"There's an incredible amount of research and a very large sum of venture capital and private investment going into the field, " says Dr. Amit Patel, a cardiac surgeon and director of Cardiac Cell Therapy at the University of Pittsburgh Medical Center.

FORBES: Despite Bush Veto, Stem Cell Research Abounds

Bolli has refined his procedure to make it less invasive -- stem cells can now be taken through a catheter -- and none of the patients in cardiac stem cell trials have suffered serious adverse effects.

CNN: It's amazing what the human heart can do

These cells can differentiate into many different cell lines, including cardiac, neuro, or even skeletal muscle.

CNN: Dr. Sanjay Gupta: Understanding stem cell research

The long-term hope is to treat patients with some sort of stem cell that could turn into beating heart muscle and replace dead cardiac tissue with fully functioning new cells.

FORBES: Using Thigh Muscle To Fix The Heart