2. External Components
The internal TET receives magnetic waves from an exter¬nal TET coil, which transfers energy across the skin to the implanted device by a process of inductive coupling that converts the external energy to electrical energy. Thus, the device is totally internal with no cables through the skin. A console the size of a laptop computer houses a battery that powers the device for approximately 45 minutes. The external TET coil attaches to the console and provides a constant power supply. The console is plugged into a wall outlet and is disconnected for activities and travel.
B. Lionheart
1. Chest Size
Size constraints remain the most important hurdle. Patients must have an adequate chest cavity size or ante-roposterior thoracic dimension.
2. Power Source
The Lionheart (Arrow, Reading, PA) electrical artificial heart uses a single, implantable energy converter to drive both ventricles that are implanted within the pericardium. It avoids the problem of using a separate external drive unit for each ventricle as is done with the pneumatic system. The electrical unit uses a single implantable energy converter to drive both ventricles and requires a mini¬mum energy of 14 W. Unfortunately, implanted batteries are not capable of supplying the power that is required. The development of high-energy density batteries hope¬fully should eliminate the need for the present use of a primary external power source as this is a major hurdle still left to overcome.

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