The Surgeon’s Role in Convergent Procedures for Atrial Fibrillation

Overview

Atrial fibrillation (AF), the most common cardiac arrhythmia, is one of the most challenging medical conditions to manage. Clinical manifestations are highly variable, ranging from no symptomatology to complete hemodynamic collapse. The incidence of AF is rising worldwide as more communities are aging.¹ In the United States, AF affects an estimated 2.7 to 6.1 million people, and is the primary diagnosis in 480,000 annual hospital admissions. AF treatment leads to significantly greater incremental healthcare costs; $8705/patient and $6 billion/year nationally.² Moreover, AF is associated with increased risk of stroke, heart failure, dementia, chronic kidney disease, and death. The incidence of AF is expected to double in the next century with aging societies, placing a heavier burden on fragile healthcare systems.¹

AF results from aberrant, atrial activity caused by structural or electrical abnormalities in conduction tissue due to inflammation or tissue damage.³ Atypical atrial contractions produce an irregular heartbeat and discoordinated blood flow through the heart. There are five classifications of AF: paroxysmal, persistent, long-standing persistent, permanent, and nonvalvular AF. Paroxysmal AF is defined as >2 episodes of AF that terminate spontaneously within 7 days or <48 hours of AF that is terminated electrically/pharmacologically. Persistent AF is defined as AF lasting for >7 days or is electrically/pharmacologically terminated >48 hours from onset. Long-standing persistent AF is continuous AF for >1 year. Permanent AF refers to patients who remain in AF despite attempts at conversion and are no longer attempted for medical/electrophysiologic conversion.⁴ Nonvalvular AF occurs in the absence of rheumatic mitral stenosis, mitral valve repair, or surgical valvular replacement.⁵

Pharmacological AF Treatment

Pharmacological management is the first-line approach for AF treatment. Three arms of management exist: rate control, rhythm control, and stroke prevention.⁶ While hemodynamic instability mandates electric cardioversion, those patients who develop AF and are hemodynamically stable can be managed by ventricular rate control with beta blockers, non-dihydropyridine calcium channel blockers (e.g., verapamil and diltazem) or digoxin. The CAST study, one of the first to shine light on the dangers of antiarrhythmics as first-line therapies,⁷ compared encainide and flecainide to control ventricular ectopy following myocardial infarction. This study was discontinued prematurely because of antiarrhythmic-related increases in rates of morbidity and death. Ten years later, the AFFIRM trial studied the efficacy of rhythm control strategies in AF.⁸ This study compared rhythm control (using one or more of the following antiarrhythmics: amiodarone, disopyramide, flecainide, moricizine, procainamide, propafenone, quinidine, sotalol, or a combination of these drugs) with rate control (using beta-blockers, verapamil, diltiazem, digoxin, or a combination). The trial concluded that rhythm restoration had no advantage over ventricular rate control. Furthermore, a high rate of crossover was reported from the rhythm control group to rate control group due to failure of antiarrhythmics.⁸ The RACE trial further helped to prove the benefits of rate control in AF. This trial confirmed that rate control was non-inferior to rhythm control in preventing cardiovascular death and morbidity in anticoagulated, persistent AF patients.⁹ The follow-up study, RACE II, sought to determine whether the degree of rate control limited adverse events of AF. Over their 2- to 3-year follow-up, investigators concluded that lenient rate control strategy (<110 bpm) was just as effective at limiting cardiovascular events, hospitalization, and death compared to strict rate control (<80 bpm resting, <110 bpm exercise) strategy.¹⁰ The RATE-AF trial, launched in December 2016, is the first head-to-head trial of digoxin versus beta-blockers for the control of permanent AF.¹¹ As stated in the 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation, beta-blockers are the most commonly utilized medication for rate control, followed by calcium channel blockers, digoxin, and amiodarone.5 These drugs can be used in combination, but should be titrated to avoid bradycardia and hypotension. Rhythm control strategies are commonly considered in the following situations: young patient age, difficulty in achieving rate control, tachycardia-mediated cardiomyopathy, first episode of AF, AF that is precipitated by an acute illness, and patient preference.⁵ 

Stroke, the most dreaded complication of AF, increases fivefold in AF.¹² AF-associated stroke risk has traditionally been assessed using CHADS₂ scoring, and more recently, with CHA₂DS₂-VASc scoring, to determine if patients require anticoagulation.¹² Stroke risk must be balanced by bleeding risk in these patients, using HAS-BLED, RIETE, HEMORR2HAGES, or ATRIA scoring systems, as demonstrated in multiple clinical trials.⁵ The oral anticoagulant regimen selected, whether an oral antiplatelet, vitamin K antagonist, novel oral anticoagulant (NOAC), or a combination of these medications, should be patient specific. Several mechanical options for preventing stroke in AF can also be utilized, including the WATCHMAN device (Boston Scientific), surgical left atrial appendage (LAA) ligation, and various LAA clip occlusion devices.  

Non-pharmacological AF Treatment

Rapid firing atrial impulses originating near the pulmonary veins and/or LA have been implicated in playing a major role in the initiation and maintenance of AF. AF ablation of such aberrant foci is currently indicated for symptomatic patients taking at least one antiarrhythmic that is poorly tolerated or ineffective.⁵

Clinical outcomes of AF ablation, compared to antiarrhythmic regimens, have been reported in multiple clinical trials, including the RAAFT-2 and MANTRA-PAF studies. These trials have shown improved 1-year freedom from AF and improved 2-year control of symptomatic AF with ablation compared to antiarrhythmic drugs, respectively.^6,13-14 Two ongoing trials, CABANA and EAST, are focused on determining the benefit of AF ablation for controlling AF-related stroke and cardiovascular complications.^6,15 

Surgical AF ablation, known as the Cox-Maze procedure, was developed in the 1980s by James Cox, MD. It is a highly complex and technically difficult surgical procedure for isolating the pulmonary veins and posterior LA where ectopic foci are believed to originate.¹⁶ This technical complexity has led to the development of other less complex ablation strategies. For instance, the ABLATE trial evaluated Cox-Maze type lesions-sets using the Synergy Ablation System (AtriCure, Inc.); this trial demonstrated freedom from AF at 12 months was 75%, leading to this system’s FDA approval. Radiofrequency ablation — particularly the full biatrial Cox-Maze procedure, pulmonary vein isolation alone, and pulmonary vein isolation combined with LA lesion-sets¹⁶ — have become increasingly utilized to treat AF. Surgical LAA occlusion devices have also been introduced into the operating room to decrease the risk of AF-associated stroke. While these devices are not intended to control the incidence or recurrence of AF, their utility in AF-associated stroke prevention remains uncertain. 

Hybrid epicardial and endocardial ablation, known as the Convergent procedure, developed to overcome the inconsistency and complexity of surgical AF ablation, is gaining broader interest. Ablative epicardial and endocardial lesion-sets are performed, including endocardial ablation of the mitral valve annulus and cavotricuspid isthmus, that enable complete Cox-Maze equivalent lesions, without arresting and opening the heart. As an added benefit, electrophysiologists are able to perform completion mapping/interrogation to elicit residual AF foci.¹⁷ Several single institutional reports have found improved freedom from AF with the Convergent procedure compared to endocardial ablation alone. Geršak et al reported one European, multicenter experience with the Convergent procedure for persistent and long-standing AF in 73 consecutive patients; six- and 12-month maintenance of sinus rhythm was 82% and 80%, respectively.¹⁸ Furthermore, Geršak recently reported long-term success rates with the Convergent procedure at their center, including sinus rhythm of 88% at 6 months, 85% at 1 year, 85% at 2 years, 84% at 3 years, and 81% at 4 years of follow-up.¹⁹ Eighteen percent of patients required repeat ablation after 4 years. Gehi et al found a 6% need for repeat ablation in their single-center experience of 101 patients;²⁰ they reported AF-free survival of 66.3% at 1 year after a single procedure and 70.5% after repeat ablation. An expert consensus statement on catheter and surgical ablation of AF, developed in collaboration with and endorsed by the Society of Thoracic Surgeons (STS), American Heart Association (AHA), American College of Cardiology (ACC), and multiple international heart rhythm societies, was published in 2017;¹⁶ this update elaborated on the indications, physiology, and utility of available AF ablation techniques.

How We Perform the Convergent Procedure

The approach to staged hybrid ablation using thoracoscopic epicardial ablation, combined with percutaneous transvenous, transseptal endocardial ablation, has been in evolution over the last decade. Minimally invasive techniques to access the pericardium have included thoracoscopic, laparoscopic, and open subxiphoid approaches.^20-21 Early in our experience, we adopted a transabdominal, transdiaphgramatic approach to access the pericardium. We have now transitioned to exclusively performing the lesser invasive subxiphoid approach to limit peritoneal entry. Following intubation, an esophageal temperature probe is first placed using fluoroscopic guidance, 1.5 vertebra below the carina. Esophageal temperature is constantly recorded during the procedure in order to avoid thermal esophageal injury during the creation of epicardial lesions. We pause the procedure if we observe an elevation of 0.5 ºC above the baseline temperature, and irrigate the pericardium with room temperature saline. The surgical procedure is performed though a standard subxiphoid window via a 2-3 cm incision, amputating the xiphoid if needed to facilitate access and exposure (Figure 1A). Blunt and cautery-assisted dissection is used to expose the anterior-inferior pericardium at its diaphragmatic insertion (Figure 1B). Once the pericardium is exposed, we utilize the flat surface of hook cautery to gain initial access into the pericardium. At that point, the pericardial window is developed by lifting the pericardium away from the heart while extending the entry point using hook cautery. In order to avoid unintended contact with the heart, ventilation is temporarily halted. Once pericardial access is attained, a pericardioscope is inserted into the pericardial well under direct visualization of a 5 mm laparoscopic camera. We utilize the Subtle Cannula with Guide (30 cm or 40 cm, AtriCure, Inc.), a sterile, single-use cannula comprised of a large bore tube, vacuum port, guidewire, and beveled distal tip (Figure 1C). Once the cannula and accompanying laparoscope are positioned at the pericardial entry point, extreme caution is used to avoid contact with the heart, directing the pointed tip toward the diaphragm. After the cannula is positioned within the pericardium and all anatomical landmarks are identified, an EPi-Sense Coagulation Device (AtriCure, Inc.) is directed toward the posterior LA wall for lesion creation (Figure 1D). The boundaries of the epicardial box lesion include the inferior vena cava, coronary sinus, posterior wall of the LA, posterior pericardial reflection of the oblique sinus, and left inferior pulmonary veins. Under endoscopic visualization, the EPi-Sense device is applied to the visible LA wall and suction is applied. We fill the cannula with room temperature saline during ablation to minimize heat transfer to nearby structures. Completed lesions appear charred compared to native atrial tissue (Figure 1E). Following completion of each 90-second lesion, the saline is suctioned from the cannula, and suction is ceased to the EPi-Sense device. This process is repeated until the entire posterior LA surface is ablated. After epicardial ablation is completed, a Jackson-Pratt drain is placed through the Subtle Cannula into the pericardium, and the cannula is removed. The drain is brought out through a separate stab incision. Fascia and subcuticular layers are closed, preserving cosmesis (Figure 1F). Video demonstration of this technique is included (Video 1). After the operative component is finished, the patient is taken to the catheterization laboratory for completion of endocardial mapping and ablation (Figure 2).

Summary

We have been very pleased with our early experience using the Convergent procedure at Emory University Hospitals in over 100 candidate patients. Detailed characteristics and outcomes are currently being prepared for publication. Encouraged by this experience, we have shared our technique with surgeons at Navicent Health in Macon, Georgia, effectuating a newly announced cardiothoracic surgery partnership between Navicent Health and Emory Healthcare.

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