A
cardiac assist system includes a pneumatic
effector which is implanted beneath a pericardial sac and over a myocardial surface overlying the patient's left
ventricle. A port is implanted and receives a percutaneously introduced cannula. The port is connected to supply a driving gas received from the cannula to the pneumatic
effector. An external drive unit includes a pump
assembly and control circuitry which operate the pump to actuate the pneumatic
effector in response to the patient's sensed heart
rhythm. A connecting tube has a pump end connected to the pump and a
percutaneous port-connecting end attached to the implantable port.