Efficacy of pulmonary vein isolation with a novel hot balloon ablation catheter

Bioinspired balloon catheter integrated with stretchable "flounder" electrodes under high voltage for uniform pulsed field ablation

Atrial fibrillation leads to severe diseases such as heart failure and strokes. While catheter ablation is prevalent for the treatment, existing techniques hardly can achieve both tissue selectivity and ablation uniformity. Here, we propose a bioinspired strategy for balloon-based pulsed field ablation (PFA) systems based on "flounder" electrodes. Inspired by a flounder skeleton and citrus peels, the microfabricated electrodes are ultrathin, stretchable, and have a scattered configuration, withstanding large balloon deformation (87% compression), high voltage (1200 volts), and owning exceptional tissue conformability (720° twists). Mechanical-electrical coupled stimulation optimizes balloon electrodes with hemispherical electric field uniformity. A water lily-inspired transfer printing method enables one-step integration of multielectrodes with the balloon. A comprehensive PFA system is complemented, achieving ablation depths of 3.8 millimeters (potato), 3.1 millimeters (rabbit), and 2.3 millimeters (swine) with good uniformity and electrophysiological isolation. These results shed light on the quantitative design of PFA systems, with high potential for more precise, safe, and effective catheter ablation therapies.

Balloon surface temperature-controlled ablation using a second-generation radiofrequency HotBalloon: an in vivo feasibility study

AIMS

The first-generation radiofrequency HotBalloon (RHB) is a size-adjustable single-shot device used in atrial fibrillation. The energy output is determined by its central temperature and not by its balloon surface temperature (BST), thus limiting its efficacy and safety. Therefore, a second-generation RHB was developed to monitor BST and enable BST-controlled ablation. This animal study aims to evaluate the accuracy of a newly developed BST-monitoring system and validate the optimal BST for ablation.

METHODS AND RESULTS

In Protocol 1, thermocapsules were attached to the superior vena cava (SVC) epicardium. The accuracy of BST monitoring was examined during SVC isolation. In Protocol 2, the efficacy and safety of different BST-controlled ablations were examined. In the acute model, electrophysiological and pathological findings were assessed after energy applications with BST at 51, 54, 57, and 60°C. In the chronic model, the lesion durability and pathological findings were assessed 8 weeks after BST-controlled ablation (57 and 60°C). A significant positive correlation was found between the epicardial temperature and the BST-monitoring value (r = 0.98). In the acute model, all target veins were electrically isolated with BST-controlled ablation at ≥57°C (18/18, 100%). In the chronic model, durable lesions were observed in all veins at 60°C, while 44% of the veins showed reconnection at 57°C. In both pathological analyses, significantly greater lesions were observed at 60°C than at 57°C. There were no significant differences in adverse events between the two groups.

CONCLUSION

Balloon surface temperature-controlled ablation at 60°C using the second-generation RHB may be optimal for creating durable lesions without compromising safety.

Chronic Effect of HotBalloon-Based Wide Planar Ablation on Epicardial Adipose Tissue in Persistent Atrial Fibrillation

Background: Adverse atrial remodeling, including epicardial adipose tissue (EAT) deposition in the left atrium (LA), is implicated in atrial fibrillation (AF). Radiofrequency hotballoon (RHB) ablation can produce wide planar lesions because the balloon is highly compliant; however, chronic effects of RHB ablation on structural remodeling remain unknown. This clinical-experimental investigation characterized chronic effects of RHB ablation on EAT in persistent AF (PsAF). Methods and Results: The clinical study involved 91 patients (obese, n=30; non-obese, n=61) undergoing RHB ablation for PsAF. LA-EAT was assessed from computed tomography images obtained before ablation and 6 months later. Tissue effects of RHB ablation were explored in a chronic swine model. RHB ablation significantly reduced LA volume (mean [±SD] 177.7±29.7 vs. 138.4±29.6 mL; P<0.001) and LA-EAT volume (median [interquartile range] 22.0 [12.4-33.3] vs. 16.5 [7.9-25.8] mL; P<0.001). The reduction in EAT was significantly greater in the pulmonary vein (PV) antrum than in other LA regions (37.9% vs. 15.8%; P<0.001). The percentage reduction in PV antrum EAT was equivalent between obese and non-obese patients, as was the postablation success rate (73% vs. 70%; P=0.77). RHB ablation produced transmural lesions reaching the pigs' epicardial fat region. Conclusions: RHB-based planar-transmural lesions altered the structurally remodeled LA, including EAT. Further studies are needed to determine whether factors other than PV isolation contribute to the clinical success of RHB ablation.

HotBalloon Pulmonary Vein Isolation Registry Study - Real-World Efficacy and Safety of HotBalloon Ablation

BACKGROUND

Radiofrequency hotballoon (RHB) is an ablation device used for atrial fibrillation (AF) treatment. The efficacy and safety of RHB-based pulmonary vein isolation (PVI) in real-world practice are unknown.

METHODS AND RESULTS

A multicenter, prospective registry study (UMIN000029567) enrolled AF patients who underwent RHB-PVI. The primary endpoint was the AF recurrence-free survival rate at 12 months after PVI. Of the 679 patients enrolled, 613 (90.3%; paroxysmal AF, n=370; persistent AF, n=136; long-standing AF, n=107) underwent initial RHB-PVI. Acute isolation using only the RHB was successful for 55.6% of patients and 83.5% of pulmonary veins (PVs). The acute isolation rate was higher for patients with paroxysmal AF and more experienced centers. Antiarrhythmic drugs were prescribed after 3 months for 47.5% of patients. The AF recurrence-free survival rate at 12 months was 83.7%. Procedure-related complications including atrio-esophageal fistula (n=1) and phrenic nerve injury (persistent; n=4, permanent; n=2) were observed in 19 (3.1%) patients. Five (1.7%) of the 302 patients who underwent pre-procedural and post-procedural multidetector computed tomography had severe PV stenosis.

CONCLUSIONS

The size-adjustable RHB has been used for the treatment of various AF types. The arrhythmia recurrence-free rate at 12 months, with the use of antiarrhythmic drugs in approximately half of the patients, was acceptable, but the acute isolation rate using the RHB requires further improvement.

Impact of monitoring surface temperature during pulmonary vein isolation in a second-generation hot balloon system

Background

Methods

Results

Conclusions

A porcine study of the area of heated tissue during hot-balloon ablation: Implications for the clinical efficacy and safety

INTRODUCTION

Hot-balloon ablation depends solely on thermal conduction, and myocardial tissue is ablated by only conductive heating from the balloon surface. Despite growing clinical evidence of the efficacy and safety of hot-balloon ablation for atrial fibrillation (AF), the actual tissue temperature and the mechanism of heating during such ablation has not been clarified. To determine, by means of a porcine study, the temperatures of tissues targeted during hot-balloon ablation of AF performed with hot-balloon set temperatures of 73°C or 70°C, in accordance with the temperatures now used clinically.

METHODS

After a right thoracotomy, thermocouples with markers were implanted epicardially on the superior vena cava (SVC) and pulmonary veins (PVs) in six pigs. The tissue temperatures during hot-balloon ablation (balloon set temperatures of 73°C and 70°C, 180 s/PV) were recorded, and the maximum tissue temperatures and fluoroscopically measured distance from the balloon surface to the target tissues were assessed.

RESULTS

Sixteen SVC- and 18 PV-targeted energy deliveries were performed. Full-thickness circumferential PV lesions were created with all hot-balloon applications. A significant inverse relation was found between the recorded tissue temperatures and distance (r = -.67; p < .001) from the balloon surface. No tissue temperature exceeded either of the balloon set temperatures. The best distance cutoff value for achieving lethal tissue temperatures more than 50°C was 3.6 mm.

CONCLUSION

The hot-balloon set temperature, energy delivery time, and tissue temperature data obtained in this porcine study supported the clinical efficacy and safety of the hot-balloon ablation as currently practiced in patients with AF.

Radiofrequency Balloon Devices for Atrial Fibrillation Ablation

Despite technological advancements, radiofrequency catheter ablation for pulmonary vein isolation remains a challenging procedure, as maneuvering the catheter to obtain effective lesions is technically complex and time consuming. For this reason, balloon-based ablation systems have been developed, which can quickly and easily isolate the pulmonary veins (single-shot), with outcomes comparable with point-by-point catheter ablation in the paroxysmal atrial fibrillation population. In this review, we discuss 3 balloon-based devices that use radiofrequency to obtain permanent lesions, a relatively emerging technology that may pose as an alternative option to cryoenergy or laser for single-shot pulmonary vein isolation.

Current hot potatoes in atrial fibrillation ablation

Atrial fibrillation (AF) ablation has evolved to the treatment of choice for patients with drug-resistant and symptomatic AF. Pulmonary vein isolation at the ostial or antral level usually is sufficient for treatment of true paroxysmal AF. For persistent AF ablation, drivers and perpetuators outside of the pulmonary veins are responsible for AF maintenance and have to be targeted to achieve satisfying arrhythmia-free success rate. Both complex fractionated atrial electrogram (CFAE) ablation and linear ablation are added to pulmonary vein isolation for persistent AF ablation. Nevertheless, ablation failure and necessity of repeat ablations are still frequent, especially after persistent AF ablation. Pulmonary vein reconduction is the main reason for arrhythmia recurrence after paroxysmal and to a lesser extent after persistent AF ablation. Failure of persistent AF ablation mostly is a consequence of inadequate trigger ablation, substrate modification or incompletely ablated or reconducting linear lesions. In this review we will discuss these points responsible for AF recurrence after ablation and review current possibilities on how to overcome these limitations.