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The patch is made of vicryl, a material used for suturing injured tissue that is later absorbed by the body, explained Jordan J. Lancaster, a predoctoral fellow at the Southern Arizona VA Medical Center in Tucson, who reported on the animal studies Wednesday at an American Heart Association meeting in Keystone, Colo.
"The mesh is grown in a bioreactor with human dermal fibroblast cells," Lancaster said. When the patch is placed on the heart, it delivers cells that grow to strengthen the heart muscle.
After a heart attack, he explained, there is abnormal enlargement of the left ventricle, which pumps blood to the body. The ventricle also works harder, which can ultimately lead to heart failure.
Applying the patch to rats after a heart attack, "we were able to prevent the negative functioning and the negative remodeling," Lancaster said. Blood flow to the heart muscle increased by 37 percent for rats who got the patch immediately after a heart attack, and the blood-pumping ability of the heart increased by 40 percent.
A second series of experiments applied the patch to rats three weeks after a heart attack to study its effect on heart failure. Blood flow was improved by 116 percent, and blood-pumping ability improved by 21 percent.
The animal studies were sponsored by Theregen Inc., a San Francisco company that has started human studies of the patch. A first study, primarily to test the safety of the patch, was done last year by Dr. Bartley P. Griffith, chief of cardiac surgery at the University of Maryland.
"We were very pleased," Griffith said of the trial, which included 12 heart attack patients. "In our patients, the application of the patch was not associated with any complications. The application of the patch is quite simple. Four stitches are enough to attach the patch."
One of the people given the patch died, and a study of the heart showed "remarkable new blood vessel formation," Griffith said. "We had generally very positive outcomes."
A second round of human trials has begun, said Dr. Gary Gentzkow, chief medical officer of Theregen. One trial is designed to study the effect of the patch on heart function. The second trial is intended to get a detailed look at heart tissue after the patch is applied. The subjects are people with heart conditions severe enough to require implanted heart-assist devices.
The trials are being done at several medical centers in the United States, Gentzkow said. "Enrollment is finished in the studies," he said. "We are in the follow-up phase. We expect complete follow-up results this year."
Further human studies depend on the results of those trials, Gentzkow said.
SOURCES: Jordan J. Lancaster, predoctoral fellow, Arizona VA Medical Center, Tucson; Bartley P. Griffith, M.D., chief, cardiac surgery, University of Maryland, Baltimore; Gary Gentzkow, M.D., chief medical officer, Theregen Inc., San Francicso; July 30, 2008, American Heart Association's Basic Cardiovascular Sciences Conference, Keystone, Colo.
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