But they can't be used for tiny arteries, so when those are closed, patients can still have pain.
Dr. Verma recalls one patient.
"She had difficulty walking from her bed to her bathroom - she had angina from that. She had the chest pain walking up a flight of stairs going to her bedroom," says Dr. Verma.
In this trial, Dr. Verma creates an electrical map of a patient's heart to locate ailing muscle that has the best chance of being revived.
As he looks at the map, he notes, "The blue areas in this patient are the areas that were not receiving enough blood supply, but were still viable."
Then, through a tiny catheter threaded up to the heart, stem cells collected from a patient's blood are injected into those spots.
"The theory is that will help the heart muscle improve in that area, help create small blood vessels in that area," says Dr. Verma.
In earlier tests, stem cell recipients DID have less pain. These bigger trials will measure the amount of improvement. This is the first trial of stem cells for heart problems to get to the Phase 3, the final phase.
Temple University is also taking part in these tests.