In a major policy change, the government this fall will start paying for a limited number of heart transplants for Medicare beneficiaries, expected to total 65 the first year and 143 annually in five years, Secretary of Health and Human Services Otis R. Bowen announced yesterday.

"Heart transplants, when performed in specialized facilities by trained personnel on patients who have been carefully screened, will be considered reasonable and necessary treatment and will be covered by the Medicare program," Bowen said. The decision, he said, "was made by me with the concurrence of the president."

The announcement begins a new era for the government, adding to Medicare a major high-cost procedure previously considered experimental and opening the door for decisions in the future on liver, pancreas and other such procedures if they prove out medically.

Medicare, primarily designed for elderly Americans, has 30 million beneficiaries. But because of the medical standards expected to be used by major transplant centers to choose eligible heart recipients, most if not all Medicare beneficiaries 65 and over will not be eligible for Medicare-paid transplants.

Existing standards generally followed by transplant facilities require that the candidate be in vigorous health, likely to withstand the rigorous procedure and aftermath and have no complicating conditions. People over about 55 (the age standard is not a hard-and-fast one) generally are not considered good candidates.

The Medicare administrator, Dr. William L. Roper, said that while no absolute age cutoff is being set by Medicare, he expects the estimated 10 major medical centers that the government will choose to perform heart transplants eligible for Medicare reimbursement will follow accepted medical criteria.

As a result, most recipients will be chosen from the nearly 3 million disabled persons under 65 who are eligible for Medicare because they are receiving Social Security disability insurance. This group ranges in age anywhere from the 20s up.

The estimated cost to Medicare will be $5 million the first year and $25 million the fifth year.

A transplant costs from $100,000 to $200,000 and there are follow-up expenses as well. The Medicare payments will not cover out-of-hospital costs for immuno-suppressant drugs designed to prevent rejection of the heart by the body tissue, which run about $5,000 a year.

Sen. Albert Gore Jr. (D-Tenn.), who has been pressing for Medicare heart transplants for more than a year, praised the decision but said, "The policy won't work unless Medicare provides the immuno-suppressant drugs once the patient goes home that make transplants work."

Although 730 heart transplants were performed nationwide last year on people of all ages and 300 more in the first three months of this year, Medicare has never paid for heart transplants on a regular basis since it regarded them as experimental. The program does pay for kidney transplants.

The issue of Medicare heart transplants has been under study for several years. A year ago, then-HHS Secretary Margaret M. Heckler proposed to go ahead but was blocked by the White House, in part out of fear that costs would balloon if medical standards were later broadened.

John Marshall, director of the HHS National Center for Health Services Research, said that from 1,400 to 2,000 people a year nationwide could benefit from heart transplants under existing standards that limit transplants to persons on "the low side of middle age with no complicating diseases."

The difficulty of obtaining donor hearts, however, has held the number of transplants to a much lower figure. Marshall said it is estimated that at maximum only 7,000 to 8,000 usable hearts a year would be available for transplant.

Medicare often is followed by other medical systems once it makes a decision on a policy, and yesterday's announcement is expected to spur heart transplants in other programs.

Roper said that 25 states allow such transplants in their state Medicaid programs, and the Veterans Administration permits them, mainly at its Richmond medical center. The Civilian Health and Medical Program of the Uniformed Services (CHAMPUS) for military personnel and dependents is considering the issue, while the Indian Health Service does not pay for transplants. Many nongovernment insurance programs already cover heart transplants.