Princeton businesswoman Kim Pimley serves on nonprofit boards, ran for mayor a few years back, and keeps in shape by bashing a 150-pound punching bag.

The type of person who runs up escalators, the 55-year-old was always overflowing with energy.

Until, all of a sudden, she wasn't.

She started to feel short of breath in early January, and wondered whether she had caught a bug. But she felt progressively worse, at one point unable to climb the stairs without sitting to rest halfway up. Within days she was sent to the Hospital of the University of Pennsylvania, where she received unthinkable news:

A rare, aggressive disease, its cause unknown, was attacking her heart. She needed a transplant, and fast.

Events unfolded in rat-a-tat succession, best appreciated in a timeline.

It is a story both of fast-acting physicians who made the right calls, and of a savvy patient who never stopped asking questions.

Otherwise she might not be around to tell the tale.

Monday, Jan. 11

Pimley called her primary-care doctor after several days of feeling breathless. Less than a week earlier, she and her son Oliver had come home from a trip to Hawaii, where she had felt great. Mother and son had done three six-hour sessions of Krav Maga, the self-defense regimen developed by the Israeli military.

She was ready to plunge back into work with her husband, Michael, providing training programs for banks and insurance companies. In her spare time, she planned to prepare for a meeting of the Princeton HealthCare System board of trustees, which she chairs.

But first came that medical visit.

Pimley had suffered a bad bout of bronchitis in November. The doctor suspected this was the same thing, and prescribed an inhaler.

She was not convinced.

"Could I have a prescription for a chest X-ray?" she asked.

The doctor obliged, but said Pimley could wait up to a week to get it done.

Tuesday, Jan. 12

Pimley got it done the very next day. After getting the results, the doctor called that evening and told Pimley she had fluid around her lungs.

He told her to see a pulmonologist as soon as possible.

Wednesday, Jan. 13

Feeling even worse, Pimley managed to drive herself to her 3 p.m. appointment but parked on the wrong side of the building.

She felt tired just walking to the pulmonologist's door.

"He took one look at me and said: 'You need to go to the emergency room.' " she recalled.

Pimley felt able to drive herself but was worried about the long walk to her car, so the obliging doctor agreed to fetch it for her.

Pimley knew University Medical Center of Princeton at Plainsboro well, as it is part of the system whose board she leads.

But this was her first time there as a patient.

Thursday, Jan. 14

Cardiologist Andrew Costin knew Kim Pimley socially, and loved her vivacious spirit and energy.

"She would be the last person that you would think would have heart disease," he said.

Test results told another story.

A key measure of a heart's pumping ability is the ejection fraction of the left ventricle. A healthy level is 60 percent. Pimley's measured 25.

Costin knew that the next step was a catheterization to check for coronary disease, but because of her rapid decline and irregular heartbeat, he suspected that was not the answer.

He wondered whether she had some kind of myocarditis - an inflammation of the heart muscle - which has a wide range of causes, including various viruses and bacteria. Her condition was so poor that he suspected she might need a heart biopsy, which a community hospital such as Princeton could not offer.

Within hours, Pimley was in an ambulance to the Hospital of the University of Pennsylvania.

In the case of a patient suffering heart trouble, a hospital commonly performs a coronary angiogram to rule out arterial blockage.

But when cardiologist Anjali Vaidya examined Pimley at Penn, the swift decline and odd heart rhythm led her to the same conclusion as Costin. Classic heart disease did not fit.

"This is a very healthy woman who all of a sudden could not walk across the room," Vaidya said.

She spoke to Penn cardiology colleague Daniel Kolansky, who agreed to skip the angiogram and do a biopsy, going in through a vein in Pimley's neck to extract tiny samples of heart tissue. Kolansky also put in an intra-aortic balloon pump to boost the patient's blood flow.

Vaidya shared Costin's suspicion of myocarditis, but suspected it might be a very rare kind: giant cell myocarditis, in which the heart is "invaded" by abnormal cells of unknown origin, disrupting the organ's rhythm.

The disease has been reported just a few hundred times in the medical literature, and Vaidya had seen just a handful of such cases. The physician was so concerned that even before the biopsy results came back, she asked Pimley to sign a consent form to be evaluated for a heart transplant.

Pimley's husband got there that night, racing back from a business trip in Atlanta. And their son, who had returned to Tokyo for his job teaching English, made plans to jump on a plane back to the United States.

Friday, Jan. 15

Pimley was going downhill fast. Early in the morning, her heart raced into persistent ventricular tachycardia, a dangerously rapid, irregular rhythm. She went into cardiogenic shock, meaning the heart could not deliver adequate blood to the body and was at risk of stopping entirely. She was placed on extracorporeal membrane oxygenation, a form of life support.

By mid-morning, the biopsy results came back.

Bingo. Giant cell myocarditis.

One theory is that the disease is triggered by an autoimmune response, so some doctors have treated it with immune-suppressing drugs.

But Pimley was so sick that Vaidya thought that approach would not get the job done. That afternoon, Penn's heart transplant team convened an emergency meeting and decided that she should be listed for transplant in category 1A, the most urgent.

Monday, Jan. 18

Pimley was in luck. A possible donor heart was identified Sunday night, and by the next morning it was confirmed as a good match based on size, blood type and other factors.

Even as she grew so dangerously ill, the patient who was also a hospital board member kept asking questions, quizzing caregivers about her vital statistics or the function of this or that piece of equipment.

"This, on a kind of intellectual level, was interesting, and maybe it helped me," she said. "It was really fun to be up all night, asking the nurses about their jobs, and how they input data. I got kind of excited every time they took blood."

Surgeon Pavan Atluri went to work early that morning. Pimley was back in the intensive-care unit by early afternoon, and went home two weeks later.

Little by little, her energy level is building back to normal. She must take close to 40 pills a day: immune-suppressing drugs, antibacterials, multivitamins, anti-nausea medicine, anti-clotting agents.

She wonders whether her November bout of bronchitis somehow triggered the freak crisis. Vaidya said that is unlikely, and that the real culprit was probably some sort of poorly understood autoimmune reaction. In rare cases, the physician said, it could even happen again.

But all seems well, and Pimley made it to the March 14 board meeting of the hospital system where she was first treated.

"I don't think consciously, 'I have this new heart, How's it doing?' " she said. "I just know that it feels really good."

Soon, she will undergo a cardiac stress test, in order to be cleared for full activity.

Including, she is quick to say, a few jabs at her 150-pound punching bag.