Every year in the United States alone, 785,000 people will have a first heart attack and 470,000 more will suffer a repeat heart attack, according to the Centers for Disease Control and Prevention. These heart attacks leave behind damaged, scarred heart muscle that can lead to heart failure. For years, scientists have been developing and testing methods for using stem cells in an attempt to repair scars and regenerate heart muscle.

On Monday, The Lancet published the results of a study, led by Eduardo Marbán of the Cedars-Sinai Heart Institute, in which a patient’s own cardiac stem cells were harvested, multiplied in a lab, and then injected back into the patient’s heart. They showed that among 17 patients with damaged muscle who received the treatment, there was an average of 50 percent reduction in the size of their scars after one year, with minimal complications. Eight patients who were part of the control group that received traditional post-heart-attack care showed no reduction in scar size.

Past studies have looked at the effectiveness of using stem cells derived from bone marrow to heal damaged heart muscle, although the results have been mixed. In November of last year, a study showed the time frame after a heart attack during which bone marrow stem cell injections were effective was severely limited, within a week. This does not seem to be the case with the new cardiac-derived stem cells, as some patients were treated several weeks after their heart attacks. Studies have shown some success in treating damaged muscle, but none as significant as the new development, and improvements were only slight.

Marbán and his team performed the first treatment for the study in June 2009. The patient, Ken Milles, was 39 and had suffered a heart attack that May as a result of an artery that was 98 percent blocked. Almost two and a half years later, Milles told CBS News that he experiences no pain or shortness of breath. Additionally, doctors said that Milles’ heart looks almost normal, indicating that this type of treatment could eventually erase the damage of a heart attack.

The success of Marbán’s clinical trial could be just the beginning of using stem cells in repairing the heart. If the heart muscle can regenerate, then it is possible that heart disease, the leading cause of death, could be reversed, and the need for devices or heart transplants erased. It is also a huge step for stem cell treatment and organ regeneration in general. Techniques like the one developed by Marbán to grow the heart cells could be applied to other organs, opening the door to reversing devastating effects of a large number of diseases and types of injuries.

Marbán’s cell-growing process was developed while he was a member of the faculty at Johns Hopkins University. The university has filed for a patent and licensed it to Capricor Inc., a company of which Marbán and his wife are founders.

Dr. Marbán discusses this breakthrough in the video below.