Title
Loss of Flow on VVA ECMO: Mechanical Thrombectomy of Clot Surrounding Drainage Cannula
Introduction
Mechanical thrombectomy serves as a viable option for removal of sub-massive and massive pulmonary emboli. To our knowledge, this is the first case of patient on Veno-Veno-Arterial (VVA) Extracorporeal Membrane Oxygenation (ECMO) to undergo mechanical thrombectomy of massive pulmonary emboli. During case, decreased flows on ECMO cannula were noted, resulting in identification and removal of clot in inferior vena cava surrounding the drainage cannula.
Clinical Case
63-year-old woman admitted with pontine hemorrhage, diagnosed with massive pulmonary emboli on hospital day 9 as evidenced on computed tomography with angiography. Patient was decompensating on several vasopressor drips and had evidence of severe right ventricular dysfunction on transthoracic echocardiogram (TTE). Patient was placed on VVA ECMO for mechanical support with a right common femoral 25-French venous cannula, left common femoral artery 17-French arterial cannula, right femoral vein 19-French bullet tip Biomedicus venous cannula with tip located in right atrium. Given pontine hemorrhage, thrombolytics were contraindicated, and decision was made to pursue mechanical thrombectomy with Inari FlowTriever system. Patient underwent mechanical thrombectomy of pulmonary emboli on hospital day 10. Right common femoral venous cannula was exchanged for 22-French Gore DrySeal device. Angled pigtail catheter was navigated with J-wire into right main pulmonary artery (PA). Amplatz super stiff wire was advanced into distal lung parenchyma along with Inari FlowTriever system, and multiple rounds of suction thrombectomy were performed. Comparison of angiography images before intervention and after revealed complete evacuation of main PA thrombus. Procedure was complicated by loss of VVA ECMO flows as system was being removed. After attempts to troubleshoot cannula and ECMO circuit, inferior venocavogram was obtained which revealed large, bulky mass in inferior vena cava (IVC) surrounding and displacing ECMO multi-stage drainage cannula. Inari FlowTriever was reintroduced with upsizing of Gore DrySeal sheath from 22-French to 26-French. Multiple rounds of suction thrombectomy were performed; ultimately the Inari FlowTriever catheter was withdrawn into 26-French Gore Dryseal sheath and removed over the Amlpatz wire as one unit, resulting in removal of extremely large thrombus burden. Post procedure inferior venocavogram was performed, with wide patency and complete evacuation of thrombus noted. After mass extraction, ECMO flows normalized. Patient's clinical status improved, resulting in decannulation of ECMO on hospital day 16, discontinuation of vasopressors and inotropic therapies on hospital day 19, normal right ventricular function noted on TTE on hospital day 20.
Discussion
Mechanical thrombectomy should be considered in patients with massive pulmonary emboli on mechanical support with ECMO. Pursuing mechanical thrombectomy in the setting of ECMO mechanical support could provide for unique presentations of otherwise familiar complications with ECMO. Loss of flow or low circuit flows can be seen in obstructive physiology due to thrombus formation. In this case, the extraction of pulmonary emboli alongside the drainage cannula led to retention of clot in the IVC, surrounding ECMO drainage cannula, resulting in loss of flow. Mechanical thrombectomy should also be considered in removal of thrombus resulting in obstruction of ECMO cannulas.