Sometime in the first seven weeks of life in the womb, Zachary Davis's heart got the wrong instructions.

The intricate folding, splitting and sprouting that produces the heart's four chambers and a tree of major blood vessels did not follow the normal genetic plan. The heart he was born with on Oct. 20 was not the engineering marvel that can take people through nine decades.

Still, Zachary's heart was a marvel in its own right. It shared many features of known congenital malformations. But it also had something not previously recorded in the annals of medicine. His coronary arteries, which normally deliver oxygen and nutrients directly to the heart muscle, were instead supplied by a bizarre circuit routed through his brain. It was as if an important package were being sent from one house in Washington to another down the street via . . . Baltimore.

"It usually takes lot for us to say, 'That's amazing,' " Richard A. Jonas, a heart surgeon at Children's National Medical Center, said last week. "We see a lot of unusual things. But this was out there."

This exotic misassembly was good enough to get the baby through gestation. It would not be good enough to get him through life. A week after Zachary was born, Jonas took his heart apart, added missing pieces and reconstructed it to something close to its original specifications. It took about four hours and included a 25-minute period when the infant was packed in ice, with no blood circulating.

One day soon, Zachary and his mother, Jessica Davis, will go home to La Follette, Tenn., a town of 8,000 on the Kentucky border. On this Thanksgiving holiday, however, the baby is still learning to eat enough to enable him to grow. He will need at least two more operations on his heart as he gets bigger. But doctors expect him to have a normal life.

"There are only a handful of people in the world who can take a problem like this, think it through, do a complete repair, and have the child turn out so well," Mary T. Donofrio, Children's director of fetal cardiology, said of Jonas. "He actually did three operations, and [Zachary] had no leftover heart defects."

Jonas, 54, a native of Australia, went to Children's last year after 20 years in Boston, where he was a professor at the Harvard Medical School. He is an advocate of "early primary repair" -- fixing heart malformations right after birth in a single operation. The team being assembled around him is turning Washington into a referral center for ultra-complicated pediatric heart surgery. Last week, he operated on an infant flown in from Abu Dhabi.

Early primary repair is difficult, even daring. How Zachary would tolerate a one-stop solution to his many heart defects, including the unique one, was hard to predict.

"What did I anticipate? It was sort of hard to have an anticipation," the surgeon said.

A Broken Arch

Jessica Davis is a 17-year-old high school senior. Zachary is her first child. The baby's father at this point is not in the picture, she says.

She went to school until April, when she left and began studying for her General Educational Development (GED) certificate at home. She hopes to return after Christmas and graduate with her class. She would like to be a cosmetologist.

Jessica knew something was wrong with her fetus before he was born. A fetal ultrasound detected an abnormal heart and circulatory system. She was on bed rest for the last two months of the pregnancy.

Zachary was born nearly at term on Oct. 20 at a hospital in Knoxville. He was apparently healthy and weighed 8 pounds, 1 ounce. But the heart defect made his condition unstable, and he was immediately taken to the intensive care unit. Jessica did not hold him until he was more than two weeks old.

The aorta is the body's biggest artery. It leaves the heart's main pumping chamber -- the left ventricle -- and sweeps upward in an upside-down U, giving off arteries to the heart muscle, head and arms before heading down the chest into the abdomen to serve the lower body. This first part of the aorta just outside the heart is called the "aortic arch."

In Zachary's case, the arch did not exist as a single structure. The segment of the aorta that left the heart was abnormally narrow. The segment sent off two branches, the coronary arteries, which deliver oxygen and nutrients to the heart muscle. But then, instead of arching around and giving off many more branches, the aorta simply divided into two vessels, the carotid arteries, which send blood to the brain.

The part of the aorta that would normally have been the far end of the arch was attached to a structure called the pulmonary trunk. It gave off its usual branches. But it had no direct connection to the underdeveloped first part of the aorta.

The "interrupted aortic arch" was not the infant's only problem. There were others.

The valve that normally lets blood out of the left ventricle into the arch was permanently closed. Consequently, blood pumped by that ventricle went instead into the neighboring right ventricle through a large hole in the wall separating the two chambers. From there, it went out of the heart and eventually into the far end of the aortic arch.

A big question in this odd circuitry was how blood was getting to Zachary's coronary arteries. They normally receive blood just as it leaves the heart. But in his case, no blood left by that route.

It was still a mystery when one of Mary Donofrio's former cardiology trainees called her from a hospital at the University of Tennessee in Knoxville and said they had a baby whose problems were too complicated for doctors there to handle. It was only when the infant arrived in Washington by air ambulance at two days old and Donofrio did further tests that she was able to figure it out.

What she found was that Zachary's heart muscle was living off blood that went up the vertebral arteries to the brain, around a Beltway-like structure there called the "circle of Willis," and then down the carotid arteries in the opposite direction of the normal flow. At the end of this journey, the blood entered the dead-end stub of the aortic arch and fed the coronary arteries that came off it.

This long detour was something Jonas had never seen. He had just published a single-author text on the repair of heart defects -- a book with 300 drawings of anomalies and how to correct them -- so he was pretty sure he knew what had been reported by other surgeons over the years.

He checked the electronic database of journal articles again last week. He was right; the defect was unique.

Stopping the Blood

Some of the surgery Jonas would do to fix Zachary's heart could be performed while the baby was on a heart-lung machine that pumps and oxygenates blood. But not the most important tasks.

That's because the machine needs to have an aorta to pump blood into, and during much of the operation Zachary's aorta was going to be in pieces. Jonas was going to have to cut it open, graft on a piece of vessel from an organ donor, and sew the reconstructed arch to its proper attachments.

During that time the infant would have no circulation. He would be cooled in ice to below 60 degrees Fahrenheit, a state of "deep hypothermia" that slows metabolism and reduces the body's demand for oxygen.

A newborn's heart is about the size of a large walnut. The operation is done with the surgeon wearing jeweler's magnifiers attached to glasses. How long a baby can be kept safely in "circulatory arrest" varies, but it is generally not more than 45 minutes. With each minute beyond a time limit that the surgeon cannot pinpoint exactly lies brain damage, a lifetime of lost potential, unhappiness and death.

There was no part of the repair of Zachary's heart that Jonas had not done many, many times. The outcome hinged on preparation, timing, speed, accuracy and imponderables -- including the chance that Zachary's unique feature might somehow affect his odds.

Jonas sketched out the repair, determined the order of his work and kept a running total of how long it would take. (He prefers to do this the night before, explaining that "you do literally sleep on it; you run through the steps in your sleep.") There were 10 steps, the first seven requiring circulatory arrest.

"What is difficult about an operation like this is coordinating all those modules," Jonas said. "You do not have an unlimited amount of time." The right order of work is not always obvious. In this operation, for example, he sewed one end of a donated vessel as Step 6, and the other end as Step 10. The price of doing things in the wrong or inefficient order can be very high.

"You can paint yourself into a corner. You can literally get in a position where you can't get there anymore because you did things in the wrong sequence."

Planning, though, only goes so far. "Early primary repair" requires fast, near-perfect work against deadlines that nature imposes. Some of the work can be very difficult.

For example, to create a normal two-ventricle heart in Zachary, Jonas had to cut a slit in one wall of the tiny organ. Through it he poked a piece of tissue, which he then installed as an interior ceiling for the right ventricle. In effect, he sewed a floppy object the size of a quarter to something inside a space the size of a ping-pong ball through a hole a half-inch long. It took him about 30 minutes.

"I have literally done that thousands of times," he said by way of explaining it was not so unusual. Pushed, he added, "It wasn't easy the first thousand times."

He gives a lot of credit to people who tell him what to expect -- non-surgical specialists such as Donofrio.

"I have to know what I'm going to see when I go in. If I have to consume time figuring out the anatomy -- trying to understand exactly what the child's anomaly is -- then that disrupts the whole operation."

Nothing like that happened with Zachary Davis. Zachary ended up with a normal appearing four-chambered heart in which the blood flows in the right direction.

"I was absolutely thrilled to see that the child did exceedingly well," Jonas said.

Away From Home

Last week, Jessica Davis cradled and nuzzled Zachary with confidence as her mother, Jenny Slover, 42, looked on. He looked like a normal baby except for the wires emerging from his pajamas to an EKG monitor and the blinking blood oxygen sensor clamped on one of his fingers.

But the entire family was restless, waiting for Zachary's feeding to reach the 2.5 ounces per session he needs to be discharged.

"I just want to take him home," Jessica said.

Jessica will live at home, and her mother will care for Zachary during the day. That was always the plan, even before the problems.

"We're looking forward to being able to say the journey's over," Slover said. "To get where we can walk through our door and say, we're home."

Jessica Davis of La Follette, Tenn., embraces her newborn son, Zachary, who was diagnosed with a rare heart ailment that called for major surgery.

Richard A. Jonas, in a four-hour operation at Children's National Medical Center, gave the baby a four-chambered heart in which the blood flows in the right direction.

In Zachary's room, his mother, Jessica Davis, 17, center, is joined by her mother, Jenny Slover, right, who holds her youngest daughter, Jadan, 3. Doctors say Zachary will need at least two more operations on his heart as he grows.