The present invention relates to an apparatus and methods for pumping blood from the venae cavae to the pulmonary arteries and thereby bypassing the right ventricle of the heart. The apparatus includes a pump and an inflow and outflow cannula. In one embodiment, the inflow and outflow cannula are inserted through a single percutaneous opening into a subclavian vein and advanced into the venae cavae. When the outflow cannula is advanced into a pulmonary artery, it is redirected into same. The pump at a proximal end of the bypass apparatus is disposed in a cavity of the body such as near a patients rib cage. In operation, blood is carried through the inflow cannula from the venae cavae into the pump and then pumped through the outflow cannula into at least one of the right or left pulmonary artery.