Thrombotic Restenosis After Minimally Invasive Implantation of Aortic Valve Stent
An 84-year-old woman underwent successful, minimally invasive, transapical aortic valve implantation (Edwards SAPIEN 23 mm) to address symptomatic high-grade aortic stenosis and logistic EuroScore of 22%. Echocardiographic control after 11 and 41 days demonstrated the valve in good position without relevant paravalvular leakage or aortic regurgitation. Mean gradients over aortic valve implant were 17 mm Hg and 19 mm Hg, respectively. At echocardiographic follow-up at 6 and 8 months, mean gradient increased to 40 mm Hg and 53 mm Hg, respectively. The patient also developed dyspnea on exertion again. Transesophageal echocardiography at 8 months demonstrated 1 well opening aortic valve leaflet at the septal side, whereas an echodense structure was visible at the opposite side (Figure 1 and online-only Data Supplement Movie I). Aortic angiogram was performed and demonstrated a large round contrast defect at the height of the aortic valve stent below the left coronary artery (Figure 2 and online-only Data Supplement Movie II).
Thereafter, successful open-heart surgery was performed to replace the restenotic aortic valve stent by a conventional aortic valve bioprosthesis. At this time, large, organized thrombi on 2 of the leaflets, as cause of the valve restenosis, were detected (Figure 3). Histology revealed a thrombus formation with fibrous organization without evidence for an infectious endocarditis.
Thrombotic restenosis after aortic valve surgery using bioprosthesis is very uncommon1 and has not yet been described after minimally invasive aortic valve stent implantation. Of note, leaflets of the Edwards SAPIEN aortic valve stent are processed in the same way as established for conventional aortic bioprosthesis, making it unlikely that thrombogenicity of leaflets is per se enhanced with this aortic valve stent.
There are 3 possible reasons, or a combination of those, for development of thrombosis in this patient: First, the patient reported that she did not take aspirin and clopidogrel any more than beyond 6 weeks after valve implantation, despite oral and written recommendations. Clopidogrel is recommended for 6 months and aspirin lifelong after Edwards SAPIEN valve implantation.
Second, a coagulation disorder may predispose for thrombus formation on aortic valve stent leaflets. Subsequently, screening tests for thrombophilia were performed, which excluded common disorders, including antiphospholipid antibodies and abnormalities in protein C, antithrombin III, and genetic analysis of factor V and II. However, mild reduction of protein S activity (50%) and positive cold agglutinins were detected.
Third, another possibility is geometric deformation of the aortic valve stent, which may predispose for thrombus formation as a result of flow turbulences.2 Using Cribier-Edwards/SAPIEN aortic valve stents, it is recommended to oversize valve diameter compared with aortic annulus in order to minimize aortic regurgitation due to paravalvular leakage.3 Likewise, in this patient, a 23-mm valve was implanted into an 18-mm annulus (diameter measured by transesophageal echocardiography). However, no relevant aortic regurgitation was detected by transesophageal echocardiography immediately after valve stent implantation, excluding maladaptation of the leaflets due to gross geometric distortion of the valve.
Dr Doss has received support as Proctor (Edwards Lifesciences). Dr Schächinger reports research support (<$10k) for the Partner–Trial from Edwards Lifescience. The remaining authors report no conflicts.
The online-only Data Supplement can be found at http://circ.ahajournals.org/cgi/content/full/120/4/e23/DC1.
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