THE FIRST HUMAN implantation of a mechanical heart is being hailed as the cardiac equivalent of man's first step on the moon. Despite the poignancy and drama of the surgical extravaganza in Salt Lake City, it should be recognized for what it is: a medical high-wire act that is grotesque in terms of the welfare of the patient and nearly worthless in its avowed purpose of advancing the healing arts.

The valid and obvious argument about the misdirection of costly medical and research resources -- $160 million over 10 years -- requires no elaboration, especially in this period of scarcity and deprivation for many Americans.

Less obvious, and perhaps more significant, is that the mechanical heart is the product of a technological exuberance tied to philosophical bankruptcy. The implantation was done because it could be done, not because by any rational standard it was worth doing.

The potential benefit for the pioneering patient can be dramatically formulated as life versus death, but what kind of life, for how long, and at what cost to others? The answers to those questions are considerably less glittering than the telegenic apparatus of mechanical heart implantation.

The surviving implant patient must be attached without interruption to a 350-pound compressor that powers the mechanical heart. The psychological effects of such a bizarre and threatening dependency are unknown. But physicians experienced with kidney dialysis patients point out that while many adapt successfully to their mechanical dependency -- which is periodic, rather than continuous -- a significant proportion are afflicted by depression and other psychological disorders.

In any case, with present knowledge, the life expectancy that experts foresee for mechanical heart-implant patients is not encouraging: less than a year for the average patient, according to an estimate by the congressional Office of Technology Assessment. With some 50,000 patients a year considered medically eligible for heart replacement, the cost is estimated at $24,000 to $75,000 per case, plus $1,800 to $8,800 per year for care.

The numbers, though uncertain and wide-ranging, are great. Even greater, though not subject to quantification, is the psychological toll that would be exacted from the families of survivors of this peculiar manifestation of medical inventiveness.

It can be argued, of course, that the first mechanical hearts, no matter how costly and awkward, represent necessary first steps toward more sophisticated and economical devices.

The answer is that in medicine, as in other endeavors, you make your choices and spend your money. The quest for a mechanical heart transplant is probably inevitable in a health-oriented, high-tech society, and it is apparently destined to be part of our great biomedical-research enterprise.

The unresolved issues are pace and priority. What is the purpose of rushing to the operating room with this cumbersome and primitive technology that obviously lacks an easily portable power source, particularly when that lack will be corrected eventually?

And in combating heart disease, the leading cause of medical disablement and death, are we getting the best buy for our money by promoting a technology that calls for gargantuan expenditures on a relatively small number of citizens, usually of extremely poor health and advanced age? Not likely.

That didn't forestall the Salt Lake City surgery enthusiasts from going ahead. The first mechanical heart was great drama, but contrary to the impression created by the surrounding hoopla, it wasn't one of the great moments in medicine.

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