Low rates of device-related thrombus found with Amplatzer Amulet occlusion device

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Device-related thrombus (DRT) following left atrial appendage occlusion (LAAO) with the Amplatzer Amulet device (Abbott) was “infrequently” observed according to a report published in JACC: Cardiovascular Interventions (JACC: CI).

Writing in JACC: CI, Adel Aminian (Centre Hospitalier Universitaire de Charleroi, Charleroi, Belgium) and colleagues say: “While the presence of DRT was associated with an increased rate of ischaemic stroke or transient ischaemic attack (TIA) as compared to patients without DRT, the large majority of DRT patients (82%) did not experience any ischaemic neurologic events.”

The prospective global observational study evaluated the incidence, characteristics, and clinical impact of device-related thrombus following left atrial appendage occlusion (LAAO) with the Amplatzer Amulet device. Potentially, device-related thrombus can be a serious complication of LAAO, but its incidence and clinical impact in a real-world setting has not been well characterised. Aminian et al describe the multicentre study as “the largest collection of patients undergoing LAAO with the Amplatzer Amulet device in a real-world observational setting”.

They enrolled 1,088 patients and followed them for one year, with all events including DRT adjudicated by an independent committee. Patients with DRT were reviewed for suboptimal device implantation and characterisation of DRT formation, and multiple Cox regression was performed to identify predictors of DRT formation.

Implantation was successful in 1,078 patients (99%), with one year follow-up completed in 96.3% of patients. In all, 18 DRT occurred in 17 patients (1.7%/year); one patient had a second DRT following complete resolution of an initial one. The left upper pulmonary vein (PV) ridge was not covered by the Amulet disc in 82% of DRT patients, indicating suboptimal implantation, with most thrombus developing in the untrabeculated area of the LAA ostium between the PV ridge and the upper edge of the disc.
Aminian and colleagues say that their findings support the “recent change in perception that DRT may be associated with deleterious clinical events”. There was a seven times greater rate of annualised ischaemic stroke in patients with DRT (18.3%/year) than in those without DRT (2.6%/year). And 29.4% of DRT patients had an ischaemic stroke, TIA, or death adjudicated as cardiovascular in nature, with a rate of 7.2% experiencing the same outcomes among non-DRT patients.

Patients with a DRT were at a greater risk for ischaemic stroke or TIA compared to non-DRT patients (hazard ratio [HR] 5.27, 95% confidence interval [CI] 1.58–17.55; p=0.007), following adjustment for baseline CHA2DS2-VASc and HAS-BLED scores. Larger LAA orifice width was a predictor of DRT formation (HR 1.09, 95% CI 1.00–1.19; p=0.04).

Among the limitations highlighted by the authors are that there may be other implant characteristics associated with DRT formation that were not assessed, and that the results of the study may not be applicable to other LAAO devices. Additionally, because relatively few patients experienced a DRT it limited their ability to evaluate if some DRT characteristics are associated with ischaemic stroke or TIA.

Aminian et al conclude: “Although most patients with DRT did not experience an ischaemic stroke, the presence of DRT was associated with an increased rate of ischaemic stroke or TIA, suggesting the importance of close clinical monitoring following DRT diagnosis.”


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