Small thrombi and incomplete endothelialization detected by cardiac endoscopy after left atrial appendage closure using Watchman device

Percutaneous left atrial appendage closure (LAAC) using the Watchman device (Boston Scientific, Marlborough, MA, USA) prevents stroke and systemic embolism in high bleeding risk patients with atrial fibrillation (AF). Recently, there has been increasing concern over the incidence of device-related thrombus (DRT), which may be associated with critical embolic events.

A 78-year-old woman with persistent AF and secundum atrial septal defect (ASD) underwent anticoagulation therapy for persistent AF with a CHA₂DS₂-VASc score of 6. Conversely, she was at a high risk of bleeding with a HAS-BLED score of 3. Therefore, she was considered a good candidate for LAAC. On transthoracic echocardiography, she had right atrial and ventricular enlargement due to secundum ASD with a Qp/Qs ratio of 2.5. We planned LAAC with a 27 mm Watchman device prior to percutaneous ASD closure using Amplatzer Septal Occluder (Abbott Structural, Menlo Park, CA, USA). Owing to the lack of clarity regarding the actual mechanism of DRT and concern of development of thrombus on the Watchman device, we observed the surface of the device by cardiac endoscopy on access to the left atrium during percutaneous ASD closure. Therefore, after LAAC, 100 mg of aspirin and adequate doses of warfarin were administered and continued until ASD closure was achieved with target prothrombin time (international normalized ratio 2.0). Cardiac endoscopy, subsequently performed 70 days after LAAC with adequate antithrombotic therapy (Panel A), revealed small thrombi on the superior–posterior side of the device (yellow arrowheads, Panel B and Video 1) with a partially uncovered surface (Panel C and Video 2). Notably, transoesophageal echocardiography and cardiac computed tomography did not markedly reveal any thrombus on the device (Panel D).

Hence, cardiac endoscopy may be useful to precisely evaluate small thrombi formation and endothelialization on the surface of the Watchman device, which cannot be detected by other imaging modalities, such as transoesophageal echocardiography or cardiac computed tomography. Further study is required to evaluate the clinical significance of a thrombus with an uncovered surface and the optimal antithrombotic therapy after LAAC.

Consent: The author/s confirm that written consent for submission and publication of this case report including image(s) and associated text has been obtained from the patient in line with COPE guidance.