ablation (PFA) could be superior to radiofrequency ablation (RFA) in terms of being able to ablate the viable myocardium separated from the catheter by collagen and fat, as yet there is no formal physical-based analysis that describes the process by which fat can affect the electric field distribution. Our objective was thus to determine the electrical impact of intramyocardial fat during PFA by means of computer modeling. Computer models were built considering a PFA 3.5-mm blunt-tip catheter in contact with a 7-mm ventricular wall (with and without a scar) and a 2-mm epicardial fat layer. High voltage was set to obtain delivered currents of 19, 22 and 25 A. An electric field value of 1000 V/cm was considered as the lethal threshold. We found that the presence of fibrotic tissue in the scar seems to have a similar impact on the electric field distribution and lesion size to that of healthy myocardium only. However, intramyocardial fat considerably alters the electrical field distribution and the resulting lesion shape. The electric field tends to peak in zones with fat, even away from the ablation electrode, so that 'cold points' (i.e. low electric fields) appear around the fat at the current entry and exit points, while 'hot points' (high electric fields) occur in the lateral areas of the fat zones. The results show that intramyocardial fat can alter the electric field distribution and lesion size during PFA due to its much lower electrical conductivity than that of myocardium and fibrotic tissue.

A Predictive and an Optimization Mathematical Model for Device Design in Cardiac Pulsed Field Ablation Using Design of Experiments

Cardiac catheter ablation (CCA) is a common method used to correct cardiac arrhythmia. Pulsed Field Ablation (PFA) is a recently-adapted CCA technology whose ablation is dependent on electrode and waveform parameters (factors). In this work, the use of the Design of Experiments (DoE) methodology is investigated for the design and optimization of a PFA device. The effects of the four factors (input voltage, electrode spacing, electrode width, and on-time) and their interactions are analyzed. An empirical model is formed to predict and optimize the ablation size responses. Based on the ranges tested, the significant factors were the input voltage, the electrode spacing, and the on time, which is in line with the literature. Two-factor interactions were found to be significant and need to be considered in the model. The resulting empirical model was found to predict ablation sizes with less than 2.1% error in the measured area and was used for optimization. The findings and the strong predictive model developed highlight that the DoE approach can be used to help determine PFA device design, to optimize for certain ablation zone sizes, and to help inform device design to tackle specific cardiac arrhythmias.

A novel polarity configuration for enhancing ablation depth of pulsed field ablation: Design, modeling, and in vivo validation

BACKGROUND

Pulsed field ablation (PFA) has been increasingly used to cut off the delivery of abnormal electrical signals in the treatment of cardiac arrhythmias. A successful cut off requires forming a layer of transmural damage on the heart wall, and this layer depends on the depth of ablation by PFA.

PURPOSE

This study aims to propose a novel polarity configuration of PFA to increase the ablation depth in the treatment of cardiac arrhythmias.

METHOD

A novel polarity configuration was designed for a multi-electrode system, where the number of electrodes is greater than two. The polarity configuration in such multi-electrode system is called the paired-electrode interlaced configuration (PIC). The existing configuration called the single-electrode interlaced configuration (SIC) was used to compare with the PIC. To both the SIC and PIC, a full-SIC or a full-PIC is called when all electrodes (anode, cathode) in a catheter is used otherwise partial-SIC or partial-PIC is called. By the comparison between the full-SIC and full-PIC, the benefit of the PIC was exhibited as opposed to the SIC, but an extra ablation step was added in the PIC in order to form a continuous ablation zone. The other comparative study was taken between a partial-PIC and a partial-SIC with the same number of ablation step. In this study, a rabbit model was built by infusing 0.4% saline solution (at 37°C) into the rabbit's abdominal cavity which surrounds the liver. This model was considered as a biometric environment of the heart, namely cardiac-mimetic model (CMM).

RESULT

The experimental results have shown that the full-PIC is superior to the full-SIC in the ablation depth, specifically in both the maximum (4.14 ± 0.55 mm vs. 3.35 ± 0.26 mm, p < 0.01) and the minimum (3.18 ± 0.29 mm vs. 2.76 ± 0.28 mm, p < 0.05), and in the ablation width, specifically only in the maximum (8.27 ± 0.76 mm vs. 7.09 ± 0.51 mm, p = 0.019) under an identical ablation time (i.e., 5 s). It is noted that the minimum ablation width did not show a significant difference between the full-PIC and full-SIC (specifically, 5.61 ± 0.86 mm vs. 4.67 ± 0.73 mm, p = 0.069). Considering the lethal electric field threshold (LEFT) to be 600 V/cm for liver tissues, the maximum and minimum ablation depth generated by the full-PIC was found larger than that by the full-SIC (3.90 vs. 3.52 mm, and 3.03 vs. 2.48 mm, respectively) in the simulation. Meanwhile, similar experiment results by comparing the partial-PIC and partial-SIC have been obtained, which shows a significant increase in both the maximum ablation depth (4.81 ± 0.87 mm vs. 3.30 ± 0.73 mm, p < 0.001) and the maximum ablation width (8.19 ± 0.85 mm vs. 6.47 ± 1.13 mm, p = 0.001).

CONCLUSIONS

(1) The electric field in the PIC is concentrated around the pair of electrodes, and the pattern of the field is a significant factor in the energy delivery along the direction of the depth. (2) The increase of the ablation depth can significantly expand the range of the tissue on the heart, where the PFA can apply, and can therefore readily form a layer of transmural damage on the heart wall at positions at which the wall is thicker.

Transient conduction disturbances acutely after pulsed-field cavotricuspid isthmus ablation: a case report

Background

Cavotricuspid isthmus pulsed-field ablation has been recently described to be safely performed despite initial reports on coronary arterial spasm while conduction disturbances as a complication of cavotricuspid isthmus ablation are rare and have been reported exclusively for radiofrequency catheter ablation.

Case summary

A 64-year-old female patient with mechanical prosthetic valves underwent atrial fibrillation ablation using the pentaspline pulsed-field ablation catheter. At the end of the uneventful pulmonary vein isolation, an atrial tachycardia depended to the cavotricuspid isthmus occurred. A single pulsed-field application at the cavotricuspid isthmus resulted in right bundle branch block combined with posterior fascicular hemiblock and PR prolongation that resolved spontaneously within 12 h.

Discussion

This is the first report of transient conduction disturbances as a complication of cavotricuspid isthmus pulsed-field ablation. Although the underlying mechanism, either single or miscellaneous, was not verified, this case highlights that caution should be taken when the pentaspline pulsed-field ablation catheter is used for cavotricuspid isthmus ablation.

Pulsed Field Ablation for Atrial Fibrillation

Catheter ablation is a widely used, effective and safe treatment for AF. Pulsed field ablation (PFA), as a novel energy source for cardiac ablation, has been shown to be tissue selective and is expected to decrease damage to non-cardiac tissue while providing high efficacy in pulmonary vein isolation. The FARAPULSE ablation system (Boston Scientific) follows the idea of single-shot ablation and is the first device approved for clinical use in Europe. Since its approval, multiple high-volume centres have performed increasing numbers of PFA procedures in patients with AF and have published their experiences. This review summarises the current clinical experience regarding the use of PFA for AF using the FARAPULSE system. It provides an overview of its efficacy and safety.

Comparative Analysis of Temperature Rise between Convective Heat Transfer Method and Computational Fluid Dynamics Method in an Anatomy-Based Left Atrium Model during Pulsed Field Ablation: A Computational Study

The non-thermal effects are considered one of the prominent advantages of pulsed field ablation (PFA). However, at higher PFA doses, the temperature rise in the tissue during PFA may exceed the thermal damage threshold, at which time intracardiac pulsatile blood flow plays a crucial role in suppressing this temperature rise. This study aims to compare the effect of heat dissipation of the different methods in simulating the pulsatile blood flow during PFA. This study first constructed an anatomy-based left atrium (LA) model and then applied the convective heat transfer (CHT) method and the computational fluid dynamics (CFD) method to the model, respectively, and the thermal convective coefficients used in the CHT method are 984 (W/m²*K) (blood-myocardium interface) and 4372 (W/m²*K) (blood-catheter interface), respectively. Then, it compared the effect of the above two methods on the maximum temperature of myocardium and blood, as well as the myocardial ablation volumes caused by irreversible electroporation (IRE) and hyperthermia under different PFA parameters. Compared with the CFD method, the CHT method underestimates the maximum temperature of myocardium and blood; the differences in the maximum temperature of myocardium and blood between the two methods at the end of the last pulse are significant (>1 °C), and the differences in the maximum temperature of blood at the end of the last pulse interval are significant (>1 °C) only at a pulse amplitude greater than 1000 V or pulse number greater than 10. Under the same pulse amplitude and different heat dissipation methods, the IRE ablation volumes are the same. Compared with the CFD method, the CHT method underestimates the hyperthermia ablation volume; the differences in the hyperthermia ablation volume are significant (>1 mm³) only at a pulse amplitude greater than 1000 V, a pulse interval of 250 ms, or a pulse number greater than 10. Additionally, the hyperthermia ablation isosurfaces are completely wrapped by the IRE ablation isosurfaces in the myocardium. Thus, during PFA, compared with the CFD method, the CHT method cannot accurately simulate the maximum myocardial temperature; however, except at the above PFA parameters, the CHT method can accurately simulate the maximum blood temperature and the myocardial ablation volume caused by IRE and hyperthermia. Additionally, within the range of the PFA parameters used in this study, the temperature rise during PFA may not lead to the appearance of additional hyperthermia ablation areas beyond the IRE ablation area in the myocardium.