In this work we present numerical simulations of continuous flow left ventricle assist device implantation with the aim of comparing the ascending and the descending aorta anastomosis of outflow cannula. Despite the fact that the second approach is less invasive, since it does not require a sternotomy and a cardiopulmonary bypass, its benefits are still controversial. With the aim of assessing the differences between these two approaches in terms of flow rate and pressure wave forms, we set up numerical simulations of network of one-dimensional models where we account for the presence of an outflow cannula anastomosed to different locations of the aorta. Then, we use the resulting network to compare the results of the two different cannulations for several stages of heart failure and different rotational speed of the device. The inflow boundary data for the heart and the cannulas are obtained from a lumped parameters model of the entire circulatory system with an assist device, which is validated with clinical data. The results show that ascending and descending aorta cannulations lead to similar wave forms and mean flow rate in all the considered cases. Moreover, regardless of the anastomosis region, the rotational speed of the device has an important impact on wave profiles; this effect is more pronounced at high RPM.