Risk Factors for Thrombus Formation on Cardiac Plug in A-fib Patients Identified

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The risk of thrombus formation after percutaneous left atrial appendage (LAA) occlusion with a plug device is increased in patients with higher CHADS₂ and CHA₂DS₂-VASc scores and platelet counts, as well as lower ejection fractions, according to a study published in the June 2013 issue of JACC: Cardiovascular Interventions. The findings underline the need for close follow-up of such patients and consideration of the use of postprocedural vitamin K antagonists, the authors say.

Bjoern Plicht, MD, of University Hospital Essen (Essen, Germany), and colleagues looked at 34 A-fib patients implanted with the Amplatzer Cardiac Plug (St. Jude Medical; St. Paul, MN) and receiving dual antiplatelet therapy. The plug consists of a self-expandable device with a distal lobe and proximal disc connected by an articulating waist.

Using transesophageal echocardiography (TEE), the researchers identified thrombi in 3 patients before discharge, and in 3 more at 3-month follow-up (17.6% overall). While there were no differences in left atrial volume, LAA velocity, spontaneous echo contrast, transmitral gradient, or mitral regurgitation between patients with and without thrombi, those with thrombi had higher CHADS₂ and CHA₂DS₂-VASc scores and pre-interventional platelet counts as well as lower ejection fractions (table 1).

Table 1. Thrombus Risk Factors

 
While high stroke risk scores (CHADS₂ score ≥ 3 and CHA₂DS₂-VASc score ≥ 6) and low EF (< 50%) had poor positive predictive values, they also provided strong negative predictive value (100% and 95%, respectively).

There were no differences in the prevalence of diabetes and renal insufficiency or procedure-related factors like occluder size or placement in relation to the rim between the groups.

Amplatzer Device, Insufficiency of Antiplatelet Therapy Possible Culprits

“We demonstrate unexpected thrombus formation on the [Amplatzer Cardiac Plug] and, therefore, raise safety concerns for this novel treatment option in [A-fib] patients,” Dr. Plicht and colleagues write, adding that the efficacy of LAA occlusion has been sufficiently demonstrated in the PROTECT-AF trial with the Watchman device (Boston Scientific; Natick, MA).

Questions remain regarding the Amplatzer device, however. The proximal disc is “intended to cover the rim of the LAA at the orifice of the upper left pulmonary vein. It is uncertain whether or not the occluder can always be positioned in this way and whether or not position is a risk factor for thrombus formation,” the authors explain.

Noting that the thrombosis rate of 17.6% in the study is much higher than what has been previously reported, Dr. Plicht and colleagues say this may be explained by “post-interventional anticoagulation/antiplatelet regime, implantation technique, or the [Amplatzer] device itself.”

However, they zero in on the potential role of dual antiplatelet therapy, suggesting that it was not sufficiently protective. “This emphasizes the need for oral anticoagulation with [vitamin K antagonists], in line with the PROTECT-AF trial in which all patients received oral anticoagulation for 45 days after implantation followed by dual antiplatelet therapy for 6 months and had fewer thrombi,” the authors write, adding that, “a risk-stratified anticoagulation/antiplatelet regime appears justified according to our results, given that patients with low risk scores and good EF developed no thrombi on dual antiplatelet therapy.”

Dr. Plicht and colleagues advocate for a larger prospective trial to “confirm this concept of adjusting the post-implantation antiplatelet/anticoagulation regime to the individual risk profile.”

 

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Source:
Plicht B, Konorza TFM, Kahlert P, et al. Risk factors for thrombus formation on the Amplatzer Cardiac Plug after left atrial appendage occlusion. J Am Coll Cardiol Intv. 2013;6:606-613.

 

 

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