The unique anatomic configuration of the left atrial appendage (LAA) inherently increases the risk of thrombus formation in patients with atrial fibrillation (AF), with nearly 90% of left atrial thrombi being discovered within its intricate trabeculations. Oral anticoagulation (OAC) is the first-line therapy for thromboembolic prevention, although the increased risk of bleeding is considered a potential contraindication to long-term anticoagulation in high-risk patients. Thus mechanical LAA closure, either via a percutaneous or surgical approach, has gained popularity over the past decade not only for thromboembolic risk control but also for its possible impact on AF ablation.
Although the overall evidence has yielded mixed results and professional guidelines continue to evolve based on emerging data, percutaneous approaches to LAA closure have thus far failed to show a clear benefit in preventing thromboembolic cerebrovascular events compared with OAC. The combined 5-year outcomes of the two landmark trials, PREVAIL and PROTECT AF, have demonstrated that percutaneous LAA occlusion (LAAO) with the Watchman device (Boston Scientific) provides a level of overall stroke prevention in non-valvular AF that is comparable to that of warfarin. This includes, however, a reduction in hemorrhagic stroke, other significant bleeding, and mortality with the percutaneous Watchman device. The recent randomized trial PRAGUE-17 compared percutaneous LAAO with the Watchman and Amulet (Abbott Medical) devices with the most updated direct AOC treatment. The 4-year outcomes confirm non-inferiority of composite ischemic and bleeding outcomes, albeit with a limited sample size.
Apart from its persistently unclear benefits compared with medical therapy, percutaneous occlusion of the LAA is achieved endocardially and for this reason requires OAC, dual antiplatelet therapy (DAPT), or single antiplatelet therapy early after implant to allow time for neo-endothelization to occur. Although a “bridge therapy” with DAPT seems to offer the best risk-to-benefit ratio, it may not be ideal in patients at high risk of bleeding, as is typically the case in those who are referred for LAAO. Moreover, certain specific anatomic features of the LAA ostium can often pose a technical limitation for percutaneous approaches.
There has been renewed interest in the surgical field to respond to the limitations of percutaneous LAAO. The LAAOS III prospective randomized trial clearly showed that in patients with AF undergoing cardiac surgical procedures for another indication, the risk of long-term follow-up ischemic stroke or systemic embolism is lower with concomitant LAAO performed during the surgery than without it. In this complex and evolving scenario, there has been a rapid evolution of techniques and technologies aimed at performing a totally thoracoscopic (TT) surgical exclusion of the LAA with the specific goal of establishing a tailored treatment to permanently exclude any anatomic variable of the LAA epicardially and to eliminate the need for anticoagulation and anti-platelet aggregation unless required for other medical reasons. This ambitious surgical goal should be achieved while maintaining peri-procedural complications at a negligible level.
The present chapter aims to give a synoptic overview of different approaches for TT LAA exclusion performed as a combined or stand-alone procedure. We summarize the evolution of this still-evolving technique, emphasizing the crucial steps that have evolved into a standardized, simplified, and consistently reproducible TT approach.
The Path
Before adopting a TT approach, surgical closure of the LAA was performed primarily as a concomitant procedure that achieved variable levels of success using different strategies and closure devices. Indeed, different surgical techniques for LAAO have been proposed, including LAA stapling, suturing, and amputation, using different surgical approaches, including full sternotomy, mini-thoracotomy, and thoracoscopy. Surgical success is typically defined by the absence of echocardiographic residual flow between the LA and LAA and a residual LAA stump smaller than 10 mm. , Incomplete LAAO is correlated with a higher incidence of stroke regardless of the type of surgical technique used. In a prospective pilot comparison, the overall failure of complete LAA exclusion was more than 50%, 63% for the endocardial suturing and ligation, 60% for the stapler excision, and 50% for the surgical amputation. Because of these drawbacks, safer and more effective options for LAAO were required. Thus, surgical devices have been developed, and most of them are designed to occlude the LAA rather than excise it. The effectiveness of these epicardial devices depend on their ability to occlude the LAA parallel to the LAA ostium without tearing it or causing embolization while providing electrical isolation of the LAA with a negligible rate of complications. The introduction and regulatory approval of specifically designed LAA clip occlusion devices have simplified LAA surgical management, providing consistently permanent and reliable occlusion and electrical isolation of the LAA compared with previous surgical strategies.
Evolution of Totally Thoracoscopic Left Atrial Appendage Occlusion
TT LAA occlusion (LAAO) was first described in 1996 as a stand-alone procedure by Odell et al., who used a stapler and an endo-loop in a canine model. This was followed in 2003 by a report from the same group on 14 patients who were treated using two customized endo-loops and a series of row staplers (the so-called “LAPTONI procedure”) with one emergent surgical conversion and no late neurologic events at follow up.
The first experience of LAA stapling was reported in 1988 by DiSesa and coworkers in a sheep model. However, because the staplers were designed for intestinal stapling procedures, using them for LAAO was often complicated by serious bleeding. Unfortunately, the latest generation of staplers has not yet overcome these limitations. Moreover, when assessed with transesophageal echocardiography (TEE), LAA stapling was noted to have a significant rate of incomplete LAA exclusion as well residual pouches deeper than 1 cm. The authors suggested that a thoracoscopic approach could facilitate a more suitable angle of instrumentation of the stapling device along the long axis of the oval-shaped shape of the base of the LAA. In this way, a complete exclusion of the LAA can be achieved more quickly.
The first feasible epicardial LAA clip was reported by Fumoto and colleagues in 2008 when an early prototype of an epicardial LAA excluding device consisting of two parallel, straight, rigid titanium tubes and two nitinol springs with a knit-braided polyester fabric was implanted using a median sternotomy approach. In subsequent years, the AtriClip device (AtriCure, Inc., Mason, OH) emerged as a safe, effective, and reproducible way to deal with the LAA during open concomitant surgery. The device resulted in a watertight proximal LAA exclusion, and no residual leaks were reported through the line of LAA closure. AtriCure received US Food and Drug Administration 510(k) clearance for the AtriClip device in June 2010 based on the successful results of the EXCLUDE trial. At that point, surgeons had a new addition to their armamentarium that could safely and completely exclude the LAA and support a safe transition to a TT approach.
As experience with the stand-alone TT LAAO increased, it became clear that the AtriClip provided complete anatomic and electrical isolation of the LAA, consistently decreasing the AF burden in patients for whom rhythm control was also needed. In the ensuing years, emerging series of combined or stand-alone TT LAA exclusion procedures were described. Different surgical techniques, including robotically assisted approaches, and evolving indications for LAAO have been proposed and are discussed briefly in the following sections of this chapter.
Tips for Totally Thoracoscopic Left Atrial Appendage Occlusion
The LAA is a remnant of the embryonic left atrium (LA) that forms during the third week of gestation. It is located on the lateral wall of the heart near the circumflex coronary artery and the great cardiac vein. On the endocardial surface, the LAA orifice is within 1 cm of the mitral valve annulus, and the orifice of the left superior pulmonary vein, forms a narrow junction with the LA, and angles downward from its origin. However, it may also project into the transverse sinus with one or more lobes. The LAA rests freely within the pericardial sac, with the left phrenic nerve having a variable superimposed course as part of the pericardiophrenic neurovascular bundle. , Endocardially, the LAA is differentiated from the surrounding atrium by rich endocardial trabeculations, which contribute to thrombus formation, formed by parallel muscle bars termed pectinate muscles. In approximately 30% of individuals, muscular trabeculations can be found extending inferiorly from the appendage to the vestibule of the mitral valve. The LAA ostium shares an essential relationship with the left superior pulmonary vein endocardially and the coronary vessels epicardially, with the left aortic sinus and the left main coronary artery lying posterior and medial and the greater cardiac vein and circumflex artery lying inferiorly less than 2 mm from the LAA ostium. The left anterior descending coronary artery runs underneath the LAA body, emerging at a point immediately below the LAA tip, although the tip’s position may vary. , , The LAA ostium is oval in 70%, ovaloid in 18 %, triangular in 8%, and round in 6% of patients. As previously elucidated, such variability in the shape of the LAA orifice shape is one of the critical aspects of endovascular occlusion devices, which are generally quite compliant, with an LAA that has a round, symmetrically shaped orifice. In a minority of patients, the sinus node artery arises from the circumflex artery and runs near the LAA where it can assume an S-shape as it courses between the LAA and the left superior pulmonary vein. Coronary vessels should be visualized before epicardial closure of the LAA ( Fig. 45.1 ). , The number of LAA lobes may vary, and their shape has been associated with different risks of thrombosis, according to four prevalent morphologies, namely “windsock,” “chicken wing,” “cauliflower,” and “cactus-like.”
Intraoperative visualization of the circumflex artery and its relationship to the base of the left atrial appendage (LAA).
Electrophysiologically, an underappreciated role of the LAA is its function as a trigger for recurrent AF. Therefore, in the setting of a rhythm control strategy, successful management of the LAA should include its complete electrical isolation to enhance the efficacy of AF ablation (see Chapter 43 ). Finally, the LAA and the right atrial appendage (RAA) are the primary sources of atrial natriuretic peptide, with concentrations in the appendage walls being 40-fold higher than in the left atrial free wall and ventricles. It is postulated that atrial natriuretic peptide is released in response to the stretch of the LAA wall and stimulates diuresis, thus playing a role in volume control and arterial pressure homeostasis (see Chapter 42 ). ,
Left-Sided Totally Thoracoscopic Left Atrial Appendage Occlusion
Patient and Port Positioning
The most common approach to perform TT LAAO is via the left chest as a stand-alone procedure or concomitantly with AF thoracoscopic ablation. Under general anesthesia, a double-lumen tube for selective lung ventilation is positioned, and external defibrillation pads are placed (parasternal right and posterior paravertebral left). The patient is positioned supine, and an inflatable bag is placed vertically along the left scapula to gently lift the left thorax by approximately 30 degrees, thus enhancing exposure. Both arms are positioned next to the thorax and a TEE probe is inserted to confirm that both the LA and the LAA are free of thrombi. The presence of thrombi involving the proximal part of the LAA and its ostium supports aborting the procedure. If the presence of thrombi is excluded by TEE, a camera port (5 or 10 mm) is positioned through the third intercostal space at the midaxillary line. CO 2 is then delivered into the pleural space at a pressure of 8 to 10 cm H 2 O to achieve left lung collapse and a convenient rightward shift of the mediastinum and heart. As an option to minimize the risk of lung injury, a left pneumothorax can be induced by delivering CO 2 into the pleural space with a needle before positioning the camera port, but close attention must be paid to the patient’s hemodynamics if this is done. Therefore, two working ports (5 mm) are placed through the second and fifth or sixth intercostal spaces (12 mm, for the clip insertion) between the mid- and anterior axillary lines. A 5- or 10-mm 0-degree standard camera is then inserted through the central port ( Fig. 45.2 ).
Ports setup for left-sided thoracoscopy. See text for further description.
Pericardiotomy
The left phrenic nerve pedicle should be visualized before opening the pericardium ( Fig. 45.3 ). The pericardium distal to the left pulmonary vein hilum is retracted, and a longitudinal pericardiotomy is placed at least 2 cm posterior and parallel to the phrenic nerve bundle ( Fig. 45.4 ). The pericardiotomy is usually extended from the level of the ligament of Marshall to the base of the left ventricle just caudal to the circumflex coronary artery. This provides exposure of the entire LAA (lobes, base, and surrounding structures), reducing the risk of incomplete closure and peri-procedural complications. Pericardial stay sutures are generally not needed but may be used if necessary to optimize the exposure.
Thoracoscopic view of the left phrenic nerve bundle.
Thoracoscopic pericardiotomy from the left side. (A) Subphrenic posterior approach. (B) Antephrenic anterior approach. LAA, Left atrial appendage.
Left Atrial Appendage Clip Placement
After being exposed, the base of the LAA is measured along its long axis ( Fig. 45.5 ). An AtriClip epicardial LAAO device (AtriCure, Inc., Mason, OH) is passed through the lower port and positioned around the base of the LAA. The whole LAA is gently teased into a position within the open clip using an Endo-Kittner to avoid excessive manipulation while simultaneously position the clip softly all the way down to the LAA base ( Fig. 45.6A ). Only after the LAA is fully engaged within the clip can forceps be used to enhance the positioning of the clip at the true base of the LAA ( Fig. 45.6B ). Before triggering the clip device to close, one should visually confirm that the two ends of the clip in the transverse sinus include all lobes of the LAA. The final landing of the device should entail a clockwise rotation of the whole delivery system to prevent a residual pouch on the left pulmonary vein side of the clip. This last step before final clip closure is necessary because the anatomic base of the LAA is at the side of the heart, not in front of it ( Fig. 45.7 ). With the LAA clip in a closed position but before its final release, the TEE image is checked for completeness of the LAA exclusion with no residual stump ( Fig. 45.8 ). An electrocardiogram (ECG) is checked to detect any signs of myocardial ischemia resulting from compression or kinking of the circumflex coronary artery. If the ECG shows any ischemic changes or if TEE shows a significant residual stump, the LAA clip is reopened. If bleeding occurs during LAA manipulation, we advise closing the device proximal to the tear and using it as a hemostatic tool. At the end of the procedure, the left pericardium is partially closed, and a chest tube is placed in the chest cavity.
Thoracoscopic sizing of the left atrial appendage base.
Engagement of the left atrial appendage (LAA) within the AtriClip exclusion system. (A) The tip of the LAA is smoothly accommodated by means of an atraumatic tool (“Endo-Kittner”). (B) After being engaged, the LAA is manipulated for final positioning by means of forceps.
Before releasing the exclusion device (A), a clockwise rotation (B) may be useful to engage the left atrial appendage all the way to its base.
Intraoperative transesophageal echocardiography confirming the absence of any residual stump greater than 1 cm in depth after left atrial appendage (LAA) occlusion.
Epicardial LAAO can also be safely and effectively achieved using robotic-assisted video-thoracoscopy. The patient is positioned and prepped as previously described for a TT left-sided approach. Three dedicated ports (12 mm) for robotic arms are positioned at the level of the second (mid-clear line), sixth (anterior axillary line), and fourth (mid-clear line, camera port) intercostal spaces. An accessory working port close to the posterior axillary line in the seventh intercostal space may be helpful for introduction of the clip device. A robotic platform supports improved visibility and manoeuvrability. The patient’s body size and habitus seem to have a lesser effect on procedure execution when adopting a robotically enhanced approach.
Right-Sided Totally Thoracoscopic Left Atrial Appendage Occlusion
Although the left-sided approach has been suggested as the most direct way to address the LAA thoracoscopically, a right-sided TT approach has also been proposed for LAAO by van Putte’s group. , A detailed description of their AF ablation technique is described in Chapter 32 . At the end of the AF ablation, an AtriClip is introduced into the transverse sinus via the lower or upper right-sided working port. The LAA is gently manipulated between the two arms of the AtriClip using a suction device, and complete closure with no residual stump is confirmed by TEE. An ECG is used to rule out any disturbance of blood flow through the circumflex coronary artery.
Imaging for Totally Thoracoscopic Left Atrial Appendage Occlusion
Transesophageal Echocardiography
TEE remains the gold-standard tool for detecting LAA thrombus , and is considered the standard imaging modality to guide all phases of LAA management. TEE accuracy is operator dependent and relies on the quality of the acquired images. Intraoperatively, TEE is essential to confirm the absence of thrombi and to guide the proper placement of the epicardial clip device for LAAO.
Computed Tomography Scanning
Although a computed tomography (CT) scan is not mandatory, it can be a valuable tool for effective surgical planning and post-procedural monitoring in all TT LAAO procedures.
Indeed, advanced CT imaging facilitates the creation of a virtual patient avatar that displays the LAA and its topographic relationship to the surrounding cardiac, thoracic, and skeletal anatomy. Furthermore, the ability of CT scans to detect thrombi may improve with the use of delayed acquisition protocols. This approach optimizes test specificity for intracardiac thrombosis, reducing false positives and avoiding unnecessary cancellations of prescheduled procedures.
The LAA has complex and varying morphology that can be accurately identified by CT imaging ( Fig. 45.9 ), and it can impact not only periprocedural management but also follow-up outcomes. Whereas TEE is used for intra-procedural guidance, CT angiography can serve as an adjunct for pre- and post-procedural assessment. It has been suggested that a combined approach using both modalities can identify anatomic characteristics of the LAA and the LA that predispose patients to a post-procedural residual stump. ,
Postoperative computed tomography scan confirming complete occlusion of the left atrial appendage (LAA) highlights the close proximity of the exclusion device to the circumflex artery.
CT scans can also help identify rare anatomic variants that could preclude specific treatment approaches. For example, the detection of an LAA lobe projecting into the transverse sinus is a deterrent for transcatheter LAAO with the LARIAT device. Furthermore, pre-procedural CT scans can help identify a persistent superior vena cava or rare coronary variants that can impact the percutaneous delivery technique.
CT scans have proven to be valuable for measuring the size (depth) of a residual stump after LAAO, and they are a sensitive modality for detecting potential device-related thrombosis. However, no definitive comparison between CT and TEE has been conducted after TT exclusion of the LAA. ,
Indications for Totally Thoracoscopic Left Atrial Appendage Occlusion
Surgical LAAO as a stand-alone procedure was not explicitly addressed in either the 2020 European Society of Cardiology/European Heart Rhythm Association/European Association for Cardio-Thoracic Surgery European guidelines or in the 2023 American College of Cardiology/American Heart Association/American College of Clinical Pharmacy/Heart Rhythm Society US guidelines. The US guidelines recommend percutaneous LAAO (Class 2, level A) in patients with a moderate to high risk of stroke (CHA 2 DS 2 -VASc score ≥2) and a contraindication to long-term OAC from a nonreversible cause. In patients with no absolute contraindication to anticoagulation but with a high risk of significant bleeding on OAC, percutaneous LAAO is recommended (Class 2b, level B). The 2020 European guidelines recommended percutaneous LAAO only in patients with contraindications to long-term anticoagulation (Class 2b, level B).
In patients with AF undergoing cardiac surgery with a CHA 2 DS 2 -VASc score of 2 or less or equivalent stroke risk, surgical LAAO with continued anticoagulation is recommended by the 2023 US guidelines (Class 1, level A). These guidelines specify that a surgical technique that blocks blood flow across the line of occlusion with a stump smaller 1 cm as determined by intraoperative TEE should be used as the criterion for successful LAAO. However, the guidelines also state that the benefit of surgical LAAO in the absence of continued anticoagulation to reduce the risk of stroke and systemic embolism is uncertain (Class 2b, level of evidence A). The European 2020 AF guidelines remain less specific on the surgical occlusion of the LAA that may be considered for stroke prevention in patients with AF undergoing cardiac surgery (Class 2b, level of evidence C).
It should be emphasized that there is a need for adequately powered clinical trials to determine the best treatment strategy in patients with absolute or relative contraindication to OACs. The COMPARE LAAO trial will assess the safety and efficacy of percutaneous LAAO in patients with AF who are ineligible to use OAC. Moreover, evidence is needed concerning the most appropriate treatment in patients experiencing a stroke of ischemic origin despite OAC and to define the best regimen and duration of antithrombotic therapy after either percutaneous or surgical LAA management.
Surgical LAA exclusion is supported in the guidelines mainly because of the prospective randomized trial LAOOS III (see Chapter 46 ). According to the most recent European Guidelines on Valvular Heart Disease, occlusion of the LAA should be included with the Maze procedure when performing concomitant valve or coronary artery bypass graft surgery to decrease the risk of stroke in patients with AF (Class 2a, level B). The LAOOS III trial investigated nonthoracoscopic procedures, and it seems reasonable to extrapolate these results to TT procedures as the epicardial LAA clip has the same features.
Sparse real-world data support the fact that surgical LAAO via a minimally invasive TT approach could eventually be seen as the preferred strategy, particularly in patients with increased cerebrovascular ischemic or hemorrhagic risk, in those with previous major or recurrent bleeding (mainly gastrointestinal followed by cerebral hemorrhage), and in other situations including prohibitive LAA and access anatomy. , ,
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