The first hour examines the heart as a muscle.

The first hour examines the heart as a muscle - pumping almost 100,000 times a day, pushing six liters of blood in a ceaseless circuit to deliver oxygen to every cell in the human body.  The hour tells the story of the normal heart through the histories of three people with end-stage heart failure, where a pump may be a temporary remedy, but in the long term, a transplant is almost always necessary.