Leaflet thrombosis can occur from 1 month to years after implantation. If the patient is stable and has no contraindication to long-term anti- coagulation, a trial of oral anticoagulation with VKA may result in resolution of the thrombus and improvement in hemodynamics.6 13 However, these patients are at increased risk of recurrent thrombosis (if the anticoagulation is stopped) and early structural deterioration, and thus they require close follow-up.17 11.9. Prosthetic Valve Regurgitation Regurgitation in a mechanical prosthetic valve may be transvalvular, caused by impaired motion of the valve disk secondary to pannus, thrombus, or vegetation in- terfering with complete closure of the valve occluders, or paravalvular, caused by suture line disruption related to technical error at implantation, suture failure, annu- lar disruption, or endocarditis. Patients with severe mi- tral annular calcification are particularly vulnerable to developing late paravalvular leak. Regurgitation in bio- prosthetic valves may be paravalvular but more often is CLINICAL STATEMENTS AND GUIDELINES transvalvular, caused by leaflet immobility secondary to calcification or leaflet perforation or flail associated with areas of focal calcification.1 Echocardiographic defini- tions of prosthetic valve regurgitation severity have been published by the American Society of Echocardiography.2 11.9.1. Diagnosis of Prosthetic Valve Regurgitation Recommendations for Diagnosis of Prosthetic Valve Regurgitation Referenced studies that support the recommendations are summarized in Online Data Supplement 41. COR LOE Recommendations In patients with suspected mechanical or bioprosthetic valve regurgitation, TTE and TEE are recommended to determine the cause and severity of the leak, assess ventricular function, and estimate pulmonary artery systolic pressure.1 4 In patients undergoing a transcatheter procedure for paravalvular prosthetic regurgitation, 3D TEE is recommended for Synopsis The clinical presentation of prosthetic valve regur- gitation varies depending on its severity, hemody- namic effects, and etiology. 