Under the metallic glare of operating theater lights, a middle-aged man lies on a surgical table at Inova Fairfax Hospital, naked and unconscious. At 180 pounds, he is not overweight, but elevated cholesterol and high blood pressure have choked his coronary arteries with plaque, a fatty substance that accumulates on the artery walls and impedes blood flow to the heart. In preparation for surgery, nurses have covered every inch of the patient's skin with a saffron yellow antiseptic film, giving him a jaundiced glow. Blue drapes conceal his face and genitals, but his hairless chest is laid bare, awaiting the touch of the scalpel.

While the surgical team reviews X-rays, prepares instruments and monitors vital signs, 13 high school seniors from the Arlington Career Center gaze at the patient through the windows of "the Dome," one of the only cardiac surgical theaters in the United States open to middle and high school students. They've come with their teacher, Sheila Napala, as part of a course in physical therapy and sports medicine. She wants to see if the students, some of whom are interested in medical fields, can "handle a situation where they're going to see blood or the aftermath of surgical procedures." Most are bundled up in hooded sweatshirts because the room is a cool 62 degrees, a temperature necessary to preserve tissues during surgery. At 7:30 a.m., they sit in silence, nursing bottles of soda and cups of coffee, about to witness a surgery that is necessary for more than half a million Americans a year.

They are joined by nurse Marsha Taylor, director of education programs in the Dome, which has hosted 16,000 students from the Washington area over the past nine years.

Classes come for many reasons, ranging from career education to learning about the human circulatory system. The hospital has its own agenda, says Edward LeFrak, the cardiac surgeon who's been the driving force behind Inova Fairfax's educational program. It invites students to the Dome to preach a heart-healthy lifestyle to teenagers whose love affair with junk food, television, video games and the Internet may already be putting them at risk for heart disease.

"Most young people think they're immune to all of this," says LeFrak. "Or that it's going to happen to somebody else. Or that it's too far in advance, so it's not an issue to worry about." As the students from the Arlington Career Center are about to learn, it's never too early to start protecting your heart from the ravages of cigarette smoke, fatty foods and couch-potato tendencies.

TAYLOR, A 10-YEAR VETERAN of the cardiac operating room, cradles a plastic model of a heart in her hand and explains the patient's condition to the bleary-eyed students.

"The heart has five major coronary arteries," she says, tracing her finger along the tiny red vessels that branch out like tributaries over the surface of the plastic model. "This man has blockages in three of the five."

If a clot forms on top of one of these blockages, blood flow to the heart can be slowed or interrupted, causing everything from chest pain to sudden death from a heart attack. More than 1.1 million Americans suffer heart attacks annually, and for nearly half of them, the event is fatal.

To stave off this danger, the occluded arteries can be rerouted, or "bypassed," using healthy artery or vein tissue harvested from the leg and chest wall. These vessels will be sewn above and below the area of blockage, providing an alternate route for blood to flow. Inova surgeons performed 1,800 bypass operations in 2002, sometimes as many as 15 a day.

When the surgical team is ready, a nurse swabs the patient's sternum with a betadine-soaked sponge, leaving a rusty streak. The surgeon leans over the patient's chest holding an "electric scalpel," a tool that looks like a soldering iron, and burns a vertical line on the skin. Wisps of gray smoke rise from the tip of the instrument, which cauterizes as it cuts, creating a wound that's almost bloodless. As the incision deepens to an inch, a thick yellow layer emerges. "That stuff is fat," Taylor says. "We all have some of it."

As a gap opens in the patient's chest, some students grow wide-eyed before the panes of soundproof glass; others back away from the windows, looking at the floor or pacing around. Taylor, dressed in a white lab coat, stands behind the group and offers reassurance. "If anybody feels weak," she says in a hospitable North Carolina lilt, "just sit."

Placing the scalpel aside, the surgeon parts the incision with his fingertips, revealing the clamshell-white sternum. Then, grasping an electric tool that looks like a modified saber saw, he eyeballs his next cut. With a steady hand, he raises his elbows and engages the power switch; the whirring of the saw penetrates the thick glass that separates the students from the operating room.

Lowering the blade onto the notch at the throat, he guides the saw toward the base of the rib cage, slowly cleaving it in two. Sighs and groans spread across the room as the breastbone pops. John Crone, a broad-shouldered fullback from the Yorktown High School football team, hides his face in a hooded sweatshirt and mutters to himself. Alex Brazell, a lanky Yorktown soccer player with a gelled-up crew cut, looks pale and distressed as he sits before the window with his elbows on the counter and his palms pressed into his cheeks. "It just doesn't look real to me," he says, speaking to no one in particular.

ALTHOUGH HEART DISEASE IS THE LEADING CAUSE OF DEATH IN THE UNITED STATES, it mainly afflicts the middle-aged and elderly. As one Arlington student aptly points out, "There's not that many teens dying of heart attacks."

But a large body of evidence, much of it collected by the Bogalusa Heart Study, suggests that the causes of heart disease are established in adolescence or even earlier. In 1972, researchers from Tulane University began to collect data on the factors that contribute to heart disease in 14,000 children in Bogalusa, La. They wanted to see if they could track the progression of heart disease from childhood to adulthood. After 32 years of research, Gerald Berenson, lead investigator on the study, states, without hesitation, that "heart disease begins in childhood."

As part of his research, Berenson examined the coronary arteries of 204 young people participating in the study who died unexpectedly after accidents or other trauma. When their arteries were dissected, Berenson discovered "fatty streaks" and "fibrous plaques," which are precursors to heart disease, in the vessels of more than 35 percent of subjects from age 16 to 20. In the 21- to 25-year-old age group, 55 percent of those examined showed early signs of heart disease.

Young people who smoked, had high blood pressure, were overweight or had a family history of heart disease exhibited the most damage to their arteries, though most of them hadn't experienced symptoms of heart disease yet, Berenson found. He also saw a direct correlation between the number of risk factors a patient possessed and the severity of the lesions in his or her arteries.

"People don't have any kind of symptoms from it for years," he says. "When they have a heart attack, they've had the disease for a long time before that."

American teenagers are jeopardizing their health in all sorts of ways, according to statistics compiled by the Centers for Disease Control and Prevention and by the American Heart Association. One in three high school students smoke, a habit that more than doubles their risk of having a heart attack. Eighty-five percent of young people eat too much fat on a daily basis, gobbling french fries, burgers, pizza and potato chips every chance they get. Many teens combine a high-fat diet with long hours playing video games, watching television or surfing the Internet. The CDC reports that 22 percent of children from age 9 to 13 get no exercise at all.

The result: an ominous rise in the cholesterol, blood pressure and weight of America's young people. The average cholesterol level in teenagers, 165 mg/dl, is 15 higher than the maximum recommended to keep heart disease at bay. Ten percent of teens already have a total cholesterol level higher than 200 mg/dl, which places them squarely in the "borderline risk" category for developing heart disease, and another 10 percent have high blood pressure that merits treatment. Fifteen percent of teens are obese, which is a major risk factor for developing heart disease.

The explosion in childhood obesity has serious health consequences, doctors warn. Excess body weight increases blood pressure and cholesterol and frequently leads to Type 2 diabetes. A person who is diabetic before age 45 is 14 times more likely to have a heart attack than someone without the disease.

While there's shock value in showing teens what their lifestyle can lead to, LeFrak has modest expectations for the Dome's impact. Not even the sight of a man undergoing bypass surgery is going to change lifelong habits overnight, he says.

"It's one more piece of education," he says, "I don't expect one day to change the whole gestalt of their lives."

Or as Taylor puts it: "The best you can hope for is to plant some seeds. They might not go out and get a gym membership after coming to the Dome, but we can get them thinking and questioning some of what they're doing."

AS THE SURGEON OPENS THE PATIENT'S CHEST, a flabby sac of yellow tissue jiggling at regular intervals becomes visible. "Is that the heart right there?" asks Wendy Reyes, a slim, dark-haired graduating senior from Wakefield High School who works part time at Gold's Gym.

Taylor tells the students that they are looking at the sac surrounding the heart, called the pericardium, a membrane that the surgeon will later cut open to work on the surface of the heart.

Reyes recognizes a lung and notices what looks like a dark spot. Taylor points out that a high percentage of bypass patients are or were smokers and that smoking constricts arteries and makes them more prone to clots. Reyes, who smokes "a few times a week" but who also maintains a regular workout routine, turns in disgust. "God, that's gross," she says.

With the chest open, the surgeon takes the electric scalpel and gets to work detaching the internal mammary artery from the underside of the chest wall, a vessel that will provide one of the grafts for the heart. The other grafts will come from the patient's left leg. To remove this vein, an assistant makes an incision two inches deep that runs from the ankle up to the knee. He clamps and cuts the vein, then begins to tug at the end with a pair of tweezers, as if he's trying to pluck a worm from the ground without breaking it.

As the pink eight-inch blood vessel emerges from the calf muscle, Alex Brazell points at the window and exclaims, "Ooh, look at that vein!"

With the replacement vessels in hand, the surgeon is now ready to work on the heart. To make room inside the chest, he inserts a sternal spreader between the ribs and turns a crank. The whole room oohs and aahs as, inch by inch, the chest creaks open. Brazell, who is now kneeling on a counter in front of the window, blurts out, "Oh, damn! Jeez!"

Taylor sympathizes with the kids. "To me, even after all of these years, it's intense." She assures the students that the patient is under the influence of anesthesia and feels nothing. Sometimes a person will even snore on the table.

"What do you think about when you're down there?" asks Crone, trying to comprehend how the medical staff can tolerate the blood. A heavily recruited football player bound for the University of Richmond, he has no problems crashing through a defensive line, but watching the surgery has made him increasingly uneasy.

"You're really focused on the job," Taylor replies. "That's what you have to do."

With the ribs spread open, Taylor points out that the patient's heart is flaccid and enlarged. "A swollen heart is bad," she says, shaking her head.

As the heart limps toward each contraction, Taylor explains how a narrowing of the coronary arteries forces the heart muscle to work harder than it should. This added pressure weakens and inflames the tissue. A quick look at the electrocardiogram monitor on the wall confirms this assessment. In a healthy heart, the line on the screen will be punctuated with sharp spikes at regular intervals. But this patient's EKG line has a series of hump-shaped waves that look like swells on the ocean.

"He has a rolling heartbeat," Taylor says. "Instead of the heart going boom, boom, it goes kind of blah."

Reaching into the patient's chest, the surgeon runs his fingers over the surface of the heart, feeling for blockages. Although he's studied the patient's angiogram, which gives him an X-ray of the coronary arteries, the film doesn't pinpoint the exact size or location of the obstructions. For a precise diagnosis, he must rely on his highly refined sense of touch. "You can't see the blockages," Taylor says, "but you can feel them."

A blockage the size of a BB pellet can drop a 200-pound man to the floor instantly.

Each graft is approximately 8 millimeters in diameter, which is about the width of a pencil. The surgeon will need to make 10 to 12 stitches around the circumference of each end using a needle the size of an eyelash and a strand of polypropylene thread the thickness of a baby's hair. To accomplish such delicate work, he first must stop the patient's heartbeat. This can be done with the assistance of the heart-lung machine, a mechanical pump that supplies the blood with oxygen and pumps it through the circulatory system for the two or three hours it takes to sew the bypass grafts.

To prepare the heart for connection to this device, the surgeon plants one plastic tube in the right atrium, which will take blood out of the body, and another in the aorta, the route through which it will return. The moment the tubes are inserted, a stream of dark blood rushes through and spurts into a stainless steel basin. But within a couple of heartbeats, the tubes are attached to the heart-lung machine, and the blood begins to swirl into two turning cylinders that look like the front of a Slurpee dispenser.

The surgeon can now safely stop the heart. Flicking a switch, he sends an electric current through a wire to the surface of the heart. The muscle begins to quiver and, in a moment, the blipping EKG line flattens. With its electrical impulse disrupted, Taylor says, the heart can no longer make an "organized contraction" and is therefore unable to pump blood. The students have just witnessed a controlled heart attack.

An assistant puts on a white cotton glove and slides his hand into the patient's chest. Lifting the limp heart, he exposes an area on its backside where the surgeon will sew a vein graft. The cotton glove keeps the assistant's hand from slipping while the surgeon works. The assistant cannot move even a centimeter for up to 20 minutes; an unexpected jitter could tear a vessel or cause an errant stitch.

With a scalpel, the surgeon makes a small nick in what looks like a mound of fat but what is actually a coronary artery. A trickle of dark blood bubbles out. Then, picking up a needle, he begins to sew what was once a leg vein onto the heart, suturing the entire circumference of the graft without ever cutting the thread.

"It's amazing how small the stitches they sew are," Taylor says, pinching together her thumb and index finger nails and squinting to see the minuscule space between them.

"How do you not shake?" a student asks.

Taylor smiles. "If you do that, you shouldn't be a surgeon. There's a natural weeding-out process."

With one end of the bypass attached, the surgeon takes a scalpel with a round blade, punches a tiny hole into the aorta and attaches the other end of the graft. The patient now has one of three bypasses, one that should last him 15 years, if he eats properly, gets exercise and doesn't smoke.

While the surgeon sews the next graft, Taylor asks for the students' attention. "We like to talk about things you can do so this won't happen to you."

She pulls out a set of test tubes filled with a Crisco-like substance, each representing the amount of fat in various brands of junk food. The tubes are labeled with names such as Snickers, Big Mac, potato chips. She holds up a tube packed almost to the top. "This is how much fat you get with one piece of thin crust pizza from Pizza Hut."

Kevin Telleria, a skinny kid with a ponytail from Wakefield, arches his eyebrows in disbelief, though what he's just learned doesn't change his mind about wanting to go out for pizza with his classmates after they leave the Dome. Others question those plans, and little discussions break out around the room about whether they should stick with pizza.

Scott Tsuchitani, a Yorktown soccer player who plans to study physical therapy in college, pushes his baseball cap back on his head. "This is why I'm gonna die," he declares. "I ate 20 pieces of pizza yesterday."

Taylor's son had a similar reaction after his class came to the Dome. "I just ruined my son's life when his class came here, and I showed them the pizza tube. He stopped eating pizza for about a week."

Taylor hands out a fact sheet listing the fat content in fast foods. Christian Ficara, a Yorktown soccer player, pores over the sheet and ticks off a list of his favorites. "I eat that and that and that and that," he says, rubbing his unshaven cheek, astounded by what's in a Whopper, a Big Mac, Chicken McNuggets and a Quarter Pounder. "I'm definitely resorting to Subway after this. Less fat. Less calories. It's like half of anything on this."

Taylor knows that these students are likely to eat fast food no matter what she says. But if they're aware of what's in the food and of the impact that it can have, perhaps they'll eat a little less. The American Heart Association suggests that people with normal cholesterol levels should eat no more that 67 grams of fat per day. But if you eat a Big Mac and large fries, and wash it down with a shake, you've just ingested the entire recommended daily allowance in one sitting.

Next Taylor hauls out her "fat suit," a cotton vest with 25 pounds of mushy yellow rubber sewn to the midsection. She asks for volunteers to try it on. Wendy Reyes slips her lithe arms through the sleeves. Taylor instructs her to sit down and then to stand up. She stumbles as she rises from the chair, clutching the imitation belly. "I probably wouldn't be able to walk if I gained this much weight," she says, hurriedly shedding the vest.

Reyes has seen how serious obesity can become. A friend of hers in his early twenties recently died from obesity-related heart complications. "He couldn't walk around that much. His legs couldn't support his weight, so he stayed in bed all the time and ate. His attitude was, 'I'm 400 pounds. There's no point to stop eating.' "

Reyes is indignant with the fast-food companies. She stopped eating at McDonald's last year and blames the country's obesity problem, in part, on economics. "Ever since they put up that Dollar Menu," she says, "it just gets everybody fatter. You can go up there and get a double cheeseburger for a dollar. Subway is, like, $6 for a sandwich. Do you know how much food you can buy at McDonald's for $6? That's why all of us are getting fat -- because fast food is so much cheaper."

Taylor's final prop of the day is a jar filled with gooey brown liquid with cigarette butts floating on top. "This is how much tar and nicotine you'd get in your lungs if you smoked half a pack of cigarettes a day for a year," she says as she sloshes the contents around. "Smoking affects the blood vessels and makes them paralyzed. If you have blockages in your arteries, it will take less plaque to create an obstruction. If you don't smoke, don't start. If you do smoke, find a way to stop. It causes all kinds of terrible problems."

DOWN IN THE OPERATING ROOM, the surgeon finishes sewing the third bypass graft and is ready to revive the patient's heart. As he removes the heart-lung machine tubes, the muscle twitches momentarily, and after a quick shock from the defibrillator, it begins to beat in a regular rhythm.

Alex Brazell, who thinks he will major in biology or premed in college, has been watching the procedure closely. Heart problems have been on his mind lately. His uncle had angioplasty not long ago and received a stent to open a coronary artery, and his mother was put on medication to regulate her heartbeat. Brazell notices right away that the Dome patient's heartbeat has changed.

"The beat looks more crisp now," he says. Taylor explains why: "That's because the blood flow is increasing. It's becoming more efficient."

For all of the relief bypass surgery offers to patients, it doesn't cure heart disease. Blood flow is restored to the heart, staving off a potential heart attack, but the underlying disease processes will continue unabated unless a patient changes his or her diet and lifestyle.

Bypass surgery presents the patient "an opportunity to regroup," LeFrak says. "The surgery is actually easy for the patient. They go to sleep, we do all of the work, and they wake up. It seems hard because they have some discomfort for a few weeks. In reality, that's easier than stopping smoking or starting an exercise program or losing weight or eating low-fat food. Those really take some work. You can't do that under anesthesia."

After more than three hours on the operating table, the surgeon is ready to close the patient's sternum. He threads a length of stainless steel wire through the edges of the ribs to lace them back together.

Scott Tsuchitani watches and wonders about his own risk for heart disease. His father and sister have high blood pressure, and he recently learned that he, too, has the condition. Even though he's in top physical shape, his coach recently told him that he had to sit out soccer practice until his blood pressure came down.

"It's a big realization that you're responsible for what you eat, that this can happen," Tsuchitani says as the surgeon and his assistant pull with pliers on the ends of the wire and draw the ribs back together. Although he has a weakness for pizza, he says he has quit drinking soda and eats almost no fast food.

In the hallway outside the Dome, Sheila Napala gathers her class together. Some look beleaguered after more than three hours of sometimes gut-wrenching observation. One student was so disgusted by what he saw that he ran to the bathroom to throw up.

"Subway today, okay?" Napala says. "Not pizza." More than half the group nods in agreement.

Paul Gustafson teaches English at Quinnipiac University. His e-mail address is Paul.Gustafson@quinnipiac.edu.