A heart attack can leave lasting damage on the heart muscle of a person. Researchers are hoping a new patch can help the heart to mend after such a cardiac event.
Jianyi “Jay” Zhang, MD, PhD, the chairperson of the University of Alabama at Birmingham Biomedical Engineering, created human cardiac muscle patches and tested them in pigs.
“One of the things that happens after a heart attack, where a significant amount of heart muscle is damaged, is that the shape of the left ventricle changes — often leading to dilation to help make up for the loss of function… increasing the stress of the rest of the heart muscle, which long-term negatively affects the efficiency of heart pumping activity,” explained Dr. Elizabeth Klodas, a cardiologist from Minnesota who wasn’t involved in the study.
“Left ventricular dilation can even lead to heart valve leaks (mitral valve specifically) because the supporting structures for the valve get distorted by the change in shape of the left ventricle,” she told Healthline.
The patch helps prevent all that.
Each patch is about 1.5 inches by 0.80 inches in size and is about as thick as a dime.
When Zhang and his team transplanted two patches into the injured pigs’ heart, it significantly improved function in the left ventricle. That’s the major pumping area of the heart.
The patches reduced the size of damaged tissue as well as apoptosis (cell death) in the scar area.
The researchers also found that the patches didn’t start heart arrhythmia, which is a serious complication.
Placing the patches requires open-heart surgery.
Using stem cells
The patch is made from human-induced pluripotent stem cells, or hiPSCs.
There are three types of cells in the patch: 4 million cardiomyocytes (heart muscle cells), 2 million endothelial cells (they aid in cardiomyocyte survival), and 2 million smooth muscle cells (to line the blood vessels).
The three cell types were grown in a three-dimensional fibrin matrix that was rocked back and forth for a week.
The cells begin to beat synchronously after one day. This produced heart muscle cells that were more mature, compared to other heart muscle patches made from a monolayer of cells.
Essentially, these patch cells are more similar to the body’s original heart muscle tissue.
Trying to get heart patch technology to work is nothing new.
In the past, an injection of cells or a thin film has been attempted with low survival rates.
Zhang’s research showed a high rate of engraftment, with 11 percent of patches adapting well four weeks after transplantation. They also showed improved heart recovery after transplantation.
“The human cardiac muscle patch significantly improved heart function and reduced the heart scar size caused by the heart attack,” Zhang said.
In addition to treating patients, the patches are also useful as human models for new drug testing and heart disease modeling, he said.
The patch improves heart function after heart attack, he added.
Because the biodegradable patch is made from fibrin gel, Zhang said he expects that the cells would survive after the four-week mark and integrate into the body’s myocardium in the long term.
He plans to do more research on the patch, and wants to test if it can be combined with angioplasty or fibrinolysis.
“In the past, we’ve tried to inject muscle cells directly into areas of heart muscle damage, but that did not work,” Klodas said. “This seems to have a lot more potential.”
Candidates for cardiac patches
The patch isn’t necessarily for everybody.
“Not all heart attack sufferers need this,” Klodas said. “Heart attacks that are caught early get blood flow to the heart muscle restored quickly, resulting in minor heart muscle damage, which would not be expected to affect heart function much.”
A leading cause of heart failure is having a prior heart attack with significant muscle damage, so the technique has the potential to have an impact on the care of people who don’t get to the hospital in time to restore blood flow quickly.
Zhang said patients with acute myocardial infarction, chronic myocardial ischemia, or dilated/ischemic cardiomyopathy wouldn’t be good candidates for patch transplantation.