A clinical trial at Methodist Hospital is using stem cells in an attempt to regenerate heart muscle.
James Mason is one of the first to take part in the study.
Although he's only 49, he suffered his fifth heart attack last week -- despite already having had a defibrillator, five stents and open heart surgery.
"It's kind of scary, but I have it. I just have to deal with it," he said.
Mason said he's hoping the new study will help his recovery.
"Anything that can help me at this point is not a bad thing, so being a part of this study -- if it helps me -- (is) great," said Mason.
Shortly after his heart attack, doctors removed stem cells from bone marrow in his hip. The stem cells were then sent to a lab for purification and later injected directly into the affected heart artery.
Dr. Nandish Thukral, an interventional cardiologist at Methodist Hospital, said a catheter was inserted through the groin into the heart and the cells were injected to the heart muscle.
Mason was awake during the procedure and Thukral said he wouldn't feel any pain.
"What we're hoping is in the healing process in the first week after the heart attack, as the body is healing the heart, instead of forming a scar where the heart attack was, the heart would actually take up those stem cells (and) use them to rebuild functional heart muscle there," Thukral said.
Thukral said it wouldn't prevent future heart attacks, but could possibly curb a patient's chances of developing congestive heart failure, abnormal heart rhythms or even sudden death.
It is a double blind study, so neither the doctor nor the patient knows whether if the injection is a placebo or actual stem cells.
Either way, Thukral said the study could change the way heart attack patients are treated in the future.
Mason will have periodic evaluations over the next six months to see if there's a difference.
He said he's hopeful either way.
"It could be something that helps not just myself but everybody," he said.
Methodist is the only place in South Texas participating in the national trial.
Almost anyone who has had a heart attack is eligible to take part within four days of the incident.