A New Horizon for Heart Repair

U researchers robotically implant stem cells to improve damaged pigs’ hearts and raise human hopes.

By Patricia Kelly

Cardiovascular disease can put you in a catch-22 situation—you need heart surgery to improve your heart function, but poor heart function makes it impossible for you to have the surgery.

Doris Taylor, director of the University’s Center for Cardiovascular Repair, and her team are working hard to change this unfortunate circumstance.

Taylor and Harald Ott (now a surgery resident at Massachusetts General Hospital in Boston) co-led a study that helped prove the feasibility of using robotic surgery and stem cells for human cardiovascular repair. Taylor and Ott used the da Vinci robot at the U’s Experimental Surgical Services lab to inject stem cells labeled with iron nanoparticles into the damaged hearts of pigs. Followup magnetic resonance imaging showed the cells had taken hold and had significantly improved the function of six out of seven of the pigs’ hearts. In distilling the core purpose of the study, Taylor says, “Here’s the problem we were trying to solve. There are up to 22 million people living with heart failure right now. And (stem) cell therapy is of potential benefit to them because it works to replace missing or damaged heart cells and blood vessels. But many of them are too sick to have an open-chest surgery. So we are committed to finding a better way.”

The surgical robot allowed Taylor and Ott to inject stem cells into a pig’s beating heart through three small incisions (from one-half to one inch long) in the chest. (Traditional openheart surgery is much more invasive and traumatic. The incision is about 14 inches long, the heart must be stopped and the surgery takes much longer.) To operate the robot, the surgeon sits at a console, looks through a magnified screen and manipulates controls with wrist movements, which in turn direct the movements of three robotic arms. The robot’s software eliminates even the slightest hand tremor.

“The robot lets us reach places we can’t reach with our hands,” says Taylor. “It gives us a precision we don’t otherwise have. And it will let us treat patients we wouldn’t otherwise be able to treat.”

Taylor and Ott’s study gave rise to another first. To create damaged tissue in the young pigs’ hearts, cardiologist Johannes Brechtken used a new technique to induce a heart attack in the pigs’ hearts—no easy task. “The tricky part is to not make the heart attack too big, so the pig doesn’t die.” Brechtken’s innovative process involves using both a balloon (to mechanically block the major artery) and an injection of arteryblocking material to impede blood flow in the smaller vessels downstream.

“It was a beautiful model for advanced heart-failure,” Brechtken says. “And it was more appealing than working with rats or mice. Pigs are quite close to humans in anatomy and heart function—so it was a big step.”

Clinical trials with human beings will be the next phase. Ideally, one day this minimally invasive robotic procedure will produce results equal to or better than those from traditional heart surgery.

Taylor, always looking to the next horizon, says, “The robotic surgery is important, but what’s equally important is that it’s just a small piece of what we do.” Since the study was published, Taylor and her University colleagues have already found a more promising population of stem cells to use for cardiovascular repair. She and her team are working on a stem-cell measurement process to predict a person’s risk of developing cardiovascular disease. And, the team is in the early stages of building a “bioartificial” heart from stem cells.

“We do have a lot of irons in the fire,” says Taylor, “but that really helps us stay ahead of the curve. We’re helping to create the curve!”