Implantation of a TAH is done with the patient under general anaesthesia and on cardiopulmonary bypass. The native left and right ventricles, and all 4 cardiac valves are excised. The TAH device is implanted and attached to the atria, for blood inflow, and pulmonary artery and aorta, for blood outflow. Depending on the type of TAH, power is supplied either by drive lines connected percutaneously to an external biventricular pneumatic pump (which may be portable or static) or by batteries that are implanted internally and can be recharged through the skin using a transcutaneous energy transfer system. When the device begins to pump and restores blood flow around the body, cardiopulmonary bypass is stopped and the chest incision is closed.