Wider Use Ahead : Heart Pump: Stopgap for Emergencies
It was a little-noticed operation, but San Francisco surgeon J. Donald Hill was making medical history.
Last September, Hill, of the Pacific Medical Center, became the first to successfully use what doctors call a left ventricular assist device to sustain the life of a dying heart patient awaiting a human donor heart.
Hill’s achievement was in part the culmination of a goal almost two decades old. It meant that a patient desperately in need of a new heart did not have to die because no heart was immediately available. Instead, an artificial pump--the result of a nationwide research effort that has taken 15 years and hundreds of millions of dollars to produce--was used as a stopgap until a transplant could be performed eight days later.
More technologically sophisticated than the Jarvik-7 artificial heart that has gained so much publicity recently, left ventricular assist devices are being touted by most heart surgeons as the wave of the future.
Aids Failing Heart
Instead of replacing the entire heart, as the Jarvik-7 heart does, the assist device is hooked to the failing heart to assist it in providing the body with a normal amount of blood flow.
Heart experts say the greatest potential use for these temporary assist devices is with patients who do not need a transplant. These include cases in which the heart goes into shock after open-heart surgery or in which it does not restart after the heart-lung machine that maintains circulation during surgery is removed.
Left ventricular assist devices have been used more than 200 times to temporarily take over the pumping function in such cases. Doctors report a 50% success rate when the device is used for this function.
As Hill’s breakthrough showed, however, left ventricular assist devices can serve a second purpose: maintaining normal circulation for patients awaiting a transplant.
Within two to three years, researchers predict, several of the new left ventricular assist device designs under development will be ready for use as implantable permanent artificial hearts.
Free From Tether
One benefit, they say, is that the new devices are being designed to help free the patient from the tethering restrictions of the Jarvik-7 heart.
The emphasis on devices capable of assisting the pumping action of sick hearts is part of a new strategy by heart surgeons to deal with the estimated 100,000 people in the United States who are considered candidates for either temporary or permanent assist implants.
Most surgeons are convinced that with the exception of certain categories of patients, a human heart transplant will be preferable to even the most advanced permanent artificial hearts that they expect to see in the near future.
(Typically, a device must have two chambers in order to be considered an artificial heart. This is the case with the Jarvik-7. Because of their similar functions in pumping blood, left ventricular assist devices are also sometimes referred to as artificial hearts.)
The surgeons concede, however, that medical centers that do transplants must be prepared to also implant artificial hearts.
“Ten years ago it was a competition that led to the development of an artificial heart in some centers and heart transplantation in others,” said Dr. Jack Copeland of the University of Arizona Medical Center. Today, he told reporters at a recent meeting of the American College of Cardiology, most medical centers agree that the two programs go hand in hand.
Copeland dramatized that point earlier this month when, despite not having authorization from the U.S. Food and Drug Administration for such an operation, he implanted an artificial heart in a patient whose transplanted heart had failed. The artificial device, called the Phoenix heart, was used as a bridge to keep the patient alive for 11 hours until another human donor heart could be found.
The Phoenix heart was not a left ventricular assist device, but Copeland used it for the same purpose that the assist device serves.
Surgeons have been searching for a long time for a way to keep patients alive until a donor heart arrives. This drive has been fueled by the spectacular improvement in survival of heart transplant patients over the last several years.
75% to 80% Survive
Heart transplant patients now have a one-year survival rate of 75% to 80% and stand a 50% chance of living five years.
Heart transplant experts attribute these advances in survival to better methods of selecting appropriate patients, improved post-operative care and refinements in the use of drugs that prevent rejection.
This improvement has in turn led to a greater willingness by cardiologists to refer patients to transplantation centers and greater pressure on private and government health plans to pay for transplants.
The result has been a phenomenal increase in the number of heart transplants being performed. According to the registry of the International Society for Heart Transplantation, 54% of the heart transplants done worldwide since 1968 were performed in 1983 and 1984. To date, more than 1,300 transplants have been done--440 of them during 1984 alone.
In the United States, where the number of transplants rose from 180 in 1983 to 325 last year, at least 30 centers do heart transplants, and the number is increasing monthly.
The growing acceptance of heart transplantation as a legitimate therapy has, however, increased the difficulty of obtaining suitable donor hearts, a problem that has plagued centers since the first transplant in 1967.
Intense Competition
The search for alternatives has in turn led to intense competition among medical researchers.
The National Institutes of Health swung its support away from artificial hearts like the Jarvik-7, in favor of the left ventricular assist devices, in 1969. Among other reasons, the agency determined that many of the problems involved with artificial hearts--ethical issues, quality-of-life questions and the problem of portable power sources--were solved more easily with temporary devices.
Although both the Jarvik-7 and Phoenix hearts can be used temporarily, the principal difference between them and the left ventricular assist devices is that the pumping chambers of the patient’s real heart must be removed before the artificial hearts can be implanted.
With the left ventricular assist devices, however, the patient’s own heart remains intact and the mechanical pump helps it circulate blood until either the heart has recovered or a transplant has been accomplished.
Even if the assist device is used as a permanent implant, as surgeons predict it will be in several years, the designs of several of the devices enable surgeons to leave the patient’s own heart in place. Experts say retention of the original heart is important not only for psychological reasons but to maintain the natural control mechanisms that nature has built into the patient’s heart.
Dramatic Operation
Despite those differences and the federal funding cutback, work on the Jarvik-7 continued on a shoestring basis throughout the 1970s at the University of Utah. Then in December, 1982, Barney Clark became the first person to receive a permanently implanted artificial heart.
Although left ventricular assist devices were just about ready for use, the public’s attention was focused on the far more dramatic operation in which a human heart was replaced with a mechanical device.
The prime criticism of the Jarvik-7, which since its initial use for Clark has been used twice in Louisville, Ky., is centered around the bulky compressor that drives it. Not only does the more than 300-pound compressor hinder the patient’s mobility, it also requires that two hoses enter the patient’s chest to carry compressed air to the heart. Critics say that with long-term use, the hoses eventually will act as roadways for bacteria and viruses to infect the patient.
Although a portable battery-powered compressor has been developed to give the patient mobility for short periods of time, he must still be hooked up to the hoses.
“It’s not that (the Jarvik-7 heart) is inherently wrong, but that the quality of life that is offered does not come close to what most of us consider reasonable,” said Peer M. Portner, Ph.D., chief scientist for the Novacor Medical Research Corp. of Oakland and consulting associate professor of cardiovascular surgery at Stanford.
‘Realities Don’t Correlate’
“There’s been so much PR (public relations in Louisville), but realities don’t correlate with what is being promoted,” Portner said. “If the Louisville people were doing temporary implants rather than permanent ones, people would be more comfortable with it.”
Portner is one of the co-developers of the Novacor left ventricular assist device that Stanford surgeons implanted in a patient awaiting a transplant five days after Hill’s achievement in San Francisco.
Unlike other current-model assist devices, including Hill’s, which use compressed air to drive the heart, the Stanford Novacor pump is operated by an electric motor. Because compressed air is no longer required, the patient will not be tethered with air hoses, although for temporary application, a wire connected to a bedside console passes into the patient’s chest. The FDA has authorized Dr. Phillip M. Oyer, a Stanford transplant surgeon who has been working with Portner on the device since 1970, to implant the temporary assist device in 19 more patients.
The real advantage of eliminating the air hoses will come when the device eventually is converted for use as a permanent implant. By then, Novacor officials and Oyer say, it will be possible to implant a battery in the patient that can be recharged from outside the body. It will work the heart for up to two hours between charges.
For general use, however, the patient will wear a belt that will transmit power from an electric wall socket through the skin to the implanted parts pump and regulating system.
3 New Models
At least three other assist devices are in the works. An artificial heart developed by Dr. William S. Pierce at Penn State University recently received FDA approval for temporary use in six patients awaiting transplants. The device, manufactured by Thoratek, a Berkeley-based firm, is air-driven. Unlike the Jarvik-7 artificial heart, the Penn State heart is electronically controlled to automatically provide an increase or decrease in blood flow according to the patient’s needs.
Pierce also has under development a more advanced electrically powered artificial heart that, like the Stanford device, is designed to rid patients of the need to be tethered with air hoses to a compressor. Other modifications of the left ventricular assist concept have been designed by researchers at the Texas Heart Institute in Houston and the Cleveland Clinic.
Heart surgeons say the enormous amount of publicity that has centered around the Jarvik-7 heart has been a source of great frustration to them because most of them believe that a more reasonable course would be an approach that combines assist devices and transplants.
Still more frustration stems from government regulations that are intended to protect the public from insufficiently tested devices. Because the initial number of patients authorized by the FDA to receive implants is small, these regulations in effect also limit the number of centers where the devices may be tested.
As a consequence, according to a researcher at one transplant center who asked not to be identified, the expected surge of cases is creating a feeling of urgency to “get in on the ground floor.”
‘Strong Undercurrents’
“The financial and personal gains that stand to be made are creating strong undercurrents that have nothing to do with science,” the researcher said.
Part of the anxiety centers on whether the deep concern over health care costs will keep government and private insurers from covering transplants. The Health Care Financing Administration has under advisement a study that considers whether the Medicare program should pay the cost of heart transplants, regardless of the patient’s age, as it pays for kidney dialysis.
According to the Health Resources and Services Administration, 15,000 people are or soon will be candidates for transplants in this country, with the cost ranging from $57,000 to $110,000 each.
Coupled with this, the researcher said, is the anxiety that stems from there still being more transplant centers than places testing the temporary assist devices. This creates a competition among surgeons to become affiliated with the companies that make the devices. At the bottom of this concern, it is said, is the worry by institution administrators and surgeons that if they do not get started early, they will not be considered first rate.
“If you want to understand (fully), you must factor all these things in when you read about some of the things happening today in heart surgery,” the transplant center researcher said.
Baby Fae’s Case
Almost forgotten in the surge of recent cardiac surgery spectaculars is the question of transplants between species. But when the infant known only as Baby Fae received a baboon heart at Loma Linda University last October, the media coverage was as intense as for any of the four artificial heart implants performed to date.
Although Dr. Leonard Bailey, Baby Fae’s surgeon, said recently when interviewed by a Loma Linda publication that he still plans to do at least four more cross-species transplants, important questions about the advisability of the procedure remain in the minds of other researchers.
One question concerns the propriety of extending an infant’s life by only five years--the yardstick for determining efficacy of transplantation in adults. Although five more years of life may be significant to a 60-year-old, the ethical implications of enabling a newborn to live to age 5 is another matter, some scientists say. Another question is what effect the foreign tissue of another species may have on the ability of the infant’s immune system to accept a human heart transplant later.
“Immunology is enough of a black box even in human-to-human transplants. When you do a baboon transplant, there’s no way of telling what the results will be,” said Dr. Randall Morris, an immunologist on Stanford’s transplant team.
Nevertheless, Morris added, the shortage of human donors means that other species will have a place in transplantation. Much more research is needed to learn how the immune system works and how it can be controlled to prevent rejection before cross-species transplants on humans are wise, he said.
“There’s a tendency for surgeons to go ahead regardless of what difficulties may lie in the future,” Morris said. “But when you speak to people who deal with immunology, compared to surgeons who don’t deal with it, there is a tremendous respect for the immune system that can’t be treated lightly.”
