Thrombus formation following transcatheter aortic valve replacement.

OBJECTIVES: This paper reviews the published data and reports 3 cases of thrombosis involving CoreValve (Medtronic, Minneapolis, Minnesota) and 1 involving Edward Sapien (Edwards Lifesciences, Irvine, California) devices. Three of these cases had pathological findings at autopsy. BACKGROUND: Only a limited number of cases of valve dysfunction with rapid increase of transvalvular aortic gradients or aortic insufficiency post-transcatheter aortic valve replacement (TAVR) have been described. This nonstructural valvular dysfunction has been presumed to be because of early pannus formation or thrombosis. METHODS: Through reviews of the published reports and 4 clinical cases, pathological and clinical findings of early valve thrombosis are examined to elucidate methods for recognition and identifying potential causes and treatments. RESULTS: This paper presents 4 cases, 2 of which had increasing gradients post-TAVR. All 3 pathology cases showed presence of a valve thrombosis in at least 2 TAV leaflets on autopsy, but were not visualized by transthoracic echocardiogram or transesophageal echocardiogram. One case was medically treated with oral anti coagulation with normalization of gradients. The consequence of valve thrombosis in all 3 pathology patients either directly or indirectly played a role in their early demise. At least 18 case reports of early valve thrombosis have been published. In 12 of these cases, the early treatment with anticoagulation therapy resolved the thrombus formation and normalized aortic pressures gradients successfully. CONCLUSIONS: These 4 cases elucidate the occurrence of valve thrombosis post-TAVR. Consideration should be given to treatment with dual antiplatelet therapy and oral anticoagulation in patients post-TAVR with increasing mean pressure gradients and maximum aortic valve velocity. Further research should be conducted to create guidelines for antithrombotic therapy following TAVR procedure.

Sum-frequency generation of acetate adsorption on Au and Pt surfaces: molecular structure effects.

The reversible adsorption of acetate on polycrystalline Au and Pt surfaces was investigated with broadband sum-frequency generation (SFG) and cyclic voltammetry. Specifically adsorbed acetate as well as coadsorbed sulfuric acid anions are observed for the first time with SFG and give rise to dramatically different SFG intensities on Au and Pt surfaces. While similar coverages of acetate adlayers on Au and Pt surfaces are well established by previous studies, an identification of the interfacial molecular structure has been elusive. However, we have applied the high sensitivity of SFG for interfacial polar ordering to identify different acetate structures at Au and Pt surfaces in contact with HClO(4) and H(2)SO(4) electrolytes. Acetate competes with the formation of surface oxides and shifts the oxidation threshold of both Au and Pt electrodes anodically. Effects of the supporting electrolyte on the formation of acetate adlayers are revealed by comparing SFG spectra in HClO(4) and H(2)SO(4) solutions: Sulfuric acid anions modify the potential-dependent acetate adsorption, compete with adsorbed acetate on Au and coadsorb with acetate on Pt surfaces.