Public Citizen Health Research Group, a nonprofit advocacy organization founded by Ralph Nader, has asked the Food and Drug Administration to order the manufacturer of a flawed heart valve that has been withdrawn from the market to notify those still wearing the device of possible risks.

A recent congressional report stated that 389 fractures, resulting in 248 deaths, have been linked to the valve and were reported to the FDA. The artificial heart valve, implanted in the chests of 86,000 Americans between 1977 and 1986, is manufactured by Shiley Co., a subsidiary of Pfizer Inc., the giant pharmaceutical firm. The trade name of the valve is the Bjork-Shiley Convexo-Concave, or BSCC valve.

Shiley opposed a 1984 recall effort by Public Citizen. In November 1986, the company announced that all unimplanted valves would be withdrawn from the market. Shiley officials said last week they withdrew the valve because of "bad publicity." An FDA spokesman said the withdrawal occurred as the agency was preparing to take action against Shiley.

Although Public Citizen says it thinks consumers should be told about the possible risks, Shiley officials disagree. "Our policy is one of notifying physicians rather than patients on sensitive matters," said spokesman Tony Biesada. "It remains FDA's position as well as ours."

Public Citizen's request comes as the FDA is reviewing that policy. So far, the agency has held two public meetings to assess whether patients, as well as physicians, should be informed about the potential dangers of medical devices.

Public Citizen has asked that Shiley send a letter to patients who wear the valve, describing symptoms of failure and listing hospitals where open heart surgery can be performed. The letter, Public Citizen officials say, should list signs and symptoms that indicate the valve has failed: the loss of the prosthetic "click" or sound that a working valve makes, dizziness, shortness of breath, chest pain and irregular or unusual heartbeat.