Three-Dimensional CT Reconstruction for Diagnosis of LVAD Outflow Graft Twist

Abstract

<h3>Introduction</h3> Third generation LVAD, HeartMate3 (HM3) are associated with favorable prognosis. A rare life-threatening adverse event is a sudden outflow graft obstruction due to a rotational twist. There is limited data regarding the natural history of this complication. <h3>Case Report</h3> A 70-year-old male with dilated cardiomyopathy was implanted with an HM3 LVAD on September 2019. Echocardiography and cardiac CT immediately following the implantation showed appropriate left ventricular (LV) unloading and normal outflow cannula flows and patency. On April 2021 the patient complained of weakness. Clinical examination was normal, but LVAD interrogation identified decline of LVAD flow. Laboratory tests revealed INR in therapeutic range and normal LDH. An echocardiography revealed impaired unloading of the LV and opening of the aortic valve. A CTA showed a large irregular filling defect sized 7cm at the proximal outflow cannula. Differential diagnosis included outflow cannula twist or thrombosis. Three-dimensional CT volume rendering demonstrated a full rotational twist of the outflow cannula. An untwist operation using a lateral thoracotomy approach identified a >270º twist of the outflow graft. The cannula was untwisted and using a fixation device, the cannula was fixed, resulting in immediate improvement of the flow rate. Repeated transient low flow events at the end of the procedure mandated a repeat CTA to confirm the adequacy of cannula untwisting. Four months following the untwist procedure, the patient is well with stable LVAD flows. <h3>Summary</h3> This is the first case of an outflow graft twist obstruction with comprehensive CTA imaging at 3 critical time points: immediately after LVAD implantation, at twist occurrence and after surgical repair. We believe that it is very important to maintain a high degree of active awareness that a sudden drop in pump flow without signs of pump thrombosis may indicate outflow graft obstruction due to a twist, which is best recognized by three-dimensional CT reconstruction of the outflow graft.