Cardiac index (CI) is better. Because you count with the body surface. When you have a cardiac output (CO) of certain value in a small and thin person, the same value can be insufficient in a tall and fat person. In CI you devide CO by the person's surface and you get much better idea of what's going on ;)

cardiac

cardiac muscle cells are joined by intercalated disks.

Cardiac Necrosis is the death of cardiac tissue.

its not cardiac rest, its cardiac ARREST. which is a heart attack.