In a recent study published in Circulation: Cardiovascular Interventions, Pracon et al. suggested that the incidence of device related thrombosis (DRT) among patients undergoing percutaneous left atrial appendage occlusion is related to patient (history of thromboembolic events and lower left ventricular ejection fraction) and procedural (deep implantation and larger occluder size) characteristics.
Transcatheter left atrial appendage occlusion (LAAO) is performed among patients with atrial fibrillation who have a contraindication for long-term oral anticoagulation to reduce the thromboembolic risk. One of the most common complications of this procedure is DRT which is reported up to 17% of patients. DRT is classified into three categories according to the time of detection: early (at 1.5-month follow-up), late (at 3- to 6-month follow-up), or very late DRT (at 12-month follow-up).
Prior studies were performed with similar results. Plicht et al. demonstrated that reduced left ventricular fraction is associated with an increased risk of DRT. Relatively high rates of late and very late DRTs was observed by Main et al. Also, Kaneko et al. found prior thromboembolism to be more frequent but not statistically significant.
Pracon et al. attempted this study with wide variation in duration of P-DAPT, allowing for the analysis of its impact on DRT. Furthermore, in contrast to previous studies, this analysis used the two most commonly used devices for LAAO (AMPLATZER Cardiac Plug/Amulet or WATCHMAN).
The ANIN-LAAO Registry is a prospective, single-center study enrolling 102 consecutive patients with atrial fibrillation who underwent LAAO with either AMPLATZER Cardiac Plug (ACP)/Amulet (n=59; ACP in 25, Amulet in 34 patients) or WATCHMAN (n=43) device between October 2011 and May 2016. The type of device used was left at the physician choice. Follow-up was done using post-procedure left atrial imaging at intervals of 1.5, 3-6, and 12 months. TEE was used primarily for post-procedure imaging; however, cardiac computed tomography (CTT) was also used in a few patients. DRT was defined as an echo density on the left atrial aspect of the device which could not be explained by imaging artifact, was inconsistent with normal healing/device incorporation, visible in multiple TEE/CCT planes, and in contact with the device. P-DAPT was prescribed for 1 to 6 months by a team physicians performing follow-up, who also decided the duration of therapy. The predictors analyzed included prior thromboembolic events, left ventricular ejection fraction, deep implantation, peridevice leaks. The primary end-point was DRT.
“The definitions of device thrombosis vary so much, you cannot compare anything. There is always thrombosis on every device which engenders the desired endocardialization. What is pathological? Embolic events with visible thrombosis occuring in <1% after LAA closure.”- Dr. Bernhard Meier, M.D.
In this study, DRT was diagnosed in 7% of patients(n=7). Approximately 71% of patients with DRT had a prior history of a thromboembolic event when compared with patients without DRT (approx. 30%). Patients with DRT had lower median ejection fraction (50.0% [IQR, 35.0–55.0]) in contrast to patients without DRT (60.0% [IQR, 55.0–66.0]; P<0.01]). Also, Deep implantation (85.7%) and implantation with larger occluders were commonly present in patients with DRT compared to patients without DRT (39.1%). Post-procedure peridevice leak and type of device were not related to DRT.
The investigators acknowledged that the study population was small and these study findings should be confirmed using randomized data.
Dr. Bernhard Meier, Professor of Cardiology at University Hospital, Inselspital Bern, Switzerland add that “The definitions of device thrombosis vary so much, you cannot compare anything. There is always thrombosis on every device which engenders the desired endocardialization. What is pathological? Embolic events with visible thrombosis occur in <1% after LAA closure.”
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