MCI Communications Corp. Chairman William G. McGowan, who six weeks ago resumed working full time, said yesterday that he frequently thinks about how close he came to death after a heart attack last December.

Last spring, he had a heart transplant. "It's a helluva way to diet," McGowan said yesterday. He weighs 165 pounds, down from 180 before the heart attack.

"Now I sleep so well, I feel so good."

McGowan, 59, had a heart attack in December after he and his wife, businesswoman Sue Gin, had attended an arts and crafts fair near Norfolk. He underwent a transplant in April at the Presbyterian-University Hospital in Pittsburgh after his heart continued to deteriorate.

McGowan said a delay in receiving a human heart almost led doctors to implant an artificial heart at the last moment.

"They opened me up and there was no heart {ready for a transplant}... . I waited for an hour and a half," he said.

If a donor heart had not become available, an artificial Jarvik heart would have been used for the interim, he said.

Recovery was agonizing, he said. "I was receiving four drugs at the same time, the mental and physical trauma after nine hours of operation ... it was a blur, and they kept it that way."

McGowan now must take a combination of the steroid prednisone and the antibiotic cyclosporin to prevent the rejection of his new heart. He used to smoke two packs a day; now he's given up cigarettes as well as high-cholesterol food.

He notes that the survival rate for patients his age with transplants is 90 percent for the first year and 60 to 70 percent for more than five years.

With much of the trauma behind him, McGowan now turns his attention to a corporate strategy he set in motion before his heart attack: turning the company he founded into a global information services provider.

That plan includes the introduction of operator services, direct dialing by the first half of 1988 to more than 140 countries and the acquisition of RCA Global Communications, which will give MCI a 40 percent market share in the international telex business.

McGowan's heart attack came at a bleak time in MCI's history: a $448 million loss in 1986 on revenue of $3.6 billion, the first time the company had been in the red.

"In many ways it might have been good that I wasn't here for that period of time," McGowan said.

"They introduced a lot of new services that had been in long term planning, but I probably would have been pushing for more new services. But to stick with that plan ... turned out ot be good."

McGowan himself planned for the massive write-off of network assets and a staff cut of 15 percent. He was negotiating the purchase of ITT Corp.'s international telex business, a deal that eventually was done with RCA instead. "The only thing that really changed after I left was that our negotiations with ITT failed and we picked up RCA -- but it was the same deal," he said.

The strategy has worked, bringing MCI solidly back to the black this year. MCI posted $32.6 million in profits the first six months of this year. Analysts expect net profits for 1987 of at least $73 million.

V. Orville Wright, company vice chairman who was called out of retirement in April at McGowan's request to become acting chief executive officer, said McGowan is no longer the sole commander of the company.

McGowan and Wright, 66, share the office of chief executive. All decisions made at MCI will be a "consensus" between McGowan and Wright, Wright said.