Acute Thrombosis of Bioprosthetic Mitral Valve Secondary to Peri-Operative VA-ECMO; The Dangers of Flow Stasis in the Left Atrium

Abstract

Case report Veno-Arterial (VA) ECMO has been used to help patients recover from cardiogenic shock. VA-ECMO can complicate recovery due to the increase in afterload and decreased flow through the left sided chambers. We present a case of acute bioprosthetic mitral valve (MV) thrombosis in a patient who developed peri-operative cardiogenic shock. A 63 year-old male admitted for acute systolic heart failure found to have coronary artery disease and valvular heart disease underwent MV replacement, tricuspid valve repair and three vessel coronary artery bypass grafting. He developed intraoperative mediastinal bleeding requiring fresh frozen plasma, cryoprecipitate, and factor VII. The patient was unable to be weaned off cardiopulmonary bypass secondary to right ventricular failure. The patient remained centrally cannulated for VA-ECMO and had placement of a femoral intra-aortic balloon pump. The patient was transferred to the ICU in shock and on multiple vasopressors. Due to ongoing mediastinal bleeding, initiation of systemic anticoagulation was delayed by 48 hours. The intraoperative transesophageal echocardiogram (TEE) initially demonstrated a normally functioning bioprosthetic MV. The final intraoperative TEE images following conversion to VA-ECMO showed a poorly opening bioprosthetic MV, Image 1 . A TEE on postoperative day (POD) 2 demonstrated abnormal mobility of the bioprosthetic MV leaflets, left appendage thrombus and smoke-like echogenicity in the left atrium, Image 2 . On POD 5, a TEE demonstrated mean MV gradient of 22 mmHg and worsening of MV mobility secondary to thrombus, Image 3 . Because of concern for MV thrombosis, the patient was taken to the catheterization lab for placement of LV catheter to confirm MV stenosis. A thrombolytic agent was infused via a pulmonary artery (PA) catheter in order to attempt lysis of the MV thrombus. On POD 9, the PA systolic pressures reduced from 50 mmHg to 30 mmHg and the VA-ECMO flow requirements were reduced from 5 to 3.5 Liters per minute. Despite this small improvement in hemodynamics his overall clinical status did not improve. Ultimately the family decided to withdraw care. A post-mortem examination confirmed MV stenosis secondary to thrombosis of the valve extending into the left atrial appendage. Patients in cardiogenic shock who are placed on VA-ECMO are extremely sensitive to the high afterload created by retrograde arterial flow. Our patient developed severe thrombotic MV stenosis secondary to left atrial circulatory stasis when VA-ECMO was initiated. Maintaining adequate left sided flow is crucial to reduce the risk of thrombosis.