Hybrid Ablation Protocols for Atrial Fibrillation

In this article, the author discusses his clinical experience with hybrid endocardial and epicardial ablation at the Swedish Heart and Vascular Institute. Persistent and long-standing persistent atrial fibrillation (Pers-LSP AF) remains a challenging problem in interventional electrophysiology. Catheter ablation procedures have evolved to be appropriate second line therapy for symptomatic patients refractory to anti-arrhythmic therapy. Our understanding of Pers-LSP AF now recognizes the need to address both triggers as well as the underlying atrial substrate to deliver the possibility of a durable cure. Triggered activity and local reentry responsible for the initiation and maintenance of AF classically involves the pulmonary veins (PVs). Hence, the PV-left atrial (LA) junction remains the primary focus of ablation strategies for both paroxysmal and persistent forms of AF. Pulmonary vein isolation (PVI), however, is rarely sufficient in the Pers-LSP AF population. A variety of additional ablation lesions in addition to PVI are routinely used in these patients including addressing complex fractionated electrograms (CFAEs) and linear ablation most commonly over the roof of the LA, along the mitral isthmus (MI) and over the cavotricuspid isthmus (CTI). The above strategies are frequently used in various combinations in most contemporary, high-volume EP labs. Independent but parallel to the evolution of catheter ablation, cardiothoracic surgeons have developed iterations of the Cox-Maze surgical lesion set that are now totally thoracoscopic, thereby eliminating the need for cardiopulmonary bypass. Similar to most catheter-based procedures, lesions are formed with radiofrequency energy addressing the epicardial surface of the atrium. In spite of extensive ablation as delineated above, recurrent AF remains a problem for a minority of patients after 1–3 percutaneous procedures or a stand-alone surgical procedure. Many of these patients remain highly motivated to achieve a life free of AF and are not ready to consider an AV nodal ablation with resultant pacemaker implantation. At the Swedish Heart and Vascular Institute in Seattle, Washington, we have recently performed several hybrid ablation protocols attempting to capitalize on the potential benefits of both an endocardial and epicardial ablation set at a single concomitant procedure. These procedures have been reserved for Pers-LSP AF patients refractory to extensive prior percutaneous ablation procedures. The procedures are performed in an operating room with access to fluoroscopy equipment. Both a full OR team as well as a full team of EP lab personnel participate in the procedure. The fluoroscopic imaging can either be performed with fixed mounted equipment (essentially a hybrid-OR) or with a conventional portable C-arm device. The patients are prepped and draped initially for the surgical procedure, with a sterile field also made in the groin for the second phase of the operation. Procedures are performed under general anesthesia. All patients undergo a TEE post-intubation to verify the absence of thrombus in the left atrial appendage. The cardiothoracic surgeon then makes 3 incisions on the right chest wall, allowing fiberoptic visualization and subsequent delivery of radiofrequency energy through both clamp devices as well as tools that enable fixed point ablation. The right-sided lesion set typically consists of right-sided antral PVI, initial construction of a roof line, SVC and IVC isolation, and linear ablation down the lateral wall of the right atrium. Three corresponding incisions are then made on the left chest wall. The left-sided lesion set consists of left-sided antral PVI, completion of the roof and inferior lines, and a mitral isthmus line. Anatomic considerations limit the extent the latter line can be taken fully to the mitral valve/coronary sinus (CS). Attempted identification and ablation of ganglionic plexi is also performed at the discretion of the surgeon. Exclusion of the left atrial appendage is also commonly performed at either this stage or at the end of the procedure. At this juncture, the groin is exposed and a standard left atrial ablation set-up is undertaken. In our lab, this commonly consists of a coronary sinus catheter, a circular mapping catheter and an irrigated ablation catheter all placed via the right femoral vein. Although transeptal access is commonly performed under the guidance of intracardiac echo, real-time TEE imaging of the fossa ovalis has proved to be a reliable replacement for these procedures. The fluoroscopy and 3D mapping equipment are also introduced at this time. Recording and stimulation is performed with standard equipment on a movable cart. We administer heparin with a goal ACT of 300–350s. Once left atrial access has been obtained, confirmation of pulmonary vein isolation has been our first step and has been reliably verified without the need for supplemental endocardial lesions. Next steps depend on the clinical rhythm present. If AF persists, we commonly search for complex fractionated electrograms at this stage. If the prior ablations have converted the patient into a stable LA flutter or atrial tachycardia, we utilize entrainment and activation mapping in an attempt to identify and terminate this rhythm. Regardless of the individual trajectory of a patient, it is essential to verify isolation of the posterior wall confirming complete roof and inferior lines upon a return to sinus rhythm. We commonly record and pace from the “box” to confirm. Arguably, the most important maneuver upon a return to sinus rhythm is verification and usual need for supplemental endocardial and epicardial via the CS ablation for complete mitral isthmus block. This line remains challenging to complete from a surgical standpoint, and in all cases has required additional work. Failure to complete this line renders a proarrhythmic substrate and is not advised. Bidirectional block is confirmed with catheters in the CS and anterior to the line such as the left atrial appendage with conventional maneuvers. We then return to the right atrium and construct a cavotricuspid line. If performed at a prior ablation procedure, it is verified to remain complete. Protamine is then administered and the thoracoscopic incisions are closed and chest tubes placed. The patient is usually extubated in the PACU. In general, patients stay in the hospital for 3 days, with the first night in the ICU and subsequent nights on the telemetry floor. Anticoagulation is reinitiated as soon as possible post-procedure. In our experience, hybrid endocardial and epicardial ablation has proved to be a valuable addition to the armamentarium of options an electrophysiologist may consider in patients with Pers-LSP AF who have failed catheter-based ablations. The long-term safety and efficacy of this procedure is being evaluated in large-scale clinical trials. The ideal patient characteristics and appropriate timing of this option relative to conventional catheter-based ablation will require future investigation.