Thromboembolic complications of the Symbion AVAD System.

The Symbion Acute Ventricular Assist Device (AVAD) System is an experimental paracorporeal pulsatile ventricular assist device (VAD) for single or biventricular assist. Eleven patients were implanted but 2 died within 24 h and were excluded from the study. Nine patients, four with left ventricular assist devices (LVADs) and five with biventricular assist devices (BIVADs), with a mean implant time of 24 days, were studied to determine the incidence and site of thrombus formation within the device and the incidence of thromboembolic complications. Anticoagulation consisted of heparin titrated to keep the partial thromboplastin time (PTT) twice control and dipyridamole 50 to 200 mg q6h p.o. Seven of nine patients (78%) developed thrombus; five had thrombus visible within the clear housing of the device during the implant period, and two patients had thrombus discovered only after VAD explantation. Common sites of formation were the diaphragm-housing junction, the housing near the outflow orifice, and the de-airing port. Three patients with thrombus developed thromboembolic complications; two suffered strokes and one had multiorgan emboli. The Symbion AVAD System has significant thrombogenic properties that may limit its clinical application.