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Repair Patch Devised for Heart Attacks

Heart and major blood vessels


18 Apr. 2019. Researchers in the U.S. and China designed a hydrogel patch that in lab animals reduces the damage to heart muscle occurring after a heart attack. A team from Brown University in Providence, Rhode Island, Fudan University in Shanghai, and Soochow University in Suzhou, China describe the the patch and its development in the 15 April issue of the journal Nature Biomedical Engineering (paid subscription required).

A heart attack occurs when blood flow in one or more of the coronary arteries is blocked, reducing the amount of oxygen needed by heart muscles to function. Blockages often occur when cholesterol plaques building up in an artery break off and form a clot. Heart muscle tissue, in this circumstance, becomes damaged, with the amount of damage depending on the size of the area affected by the blockage. Scar tissue forms in the damaged area, and while the heart continues to pump blood, it becomes weakened as a result. National Institute on Aging says more than 1 million people in the U.S. suffer a heart attack each year, with about half of those dying.

Researchers led by engineering professor Huajian Gao at Brown, cardiology professor Ning Sun at Fudan University, and Lei Yang, a recent Brown Ph.D graduate who now studies biomaterials at Soochow University and Hebei University of Technology, are seeking solutions for fixing the damaged muscle tissue that occurs in a heart attack. “Part of the reason that it’s hard for the heart to recover after a heart attack,” says Gao in a Brown University statement, “is that it has to keep pumping. The idea here is to provide mechanical support for damaged tissue, which hopefully gives it a chance to heal.”

While mechanical patches to fix heart attack damage were tried before, little research up to now determined the optimal properties of the patch, such as thickness and stiffness, which in previous attempts varied widely. “If the material is too hard or stiff, then you could confine the movement of the heart so that it can’t expand to the volume it needs to,” notes Gao. “But if the material is too soft, then it won’t provide enough support. So we needed some mechanical principles to guide us.”

The team gained those principles from computer models of a beating heart created in Gao’s lab. The models highlight heart functions of a normal, healthy heart, then the damage when a heart attack occurs in heart muscle tissue, revealing the changes in structure that weaken the tissue. The models also provided specifications for designing a patch with adequate support in the damaged areas, while not confining the rest of the heart.

Those specifications enabled Yang’s biomaterials lab to design a patch made from a hydrogel, a water-based biocompatible polymer. The hydrogel is viscoelastic, which means it exhibits both liquid and solid properties. As a result, the patch retains its fluid properties while under stress, but solidifies when needed to provide support to the heart.

The Fudan University team led by Sun tested the patch on lab rats induced with heart attacks. The tests show the patch provides the needed mechanical support for damaged hearts, while reducing the stress on remaining heart tissue cells. The patched hearts also show less cell death in the damaged regions and less accumulation of scar tissue.

In addition, say the researchers, the patch is non-toxic, easy to produce, and low in cost, with the materials costing about 1 cent per patch. More tests with animals are planned, but the eventual goal is to advance the patch to human clinical trials.

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