Inside the Human Body

The healthy heart (left) is very supple, firm and poetic, according to Dr. Oz.

The unhealthy heart (right) is larger and paler. The lighter spot in the middle indicates that this person had a heart attack. That scarred vessel was unable to bring blood to the heart, and the damage can be seen on the inside.

Once an artery is closed, it doesn't heal, which is a devastating problem, Dr. Oz says. While medicine has gotten better at curing heart attacks, damage is still done after a heart attack, creating an epidemic of heart failure.