Doctors at Harvard affiliated Brigham and Women's Hospital (BWH) yesterday morning performed the second heart transplant operation in New England, only eight days after the same team successfully completed the first one.

The recipient, 16 year-old Matthew Shelales of Bolton, was listed in critical but stable condition last night after the four-hour operation.

Medical School Professor of Surgery John J. Collins Jr., who headed the transplant team, said yesterday that the procedure "had gone smoothly," and added that the fact that Shelales was a teenager did not complicate the operation.

Dr. Gilbert H. Mudge, assistant professor of medicine and a member of the team, told WNAC-TV last night that Shelales was "scared but relieved." He added, "he's been waiting a long time."

The identity of the donor has not been revealed but the heart was apparently taken from a patient at St. Vincent's Hospital in Worcester.

According to a WNAC-TV report, the donor was a 41-year-old woman who died of a cerebral hemorrhage, and who had two sons, one of whom is Shelales' age.

Shelales has been suffering for seven months from a terminal disease involving deterioration of the heart muscles called cardiomyopathy.

His doctors estimated that without the transplant his chance of surviving for six months was less that 15 percent.

The procedure was slightly longer than the three-and-a-half-hour operation last week on 43-year-old Gerald Boucher, a South Hadley pharmacist who received a heart from a Connecticut nurse who died of injuries received in an auto accident.

Eight days after his operation. Boucher is now listed in satisfactory condition, and doctors report that there has been no evidence that his new heart is being rejected. Doctors said Shelales' condition before the operation was worse than Boucher's had been.

The Massachusetts Department of Public Health has been approving heart transplants on a case-by-case basis since early January. Although Shelales was the first candidate approved at BWH, a suitable donor was first found for Boucher. Massachusetts is the only state in the country to require state approval for heart transplants.

The first case approved by the state was a patient at Tufts Medical Center, who died before a donor could be found.

The doctors who performed the operation--including Collins, Mudge, Professor of Surgery Lawrence H. Cohn, and Dr. Robert J. Shemin--all participated in last week's transplant. Shemin transported the donor heart from Worcester in the same picnic cooler used last week to carry Boucher's new organ.

A major factor in the success of last week's transplant was the drug Cyclosporin A, an immunosuppressant whose function is to reduce the chances that the patients body will reject the donor organ.

Cyclosporin A was developed four years ago and has been used by a handful of hospitals since then. It was formally approved by the FDA in November, 1983, and has been credited with improved success rates in liver, kidney, and heart transplants.

Although the possibility has emerged of several Harvard hospitals together starting a heart transplant program, as four have already done this fall to coordinate liver transplants, a spokesman for BWH yesterday said it was unlikely that the hospital would join such a consortium.

"We've been approaching this as an individual institution; not as a group as the liver people have done," she said.