Early on a june morning in a greenish operating room at Cornell Medical Center’s Presbyterian-New York Hospital, Wayne Isom stares at the exposed, beating heart of a prominent New York attorney. He is in the process of inducing a state of cardioplegia—stopping the organ so that he can operate on it. As the attorney’s heart, colored a sickly yellow, slows to a chug, Isom jokes and tells stories about growing up on a farm in West Texas. If he were not one of the most accomplished surgeons in the world, a bystander might be forgiven for feeling a bit queasy.

“My dad would never let me forget where I was from,” he drawls, watching the heart thump ever more feebly—an alarming effect. “Once, I’d just been elected to this prestigious medical organization and was feeling very proud and I went home to Idalou to visit, and the only thing Dad says when I arrive is, ‘Glad you showed up. A big storm’s on the way, and I’ve got corn to plant.’ I spent all weekend castrating sheep and hauling hay.”

The doctors, nurses, and technicians all laugh. Isom is a funny, engaging man, even when he is stopping a man’s heart. The laughter quickly subsides, and Isom’s team begins the more serious business of replacing the attorney’s damaged aortic valve. Now that his heart is completely stilled—his breathing and blood circulation are being handled by a heart-lung machine—Isom sets about trimming away the damaged valve with scissors.

Until recently the sixty-year-old Isom was just a brilliant heart surgeon. But in January he became famous by cracking open David Letterman’s chest and bypassing five of the television star’s coronary arteries. Letterman went to him for the same reasons thousands of other people have: because he is a rare combination of small-town charm and razor-sharp, big-city medical prowess, a genuinely nice man with a deep West Texas accent whom you would trust to cut open your chest. He grew up in Idalou; attended Texas Tech, in Lubbock, and Southwestern Medical School, in Dallas; received his medical and surgical training at the Dallas’ Parkland Hospital; then moved to New York University, which was at the time one of the leading medical schools in the nascent heart-bypass surgery revolution. After fifteen years at NYU, he was recruited to turn the cardiothoracic surgery department at Weill Medical College of Cornell University, in New York City, into one of the finest cardiac facilities in the nation. He did. Armed with lavish financial support, Isom built a cardiac-care facility that is almost a hospital within a hospital, with 112 beds, its own intensive-care unit, pharmacy, and staff of cardiologists, nurses, and technicians. It is the busiest hospital in the state (1,500 patients per year) and the only one recommended by U.S. News and World Report as a good choice for heart patients in New York.

Though he works long hours, Isom, like many heart surgeons, seems almost serenely driven. “There’s a little obsessive-compulsive in all of us [heart surgeons],” he admits. “For me, heart surgery is just like Friday night football games when I was a kid. I like the challenge and I like winning. You see people who are going to die quickly and you can change that. Larry King’s dad died of a heart attack when he was in his forties, and it’s gratifying that now Larry has lived into his sixties and gotten married and had kids at that age. It’s hard to put a price on that. And if somebody hadn’t done it, he’d have been dead.”

King was the first of Isom’s celebrity patients, in 1987. Since then, he has treated news anchor Walter Cronkite, late-night television host Jack Parr, architect Philip Johnson, violinist Isaac Stern, and Nixon Cabinet members William Rogers and William Simon, among many others. But it was the Letterman quintuple bypass this past January that finally put his name in lights. The Late Show host had a family history of heart trouble (his father had died of a heart attack at age 57) and his heart had shown irregularities during a stress test. Isom performed an angiogram and found a blockage of the left main stem of one of Letterman’s coronary arteries. “This sort of blockage can be particularly deadly,” says Isom. “I told him if he had a big problem with it, there’d be no saving him. He was frightened. The only kidding he did was to ask if we played rock and roll music while we performed surgery. I told him we treated surgery like church. And we do.” (Except, perhaps, when talking about his beloved West Texas.)

Perhaps to emphasize his point, Isom won’t leave the subject of Letterman without telling you about the non-celebrities he operated on that same weekend, which included the choir director at a Manhattan church, a Turkish industrialist who’d flown all the way to New York for high-risk surgery because no one else would take him, and a lady who had no insurance. “That’s a pretty typical sampling of our practice here,” he says. “The celebrities are just a small part of it.” (Small, but memorable. “What have you done?!” asked Letterman in mock amazement after his operation. “I was supposed to come in for cosmetic surgery!”)

One of the most striking things about Wayne Isom is how much people like him. That may seem an odd way to measure a world-class cardiac surgeon, but his colleagues and patients agree that it is his direct, folksy bedside manner and tireless work ethic as much as his dexterous hands that have taken him to the top of a very competitive quarter of medical practice. “He’s very attentive, very thorough in explaining what’s going on,” Cronkite has said of the physician who performed quadruple-bypass surgery on him. What shines through most brightly about the doctor whom Letterman dubbed the Cardiac Cowboy is a quality missing in many heart surgeons: humility. Maybe that’s the West Texas part. Growing up in Idalou (population: 2,145; eleven miles east of Lubbock) doesn’t exactly give a young man the impression that the world is awaiting his arrival with bated breath, and Isom, who after thirty years in New York still talks with a deep drawl, seems not to have forgotten the lessons of obscure beginnings.

“It’s been a real advantage to have my background,” says Isom over dinner at the Upper East Side high-rise apartment he shares with his second wife, Pat, and their two young children, Jack, eight, and Catherine, six. (He has three grown children by a previous marriage.) “I don’t treat anybody any different from anybody else. The Medicaid patient or Dave Letterman. You tell them the truth, and you treat them. You get down to it, you treat every patient like you would a member of your own family. When a patient goes to a surgeon and says, ‘I trust you to take a knife and cut into my body,’ there’s a special bond that develops. That patient has to give you almost superhuman powers. It’s gratifying. But you can’t start believing it yourself.”

One of Isom’s mentors, fellow West Texan Dr. Frank Spencer, thinks Isom’s childhood on his family’s farm has helped in other ways too. “In cardiac surgery you have to have an awareness of the unexpected problem and the capacity to solve it when it comes up,” says Spencer, who became Isom’s mentor when the latter moved to New York, in 1970. “One thing you learn growing up in West Texas is self-reliance and problem solving at an early age. So much of heart surgery is not black magic. It’s hard work, stamina, and perseverance.”

It’s also a long way from Idalou. Isom says he does not like the limelight and misses the relative anonymity of his Texas home, where his brother still runs a farm. When David Letterman returned to the air in February and introduced the doctors and nurses who’d saved his life, an actor had to stand in for Wayne Isom, who decided to take a vacation instead. Just any old world-famous heart surgeon might have set aside a day to get a little face time on television. But if you grew up in Idalou, Texas, you’d know better.