New heart patch may reduce muscle damage after heart attack

Scientists have designed an adhesive patch that can be placed on the heart and could reduce the stretching of the heart muscle which is often followed by a heart attack.

According to the research, published in Nature Biomedical Engineering, biochemical markers showed that the patch reduced cell death, scar tissue accumulation and oxidative stress in tissue damaged by a heart attack.

The patch, made from water-based hydrogel material, was developed using computer simulations of heart function in order to fine-tune the material's mechanical properties.

A study in rats showed that the patch was effective in preventing left ventricle remodelling- a stretching of the heart muscle that is common after a heart attack and can reduce the function of the heart's main pumping chamber.

The research also showed that the computer-optimised patch outperformed patches whose mechanical properties had been selected on an ad-hoc basis.

"The idea here is to provide mechanical support for damaged tissue, which hopefully gives it a chance to heal," said Huajian Gao, a co-author on the paper.

Prior research had shown that mechanical patches could be effective, the researchers said, but no one had done any research on what the optimum mechanical properties of such a patch might be. As a result, the thickness and stiffness of potential patches vary widely. And getting those properties right is important, Gao said.

"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. But if the material is too soft, then it won't provide enough support. So we needed some mechanical principles to guide us," he said.

To develop these principles, the researchers developed a computer model of a beating heart, which captured the mechanical dynamics of both the heart and the patch when fixed to the heart's exterior. Yue Liu, who led the modelling work, said the model had two key components.

"First part was to model normal heart function, the expanding and contracting. Then we applied our patch on the outside to see how it influenced that function, to make sure that the patch doesn't confine the heart. The second part was to model how the heart remodels after myocardial infarction, so then we could look at how much mechanical support was needed to prevent that process," Liu said.

With these properties in hand, Yang, a researcher and his team developed a hydrogel material made from food-sourced starch that could match the properties from the model.

The key to the material is its viscoelasticity, meaning it combines fluid and solid properties. It has fluid properties up to a certain amount of stress, at which it solidifies and becomes stiffer. That makes the material ideal for both accommodating the movement of the heart and for providing the necessary support, the researchers said.

The material is also cheap (a patch costs less than a penny, the researchers said) and easy to make, and experiments showed that it was nontoxic. The rodent study ultimately showed that it was effective in reducing post-heart attack damage.

"The patch provided nearly optimal mechanical supports after myocardial infarction (i.e. massive death of cardiomyocytes). It maintained a better cardiac output and thus greatly reduced the overload of those remaining cardiomyocytes and adverse cardiac remodelling," said Ning Sun, a cardiology researcher and a study co-author.

"More testing is required. But the initial results are promising for eventual use in human clinical trials," the researchers said.

"It remains to be seen if it will work in humans, but it's very promising. We don't see any reason right now that it wouldn't work," said Gao.