Surgical strategies and devices for surgical exclusion of the left atrial appendage: a word of caution

The Strengths and Weaknesses of Left Atrial Appendage Ligation or Exclusion (LARIAT, AtriaClip, Surgical Suture)

Left atrial appendage (LAA) epicardial exclusion has been associated with addressing 2 potential deleterious consequences attributed to the LAA, namely, thrombus formation and an arrhythmogenic contributor in advanced forms of atrial fibrillation. With more than 60 years of history, the surgical exclusion of the LAA has been firmly established. Numerous approaches have been used for surgical LAA exclusion including surgical resections, suture ligation, cutting and non-cutting staples, and surgical clips. Additionally, a percutaneous epicardial LAA ligation approach has been developed. A discussion of the various epicardial LAA exclusion approaches and their efficacy will be discussed, along with the salient beneficial affects on LAA thrombus formation, LAA electrical isolation and neuroendocrine homeostasis.

Left atrial appendage exclusion in atrial fibrillation

Although oral anticoagulants (OACs) are first-line therapy for stroke prevention in patients with atrial fibrillation (AF), some patients cannot be treated with OACs due to absolute or relative contraindications. Left atrial appendage (LAA) exclusion techniques have been developed over the years as a therapeutic alternative for stroke prevention. In this paper, we review the evolution of surgical techniques, employed as an adjunct to cardiac surgery or as a stand-alone procedure, as well as the recently introduced and widely utilized percutaneous LAA occlusion techniques. Until recently, data on surgical LAAO were limited and based on non-randomized studies. We focus on recently published randomized data which strongly support an add-on surgical LAAO in eligible patients during cardiac surgery and could potentially change current practice guidelines. In recent years, the trans-catheter techniques for LAA occlusion have emerged as another, less invasive alternative for patients who cannot tolerate oral anticoagulation. We review the growing body of evidence from prospective studies and registries, focusing on the two systems which are in widespread clinical use nowadays: the Watchman and Amulet type devices. These data show favorable results for both Watchman and Amulet devices, setting them as an important tool in our arsenal for stroke reduction in AF patients, especially in those who have contraindications for OACs. A better understanding of the different therapeutic alternatives, their specific benefits, and downfalls in different patient populations can guide us in tailoring the optimal therapeutic approach for stroke reduction in our AF patients.

The Strengths and Weaknesses of Left Atrial Appendage Ligation or Exclusion (LARIAT, AtriaClip, Surgical Suture)

Left atrial appendage (LAA) epicardial exclusion has been associated with addressing 2 potential deleterious consequences attributed to the LAA, namely, thrombus formation and an arrhythmogenic contributor in advanced forms of atrial fibrillation. With more than 60 years of history, the surgical exclusion of the LAA has been firmly established. Numerous approaches have been used for surgical LAA exclusion including surgical resections, suture ligation, cutting and non-cutting staples, and surgical clips. Additionally, a percutaneous epicardial LAA ligation approach has been developed. A discussion of the various epicardial LAA exclusion approaches and their efficacy will be discussed, along with the salient beneficial affects on LAA thrombus formation, LAA electrical isolation and neuroendocrine homeostasis.

Is there an alternative treatment for patients intolerant to antiplatelet therapy if percutaneous left atrial appendage closure is considered?

INTRODUCTION

Left atrial appendage (LAA) closure has become of major interest for patients with atrial fibrillation intolerant to oral anticoagulation therapy (OAC). Patients with a contraindication to both OAC and antiplatelet therapy are not eligible for percutaneous LAA closure. We aimed to find an alternative treatment for these specific patients.

METHODS

From March 2014 until December 2015 five patients were referred for percutaneous LAA closure. Alternative treatment was necessary due to an absolute contraindication to OAC and antiplatelet therapy (n = 4) or after previous failed percutaneous device implantation (n = 1). A stand-alone full thoracoscopic closure of the LAA using the Atriclip PRO device (AtriCure Inc., Dayton, OH, USA) was performed under guidance of transoesophageal echocardiography (TEE). After three months all patients underwent a computed tomography scan. Mean follow-up was 7.2 months [range 4.5-9.8 months].

RESULTS

All procedures were achieved without the occurrence of complications. Complete LAA closure was obtained in all patients without any residual flow confirmed by TEE. Postoperative computed tomography confirmed persisting adequate clip positioning with complete LAA closure and absence of intracardial thrombi. During follow-up no thromboembolic events occurred.

CONCLUSION

For atrial fibrillation patients with an absolute contraindication to OAC and antiplatelet therapy a stand-alone, minimally invasive thoracoscopic closure of the LAA is a safe and feasible alternative treatment. This might be a solution to avoid serious bleeding complications while eliminating the thromboembolic risk originating from the LAA in patients who are not eligible for percutaneous LAA closure.

Enlargement of the Excluded Left Atrial Appendage With Thrombus

We report progressive enlargement of the excluded left atrial appendage (LAA) with a thrombus in a patient who had undergone valve surgery and endocardial suture closure of the LAA previously. Echocardiography and CT detected no communication between the LAA and the left atrium. Magnetic resonance imaging showed the LAA was filled with fresh and old thrombi. Coronary arteriography demonstrated small left coronary artery-LAA fistulae. At surgery, successful exclusion of the LAA was confirmed after removal of the thrombi. Persistent inflow of blood through the coronary artery fistulae to the excluded LAA may be the primary mechanism of this pathology.

Intra-Atrial Excision of the Left Atrial Appendage: A Simple and Easy Technique

In patients with atrial fibrillation, closure of the left atrial appendage (LAA) is recommended to prevent thromboembolic events, however, conventional exclusion or excision techniques have potential drawbacks such as persistent blood flow into the appendage and a residual stump. We propose a simple and easy technique for LAA closure consisting of intra-atrial excision of the LAA, which is invaginated into the left atrium (LA), and direct suture closure of the orifice from inside the LA. In this technique, complete elimination of the LAA was achieved without leaving a residual stump because the LAA was excised at the orifice and was closed at the base of the LAA.

A Review Of The Relevant Embryology, Pathohistology, And Anatomy Of The Left Atrial Appendage For The Invasive Cardiac Electrophysiologist

The three-dimensional morphology of the left atrial appendage provides the substrate for thrombus generation, and is a harbinger for embolic material due to its direct connection to the left-sided circulation. Appreciating the development of the appendage from mesodermal layer to its adult form provides the basis to improve exclusion from the atrial circulation, and thereby can lead to a significant reduction in stroke risk. This process also provides insight into the role of the left atrial appendage as an endocrine organ, its involvement in fluid homeostasis, and its connection to the autonomic nervous system. Knowledge of the surrounding structural arrangement is critical to identify landmarks from both an endocardial and epicardial perspective to improve targeted device placement. Furthermore, correlation of the left atrial appendage body, neck, and ostium to the surrounding anatomy can also improve both procedural efficacy and safety. In addition, a working knowledge of the regional anatomy adds a prudent degree of awareness for procedural complications, and allows for early identification and timely intervention as these situations arise. A detailed understanding of the left atrial appendage embryology, histology, and gross anatomy is imperative to identify the correct device and approach for each individual patient. In addition, this increased awareness can identify areas that are in need of further innovation, and thus provide the ability to adapt and refine existing technologies to overcome pitfalls currently facing catheter-based approaches.

The WATCHMAN device for stroke prophylaxis in atrial fibrillation: an evolving niche

Atrial fibrillation is associated with a markedly increased risk of thromboembolic stroke. At present, lifelong antithrombotic therapy with warfarin or a novel oral anticoagulant is indicated for prophylaxis in the majority of patients. Left atrial appendage occlusion devices have been developed as an alternative to these agents, aiming to avoid issues around consistency of anticoagulation, bleeding risk, and drug-related side effects. The best evidence is available for Boston Scientific's WATCHMAN device. The safety and efficacy of WATCHMAN and other similar devices have been questioned, although the increasing body of evidence supports a role in selected settings. A recently updated randomized controlled trial of WATCHMAN (WATCHMAN Left Atrial Appendage System for Embolic PROTECTion in Patients with Atrial Fibrillation [PROTECT-AF]) demonstrates its noninferiority to warfarin and suggests an advantage in terms of functional outcome for patients, with superior net clinical benefit 6 to 9 months after starting treatment. The procedural risk associated with device implantation remains substantial, although improving device design and increasing operator experience means that this should decrease in the future. As the body of data and overall experience around WATCHMAN grow, it may come to be recognized as the best option in selected patients.

Left atrial appendage exclusion-Where do we stand?

Atrial fibrillation (AF) is consider to be the most common cardiac arrhythmia with an increasingly prevalence. It is postulated that the source of thromboembolism in 90% of patients with non-valvular AF arises from the left atrial appendage (LAA). Stroke is the most feared and life threatening consequence of thromboembolism. Oral anticoagulation (OAC) with vitamin-K-antagonists is the standard medical therapy for stroke prevention in patients with AF. Unfortunately, chronic therapy with vitamin-K-antagonists is contraindicated in 14% to 44% of patients with AF who are at risk for stroke, and its benefits are limited by underutilization, narrow therapeutic window and increased risk for bleeding, making it often undesired. Therefore, mechanical LAA exclusion is a means of preventing thrombus formation in the appendage and subsequent thromboembolic events in these patients. The LAA can be excluded from the systemic circulation via surgical, percutaneous, or thoracoscopic approaches. Several studies of percutaneous transcatheter delivery of dedicated LAA exclusion devices, such as the percutaneous left atrial appendage transcatheter occlusion (PLAATO) device, Watchman device and the Amplatzer cardiac plug, have shown encouraging results as an alternative to vitamin-K-antagonists therapy for selected patients, good feasibility and efficacy, with a high rate of successful implantation. We discuss the current evidence for LAA exclusion in patients and review their results.