Late-onset left atrial appendage occlusion device-related thrombus attributed to mitral bioprosthetic stenosis: a case report.

Background: Left atrial appendage occlusion (LAAO) is an alternative to anticoagulation for stroke prevention in select patients with atrial fibrillation (AF). In this study, we describe the case of a patient with delayed device-related thrombus (DRT) at 13 months post-LAAO in a setting of atrial stasis due to a worsening mitral bioprosthetic stenosis. Case summary: A 69-year-old woman with a history of rheumatic mitral stenosis and regurgitation post-bioprosthetic mitral valve replacement (6 years prior) and paroxysmal AF was referred for percutaneous LAAO due to recurrent severe gastrointestinal bleeding while on anticoagulation. She underwent an uncomplicated LAAO, for which a 35 mm Watchman Flx device was used. Peri-procedural transoesophageal echocardiogram (TEE) at the time of implant showed thickened and calcified mitral bioprosthetic leaflets and a mild mitral stenosis. Her 45-day post-LAAO TEE showed a mild mitral stenosis and no peri-device leak or DRT. At 12 months, the patient had worsening exertional dyspnoea and pedal oedema. Her 12-month transthoracic echocardiogram (TTE) showed a moderate mitral stenosis and LAAO remained free of DRT. Her symptoms were deemed secondary from a worsening mitral valve stenosis. Mitral valve-in-valve (MViV) replacement was planned because the patient was deemed a prohibitive risk for a redo surgical replacement. Transthoracic echocardiogram on the day of MViV showed a large thrombus on the LAAO device. MViV was postponed. After the patient completed 45 days of anticoagulation with warfarin, a repeat TTE was performed, which showed a resolution of DRT. Transcatheter MViV was performed successfully. Discussion: This case demonstrates that increased stasis and left atrial dysfunction from prosthetic mitral stenosis can be a risk factor for late DRT after successful LAAO. The use of a LAAO occlusion device in the presence of a mitral bioprosthesis requires more frequent echocardiographic monitoring to assess both the function of the prosthesis and a delayed formation of thrombus. More studies need to be conducted to assess the safety of percutaneous LAAO devices in those with mitral bioprosthesis.