Implanted devices, stem cells may replace heart transplants

Last updated on May 13th, 2019 at 02:33 pm

Someday, heart transplants may become a thing of the past. Implanted devices already are allowing people to live longer with their ailing hearts in their bodies. In the future, new heart cells, grown from a patient’s own stem cells, may be used to grow new heart tissue, which could replace the implanted device.
The techniques and technology used in heart transplants have not changed much in recent years, said Dr. Alfred Tector, who has been working with the heart transplant program at St. Luke’s Medical Center in Milwaukee for the past 35 years.
St. Luke’s is the Milwaukee area’s heart transplant leader. The hospital has performed about 600 heart transplants since 1968.
The number of heart transplants in the United States and in southeastern Wisconsin stays relatively the same because the amount of transplantable hearts stays relatively constant, Tector said.
Available hearts only become available when a person who is willing and fit for donation dies.
"The No. 1 obstacle to transplants is donors," Tector said. "We (St. Luke’s) have a waiting list of 48 right now. That is not dictated by need, but rather by donors. And even if we used every donor that was available, there still would be a significant need for more ways to support the heart."
While techniques and technology for transplants haven’t changed much in recent years, St. Luke’s is one of several medical centers across the United States that is taking part in research of implanting artificial hearts and heart-assisting pumps.
St. Luke’s has implanted more than 300 heart assist devices in patients since 1986, Tector said. Heart-assisting devices are different than an artificial heart, because the patient’s sick heart stays in the body, while the implant is placed outside of the heart, but is connected to a ventricle, usually the left one.
Most of those devices, Tector said, were implanted as a bridge to an eventual transplant.
"The device stays in and improves circulation during the waiting period for the heart," he said. "Sometimes it takes one or more years to secure a heart for patients."
Initially, the pumps were designed to pulse like a heart, but many more modern pumps have been designed with impellers, which have far fewer moving parts. Tector said devices with impellers displace no air, which makes them safer, and are smaller, which makes them easier to implant in a patient.
One drawback to the pumps that contain impellors is that patients need to go on anti-coagulant drugs, Tector said, so that blood clots do not form in or near the device.
However, for patients who are waiting to have a transplant, Tector said the heart-assisting pumps make a huge difference.
"While they are waiting for a transplant, the patients go home," he said. "And because of the increased profusion of blood to other body parts, the other organs are able to recover while they are on the pump because of improved circulation. They are able to eat a regular diet, and they’re able to get in better shape because they can resume exercise. In turn, they become better (transplant) recipients than the ones that stay in the hospital. And this becomes much better with the results."
Tector said research and use of heart-assisting pumps will be one of the most important areas for the medical profession in coming years, as the number of heart disease diagnoses grows with the aging baby boom population.
"This will keep growing as the population ages," he said.
Since the numbers of available hearts for transplantation will stay about the same, there will be a need for more pumps that can stay in a patient’s body for an extend period of time, Tector said.
"They (the pumps) will become like computers were," Tector said. "The one that is implanted is obsolete, and there will be more and more coming onto the market. The emphasis will be for more devices, and for smaller and cheaper devices."
One of the areas in which research continues is in the way the implanted devices are powered.
Most patients with the implants have small cords coming out of their bodies, where the device can be connected to a power source.
Devices that are currently implanted in patients use batteries while the patients are awake, which need to be changed every four to six hours. Tector said patients connect to a battery charger at night when they are sleeping.
Some devices currently being tested have been able to demonstrate power transfer through the skin, eliminating the need for a cord.
"The line coming through the skin is a source for infection," Tector said. "This is relatively new, and as more devices get developed, it will get more popular."
Since the number of hearts available for transplanting will likely not increase, something needs to be done for the increasing number of patients with heart disease that Tector and other physicians believe they will see in coming years.
"Everyone is realizing that we have to do something to improve the heart while it is on the devices," he said. "(The future is) cellular transplantation, where heart cells are transplanted and are given the time to grow and develop. Hopefully, they will improve the heart, and then the device is removed, and the person can live."
Tector predicted that the future of heart care will focus on stem cell therapies, which have shown the ability to grow new heart tissue from stem cells harvested from a patient’s own body tissues. Tector predicted that medical science is five to 10 years away from being able to hold clinical trials on implanted stem cell heart tissue, because there are still several issues that need to be overcome.
One of those issues is making the newly grown heart tissues able to communicate with the patient’s existing heart tissue and infrastructure, so the muscle tissue of the heart expands and contracts at the same time. Doctors also have yet to work out how the new tissues will establish their own blood supply, because heart muscles need a substantial amount of oxygen and nutrients, which must be delivered via the bloodstream.
"They have to be able to function as a normal heart," Tector said.

Wisconsin Heart Transplants
Hospital Number of transplants
St. Luke’s Medical Center 26
University of Wisconsin Hospital 26
Children’s Hospital of Wisconsin 5
Froedtert Memorial Lutheran Hospital 4
* Between July 1, 2003, and June 30, 2004.

April 15, 2005, Small Business Times, Milwaukee, WI

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