Sub-acute leaflet thrombosis: a reversible cause of aortic stenosis

Athina Chasapi, Adam Hobbs, Theodore Velissaris, Benoy N. Shah

A 77 year old male underwent elective bioprosthetic aortic valve replacement (23mm Carpentier-Edwards Perimount MagnaEase) for severe aortic stenosis. His pre-discharge transthoracic echocardiogram (TTE) was normal. He presented 9 days after surgery with dyspnoea and fever. He was in sinus rhythm. Blood cultures were taken and he was commenced on empirical antibiotics for possible infective endocarditis (subsequently all negative). Repeat TTE showed a well-seated prosthesis without regurgitation but elevated gradients (peak / mean gradients 49 / 22 mmHg respectively). Transoesophageal echocardiography (TOE) revealed marked thickening of the leaflets, without obvious vegetations. The patient was diagnosed with subacute prosthetic valve thrombosis and was anticoagulated with apixaban. He underwent repeat TOE 3 months later, which demonstrated thin, mobile valve leaflets with normalized transprosthetic gradients. Thrombosis of a bioprosthetic valve is usually diagnosed in the early postoperative period, when endothelialisation of the suture zone is incomplete. Although previously considered rare, a recent observational study using cardiac CT imaging found an incidence of 4% (5/138) and 13% (101/752) in patients with surgical and transcatheter valves respectively. Anticoagulation therapy - and not anti-platelet drugs - was associated with successful prevention and treatment of subclinical leaflet thrombosis. Indeed, American guidelines on valvular heart disease give a Class IIb recommendation for a period (3-6 months) of formal anticoagulation after bioprosthetic AVR. Patients with established risk factors, including atrial fibrillation and a history of thromboembolic event, may have most to benefit from a brief period of routine post-operative anticoagulation.