Abstract: A medical device assembly is adapted to isolate the heart from systemic circulation while perfusing oxygenated blood to the systemic arterial circulation during a minimally invasive bypass procedure. The assembly includes an arterial catheter with an external shunt valve which forms an anchor to secure the distal end portion within the aortic arch and which also forms a funnel which shunts antegrade aortic blood flow from the aortic root, into a distal flow port and through an internal flow lumen in the catheter, out an intermediate flow port along the catheter proximally of the anchor, and into the systemic arterial circulation. A distal internal valve is further provided within the internal flow lumen between the distal and intermediate flow ports. The distal internal valve selectively occludes the shunted antegrade aortic blood flow between the distal flow port and the intermediate flow port and isolates the left heart chambers from the systemic arterial circulation.