Every 10 minutes, someone is added to the national transplant waiting list, and every day, 22 people on average die waiting for a match, according to the United Network for Organ Sharing. But, thanks to innovations in bioengineering, all of that could change.
Conceived nearly 60 years ago, the total artificial heart (TAH) has helped sustain the sickest biventricular failure patients waiting for a transplant. While the design of the primary TAH used today has mostly remained stagnant since the ’80s, when it was first implanted in a patient, new models and clinical trials may lead to a better device and, one day, a permanent solution.
“We are still many years away from that,” Dr. Nader Moazami, director of the Cardiac Transplantation and Ventricular Assist Device Therapy Program at the Cleveland Clinic, told FoxNews.com of a permanent artificial heart. “Although tremendous strides have been made, biocompatibility will always remain a challenge.”
The longest an individual has lived with the most widely used device worldwide, the SynCardia temporary TAH, was nearly four years.
But now, Tucson, Arizona-based SynCardia Systems Inc. is conducting a destination therapy study, whereby it’s analyzing whether its TAH could be used as a more permanent solution for biventricular failure. The device is truly a “last resort” solution for the study’s 19 participants, who do not qualify for a donor heart transplant.
At the Cleveland Clinic and the Texas Heart Institute, scientists are exploring how continuous-flow total artificial hearts (CFTAH) may suit patients with biventricular failure who aren’t eligible for an organ transplant, or either don’t have access to the SynCardia temporary TAH or are ineligible to receive it due to its size. The SynCardia temporary TAH can only fit in large chest areas. Researchers at the Cleveland Clinic have completed a three-month study on two calves implanted with their CFTAH, which operates without a diaphragm or valves, and doesn’t require an external driver like the SynCardia temporary TAH.
“This is very important from a clinical perspective, as there is currently no ideal device for patients with severe biventricular heart failure,” lead researcher Kiyotaka Fukamachi, a biomedical engineer in the Cleveland Clinic’s Lerner Research Institute Department of Biomedical Engineering told FoxNews.com of the study, which was published in the September issue of the Journal of Thoracic and Cardiovascular Surgery.
The lack of an ideal solution may explain the discrepancy between the estimated number of people who could benefit from a TAH and patients with the implant, Fukamachi said. According to data from the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS), of the upwards of 40 percent of patients with end-stage heart failure— a majority of which suffer from biventricular failure— only less than 3 percent receive a TAH.
Although the SynCardia temporary TAH and mechanical circulatory support (MCS) devices may be available short-term solutions for these patients, some patients find the TAH’s external driver to be cumbersome, Fukamachi said, and other experts say the MCS options, which include popular ventricular assist devices (VADs), pose a risk of leading to other health complications.
The shortage of heart transplants and the need for a solution
In the late 1960s, when patients began receiving heart transplants, supply was relatively high and demand was low, Donald Isaacs, vice president of communications for SynCardia, told FoxNews.com. The Department of Health and Human Services (HHS) estimates about 4,000 people wait for donor heart transplants each day, while only about 2,300 hearts are donated.
Heart disease is the No. 1 cause of death in the U.S., claiming more than 611,000 lives in 2015, according to the Centers for Disease Control and Prevention (CDC).
Individuals with end-stage heart failure may get a left ventricular assist device (LVAD), a battery-operated, surgically implanted device that helps the left ventricle— the main pumping chamber of the organ— send blood to the rest of the body. According to the National Institutes of Health (NIH), LVADs are the most common VAD. However, according to the Mayo Clinic, LVADs can lead to a number of health complications, including internal bleeding, infection and blood clots, among other risks. According to INTERMACS, right heart failure is the primary cause of death in 4.7 percent of patients with a VD, and 2.8 percent of patients die of intractable arrhythmias and 3.4 percent of congestive heart failure while using MCS devices.
Cardiac graft failure is the major cause of death among heart-transplant patients, encompassing 44 percent of transplant deaths within five years, according to the International Society of Heart Lung Transplantation.
When implanting a patient with a TAH, surgeons remove the left and right heart ventricles, and the four heart valves— just as is done during a human heart transplant— and replace them with mechanical versions. Cuffs attach the artificial heart to the organ’s natural atria. An external driver (either portable and carried by the user, or stationary and used in a hospital setting) powers the SynCardia temporary TAH, and is connected to two large lines that stem through the skin to help power the TAH.
Ninety-six percent of implanted artificial hearts have been the SynCardia temporary TAH or one of its direct predecessors, Isaacs said. SynCardia data shows 1,123 patients have been implanted with its standard 70cc model.
John Beckingham, a 58-year-old retired contractor in Rochester, N.Y., got a heart transplant at the Cleveland Clinic on Oct. 7, 2015. He spent six months on the transplant waiting list. During that time, he used the a stationary hospital driver until he was stable enough to move onto the Freedom Driver, which is portable and weighs 40 pounds total, including a required backup driver and batteries.
“[The Freedom Driver] really helped because it made me more mobile,” Beckingham told FoxNews.com. “Anytime I wanted, I would get on a vent basically and go for a walk around the floor. I was able to go to Starbucks, get a cup of coffee with my wife, and go outside. And compared with sitting in a hospital, that’s amazing.”
Beyond bridging the gap to heart transplants
The existing SynCardia 70cc only fits in large chest areas, out-ruling eligibility for some women and all children, Isaacs said. But early findings from an ongoing SynCardia study of 23 people implanted with a smaller model of the company’s 50cc version, which pumps 50 milliliters of blood per beat compared with the 70 milliliters that the 70cc model pumps per beat, may offer promise for women and adolescents.
SynCardia also has a destination therapy study underway that began in early 2015, whereby 19 individuals ineligible for a heart transplant began using the 70cc device as a long-term solution rather than an immediate bridge to transplantation.
In their 2014 study at the Cleveland Clinic, lead study author Fukamachi and his team observed success in calves implanted with the CFTAH for three months— the longest this device, which has been in development for about the last seven years, has sustained the animal, Fukamachi said.
“It was very successful— and without any anti-coagulation, or [use of] blood thinner or anti-platelet drugs,” Fukamachi told FoxNews.com. “That was a very important milestone for us because this shows the potential for the process of development of the continuous-flow total artificial heart.”
A permanent solution for heart failure?
Keefe Manning, an associate professor of biomedical engineering at Penn State University, said for now, he thinks TAHs rather than CFTAHs offer the most immediate promise— primarily because the latter devices are so novel, and, consequently, there’s a lack of research on them. Manning’s research has focused on the fluid mechanics of the cardiovascular system and the impact that artificial devices may have on it.
“The big question, which no one knows the answer to, is ‘What are the long-term ramifications of continuous flow in the arterial system?” Manning told FoxNews.com, “and that, unfortunately, has not yet been determined because there hasn’t been a study to look at that.”
Still, he said he thought the TAH itself is a “worthwhile endeavor” and that he wished “there was more investment from the government.”
“Everyone talks about tissue engineering a heart— that’s a long way away— so there are people that are desperate for this technology,” Manning said. “I think it has the potential to save a lot of people’s lives, and with donor hearts not really increasing and in fact decreasing, there’s got to be a solution.”
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