From clot-busting drugs to bypass surgery, cardiologists have many options for treating the 700,000-plus Americans who suffer a heart attack each year. But treatment options remain limited for the 5.7 million or so Americans who suffer from heart failure, an often debilitating condition in which damage to the heart (often resulting from a heart attack) compromises its ability to pump blood.
“Severe heart damage can pretty much incapacitate people,” says Dr. Timothy Henry, director of cardiology at the Cedars-Sinai Medical Center in Los Angeles. “You can’t climb a flight of stairs, you’re fatigued all the time, and you’re at risk of sudden cardiac arrest.”
Medication is available to treat heart failure, but it’s no panacea. And some heart failure patients undergo heart transplantation, but it remains an iffy proposition even 50 years after the first human heart was transplanted in 1967.
But soon, there may be another option.
A patch for the heart
Researchers are developing a new technology that would restore normal cardiac function by covering scarred areas with patches made of beating heart cells. The tiny patches would be grown in the lab from patients’ own cells and then surgically implanted.
The patches are now being tested in mice and pigs at Duke University, the University of Wisconsin and Stanford University. Researchers predict they could be tried in humans within five years — with widespread clinical use possibly coming within a decade.
The hope is that patients will be again to live more or less normally again without having to undergo heart transplantation — which has some serious downsides. Since donor hearts are in short supply, many patients experiencing heart failure die before one becomes available. And to prevent rejection of the new heart by the immune system, patients who do receive a new heart typically must take high doses of immunosuppressive drugs.
“Heart transplants also require bypass machines which entails some risk and complications,” says Dr. Timothy Kamp, co-director of the University of Wisconsin’s Stem Cell and Regenerative Medicine Center and one of the researchers leading the effort to create heart patches. “Putting a patch on doesn’t require any form of bypass, because the heart can continue to pump as it is.”
Heart tissue in a dish
To create heart patches, doctors first take blood cells and then use genetic engineering techniques to reprogram them into so-called pluripotent stem cells. These jack-of-all-trade cells, in turn, are used to create the various types of cells that make up heart muscle. These include cardiomonocytes, the cells responsible for muscle contraction; fibroblasts, the cells that give heart tissue its structure; and endothelial cells, the cells that line blood vessels.
These cells are then grown over a tiny scaffold that organizes and aligns them in a way that they become functional heart tissue. Since the patches would be made from the patient’s own blood cells, there would be no chance of rejection by the patient’s immune system.
Once the patch tissue matures, MRI scans of the scarred region of the patient’s heart would be used to create a digital template for the new patch, tailoring it to just the right size and shape. A 3D printer would then be used to fabricate the extracellular matrix, the pattern of proteins that surround heart muscle cells.
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The fully formed patch would be stitched into place during open-heart surgery, with blood vessel grafts added to link the patch with the patient’s vascular system.
In some cases, a single patch would be enough. For patients with multiple areas of scarring, multiple patches could be used.
Delicate business
Inserting patches will be delicate business, in part because scarring can render heart walls thin and susceptible to rupture. Researchers anticipate that heart surgeons will look at each case individually and decide whether it makes more sense to cut out the scarred area and cover the defect with a patch or simply affix the patch over the scarred area — and hope that, over time, the scars will go away.
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Another challenge will be making sure the patches contract and relax in synchrony with the hearts onto which they’re grafted. “We think this will happen because cells of the same type like to seek each other out and connect over time,” Kamp says. “We anticipate that if the patch couples with the native heart tissue, the electrical signals which pass through the heart muscle like a wave and tell it to contract, will drive the new patch to contract at the same rate.”
How much would it cost to patch a damaged heart? Researchers put the price tag at about $100,000. That’s far less than the $500,000 or so it costs give a patient a heart transplant. And regardless of the cost, researchers are upbeat about the possibility of having a new way to treat heart failure.
“Using these patches to repair the damaged muscle is likely to be very effective,” says Henry. “We’re not quite there yet — it’ll be a few years before you see the first clinical trials. But this technology may really provide a whole new avenue of hope for people with these conditions who badly need new treatment options.”
