Convergent Ablation Using the Cryoballoon in the Treatment of Persistent Atrial Fibrillation

While pulmonary vein isolation remains the preferred approach to manage paroxysmal atrial fibrillation, the optimal ablation strategy to treat persistent and longstanding persistent atrial fibrillation is less clear. In contrast to paroxysmal atrial fibrillation, which is thought of as a disease localized to the pulmonary vein and antrum, persistent atrial fibrillation is associated with diffusely diseased atrial substrate. Initially thought of as a surgically managed disease, catheter-based techniques now offer a minimally invasive alternative with significantly less periprocedural complications with the tradeoff of questionable long-term success rates. Complicating the management of longstanding persistent atrial fibrillation is the myriad of ablation strategies ranging from well-established surgical approaches to more contemporary catheter-based solutions utilizing pulmonary vein isolation, linear lesions sets, and more recently, rotor mapping. “Hybrid” approaches aim to combine the comprehensive nature of a surgical-based procedure while minimizing periprocedural complications and post-procedural recovery. As an attempt to further minimize the invasive nature of traditional hybrid ablation techniques and to improve on post-procedural recovery time, the Convergent Procedure was developed. The Convergent Procedure is a closed-chest, multidisciplinary approach that was developed to combine the best technologies and techniques of cardiothoracic surgery and electrophysiology. In our institution, the procedure is performed in a single setting in the hybrid suite; the procedure combines epicardial ablation under direct endoscopic visualization with endocardial ablation to create a comprehensive atrial lesion pattern. Following the epicardial ablation, our electrophysiology team confirms isolation of the pulmonary veins and posterior left atrium using electroanatomic mapping as well as adenosine to investigate for PV reconnection.

The Convergent ablation system utilizes a unique epicardial ablation radiofrequency device that integrates suction, which draws the cardiac tissue into consistent contact, and perfusion, that uses circulating cooled saline to cool the external portion of the device and drive energy deep into tissue. The epicardial ablation device is placed through a cannula positioned through a subxiphoid incision. The energy is modulated using the ablation console, which adjusts wattage according to tissue impedance. During the epicardial component, we create overlapping lesions along the posterior left atrium, between the pulmonary veins. Following the epicardial portion, the midline incision is closed and the endocardial ablation commences using standard catheter ablation techniques to enter the left atrium. In this case, we describe a Convergent ablation using cryoablation for the endocardial portion of the procedure, using a cryoballoon to provide a wide lesion set to merge with the posterior epicardial lesion set. This specific case is unique in that visualization of the left atrium is assisted using 3D transesophageal ultrasound to provide precise localization of catheters.

Case Description

We describe an ablation strategy that not only utilizes epicardial radiofrequency ablation, but also a second-generation endocardial cryoballoon ablation system to manage persistent atrial fibrillation. The patient is a 61-year-old female with hypertension, hyperlipidemia, and a history of longstanding persistent atrial fibrillation initially diagnosed three years prior to her procedure. She was medically managed with antiarrhythmics and systemic anticoagulants, and required multiple cardioversions and hospitalizations all relating to poor maintenance of sinus rhythm. Despite conventional management efforts, the patient continued to experience recurrent episodes, prompting an invasive management approach. In preparation for her procedure, systemic anticoagulants were discontinued 2 days prior to the ablation. The patient was brought to the hybrid cardiothoracic surgical operating room in the post-absorptive state. Skin preparation was carried out in such a fashion as to prepare the patient for cardiac surgery as well as catheter ablation. The patient was intubated and placed under general anesthesia, and transesophageal echocardiogram was performed using the EPIQ 7 Ultrasound System (Philips Healthcare). The epicardial portion of the ablation was carried out first. Access was gained by a single subxiphoid vertical incision. Dissection using cautery was then used to access the pericardial space just posterior to the left atrium. The EPi-Sense Guided Coagulation Device (nContact, Inc.) was used for the epicardial ablation, which allows for electrogram recording using the proximal and distal electrodes. An anatomical-based ablation was then carried out by placing overlapping lesions beginning from the right inferior pulmonary vein antrum connecting to the left inferior PV antrum. The catheter was extended as far as the pericardial reflection allowed superiorly, and the space between the left and right superior veins was then ablated. Finally, the carina between the appendage and left inferior pulmonary vein was ablated. The epicardial ablation device and cannula were then removed, and the midline incision as well as the accessory entry sites were then closed.

The groin, having already been prepped, was accessed in preparation for catheter ablation. Under echocardiographic guidance, the atrial septum was crossed and the multipolar Achieve catheter (Medtronic, Inc.) was placed in the left atrium. A voltage map was constructed to determine the extent of epicardial ablation, and a 28 mm balloon was positioned in each pulmonary vein antrum. Ablation was carried out with the endpoint of entrance and exit block, verified by adenosine infusion at each site. Figure 1 shows a voltage map of the left atrium prior to epicardial and endocardial ablation. Purple represents viable myocardium, whereas red and grey represent scar. Figure 2 shows a voltage map after pulmonary vein isolation and posterior wall ablation. Note the extensive lesion set, which creates a functional roof line. The scar is extensive, extending from the superior aspect of the posterior wall connecting the superior and inferior pulmonary veins, including the carina between the appendage and left superior vein, and approaching the coronary sinus inferiorly. Figure 3 shows the Achieve catheter using 3D ultrasound in the left atrium. Real-time visualization of catheters and cardiac structures avoid the need for extensive fluoroscopy. The procedure concludes with an empiric cavotricuspid isthmus line. The total fluoroscopic time was 6.4 minutes. The patient was extubated and discharged within 2 days after her procedure. Antiarrhythmics were continued for three months and then discontinued. The patient was monitored with periodic event recorders to investigate for both symptomatic and asymptomatic recurrence. Systemic anticoagulation was continued as dictated by her CHA2DS2-VASc stroke risk.

Discussion

We describe a patient with longstanding persistent atrial fibrillation who underwent a hybrid epicardial radiofrequency ablation with concomitant endocardial cryoballoon ablation. This approach represents a novel technique and relatively new addition to the armamentarium used to manage this complex disease process. The approach leverages the strengths of minimally invasive surgical ablation as well as the wide lesion width afforded by a cryoballoon catheter. This allows for a seamless transmural lesion set that extends from the pulmonary vein across the posterior wall from the superior aspect of the left atrium and adjacent to the mitral annulus. As the posterior wall does not participate in any meaningful atrial function, tissue destruction in this area is less likely to have any clinical impact on atrial ejection fraction.

Optimal lesion sets are currently heavily debated, with more recent literature suggesting that the abatement of complex fractionated electrograms or linear lesion sets may not be any better than standard pulmonary vein isolation when long-term maintenance of sinus rhythm is investigated. Furthermore, an overly complicated treatment protocol might add time and potential risk with questionable advantage. Invasive management of longstanding persistent atrial fibrillation remains a complex management dilemma. The Convergent epicardial ablation system, coupled with cryoballoon ablation, is a welcomed addition. Further research is needed to determine optimal patient selection, long-term clinical outcome, and overall economic impact to the healthcare system. ■

Disclosures: Dr. Makati and Dr. Sherman report consultancy with nContact, Inc. Mr. Bourgeois and Mr. Gassman have no conflicts of interest to report regarding the content herein.