Kyle Walsh MD,1 Sunil Prasad MD,2 Arun Singhal MD PhD1
1 University of Iowa
2 University of Rochester
August 31st, 2024
Abbreviations & Definitions
ACC – American College of Cardiology
AF – Atrial fibrillation
AHA – American Heart Association
CM – Cox-Maze procedure
DOAC – Direct oral anticoagulant
LAA – Left atrial appendage
STS – Society of Thoracic Surgeons
Paroxysmal AF: AF that is intermittent and terminates within ≤7 days of onset.
Persistent AF: AF that is continuous and sustains for >7 days and requires intervention.
Long-standing persistent AF: AF that is continuous for >12 months duration.
Permanent AF: AF in which sinus rhythm cannot be sustained after cardioversion, or the patient and physician have decided against further efforts to restore sinus rhythm.
Indications & Guidelines for Management
Both the American Heart Association (AHA)/American College of Cardiology (ACC) and the Society of Thoracic Surgeons (STS) guidelines for management of atrial fibrillation (AF) were published in January 2024 and reflect growing evidence supporting the efficacy of both surgical ablation for AF as well as left atrial appendage (LAA) ligation for stroke/thromboembolism risk reduction. The AHA/ACC guidelines cover the scope of AF pathophysiology, workup, medical therapy, and catheter and surgical-based ablation. The STS guidelines are focused on indications for surgical ablation and LAA ligation. The full extent of those guidelines is beyond the scope of this chapter, but select recommendations and discussions are included to the extent they are frequently encountered by cardiothoracic surgeons and trainees.
2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation1
The updated ACC/AHA guidelines cover all aspects of AF pathophysiology, epidemiology, diagnosis, treatment, and outcomes. Relevant points that pertain to cardiothoracic surgeons are discussed. A major change in this updated guideline is the modification of the classification of AF. The previously utilized classifications, like paroxysmal, persistent, and chronic AF, are no longer recommended, and instead, the stages of AF are recommended. These stages are:
- At risk of AF: Patients who have modifiable and non-modifiable risk factors that increase their risk of developing AF (obesity, hypertension, obstructive sleep apnea, diabetes, alcohol use, male sex, age, etc.)
- Pre-AF: Evidence of structural or electrical findings suggesting a predisposition to AF (atrial enlargement, frequent atrial ectopy, etc.)
- AF: Including substages of paroxysmal, persistent, and long-standing persistent
- Permanent AF: When no further attempts at rhythm control are made
The committee discussed that this classification by stages more accurately represents AF as a disease spectrum with stages that require stage-dependent diagnostic, screening, and therapeutic approaches.
With regards to thromboembolism risk and anticoagulation therapy, the guidelines recommend using a validated clinical risk score such as CHA2DS2-VASc. Patients with an annual stroke risk of ≥2% and no contraindications should receive oral anticoagulation. Like the STS guidelines, surgical LAA exclusion receives a class I recommendation in any patient with a CHA2DS2-VASc ≥2. The goal of LAA exclusion, regardless of technique, is the absence of flow into the appendage and residual stump of <1 cm visible on intraoperative transesophageal echocardiogram. For patients on anticoagulation for AF, the guidelines recommend temporary cessation of anticoagulation without bridging in patients who have not had a recent stroke and without a previous mechanical valve.
The AHA/ACC guidelines weakly recommend surgical ablation in patients undergoing concomitant cardiac surgery. Concomitant surgical ablation is a class IIa recommendation and states that surgical ablation “can be beneficial to reduce the risk of recurrent AF.” The guidelines recommend three months of continued anticoagulation after surgical ablation to reduce the risk of stroke or thromboembolism.
Finally, the guidelines touch on the management of peri-procedural AF in cardiac surgery. Preoperative prophylactic beta blockers or amiodarone receive a IIa recommendation to reduce the incidence of postoperative AF. In patients who develop post-operative AF, both rate and rhythm control strategies receive class I recommendations depending on patient presentation and patient and physician preference. Beta blockers also receive a class I recommendation for treatment of post-operative AF. If patients do develop postoperative AF, it is reasonable to administer anticoagulation for at least 60 days and to reevaluate the need for anticoagulation at that time (Class IIa).
STS 2023 Clinical Practice Guidelines for the Surgical Treatment of Atrial Fibrillation2
The major updates in the 2023 STS clinical practice guidelines strengthen the verbiage in recommending surgical ablation in any first-time nonemergent mitral or non-mitral procedure. The 2017 guidelines reported that “surgical ablation … can be performed without additional risk of operative mortality or major morbidity and is recommended at the time of concomitant mitral operations to restore sinus rhythm.” The updated guidelines shortened the recommendations and simply state that surgical ablation is recommended for first-time nonemergent mitral or non-mitral operations to restore sinus rhythm and improve long-term outcomes.
The guidelines also strengthen the recommendation for LAA excision or exclusion to a class I recommendation from class IIa based in part on the results of the LAAOSIII trial discussed below. LAA obliteration is recommended for all first-time nonemergent cardiac surgeries in patients with a history of AF with or without concomitant ablation. Two new guidelines were also added: (1) surgical LAA obliteration can be considered in isolation in patients with longstanding AF, high stroke risk, and contraindications to or failure of long term anticoagulation (IIb) and (2) in patients with symptomatic valve disease and AF, who are deemed low to intermediate surgical risk, surgical valve repair or replacement with concomitant surgical ablation and LAA occlusion is reasonable over transcatheter valve repair or replacement alone (IIa).
Summary Table: AHA/ACC 2023 Atrial Fibrillation Guidelines.
| Clinical Setting | Class of Recommendation | Evidence |
|---|---|---|
| Antithrombotic therapy | ||
| For patients with AF and an estimated annual thromboembolic risk of ≥2% per year (eg, CHA2DS2-VASc ≥2 in men and ≥3 in women), anticoagulation is recommended to prevent stroke and systemic thromboembolism | I | 17 |
| In patients with AF who do not have a history of moderate to severe rheumatic mitral stenosis or a mechanical heart valve, and who are candidates for anticoagulation, DOACs are recommended over warfarin. | I | 18, 19 |
| In patients with AF (excluding those with recent stroke or TIA, or a mechanical valve) and on oral anticoagulation with either warfarin or DOAC who are scheduled to undergo an invasive procedure or surgery, temporary cessation of oral anticoagulation without bridging anticoagulation is recommended. | I | |
| In patients with AF on DOAC that have been interrupted, in general, resumption of anticoagulation the day after low bleeding risk surgery and between the evening of the second day and the evening of the third day after high bleeding risk surgery is reasonable as long as hemostasis has been achieved and further bleeding not anticipated. | IIa | 20 |
| LAA exclusion | ||
| In patients with AF undergoing cardiac surgery with a CHA2DS2-VASc score of ≥2 or equivalent stroke risk, surgical LAA exclusion, in addition to continued anticoagulation, is indicated to reduce the risk of stroke and systemic embolism. | I | 16 |
| In patients with AF undergoing cardiac surgery and LAA exclusion, a surgical technique resulting in absence of flow across the suture line and a stump of <1 cm as determined by intraoperative transesophageal echocardiography should be used. | I | |
| Post-cardiac surgery AF | ||
| In patients undergoing cardiac surgery who are at high risk for postoperative AF, it is reasonable to administer short-term prophylactic beta blockers or amiodarone to reduce the incidence of postoperative AF. | IIa | |
| In postoperative cardiac surgery patients, beta blockers are recommended to achieve rate control for AF unless contraindicated or ineffective, in which case a non-dihydropyridine calcium channel blocker is recommended. | I | |
| In hemodynamically stable cardiac surgery patients with postoperative AF, rate-control (target heart rate <100 bpm) and/or rhythm-control medications are recommended as initial therapy, with the choice of strategy according to patient symptoms, hemodynamic consequences of the arrhythmia, and physician preference. | I | |
| In patients who develop postoperative AF after cardiac surgery, it is reasonable to administer anticoagulation when deemed safe regarding surgical bleeding for 60 days after surgery, unless complications develop, and to reevaluate the need for longer term anticoagulation at that time. | IIa | |
Summary Table: STS 2023 Atrial Fibrillation Guidelines.
| Clinical Setting | Class of Recommendation | Evidence |
|---|---|---|
| Clinical Setting | Class of Recommendation | Evidence |
| Surgical ablation | ||
| Surgical ablation for AF is recommended for first-time nonemergent concomitant mitral operations to restore sinus rhythm and improve long-term outcomes. | I | 3-5, 8-10 |
| Surgical ablation for AF is recommended for any first-time nonemergent concomitant nonmitral operation to restore sinus rhythm and improve long-term outcomes. | I | 6,7, 8-12 |
| Surgical ablation for symptomatic AF in the absence of structural heart disease refractory to class I/III antiarrhythmic drugs, catheter-based therapy, or both, is reasonable as a primary stand-alone procedure to restore sinus rhythm. | IIa | 13-15 |
| Surgical ablation for symptomatic persistent or longstanding persistent AF in the absence of structural heart disease is reasonable as a stand-alone procedure using the Cox Maze III/IV lesion set as the preferred procedure. | IIa | 13-15 |
| Surgical ablation for symptomatic AF in the setting of left atrial enlargement (≥4.5 cm) or more than moderate mitral regurgitation by pulmonary vein isolation alone is not recommended. | III | |
| LAA management | ||
| LAA obliteration for AF is recommended for all first-time nonemergent cardiac surgery procedures, with or without concomitant surgical ablation, to reduce morbidity from thromboembolic complications. | I | 16 |
| Isolated surgical LAA obliteration may be considered in patients with longstanding persistent AF, a high stroke risk, and contraindications for or failure of long-term oral anticoagulation. | IIb | |
| Transcatheter considerations | ||
| For patients with symptomatic valve disease and AF, who are deemed of low to intermediate surgical risk, surgical valve repair or replacement with concomitant surgical ablation and LAA occlusion is reasonable over isolated transcatheter valve repair or replacement alone to restore sinus rhythm and improve long term outcomes. | IIa | |
or in the prevention of ischemic or hemorrhagic stroke or systemic thromboembolism.4,5 The PAUSE trial was developed to investigate how long oral anticoagulants should be held prior to low or high-risk surgical procedures. In this trial, oral anticoagulants were held for one day prior to a low bleeding risk procedure and for two days prior to a high bleeding risk procedure. The regimens were then resumed one day after a low bleeding risk procedure and two to three days after a high bleeding risk procedure. The study demonstrated low rates of both major bleeding complications and thromboembolism.6 The LAAOSIII trial is also cited in these guidelines to recommend surgical LAA occlusion in addition to ongoing anticoagulation.7
STS 2023 Clinical Practice Guidelines for the Surgical Treatment of Atrial Fibrillation
The recommendations from the STS guidelines are based on over two decades of randomized clinical trials and meta-analyses. Initial studies were carried out in patients undergoing mitral valve surgery, as that was the most common surgery for which the left atrium was opened. Early results consistently demonstrated a reduction of AF burden at 12 months of follow-up without significant differences in stroke rate or mortality.8–10 These data were eventually expanded to include all manner of cardiac procedures, including coronary bypass and other valve procedures besides the mitral valve. Studies continued to show an increased rate of sinus rhythm at early post-operative follow-up without an associated decrease in mortality or stroke risk.11,12 Several retrospective registry studies demonstrated decreased midterm and long-term mortality in patients who underwent surgical ablation.13–16 Finally, a recent retrospective study looking at over 100,000 Medicare patients demonstrated improved three-year survival in patients who underwent surgical ablation and LAA obliteration compared to LAA obliteration alone or no AF management.17
A series of non-randomized prospective and retrospective studies report success with isolated surgical ablation for patients with even long-standing persistent AF, with freedom from AF reported as high as 80% at ten years.18–20 Included in these studies were minimally invasive techniques such as right mini-anterior thoracotomy.
Multiple observational studies and meta-analyses have demonstrated a reduction in thromboembolic events in patients who undergo obliteration of the LAA. There was no robust data from randomized controlled trials until the publication of the landmark Left Atrial Appendage Occlusion Study III (LAAOSIII). This study showed a significant reduction (32% relative risk reduction) in thromboembolic events, including stroke, without an associated benefit to mortality.7
Ongoing Trials/Recent Publications
Several recently published or ongoing trials will likely impact future guidelines. As mentioned above, the recently published LAAOSIII trial has significantly impacted the management of the LAA in patients with AF undergoing cardiac surgery. Another ongoing trial, the LeAAPS trial, is investigating the benefit of prophylactic LAA ligation in patients who are not diagnosed with AF, but who have significant risk factors for either AF or stroke. An expanding area of research is into hybrid procedures like the convergent procedure for management of persistent AF. The CONVERGE trial was published in 2020 and demonstrated superior effectiveness (67% vs 50%) for a hybrid endocardial and surgical ablation approach compared to standard catheter ablation.21 These developing hybrid approaches have the potential to change the surgical management of isolated AF. Finally, there is a growing body of recent literature that is investigating the benefits of rhythm control over rate control. The EAST-AFNET 4 trial was a randomized controlled trial comparing rate and rhythm control that was published in 2020 and demonstrated a benefit of rhythm control in the prevention of death from cardiovascular cause, stroke, or hospitalization for cardiac cause.22
Expert Commentary
As detailed in the AHA guidelines, AF has been extensively studied. Rhythm control is superior to rate control. Two important trials that are often mentioned in cardiology communities when discussing AF are the EAST-AFNET (The Early Treatment of Atrial Fibrillation for Stroke Prevention Trial) and the AF-CHF (Atrial Fibrillation and Congestive Heart Failure) trials.22,23 The authors of the EAST-AFNET trial concluded, “Early rhythm-control therapy was associated with a lower risk of adverse cardiovascular outcomes than usual care among patients with early AF and cardiovascular conditions.” The AF-CHF trial concluded somewhat differently that rhythm control did not affect cardiovascular mortality but was associated with improved quality of life. Contemporary trials in patients with AF and heart failure, regardless of LV function, and often using catheter ablation as an important therapy, have reported trends or statistically significant improvement in clinical outcomes with rhythm control. In summary, the preponderance of evidence supports the treatment of AF in a manner to gain not just rate control but also rhythm control.
Surgical treatment of AF was pioneered by Cox et al., who formulated the Cox-Maze (CM) procedure at Barnes Hospital in St. Louis.24 The CM procedure was a technically difficult procedure that interrupted the various common reentry circuits associated with AF through multiple left and right atrial incisions that formed a set of scars which isolated the pulmonary veins and posterior left atrium, and interrupted macro-reentrant circuits thought to be responsible for AF. The current iteration, the CM 3 and 4 procedures, are the gold standard for surgical treatment of AF.25 In the hands of experienced surgeons, the efficacy of this lesion set is longstanding, with Cox reporting success rates in select patients at nearly 95% of patients at 10 years. Damaino and colleagues have developed alternative energy sources, cryoablation and bipolar radiofrequency, as alternatives transforming the difficulty of the CM 3 into the CM 4, the current iteration of the CM. Since the development of the CM lesion sets, lesser lesion sets such as pulmonary vein isolation, the convergent procedure, and the so-called left-sided CM 4 lesion sets have been described for the treatment of AF. None of these lesion sets has been shown to have the efficacy of the CM 4 lesion set. The general principles that should be familiar to any surgeon as they choose an intervention strategy are: (1) lesion set versus burden of atrial disease, (2) approach and transmurality/energy source, and (3) LAA closure.
- Lesion set versus burden of atrial disease: In permanent AF, although in small clinical trials, only CM 4 has demonstrated meaningful freedom from AF at 2 years. However, in patients with new-onset paroxysmal AF, pulmonary vein isolation may be an adequate lesion set. As surgeons deviate from the CM 4, whether isolated AF or hybrid procedures, failure rates increase.
- Approach and transmurality/energy source: In the original CM 1-3, lesions were created by surgical division of the tissue. However, to decrease morbidity, additional energy sources (cryoablation and bipolar radiofrequency) have been developed. These sources allow a variety of approaches, including the complete CM lesion set or less invasive approaches. Surgeons must be familiar with the requirements to create full-thickness lesion sets with the energy source being utilized. For example, the coronary sinus lesion requires ablation both inside and outside of the left atrium to ensure transmurality. The radiofrequency device may require multiple applications to ensure transmurality. Conversely, failure to create transmurality has worse outcomes and can result in atrial rhythm disturbances (convert AF to atrial flutter), which may be difficult to manage.
- LAA closure: In patients with AF, data consistently demonstrate the benefit of appendage management. Two important caveats exist, however. First, after closure, the appendage must have no more than a 1 cm stump. Second, at present, isolated appendage management may not be considered an alternative to anticoagulation but rather an adjuvant.
In summary, surgical management of AF and the LAA is safe, improves long-term patient outcomes, and should be considered in all patients with this rhythm disturbance.
Sources
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