21.   Doctors finally determined he was suffering from Chagas disease, caused by Tryponasoma cruzi, a single-celled protozoan that can burrow into heart muscle.

22.   Doctors are better at preserving heart muscle during surgery, and at using long-lasting arteries rather than veins in bypass procedures.

23.   Even when blood flow is restored to the heart muscle, it may be too late for the heart to repair itself, however.

24.   Embryonic stem cells have the potential to become any cell or tissue in the body, such as heart muscle, pancreatic tissue, brain or bone marrow cells.

25.   Exercise or other stress puts an even greater load on the heart muscle, increasing the demand for blood.

26.   Even if the patient survives, damage to heart muscle cannot be repaired.

27.   Excessive alcohol intake can also damage the heart, often causing damage to the heart muscle, a condition known as cardiomyopathy.

28.   For example, with the proper biochemical coaxing, it can turn into heart muscle, which could replace tissue damaged by a heart attack.

29.   Further testing revealed a condition that caused a thickening of the heart muscle.

30.   Had there been stem cells that could have regenerated his damaged heart muscle and the blood vessels that fed it, his remaining years would certainly have been better.