A heart transplant.

im writing a story about an old woman who needs a heart transplant, and I have no idea how it works,,,

like why would someone need a heart transplant ?
what are the causes ?

lease give me ANY information you have on the subject(:

Someone could need a heart transplant because they didn't take good care of their heart. Like they ate fast food a lot, and didn't take the vitamins you need to take, like B12, that protect your heart.

The need for a heart transplant can be traced to one of many heart problems, each of which causes damage to the heart muscle. The two most common heart problems are coronary artery disease (the buildup of plaque in the arteries of the heart) and idiopathic cardiomyopathy (disease of the heart muscle without a known cause).

As the heart problem gets worse, the heart grows weaker and is less able to pump oxygen-rich blood to the rest of the body. Because the heart must work harder to pump blood through the body, it tries to make up for this extra work by becoming enlarged (hypertrophied). In time, the heart works so hard to pump blood that it may simply wear out, and be unable to meet even the smallest pumping demands. Medicines, mechanical devices to assist the heart, and other therapies can sometimes help and even improve a patient's condition. But when those treatments fail, transplantation becomes the only option.

From: http://www.texasheartinstitute.org/HIC/Topics/Proced/hearttx.cfm