Retrospective review of Arctic Front Advance Cryoballoon Ablation: a multicenter examination of second-generation cryoballoon (RADICOOL trial)

Computer Simulation of Catheter Cryoablation for Pulmonary Vein Isolation

Cryoablation is a well-established medical procedure for surgically treating atrial fibrillation. Cryothermal catheter therapy induces cellular necrosis by freezing the insides of pulmonary veins, with the goal of disrupting abnormal electrical heart signals. Nevertheless, tissue damage induced by cold temperatures may also lead to other complications after cardiac surgery. In this sense, the simulation of catheter ablation can provide safer environments for training and the performance of cryotherapy interventions. Therefore, in this paper, we propose a novel approach to help better understand how temperature rates can affect this procedure by using computer tools to develop a simulation framework to predict lesion size and determine optimal temperature conditions for reducing the risk of major complications. The results showed that a temperature profile of around -40 °C caused less penetration, reduced necrotic damage, and smaller lesion size in the tissue. Instead, cryotherapy close to -60 °C achieved a greater depth of temperature flow inside the tissue and a larger cross-section area of the lesion. With further development and validation, the framework could represent a cost-effective strategy for providing personalized modeling, better planning of cryocatheter-based treatment, and preventing surgical complications.

Safety and efficacy of cryoballoon ablation for the treatment of paroxysmal and persistent AF in a real-world global setting: Results from the Cryo AF Global Registry

BACKGROUND

Cryoballoon ablation is a commonly used approach to treat patients with atrial fibrillation (AF).

OBJECTIVES

Report on the safety and efficacy of cryoballoon ablation for the treatment of AF in the largest global cohort of cryoablated patients prospectively studied within a single registry.

METHODS

The Cryo AF Global Registry is a prospective, multi-center registry. Patients with paroxysmal AF (PAF) or persistent AF (PsAF) were treated with the cryoballoon catheter according to routine practices at 93 sites across 36 countries. Primary efficacy endpoints included freedom from AF and freedom from AF/atrial flutter (AFL)/atrial tachycardia (AT) ≥30 seconds. The primary safety endpoint was serious device- or procedure-related adverse events over 12 month follow-up.

RESULTS

During this evaluation window, 2922 subjects completed an index cryoballoon procedure, and 1440 completed 12 month follow-up. The cohort was 61 ± 12 years of age, 36.3% female, and 78.7% PAF. Serious device- and procedure-related adverse event rates were 1.5% and 3.4%, respectively. Freedom from AF/AFL/AT after the 90 day blanking period was 86.4% (95% CI: 84.3%-88.3%) in patients with PAF and 70.9% (95% CI: 64.6%-76.4%) in patients with PsAF. Freedom from AF/AFL/AT in first-line PAF and PsAF was 90.0% (95% CI: 86.4%-92.7%) and 72.9% (95% CI: 58.6%-83.0%) at 12 months, respectively.

CONCLUSIONS

The Cryo Global AF Registry is the largest evaluation to demonstrate cryoablation is an efficient, safe, and effective treatment for patients with AF worldwide. Cryoablation was commonly used to treat patients prior to an AAD failure and may facilitate earlier therapy for patients on the AF disease continuum.

Cryoballoon ablation of atrial fibrillation in patients with atypical right pulmonary vein anatomy

BACKGROUND

Cryoballoon ablation is widely used for pulmonary vein isolation in patients with atrial fibrillation. There are no data regarding the clinical efficacy of cryoballoon ablation in patients with atypical right pulmonary vein anatomy.

AIM

We aimed to evaluate the impact of right pulmonary vein anatomy on the safety and efficacy of cryoballoon ablation.

METHODS

Patients referred for cryoballoon ablation of paroxysmal atrial fibrillation were enrolled prospectively. Left atrial computed tomography was performed before cryoballoon ablation to determine whether the right pulmonary vein anatomy was "normal" or "atypical". For patients with atypical anatomy, cryoballoon ablation was only performed for right superior and right inferior pulmonary veins, neglecting accessory pulmonary veins.

RESULTS

Overall, 303 patients were included: 254 (83.8%) with normal and 49 (16.2%) with atypical right pulmonary vein anatomy. First-freeze isolation for right superior and right inferior pulmonary veins occurred in 44 (89.8%) and 37 (75.5%) patients with atypical pulmonary vein anatomy, and in 218 (85.8%) and 217 (85.4%) patients with typical pulmonary vein anatomy, respectively (P not significant). Phrenic nerve palsies were only observed in patients with normal anatomy (0 vs. 26 [8.6%]; P=0.039). Mid-term survival free from atrial arrhythmia was similar, regardless of right pulmonary vein anatomy.

CONCLUSIONS

A significant proportion of patients have atypical right pulmonary vein anatomy. Procedural characteristics, acute pulmonary vein isolation success and mid-term procedural efficacy were similar, regardless of right pulmonary vein anatomy. In addition to left-side pulmonary vein isolation, cryoballoon ablation of right superior and right inferior pulmonary veins only, neglecting accessory pulmonary veins, is sufficient to obtain acute right-side pulmonary vein isolation and mid-term sinus rhythm maintenance in patients with atypical anatomy.

Balloon-Based Ablation Technologies

Pulmonary vein isolation (PVI) is widely accepted as the mainstay of interventional treatment of atrial fibrillation. Ablation with radiofrequency (RF) point-by-point catheters is highly operator dependent and may fail because of ineffective lesions or gaps. Several balloon-based catheter ablation technologies have emerged as an alternative to effect PVI. Cryoballoon ablation is widely used, and current iterations of the technology show comparable acute and long-term efficacy to RF ablation. Techniques such as time to isolation have emerged to improve efficacy and safety. Laser balloon is a highly compliant variably sized balloon that has been validated as an effective strategy for PVI.

Cryoballoon Ablation for Patients With Paroxysmal Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in clinical practice and induces cardiac dysfunction and stroke. The development of AF requires a trigger and also an electroanatomic substrate capable of both initiating and perpetuating AF. In the past decade, ectopic beats originating from the pulmonary veins (PV) have been identified as a source of paroxysmal AF. Thus, strategies that target the PV, including the PV antrum, are the cornerstone of most AF ablation procedures. Recently, alternative technologies to radiofrequency catheter ablation for paroxysmal AF such as balloon ablation modalities have been developed. The purpose of this review is to discuss cryoballoon ablation for paroxysmal AF.

Achieving contrast-free ultra-low radiation exposure without compromising safety and acute efficacy through evolving AF cryoballoon ablation procedure techniques

INTRODUCTION

In general, early experience with the first-generation cryoballoon introduced an increase in radiation exposure as compared to traditional radiofrequency ablations for atrial fibrillation (AF). However, through operator vigilance and the incorporation of various techniques and technologies, procedural radiation exposure can be managed to an exceptionally low level while maintaining the safety and efficacy of the cryoballoon procedure.

METHODS AND RESULTS

A retrospective chart review of all consecutive AF ablation procedures performed by a single operator at a single high-volume center with the second-generation cryoballoon (Arctic Front Advance) was performed between 2014 and 2017. Procedural and radiation exposure data were collected and analyzed year-over-year. 307 cases were reviewed with the majority as index procedures (95%) and patients presenting in paroxysmal AF (87%). The observed median absorbed dose was 2.4 mGy (interquartile range (IQR) = 1.0,6.2) and decreased significantly from 6.7 mGy (IQR = 1.6,6.2) in 2014 to 2.0 mGy (IQR = 1.5,4.5) in 2017 (P < 0.001). Median fluoroscopy time was 0.4 min (IQR = 0.25,0.75) and demonstrated reductions from 0.75 min (IQR = 0.40,1.4) in 2014 to 0.20 min (IQR = 0.10,0.40) in 2017 (P < 0.001). No radiopaque contrast agent was used in any procedure. A complication rate of 2% (6 total events) was observed, and no cases resulted in stroke, death, permanent phrenic nerve injury, or pulmonary vein stenosis. In total, 304 of 307 (99%) procedures resulted in complete isolation of all pulmonary veins.

CONCLUSION

Ultra-low radiation doses and contrast-free procedures can be achieved as part of an overall "safety-first" approach during cryoballoon AF ablation without compromising safety or acute efficacy.

Impedance and conductivity of bovine myocardium during freezing and thawing at slow rates - implications for cardiac cryo-ablation

Increasing impedance during freezing might be a valuable marker for guiding cardiac cryo-ablation. We provide model based insights on how decreasing temperature below the freezing point of tissue relates to the percentage of frozen water. Furthermore, we provide experimental data for comparing this percentage with the increase in impedance. Measurements were performed on a bovine tissue sample at frequencies between 5 and 80 kHz. Slow cooling and heating rates were applied to minimize temperature gradients in the myocardial sample and to allow accurate assessment of the freezing point. Computer simulation was applied to link impedance with temperature dependent conductivities. The osmotic virial equation was used to estimate the percentage of frozen water. Measurements identified the freezing point at -0.6 ^∘C. At -5 ^∘C, impedance rose by more than a factor of ten compared to that at the freezing point and the percentage of frozen water was estimated as being 89%. At -49 ^∘C impedance had increased by up to three orders of magnitude and ice formation was most pronounced in the extracellular space. Progressive ice formation in tissue is reflected by a large increase in impedance, and impedance increases monotonically with the percentage of frozen water. Its analysis allows for experimental assessment of factors relevant to cell death. Solid ice contributes to the rupture of the micro-vasculature, while phase shifts reflect concentration differences between extra- and intracellular space driving osmotic water transfer across cell membranes.

Comparing radiofrequency and cryoballoon technology for the ablation of atrial fibrillation

PURPOSE OF REVIEW

With the growing popularity of the cryoballoon tool for catheter ablation of atrial fibrillation, there has been discussion of whether cryothermal energy is just as or more effective than traditional radiofrequency. This review will compare both thermal energies for the treatment of atrial fibrillation.

RECENT FINDINGS

Although the FIRE and ICE trial established that cryoballoon technology is noninferior to radiofrequency ablation for the treatment of atrial fibrillation, both thermal technologies have undergone advancement. This review intends to explore recent changes in technology and catheter ablation technique to improve outcomes for patients with atrial fibrillation.

SUMMARY

Catheter ablation is standard treatment for patients with atrial fibrillation, which primarily focuses on electrical isolation of the pulmonary veins. Radiofrequency is the most common approach at present times; however, over time, new technology has developed. Most successful among these is the cryoballoon tool. Although the FIRE and ICE trial indicated radiofrequency and cryothermal energy to be approximately equal in efficacy and safety, there are advantages and disadvantages to both. This review seeks to address the value of each tool, as well as further development needed to better address atrial fibrillation while improving procedural safety.

Outcomes of 200 consecutive, fluoroless atrial fibrillation ablations using a new technique

INTRODUCTION

A technique was developed to eliminate radiation exposure for routine atrial fibrillation (AF) ablation, to simplify the procedure and to achieve cost effectiveness. We here report the outcomes of this approach.

METHODS

Two hundred consecutive AF ablations (55% paroxysmal) were performed by a single operator. Pulmonary vein isolation (PVI) was achieved by antral ablation without left atrial anatomic mapping, guided by contact force sensing and intracardiac echocardiogram (ICE). All ablations were performed using three ipsilateral 8 French catheters (ICE, Lasso, and ablation). Eighty-two percent of the patients underwent ablation of atrial flutter or non-pulmonary vein triggers. All patients underwent provocative testing after PVI.

RESULTS

No fluoroscopy was used for the entire study. Two ablations were performed without x-ray available due to unexpected equipment failure. The mean procedure time was 90.3 ± 17.7 (minutes) in patients who only required PVI and 106.2 ± 23.2 (minutes) for the entire cohort, with a success rate of 76% (mean follow-up of 11 months). In contrast, the procedure time and success rate were 127.9 ± 38.2 (minutes) (P < 0.01) and 74%, respectively, for the last 50 standard ablations guided by fluoroscopy (without contact force sensing). Complications included one case of partial right phrenic nerve palsy and one case of right femoral artery pesudoaneurysm. Compared to our previous ablation approaches, the new method resulted in catheter savings of $2,168-$4,568/case.

CONCLUSION

The new technique eliminated radiation exposure and shortened the procedure time without significant negative impact on safety or success rate. Substantial cost savings were also achieved by using a minimal number of mostly reprocessed catheters.