Bernadine P. Healy, research director of the Cleveland Clinic and former head of the American Heart Association, is the leading candidate to become the next director of the National Institutes of Health, federal health officials said yesterday.

The NIH directorate, one of the most critical positions in the federal health establishment, has been vacant for more than a year, as Health and Human Services Secretary Louis W. Sullivan has struggled to find someone to fill the demanding and politically sensitive post. At least four other scientists have reportedly turned down the NIH post, most recently William Danforth, the chancellor of Washington University in St. Louis, in part because of concern that the post carried with it an obligation to back the administration's antiabortion agenda.

Healy's name surfaced several weeks ago on a short list of candidates that included the deans of the Stanford and Yale medical schools. Federal officials confirmed yesterday that although her name has not yet been sent to the White House for final clearance, she is the leading candidate.

Healy, 46, a cardiologist by training, has been president of the American Federation for Clinical Research, head of the American Heart Association and deputy director, from 1984 to 1986, of the White House Office of Science and Technology Policy. If President Bush approves her candidacy and it is confirmed by the Senate, she would be the 13th director of the sprawling, world-renowned Bethesda research campus and the first woman to hold the prestigious post.

She could not be reached for comment.

Antiabortion groups expressed reservations yesterday about Healy's candidacy because of her position on fetal-tissue research, one of the most controversial biomedical issues. In 1986 she was on an NIH advisory panel that recommended that the government fund research using tissue taken from aborted fetuses, a recommendation subsequently overruled by both the Reagan and Bush administrations and condemned by the antiabortion movement.

Healy is said to be personally opposed to abortion.