Rita Tyson, a 22-year-old new mother, talks of heart transplants as modern miracles. She should know. She survived two of them within 23 hours at Washington Hospital Center.

Tyson, who developed a rare form of heart failure a month after she gave birth to her first child in August, underwent a heart transplant on the afternoon of Nov. 13.

Two hours after surgery, her body began violently rejecting the new organ.

Doctors began administering immuno-suppressant drugs, but within hours it was apparent: If Rita Tyson was to live, she needed another new heart.

At 5 a.m., medical science was blessed by fate. A second heart was located in Florida.

Doctors obtained the heart and the same day began yet another transplant. By midnight, a new heart was pumping in Tyson's chest.

"I know I could've died," Tyson said this week. "I'm never going to take anything for granted again."

Neither are her doctors. The team of surgeons, nurses and other medical staff who toiled on Tyson for four days straight are still talking about the rare hyper-acute rejection of the first heart -- it occurs in less than 1 percent of all transplants -- and what they, in hospital vernacular, call "a great save."

"The problem she had after delivery itself is unusual. That we could find a heart in this area at this time is unusual. And that we could find a second heart right when we needed it almost borders on making you want to become religious," said Albert Pfister, the cardiac surgeon who shepherded the second heart from Florida to the District.

"Fortunately both operations went like clockwork," said Steven Boyce, who with Pfister heads the hospital's transplant program. "If Dan Rather had been shooting '48 Hours,' I would've been very happy."

Tyson, an Alexandria resident, had no history of heart disease and, according to her doctors, had a healthy pregnancy and an uncomplicated delivery. But a month later, she began complaining of what seemed to be the flu. She couldn't breathe. She had no strength. She felt dehydrated.

When she started getting chest pains one night while eating a slice of pizza at her aunt's home in Silver Spring, relatives drove her to Washington Adventist Hospital.

Tests showed Tyson's lungs were filled with fluid and her heart had enlarged 1 1/2 times its normal size. For some reason, doctors said, Tyson was suffering post-partum cardiomyopathy, a disease that attacks the heart muscle. One in 4,000 women may develop such failure after delivery. Of these, only one in 15,000 has a totally unexplained onset. Tyson was the one in 15,000.

When she was told she could be a candidate for a heart transplant, Tyson said she tried not to think about it. "I put it in the back of my mind." But 13 days after she was released from Adventist Hospital, rejuvenated by bed rest and antibiotics, her symptoms returned.

She went for emergency treatment at Capitol Hill Hospital. Tests showed her lungs had filled again with fluid and her heart was distressed. She was transferred to Washington Hospital Center for further tests.

Doctors told her a transplant was necessary. The 5-foot-8, 140-pound woman stayed in the hospital to wait for a donor who matched her build, came close to her age and was compatible in blood and tissue. Unlike thousands of people who find themselves in Tyson's straits, time was on her side.

Within a month, the Washington Regional Transplant Consortium, a local registry for organs, had found a heart in this area that best matched Tyson.

Just over half the people who need transplants find suitable matches, according to the United Network for Organ Sharing, a private nonprofit group that maintains a nationwide registry of donors and people waiting for transplants.

For those who find a suitable donor, the average wait is about four months. About 15 percent of all people who need heart transplants die before the right heart is found, according to the network.

"The day they said we have a heart for you, I was glowing," Tyson said. "They said it was a perfect match. And I couldn't wait. Because I had already missed a month of my daughter's life."

As part of the routine preparations for the transplant, Tyson's blood was screened for antibodies that could react adversely to the new heart.

A negligible amount was found, doctors said. So the swift and violent rejection of the first heart that occurred about 1 a.m., within two hours of completion of the transplant, baffled doctors.

Antibodies began attacking the heart, as one doctor said, "like a wild animal." Tyson's new heart became sluggish, losing its ability to pump. Doctors reacted at first by administering massive doses of immuno-suppressants in an attempt to stem what seemed like a sudden turn toward death.

By 3 a.m., doctors gave up hope of saving the heart. Tyson was suffering a massive rejection. She needed another heart.

A call was placed to the Washington Consortium. Tyson was now a top priority to receive a heart, anywhere in the nation, because her life was in immediate jeopardy.

A search began to find an organ that could be transported within four hours, the time a heart can be kept healthy outside a body.

A hospital in Florida responded. It had a heart, meeting Tyson's needs, that matched no one in its area.

Pfister chartered a jet to Tampa and back. Doctors at Washington Hospital Center prepared Tyson for the next operation. They re-tested her blood to try to figure out what had caused the reaction.

A sample of her blood, drawn and retained before the transplant, produced the same results of the original screen: no reasons for concern. But a test of her blood after the transplant showed extremely high levels of antibodies.

"Something happened to her immune system following the first transplant. And we don't know what. The patient's own immune system became very hyperactive for unexplained reasons," Boyce said.

To try to increase Tyson's odds, doctors conducted a plasmapheresis, cleaning her blood of reactive antibodies and hoping to avoid a possible second, and likely fatal, rejection.

Pfister arrived at National Airport with his cargo of last hope for Tyson shortly before 5:30 p.m., and went by helicopter to Washington Hospital Center.

Tyson was being kept alive on a heart-lung machine. The heart was secured in her chest 3 hours and 20 minutes after it left its donor.

Fortunately for her, the huge medical bills she incurred were paid by her health insurance.

Tyson returned home this week, wearing a present from her family: a T-shirt festooned with a big red heart and the words: Can't Touch This.

She can care, in part, for her 12-pound daughter, Antinique, although she cannot lift the baby because of the strain. Laid off from her job working on a word processor two months before the baby was born, Tyson plans to use her unexpected vacation to make up for some lost time.

"I thank God every day for everything. I've been advised not to have any more children. So," she said, touching Antinique's cheek, "I'm blessed to have her."