Twenty years ago on Thursday, Dr. Christiaan N. Barnard performed the first successful heart transplant -- ushering in an age of miracle and wonder unknown in the treatment of advanced heart disease.

Since then, more than 4,000 hearts have been transplanted from one person to another in the United States, and the whole field of transplantation has exploded. Other organs, such as lungs and livers, are now being transplanted, and operations once limited to adults under the age of 50 are now performed on infants and elderly patients.

Strictly speaking, Barnard's historic transplant on Dec. 3, 1967, was not the first attempt to save a human life with such heroic surgery.

On Jan. 23, 1964, Dr. James D. Hardy of the University of Mississippi Medical Center in Jackson, Miss., transplanted the heart of a healthy chimpanzee into a man dying of chronic heart disease. The chimp heart beat for an hour and a half before it stopped and the patient died.

In early 1967, Dr. Richard P. Lower of the Medical College of Virginia in Richmond transplanted the heart of an accident victim into the chest of a baboon to see if the human heart could be removed and restarted in a foreign chest. The experiment was a success but the baboon quickly rejected the alien human tissue and died.

It was, however, Barnard's operation on Louis Washkansky, a 56-year-old grocer, in Groote Schuur Hospital in Capetown, South Africa, that put transplant technology on the road to many other advances including the artificial heart, the transplantation of hearts and lungs together and, eventually, selective control of the immune system and rejection.

It also put society on the ethical firing line as it grapples with difficult questions about selecting transplant candidates, the availability of organs and cost.

Ironically, the boom in heart transplants did not really begin with Barnard's historic operation. In fact, the days and months following Barnard's initial success were some of the darkest for heart transplant surgeons. To begin with, Barnard's first patient died of pneumonia 18 days after receiving the new heart, and few of his early patients lived very long.

Meanwhile, dozens of heart transplant centers quickly opened up all around the world and began putting new hearts in critically ill individuals. The results were disastrous. Patients were dying everywhere, some from surgical mistakes, others from inadequate control of the immune system to prevent rejection of the transplanted organ. Most died from overwhelming infections in patients whose immune systems had been shut down by immune-suppressing drugs. Physicians began talking about a moratorium on transplants. By the early 1970s, nearly all the heart transplant centers -- except Stanford University Medical Center in Palo Alto, Calif., and the Medical College of Virginia -- went out of business.

Stanford's Dr. Norman Shumway, a heart transplant pioneer who spent more than a decade studying transplant techniques in dogs, performed the first U.S. heart transplant about a month after Barnard. Lower, a Shumway colleague who had moved to Richmond, also performed some of the first American transplants.

Despite early transplant failures, both researchers continued to experiment with different techniques, searching for new and better ways to maintain the delicate balance of shutting down the patient's immune system just enough prevent rejection but not so much that the patient would be killed by some strange infection.

"The justification for continuing the research and development of this field was that even though there were few survivors, 20 percent were alive at one year and they were totally normal," said Dr. John Macoviak, director of heart and lung transplantation at the Washington Hospital Center, who trained under Shumway. "They could do normal things. They were not tethered to machinery. And although there was not a high salvage rate, 20 percent of the people were alive who would clearly be dead."

Over the years, advances began to accumulate. In 1973, surgeons developed a way to slide a catheter into the heart and remove a crumb-sized piece of tissue to test for signs that the heart was being rejected by the patient's immune system -- allowing physicians to monitor the status of the transplant and adjust drug doses. "One-year survival jumped from 20 percent to 40 percent," Macoviak said.

Around that same time, a new immune-suppressant drug called rabbit antithymocyte globulins became available, said Dr. Glenn Barnhart, surgical director for the heart transplant program at the Medical College of Virginia Hospital, part of Virginia Commonwealth University, in Richmond. As a result, patients who started to reject their transplanted heart became more manageable.

The biggest advance came in the late 1970s, when scientists testing ground fungi for new antibiotics discovered cyclosporin, a drug that shuts down the part of the immune system responsible for rejecting foreign tissue without shutting down a part of the immune system that protects the body from infections.

"Its use, and its efficacy, is what accounts for the great increase in the number of transplants done after 1983, when it was released for general use," Macoviak said. With the advent of cyclosporin, physicians rushed back into the field. There are now more than 100 heart transplant centers in the United States.

Cyclosporin, however, is no magic bullet. It's expensive, costing more than $5,000 a year, and does have some side effects, including kidney damage and an increased chance of certain cancers.

Yet the survival rate began to climb. The one-year survival rate has now reached 75 to 90 percent, and the five-year rate 50 to 60 percent.

The longest survivor -- almost 18 years -- is Willem Van Buuren of Mills Valley, Calif., who received his heart at the hands of Stanford's Shumway on Jan. 2, 1970. The success in transplantation has allowed surgeons to become more aggressive. "We can work on older patients," Macoviak said. In the past, no one older than 50 was given a new heart. "Now we can pick someone who is 58 and give him a reasonable life expectancy of 65." The oldest known transplant recipient, done at MCV, was 67.

Advances also have been seen at the other end of the age spectrum. Dr. Leonard L. Bailey, a pediatric heart transplant surgeon at Loma Linda University Medical Center near San Bernadino, Calif., has performed 12 heart transplants in babies younger than 2 years old. One was only three hours old.

Bailey first was pushed into the limelight in October 1984, after the controversial transplant of a baby baboon heart into Baby Fae, a newborn suffering a congenital heart defect. Baby Fae lived 20 days before the baboon heart failed.

The animal heart was used because of a problem faced by all transplant physicians: a shortage of human organs available for transplantation. An estimated 14,000 Americans could benefit from a heart transplant each year, yet only between 1,000 and 2,000 hearts become available.

Another difficult issue, said Daniel Callahan, director of the Hastings Center in Briar Cliff Manor, N.Y., a bioethics think tank, is economic. Heart transplants consume a huge amount of money, medical talent and hospital resources, costing $40,000 as paid by Medicare to an average of $75,000 to $100,000 or more.

"Is this a wise and sensible way to spend our money?" Callahan asked. "The consensus is that whether it is a wise way or not, it is awfully hard to not spend the money. It is a wonderful lifesaving device to be used in a desperate situation, and we tend to be very much biased to doing something in that case, especially when it is done with young people who have many years ahead of them."

In fact, heart transplants have become so accepted by the public that there is little chance of turning back the clock on this high-cost operation. "I have really not heard of any significant controversies about heart transplants for some time," Callahan said. "It is as if it is one of those procedures that has moved from experimental therapy to standard therapy. When Medicare accepted it, that was the final stamp of approval."

"There are so many transplants done now that people are starting to know people who had a transplant," MCV's Barnhart said. "This is no longer an experimental field. It has reached its own clinical age." Yet the debate continues over whether society should accept transplants as an almost routine treatment for heart disease or search for alternatives to avoid these costly procedures.

"Heart transplants are great," said Dr. John LaRosa, dean of medical affairs at George Washington University Medical Center, but they remain an example of half-way technology -- an expensive approach that does not really fix the underlying problem.

"The real treatment here is prevention," LaRosa said. "Knowing more about the basic cause of heart disease will make these things obsolete."