Pulmonary arterial hypertension (PAH) is a heart disease that is characterized by an abnormally high pressure in the pulmonary artery (PA). Without treatment PAH progresses rapidly and adversely affects the right ventricle (RV) function, eventually leading to heart failure and death. Recently, right ventricular assist device (RVAD) has been proposed as a treatment for PAH patients to unload the RV. However, because the RV is different from the LV in terms of its structure, geometry and operation, the effects of RVAD on RV are largely unknown and may be different from that of a left ventricular assist device that is commonly used to treat a failing LV. To address this issue, we developed an image-based modeling framework consisting of a biventricular finite element (FE) model that is coupled to a lumped model describing the pulmonary and systemic circulations in a closed-loop system. The biventricular geometry was reconstructed from the magnetic resonance images of two PAH patients showing different degree of RV remodeling and a normal subject. The framework was calibrated to match patient-specific measurements of the left ventricular LV and RV volume as well as pressure waveforms. An RVAD model based on the pressure gradient – flow characteristics of the SynergyTM continuous flow miniature pump (CircuLite Inc, Saddle Brook, NJ) was incorporated into the calibrated framework and simulations were performed with different operating pump speeds between 20 to 28krpm. Results showed that RVAD unloads the RV, improves cardiac output and increases septum curvature, which are more pronounced in the PAH patient with severe RV remodeling. These improvements, however, are also accompanied by an adverse increase in the PA pressure that depends on the severity of the disease. These results suggest that the RVAD implantation may need to be optimized depending on disease progression and to minimize its adverse effects.