Nancy Boucot Cummings read almost everything there was to read in the past two weeks about the first successful artificial heart transplant. But for all her excitement, she said she felt some ambivalence over the coverage of the operation.

"Science is usually not breakthroughs," said Cummings, a kidney disease specialist who serves as associate director of the National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases. "It's a lot of careful work and suddenly there's somebody who synthesizes it. But you have disappointments. A year's worth of work can produce a negative result. It's a difficult thing."

A breakthrough such as the operation that gave a dying dentist the benefit of the latest development in high-technology medicine can spur new interest in -- and, more importantly, new funds for -- medical research, she says. But she says she worries that the publicity surrounding cures for desperate illness can obscure the importance of more methodical research into the causes of disease, research that ideally would make this sort of last-ditch technology unnecessary.

She also worries that the emphasis on new medical technology and its role in preserving life obscures two of the most difficult issues in health policy: Can a nation set an upper limit on the money spent to keep people alive? And what kind of life is inherited by the patients saved by the new technology?

For the past 10 years, Cummings has had a rare vantage point on these issues, because she has been in a position to help allocate the $40 million the National Institutes of Health spent last year on kidney disease, which has its own expensive miracle technology, kidney dialysis.

In 1972, Congress committed the government to providing kidney dialysis -- a life-saving treatment for people whose kidneys have stopped working -- to everyone who needed it. Within three years, the costs of the dialysis program had increased far beyond expectations.

In 1982, the federal government is spending an estimated $1.8 billion to support the treatment of about 70,000 patients with kidney failure. Between 65 and 75 percent of that money will go to hospitals and medical centers that provide dialysis.

Compared with the artificial heart transplanted into the chest of Barney B. Clark, which tethers him to an external unit that sits on a "grocery cart" and weighs 375 pounds, dialysis is hardly confining. Patients must be hooked up to a machine for several hours two or three times a week, to have impurities removed from their blood.

But even so, Cummings says, the suicide rate for dialysis patients is similar to that of cancer patients. "Chronic therapies don't have a quality of life that most people would accept," she notes.

Not that she opposes the idea of using medical technology to save lives. But she wants a continuing balance between research that controls disease in its final stage and study that leads to an understanding of how diseases begin and develop.

The complex process of sifting through research proposals involves a large network of independent researchers, medical schools and research institutions. Cummings' day-to-day (and night-to-night) work is taken up with the minutiae of meetings and medical journals, but her aim is to pinpoint areas where more research is needed, areas where research into kidney disease will do most good.

Like science itself, such scientific management is inevitably inexact. The proposals recommended for NIH support by a panel of kidney specialists are passed on to Cummings who reads "as much as I can of them -- all the best submissions and the borderline ones." NIH is currently funding some 269 kidney research projects, with the emphasis divided between end-stage renal disease treatments like dialysis and research into causes and prevention.

Cummings is also preparing to chair a panel discussion of the ethical questions generated by expensive therapies next year at an international medical meeting. "We can do so many things now with medicine, you have to begin to ask if we're doing too much. . . . You can't leave these decisions to physicians. Our responsibility is to try and save lives. The question is at what point do you stop? Some people have done extraordinary things after they've gone on dialysis. And some have lived for five years -- which on paper looks very good. But no one talks about the quality of their life. That's the real dilemma."