Abstract
Background
Large, mobile thrombus in the left atrial appendage (LAA) carries an urgent risk of systemic embolization. Management is challenging when anticoagulation or open surgery is unsuitable in elderly or frail patients.
Case Summary
A 78-year-old woman with prior atrial fibrillation ablation was detected a large mobile LAA thrombus on surveillance imaging after self-discontinuing apixaban. Anticoagulation and systemic thrombolysis carried a high embolic risk, open surgery was unsuitable due to age and frailty, and percutaneous closure was contraindicated. Urgent robot-assisted en bloc thrombectomy with internal LAA closure via right mini-thoracotomy achieved complete exclusion. She was discharged on postoperative day 5 without complications.
Discussion
Robot-assisted cardiac surgery enables definitive thrombus removal and secure LAA closure in selected high-risk patients, offering a minimally invasive alternative to sternotomy.
Take-Home Message
In elderly, frail patients with large, mobile LAA thrombus, robot-assisted minimally invasive surgery is a safe, effective alternative when conventional strategies are unsuitable.
Key words: left atrial appendage closure, mobile thrombus, robot-assisted thrombectomy
Visual Summary
History of Presentation
A 78-year-old woman with a history of sick sinus syndrome status post dual-chamber pacemaker implantation 3 years earlier and prior catheter ablation for atrial fibrillation 6 years earlier presented for routine outpatient follow-up. She was asymptomatic, and vital signs were stable, with an atrial-paced, ventricular-sensed rhythm at 70 beats/min and a blood pressure of 110/68 mm Hg. Neurological examination was unremarkable. However, recent contrast-enhanced cardiac computed tomography (CT) performed for surveillance revealed a filling defect in the left atrial appendage (LAA) (Figure 1A), prompting further evaluation for possible thrombus.
Take-Home Messages
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Large, mobile left atrial appendage thrombus is an urgent indication for intervention due to high embolic risk.
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Robot-assisted surgery enables safe en bloc thrombus removal and definitive closure with minimal invasiveness.
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Consider this approach when anticoagulation or percutaneous therapy is not feasible.
Figure 1.
Contrast-Enhanced Cardiac Computed Tomography Demonstrating a Thrombus in the LAA
(A) Axial view shows a well-defined filling defect (white arrow) within the contrast-filled left atrial appendage (LAA), consistent with thrombus. (B) Delayed-phase image confirms persistent low attenuation in the same region (white arrow), supporting the diagnosis of a true thrombus rather than slow flow. Ao = aorta; PA = pulmonary artery; LSPV = left superior pulmonary vein.
Past Medical History
The patient had been prescribed apixaban 5 mg twice daily for stroke prevention in atrial arrhythmia but had self-discontinued the medication approximately 1 month prior to presentation following an episode of influenza. No history of prior thromboembolic events or bleeding complications was noted.
Differential Diagnosis
The differential diagnosis for a filling defect in the LAA on contrast-enhanced cardiac CT included true thrombus, circulatory stasis with spontaneous echo contrast, and imaging artifact. Given the patient's recent interruption of anticoagulation therapy, a thrombus was strongly suspected. Delayed-phase imaging confirmed persistent low attenuation, supporting the presence of organized thrombus rather than slow flow (Figure 1B). Transesophageal echocardiography (TEE) demonstrated a large, mobile mass protruding into the left atrium (LA) with a smooth surface and significant mobility, further supporting the diagnosis of a thrombus (Figure 2A). Tumor (eg, myxoma), vegetation, or atrial thrombus from another origin was considered less likely given the morphology, location, and clinical context.
Figure 2.
Transesophageal Echocardiographic Views of the LAA Thrombus
(A) Biplane mid-esophageal view reveals a large thrombus (white arrow) filling the left atrial appendage (LAA) and extending toward the ostium. (B) Pulsed wave Doppler at the LAA orifice shows significantly reduced flow velocity.
Investigations
TEE demonstrated a large, mobile thrombus measuring 15 × 32 mm, protruding into the LA. The thrombus had a relatively smooth surface and was partially attached at the LAA apex, with marked oscillatory motion observed at the LAA orifice. Pulsed-wave Doppler at the orifice revealed significantly reduced flow velocity (16 cm/s), indicating blood stasis (Figure 2B).
Baseline laboratory testing, including coagulation profile, complete blood count, and metabolic panel, was within normal limits. Head magnetic resonance imaging and contrast-enhanced CT showed no evidence of systemic embolism or cerebral infarction. There were no neurological deficits on clinical examination at the time of admission.
Management
Given the large size, high mobility, and protrusion of the thrombus into the LA, medical therapy alone was considered insufficient. Systemic thrombolysis was contraindicated due to the high risk of embolization, and percutaneous LAA closure was not feasible. Preoperative bridging with heparin or other anticoagulants was also avoided because of concerns about thrombus fragmentation and subsequent embolization. Following Heart Team consensus, urgent surgical thrombectomy was planned. To minimize operative risk in this high-risk elderly patient (STS score 11.6% and Clinical Frailty Scale 4), a robot-assisted minimally invasive approach was selected.
Under general anesthesia, the patient was positioned in the semi-left lateral decubitus position with right lung isolation via a dual-lumen endotracheal tube. Cardiopulmonary bypass was established via femoral artery and vein cannulation under echocardiographic guidance. A 3.5-cm mini-thoracotomy was performed in the right fourth intercostal space, anterior to the anterior axillary line. Three robotic ports were placed: the left-hand port in the third intercostal space, the right-hand port in the sixth, and the LA retractor port anterior to the thoracotomy in the fourth intercostal space. No pleural adhesions were encountered.
Following pericardiotomy and insertion of a root cannula, the ascending aorta was cross-clamped using a Signet aortic cross-clamp (Cardiomedical GmbH), and antegrade cardioplegia was administered to achieve cardiac arrest.
A right-sided left atriotomy exposed a large thrombus protruding from the apex of the LAA into the LA cavity (Figure 3A). The thrombus, measuring 15 × 33 mm (Figure 3D), was extracted en bloc using robotic Maryland forceps without fragmentation (Figure 3B). Internal LAA closure was performed using a double-layer running suture technique with CV-4 polytetrafluorethylene sutures (Gore-Tex) (Figure 3C, Video 1). The LA was irrigated and closed, and the robotic system was undocked. Intraoperative TEE confirmed complete exclusion of the LAA without residual flow or thrombus.
Figure 3.
Intraoperative and Gross Findings of Robot-Assisted Thrombectomy and LAA Closure
(A) The thrombus (blue arrow) is seen protruding from the left atrial appendage (LAA) orifice under robotic endoscopic view. (B) En bloc extraction of the large, multilobed thrombus (blue arrow) is performed using robotic instruments. (C) The LAA is closed internally with a double-layer running suture after thrombus removal. (D) Gross specimen of the extracted thrombus, measuring 15 × 33 mm, showing a multilobed shape.
The patient was smoothly weaned from cardiopulmonary bypass after thorough de-airing, and no blood transfusion was required. A single chest drain was placed in the right thoracic cavity, and chest and groin incisions were closed in standard fashion. Total cardiopulmonary bypass time was 103 minutes, and aortic cross-clamp time was 49 minutes.
Outcome and Follow-Up
The patient was extubated on the morning following surgery and transferred from the intensive care unit on postoperative day 1. To mitigate the risk of thrombus formation along the LAA suture line during the early healing phase, apixaban was resumed on the same day at a dose of 5 mg twice daily. The patient tolerated anticoagulation well without any bleeding complications. No neurologic deficits or other adverse events occurred. She was discharged in stable condition on postoperative day 5.
A follow-up contrast-enhanced cardiac CT was scheduled at approximately 1 month postoperatively to assess for thrombus recurrence and confirm complete and durable LAA exclusion. Anticoagulation will be continued until satisfactory closure and endothelialization are confirmed. In addition, routine neurological assessments and clinical follow-up visits will be conducted every 3 months during the first year to monitor for stroke or embolic events.
Discussion
The LAA is the predominant site of thrombus formation in patients with atrial fibrillation and other atrial tachyarrhythmias. Even brief interruptions in anticoagulation significantly increase the risk of thrombus development.1, 2, 3 Although most thrombi can be managed with anticoagulation, large and mobile thrombi pose a substantial risk of systemic embolization and present a therapeutic challenge.4
Percutaneous LAA closure is generally contraindicated in this setting because device manipulation can dislodge the thrombus.5 Current guidelines recommend anticoagulation as first-line therapy, but optimal management of large mobile thrombus remains uncertain due to limited evidence.
Thoracoscopic epicardial clipping is a minimally invasive surgical approach that avoids sternotomy and can achieve complete epicardial exclusion of the LAA orifice.6 However, because this technique does not involve removal of existing thrombus, it is unsuitable when a large or protruding thrombus is present within the LAA.
Conventional surgical approaches, such as median sternotomy with cardiopulmonary bypass and open atriotomy, allow definitive thrombus removal and LAA exclusion but carry substantial morbidity in frail or elderly patients.7 Given these limitations, especially in a high-risk elderly patient such as ours, we sought a strategy that would allow definitive thrombus removal and secure LAA exclusion while avoiding the morbidity of sternotomy. These considerations led to the selection of a robot-assisted minimally invasive approach, which combines the benefits of surgical completeness with reduced procedural invasiveness. Robot-assisted cardiac surgery addresses these gaps by providing enhanced 3-dimensional visualization and superior instrument dexterity. This enables safe en bloc thrombus removal without fragmentation and secure internal suture closure of the LAA in a minimally invasive fashion. This dual approach—mechanical thrombus removal plus definitive anatomical exclusion—was decisive in our case, where anticoagulation and percutaneous closure were both unsuitable. To our knowledge, this is the first report of robot-assisted en bloc LAA thrombectomy combined with internal closure.
Successful implementation of robotic surgery requires institutional expertise and infrastructure. At our center, an established robotic mitral valve surgery program (264 cases between 2019 and June 2025) facilitated procedural efficiency by allowing the use of a standardized port configuration and workflow. This experience suggests that wider adoption in other centers may be feasible with standardized protocols, team training, and multidisciplinary collaboration. Nevertheless, careful patient selection remains essential, particularly in those with pleural adhesions, severe pulmonary dysfunction, or hemodynamic instability.
Despite technical advances, randomized data comparing robotic and conventional surgical strategies for large, mobile LAA thrombus are lacking. Moreover, postoperative anticoagulation strategies after surgical LAA exclusion remain poorly defined. In our case, anticoagulation was resumed immediately postoperatively to prevent early thrombus formation along the suture line, as preoperative TEE demonstrated marked stasis within the LAA. Even with complete intraoperative closure, early thrombus formation remains possible; therefore, anticoagulation withdrawal was deferred until follow-up CT confirmed complete and durable exclusion.
This case illustrates that robot-assisted surgery can serve as a definitive, safe, and effective solution for large, mobile LAA thrombus in carefully selected high-risk patients, overcoming the limitations of both conventional sternotomy and thoracoscopic clipping.
Conclusions
Urgent robot-assisted thrombectomy with internal LAA closure provides a definitive, minimally invasive solution for large, mobile LAA thrombus, delivering effective treatment when anticoagulation alone is insufficient and percutaneous strategies are not feasible.
Funding Support and Author Disclosures
Dr Hachinohe is a clinical proctor for Boston Scientific. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Acknowledgments
The authors would like to acknowledge the Heart Team members at Sapporo Heart Center.
Footnotes
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
Appendix
Visual Summary.
| Time | Clinical Course |
|---|---|
| ∼Day −30 | Apixaban was self-discontinued following an episode of influenza. |
| Day −2 | Contrast-enhanced cardiac CT revealed a well-defined filling defect in the LAA, consistent with thrombus. Urgent admission. |
| Day −1 | TEE demonstrated a large (15 × 32 mm), mobile thrombus protruding into the left atrium. Heart Team recommended surgical thrombectomy. |
| Day 0 | Robot-assisted en bloc LAA thrombectomy and internal suture closure were performed via right mini-thoracotomy. |
| Day 1 | Apixaban 5 mg twice daily was resumed to prevent thrombus formation. Patient was extubated and transferred from the ICU. |
| Day 5 | Patient was discharged without neurologic or bleeding complications. |
| ∼Day 30 | Follow-up CT was planned to confirm durable exclusion of the LAA. |
Appendix
Biplane Mid-Esophageal Transesophageal Echocardiographic Shows a Large, Mobile Thrombus in the Left Atrial Appendage (LAA)
The intraoperative video demonstrates robotic left atriotomy, en bloc thrombus extraction, and internal double-layer LAA closure.
References
- 1.Regazzoli D., Ancona F., Trevisi N., et al. Left atrial appendage: physiology, pathology, and role as a therapeutic target. Biomed Res Int. 2015;2015 doi: 10.1155/2015/205013. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Sussman M., Barnes G.D., Guo J.D., et al. The burden of undertreatment and non-treatment among patients with non-valvular atrial fibrillation and elevated stroke risk: a systematic review. Curr Med Res Opin. 2022;38(1):7–18. doi: 10.1080/03007995.2021.1982684. [DOI] [PubMed] [Google Scholar]
- 3.Cools F., Johnson D., Camm A.J., et al. Risks associated with discontinuation of oral anticoagulation in newly diagnosed patients with atrial fibrillation: results from the GARFIELD-AF registry. J Thromb Haemost. 2021;19(9):2322–2334. doi: 10.1111/jth.15415. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Fang B.R., Kuo L.T. Recurrent cerebral embolism and impending detachment of a previous nonmobile left atrial thrombus following initiation of anticoagulant therapy in a patient with nonvalvular atrial fibrillation. Echocardiography. 2001;18(6):527–529. doi: 10.1046/j.1540-8175.2001.00527.x. [DOI] [PubMed] [Google Scholar]
- 5.Holmes D.R., Reddy V.Y., Turi Z.G., et al. Percutaneous closure of the left atrial appendage versus warfarin therapy for prevention of stroke in patients with atrial fibrillation: a randomized non-inferiority trial. Lancet. 2009;374(9689):534–542. doi: 10.1016/S0140-6736(09)61343-X. [DOI] [PubMed] [Google Scholar]
- 6.Ellis C.R., Aznaurov S.G., Patel N.J., et al. Angiographic efficacy of the atriclip left atrial appendage exclusion device placed by minimally invasive thoracoscopic approach. JACC Clin Electrophysiol. 2017;3(12):1356–1365. doi: 10.1016/j.jacep.2017.03.008. [DOI] [PubMed] [Google Scholar]
- 7.Pozzi M., Mariani S., Scanziani M., et al. The frail patient undergoing cardiac surgery: lessons learned and future perspectives. Front Cardiovasc Med. 2023;10 doi: 10.3389/fcvm.2023.1295108. [DOI] [PMC free article] [PubMed] [Google Scholar]
Associated Data
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Supplementary Materials
Biplane Mid-Esophageal Transesophageal Echocardiographic Shows a Large, Mobile Thrombus in the Left Atrial Appendage (LAA)
The intraoperative video demonstrates robotic left atriotomy, en bloc thrombus extraction, and internal double-layer LAA closure.