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Updated: Aug 23, 2025
The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation
Published on: February 28, 2012
Cardiac computed tomography following Watchman FLX implantation: device-related thrombus or device healing?
Anders Dahl Kramer1, Kasper Korsholm1, Jesper Møller Jensen1
1Department of Cardiology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark.
Insights
Hypoattenuated thickening (HAT) on cardiac CT after Watchman FLX left atrial appendage closure (LAAC) can indicate healing or device-related thrombosis (DRT). Flat HAT suggests healing, while protruding or pedunculated HAT may signal DRT.
Area of Science:
- Cardiology
- Radiology
- Medical Devices
Background:
- Cardiac computed tomography (CT) is crucial for monitoring patients after left atrial appendage closure (LAAC).
- Hypoattenuated thickening (HAT) is a common CT finding post-LAAC, but its interpretation as benign healing or device-related thrombosis (DRT) remains challenging.
- The specific CT characteristics of HAT associated with the Watchman FLX device have not been well-defined.
Purpose of the Study:
- To investigate cardiac CT findings in patients undergoing follow-up after Watchman FLX implantation.
- To characterize the appearance and morphology of HAT in relation to the Watchman FLX device.
- To differentiate between benign HAT (device healing) and potentially pathological HAT (DRT).
Main Methods:
- Retrospective observational study of 244 patients with successful Watchman FLX implantation and follow-up CT scans (March 2019 - September 2021).
- Blinded analysis of CT images to describe HAT localization, extent, and morphology.
- Correlation of CT findings with imaging and histological data from a canine model.
Main Results:
- HAT was observed in 64% of patients (n=156).
- Classifications included subfabric hypoattenuation (n=59), flat sessile HAT (n=78), protruding sessile HAT (n=16), and pedunculated HAT (n=3).
- Subfabric and flat sessile HAT correlated with device healing and endothelialization, while protruding and pedunculated HAT were considered high-grade and potentially indicative of DRT.
Conclusions:
- Subfabric hypoattenuation and flat sessile HAT are common findings after Watchman FLX implantation, likely representing normal device healing and endothelialization.
- Infrequent HAT morphologies, specifically protruding and pedunculated types, are potential indicators of device-related thrombosis (DRT).
- Cardiac CT provides valuable insights into interpreting HAT post-LAAC, aiding in the differentiation between healing and DRT.
Aims:
Cardiac computed tomography (CT) is increasingly utilized during follow-up after left atrial appendage closure (LAAC). Hypoattenuated thickening (HAT) is a common finding and might represent either benign device healing or device-related thrombosis (DRT). The appearance and characteristics of HAT associated with the Watchman FLX have not been previously described. Therefore, we sought to investigate cardiac CT findings during follow-up after Watchman FLX implantation with a focus on HAT and DRT.
Methods And Results:
Retrospective single-centre, observational study including all patients with successful Watchman FLX implantation and follow-up cardiac CT between March 2019 and September 2021 (n = 244). Blinded analysis of CT images was performed describing the localization, extent, and morphology of HAT and correlated to imaging and histology findings in a canine model. Relevant clinical and preclinical ethical approvals were obtained.Overall, HAT was present in 156 cases (64%) and could be classified as either subfabric hypoattenuation (n = 59), flat sessile HAT (n = 78), protruding sessile HAT (n = 16), or pedunculated HAT (n = 3). All cases of pedunculated HAT and five cases of protruding sessile HAT were considered as high-grade HAT (n = 7). Subfabric hypoattenuation and flat sessile HAT correlated with device healing and endothelialization in histological analysis of explanted devices.
Conclusion:
Subfabric hypoattenuation and flat sessile HAT are frequent CT findings for Watchman FLX, likely representing benign device healing and endothelialization. Pedunculated HAT and protruding HAT are infrequent CT findings that might represent DRT.
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