As luck would have it, the boy who usually mows Frances Leatherman's lawn did not come that Saturday two months ago. So Leatherman, who prides herself on the neat and orderly appearance of her yard, decided to do the job herself. Her husband, who it so happens is also named Francis--people call him Frank and he calls her Frannie-- suffers from congestive heart failure. Frank has to take it easy. So he was down in the basement watching a baseball game on television while his wife mowed the lawn.

Lately, Frances Leatherman, who is in her late 60s, had been having chest pains and her doctor in Hagerstown, Robert Brull, had sent her for tests. Those tests showed she had a heart problem. She was scheduled for more tests at Georgetown University Hospital in Washington. She was planning to postpone the tests, though, so she and her husband could take their Airstream trailer down to Florida and do some fishing.

Leatherman figured she had angina --chest pains caused by constricted arteries around the heart--as her mother had. Her doctor had said she could mow the lawn if she didn't overdo it. Pushing the power mower over the grass, she stopped three times to rest. The third time, she found it difficult to walk up the patio steps. By the time she got to the kitchen, she knew something was wrong. Then she passed out.

Frank Leatherman heard his wife's body hit the floor. Despite doctor's orders to the contrary, he raced up the steps three at a time. He found his wife unconscious and turning purple. Although not formally trained, he began administering cardiopulmonary resuscitation. Frances Leatherman believes her husband saved her life.

She was taken by ambulance from Ringgold, the little town where they live, to Hagerstown Hospital. Nine days later Frank drove her to Georgetown University Hospital. At Georgetown, she met David Pearle, a 40- year-old Dallas native and graduate of Amherst College and Harvard Medical School. Pearle is a cardiologist who spends much of each day diagnosing cases like Frances Leatherman's. He uses an extremely fine plastic tube passed up an artery and a vein into the heart to test its performance--a process known as cardiac catheterization. Although once a risky procedure, cardiac catheterizations are now considered relatively safe and essential for diagnosis. In Leatherman's case, Pearle used the femoral artery and vein on her right leg. After she was given a sedative and local anesthesia, Pearle inserted the tubing into the blood vessels and passed up to measure pressure in her heart chambers. Radioactive dye was then injected into the tubing and tracked by X-ray to show her heart in motion.

The X-ray motion pictures showed that Frances Leatherman's coronary arteries were constricted by plaque. The more severe problem, however, was that her aortic valve, the final gate through which oxygen-rich blood must pass before leaving the heart for the body, had become encrusted with calcium. The calcium made the valve, which consists of tissue-thin membrane, much stiffer and heavier than normal. The valve opening was only one-seventh of what it should have been. The combination of the coronary artery disease and the calcified aortic valve put a double strain on Frances Leatherman's heart. While her heart had to work much harder to pump blood out, the constricted arteries were limiting the blood being supplied to the overworked muscle.

Pearle's message to the Leathermans was simple: If the valve were not replaced, in the next six months she probably would have another incident. More than likely, the next episode would kill her.

Frances Leatherman understood that the chances were 1 in 20 that she would die during the operation. But she didn't see that as much of a risk. If she didn't survive, she said the day before the operation, "I haven't lost anything. I was going to lose anyway. I think if you take that attitude, it's better, 'cause there's nothing I can do about it. Maybe I shouldn't be like that, but that's the way I am."

Frances Leatherman was scheduled to be operated on the afternoon of May 27 by Nevin Katz (he pronounces it "cots"), a 38-year-old surgeon whose professional ambition is to know everything there is to be known about the heart. That morning, however, she became nauseated and developed a fever. Katz decided she had a flu. Fifteen minutes before the operation was scheduled to begin, Katz decided to postpone it until she had recovered. By May 29, he was able to set a tentative date of June 2.

The day before the operation, Frances Leatherman said she was without anxiety, at peace with the world. She kissed her husband goodbye when he left, giving him a little pep talk, and sent him home.

"I'm in good hands," she told a visitor. "That's a wonderful feeling. I'm not only in the hands of the doctors-- these wonderful physicians here--I'm in the hands of the Great Physician and I know I've got an appointment and if this is the appointment, I'm ready for that, too."

At 6 a.m. on June 2, Frances Leatherman was given an injection of morphine and scopolamine to sedate her. She was lifted from her bed, placed on a gurney and covered with a sheet. Then she was wheeled 100 feet down the corridor to the elevator that would take her down six floors to the operating room.