BACKGROUND : Left ventricular assist devices (LVADs) have revolutionized the treatment of advanced heart failure, but proliferation of device therapy has unmasked potential complications. Reports have emerged of outflow graft narrowing due to extrinsic compression. RESULTS : The records of patients with LVADs that had been implanted at our institution were reviewed. Those who had postimplantation computed tomography angiographies sufficient to analyze the outflow graft lumen were identified, and the studies were analyzed to characterize the outflow graft lumen. We identified 241 patients; 110 (46%) had suitable computed tomography angiographies. Of those, 15 (14%) had evidence of outflow graft lumen narrowing, all in HeartMate devices and all within the portion covered by the bend relief. Of the 15, 3 underwent invasive examination, all without intraluminal thrombus but, rather, with biodebris between the bend relief and the outflow graft. Patients with HeartWare devices had a wide range of biodebris accumulation surrounding the outflow graft but no cases of lumen narrowing. On multivariable analysis, 1) time from device implant to scan, 2) nonischemic cardiomyopathy and 3) age at implant were significantly associated with higher risk of graft narrowing. CONCLUSIONS : Outflow graft narrowing can be seen in a number of patients with HeartMate LVADs within the portion covered by the bend relief. In the limited number of patients who underwent invasive evaluation, the narrowing was found to arise from extrinsic compression rather than intraluminal thrombus. The clinical significance of this requires further investigation.