Last December, just at a time in his life when he felt he had everything to live for, 56-year-old comic Jerry Lewis felt sharp jabs of pain in his side one night, took two Tums for indigestion and very nearly died laughing at the threat of fatal heart failure.

Lewis already had come through a bitter, splashy chronicled split from his wife of 36 years, Patti, and was starting afresh in Las Vegas with dancer Sandra "Sam" Pitnick, 32. Patti remained in the Bel Air mansion they once shared with their six sons while it was placed on the market for $7.5 million. The divorce recently became final and he and Sam were planning to marry in February.

Lewis' career was in its best shape in years. A self-lacerating autobiography, Jerry Lewis: In Person, was off his chest and in the bookstores, detailing, for instance, his recovery from an eight-year addiction to Percodan to deaden chronic pain from a spine injury. Three movies were in the pipeline for 1983- the most awaited was Martin Scorsese's The King Of Comedy, with Robert DeNiro, set to open Feb.18. The film is sure to stun critics and fans, for it features Lewis in a mold-breaking straight dramatic role.

But a renewed career was far from Jerry's mind as the pains persisted the following morning. "I knew I was in trouble," Lewis recalls. "I had eaten lightly the night before. I told Sam, 'This is no indigestion. I'm having a heart attack.'"

Lewis knew exactly what had hit. One of his close friends- and idols- is famed heart surgeon Dr. Michael Debakey. "I've scrubbed with him in operating rooms," says Lewis, who carries DeBakey's picture in his wallet and has also taken some graphic photos of patients during Debakey's open heart operations. By the time tests were administered at the nearby Desert Springs hospital, Lewis had self-diagnosed a "critical heart attack. Suddenly my eyes rolled, the pain was a son-of-a-bitch, and they stuck nitro under my tongue. Next thing I knew, I was in ICU. My kind of heart attack is the worst. It's like a TV going off at night when they say 'That concludes our programming for today.' I felt my body freeze. If they don't catch it in time, your heart muscle stops, you're dead."

The muscle did stop- and he was dead, clinically, for seconds. As DeBakey flew in from Houston on a chartered jet to be with Lewis and consult on his treatment, Dr Harold Feikes performed emergency double by-pass surgery to open an artery 90 percent shut- in part, Lewis assumes, due to four packs daily of French Gauloises plus junk food.

"Fear and a little knowledge," Lewis now recalls, "are very dangerous. You know they use a retractor to open your ribs 14 inches, you know they tie you up inside with something like piano wire. When the doctor said 'Start surgery,' I was thinking Black & Decker."

Lewis beleives that being famous added to his woes. "You could die from being a celebrity," he says. "Some medical personnel are intimidated and move with uncertainty. It's scary because in medicine, time is the difference between making it or not."

When Jerry awoke after the two-and-a-half hour operation, DeBakey was standing by his bed. "I went to hug him, but my arms were tied down, I had stuff in my mouth- pipes, tubes," Lewis remembers. With recovery (he was in the hospital eight days) came the emotional ups and downs that doctors advised were typical. "You go into a state of tearies that you don't lose for four weeks," says Lewis.

Jerry got particularly weepy over missing his Shih tzu, Angel. "I kept asking Sam if I could just hold her. I was literally sobbing." When Sam got the dog into the hospital through security, Jerry was thrilled. "But I had to put pillows on my chest to protect my incision from her claws." Despite the ordeal, Sam recalls, Jerry's one-liners continued to flow." There's a lot of metal in you," Sam remembers saying. "I hope you don't rust."

Indeed, Lewis is likely to shine before he rusts. He now feels he owns a new heart and is mending right on cue. If they had just given me medication, I would have had to live with a time bomb. It was Sam who made it crystal clear what would happen if I'd not had the surgery. You carry nitro; you take medication; you think, 'What day is it going to happen?' I'm not the kind of person who could cope with that."

If Lewis had any vision of the beyond, he says it wasn't paradise. "No white picket fences, no little girls in white. Just black and bleak. But now I feel my body is clear, my mind is clear. I took out a loan. It's a miracle. I've been given another chance."

Certainly, The King Of Comedy will revive one of America's most celebrated Hollywood careers. The film is thematically dark, and Lewis is unnervingly subdued as a Johnny Carson-type TV star who becomes perilously entwined in a scheme by a whacked-out stand-up novice (De Niro) to get his big break on Lewis' show.

Though Scorcese and De Niro, who teamed up for Mean Streets, Taxi Driver and Raging Bull, have been his fans, they didn't make it easy for Lewis, who almost always retains directorial star control of his own projects. This time he didn't ask for it. Instead, they imposed the madness in their Method-acting tricks on the Old Pro. DeNiro, for instance, refused to have dinner with Lewis during the New York shooting because of their adversary relationship in the film. "I wanna blow your head off," Jerry remembers De Niro telling him. "How can we have dinner?"

There were bizarre tirades designed to pump up Lewis' anger. Once, when Lewis was required to explode at him, DeNiro opened their scene by hurling anti-semitic epithets and insisting that the Jews have "turned this world into garbage for 5000 years."

Naturally, the ploy worked to perfection. "I forgot the cameras were there," Lewis says. "At the end, Marty couldn't just say 'cut.' I was going for Bobby's throat."

Traditionalist Lewis also arrived on time, if not early, for 9 a. calls; Scorsese and De Niro usually rolled in by midafternoon. "'What is this?' I asked myself. I saw the crew giggling when I arrive. It goes against my filmmaking," says Lewis, winner of eight best director awards internationally. "It's carelessness, a studied undisciplined discipline. But he gets it onscreen."

There were other eye-openers. "When I saw Take 29 for a scene with no words- just walking from a theater to a limo- I said, 'We're in a mess.' I never saw the number 29 before in my career! When I saw we had four pages of dialogue the next day, I said to one of the crew, "if this doesn't go to 136 takes, I'll buy your car.'" Yet Lewis, who rarely needed three takes for any scene, no matter how physically complex, came away a dedicated DeNiro fan. "Take 1, Bobby's getting oriented. By 10, you're watching magic. By 15, you're seeing genius."

If anything has helped pull America's ageless clown through the recent trials, friends agree, it is the etite, soft-spoken Sam. They met in early 1979, when Lewis auditioned 150 disco dancers for his Hardly Working film. Pitnick, a former stewardess, divorced, native of North Carolina, had danced with the Harness Ballet Company. "She was the best dancer of them all,"Lewis glows. She got the part, then flowers and thanks. "I didn't see her again for a week," he recalls. "When I'm filming, I'm so involved I can't tell a boy from a girl, a dog from a horse." But he clearly knew a good match when he saw one, and they've been together ever since.

Lewis is quick to note Sam did not end his marriage. "I had aready made plans to change my life long before. It wasn't the case of Sam creating the problem with Patti. I wasn't making anybody happy the way I was."

Sam seems to be doing it. But Jerry's new life with her provoked some bitter confrontations with his sons, now 19 to 37. Scott, an assistant film director, recently reminded Lewis of something he had once told Scott last year: "I love you but I didn't work my fingers to the bone for you or your mother. I did it all for me. All of you got in the way, and so I'm releasing myself from those obstacles to see if I can enjoy my life totally."

The wounds have been slow to heal. Not long ago, at a dinner with Chris,25, Chris' bride-to-be and Sam, Lewis says his son couldn't look him in the eye. "I'm almost resentful the boys weren't quicker in coming around to me. I wanted to be in his eyes, where I belonged. There was nothing like the closeness I had had with my sons."

Not surprisingly, Lewis' often brutal self-eamination led to worry about his other "kids"- the millions of muscular dystrophy victims on whose behalf his tireless telethon crusade has raised a phenomenal $500 million over 32 years. Lewis feared a tarnished public image would hurt their cause. "That was my biggest responsibility," he says. "And that kept me from moving sooner. I will not stop doing what I do until I beat MD."

Lewis' earlier missions in life were far less lofty. The son of show business parents , Lewis casts himself as a New Jersey misfit who dreamed of murdering his grandfather, resenting his parents for not attending his bar mitzvah, and often got into fistfights with anti-semites. His marriage, at 18, to singer Patti Palmer- six years his senior and a catholic- helped stabilize his life.But it was his eventual team-up with Dean Martin that dazzled a generation of slapstick-happy movie fans the world over through 16 movies until the duo split (over personality conflicts) in 1956. They rarely speak now (Martin has not called since the bypass), and though Lewis remains tentatively open to a reunion, he figures Martin isn't. "I don't think it's in the cards," says Jerry. "Our life-styles and careers are separate and apart. But if you told me he was outside right now, it would be a joy to jump on his neck."

With a 14 inch scar along one calf- where a healthy vein was removed for insertion near the heart- another red slash bisecting his chest, Lewis' joys these days will be more sedate. He and Sam are "heat people", who thrive in the Las Vegas climate. Their small house is loaded with pictures of clowns, electronic gadgets and photo equipment for Jerry's passionate hobby. his five-handicap golf game will have to wait, since he's limited to 200 yard strolls while recuperating. He's cold-turkey cigarettes, cleaned up his diet, and still does not drink. There is plenty of work ahead.

Lewis hopes to resume editing his starring vehicle Smorgasbord, set for summer release; he hopes to re-edit the film version of Kurt Vonnegut's novel Slapstick, in which he also stars, before its American release. And he would like to write and act in a French film, shot in Paris, where he has reigned as King of Comedy for three decades.

Lewis has crammed a lot of learning into the past few sobering years. "I don't want the Beverly Hills cocktail circuit. I haven't got time for people who ask how your grandchild is and don't listen to your answer. I haven't got the time to be diminished. It's taken me a long time to feel I'm worth something." {written by Jim Jerome, reported by Doris Klein Bacon}