How Doctors Think (19 page)

One of the most common congenital abnormalities of the heart is a hole between the two upper chambers, between the right atrium and the left atrium. Since the pressure in the left side of the heart is higher than in the right, blood will flow from the left atrium through the hole into the right atrium. This aberrant blood flow is called a shunt and can overload the right side of the heart, leading to heart failure and other complications. Lock told me that doctors send children for surgery to close these holes if there is a two-to-one shunt, meaning that twice as much blood flows through the right side of the heart than the left.

"Do you know where that two-to-one number came from?" Lock asked. I imagined it was from careful clinical studies of children with the hole. "You would think so. But you'd be wrong. At a medical meeting in the 1960s, a pediatrician presented the question 'When should the hole be closed?' to a group of cardiologists. There was a heated debate about how much shunting required a surgical fix. So the meeting organizers, out of desperation, took a vote. Some voted for a lower number, some for a higher number. The median ended up being two-to-one. This was published in the
American Journal of Cardiology.
So now all textbooks have as the
truth
that you should close a hole when the shunt is two-to-one. But," Lock continued, "children can have a two-to-one shunt and still have a good chance of being healthy and never needing any specific treatment. Many children with two-to-one shunts undergo surgery and probably don't need the operation.

"Why are we still making it up? Because you can't do the clinical study to really find out. You would have to randomize five hundred kids to closure versus nonclosure. It would take forty years to do it." And there are ethical and moral constraints to such a study: "You can't do the kinds of studies in human beings that you can do in cars. You can't crash test a human being," Lock said. So you have to deduce answers from the data on hand, limited though such data may be.

In Lock's specialty a keen spatial sense is essential to deducing those answers. "You need to be able to look at a single-plane image and reconstruct it in three dimensions almost instantaneously." For example, during a cardiac catheterization, the cardiologist manipulates the catheter through the child's blood vessels and into his heart. The catheter appears as a thin white line on a flat monitor screen next to the table. It can be difficult in such a two-dimensional projection to know the catheter's position. "The combination of how your hand moves and what the image looks like will tell you whether the catheter is pointed toward you or away. I can tell where it is even if my hand is off the catheter. Knowing in which direction you are going shouldn't be something you need to think about."

Lock spoke about "physical genius," the kind of genius displayed by stellar athletes who can anticipate exactly where the ball is headed. Growing up, Lock idolized baseball players who could connect with a breaking curve ball and hit it out of the park; he worshiped wide receivers who could run without looking back and place themselves within reach of a spiraling football. "You need to process what you see very quickly and act on the information in a split second," Lock said, "because the heart is beating. It's not like you can stop the child's heart and ponder. Once you are inside of a kid's heart with a catheter, you have an enormous amount you have to accomplish, and there is a great deal of risk if what you do is not done quickly and well."

Recent studies contradict the popular notion that doctors who perform challenging procedures, like Lock, are "born with good hands," that they have innate talent in manual dexterity. Of course, if you are a complete klutz, manipulating instruments in a child's heart would not be your ideal career path. But this research on physician performance of procedures shows that "visual-spatial" ability, meaning the capacity to see in your mind the contours of the blood vessel or the organ, rather than the nimbleness of your fingers, is paramount. Although at the beginning of training there are differences among doctors in their visual-spatial ability, as Geoffrey Norman, a researcher at McMaster University in Ontario, has emphasized, this ability can be enhanced to the expert level by repeated practice and regular feedback about success and error in technique.

Tom and Helen O'Connell had eagerly anticipated the birth of their first child. Tom was a gym teacher in a local Catholic high school, and Helen was an accountant. Every evening they practiced breathing techniques from their birthing class. Tom joked that being a coach was natural for him. They knew from the ultrasound that it was a boy, and decorated the baby's room with Red Sox pennants and a New England Patriots football.

Helen's labor took eight hours and went smoothly until the baby emerged, blue and gasping. The obstetrician and nurse quickly removed a thick brown liquid from his mouth. If there is distress during the birth, the infant defecates this liquid fetal stool, called meconium, and breathes it in during the struggle.

"Even after they aspirated the meconium, the kid was extremely blue," Lock told me. Baby O'Connell was rushed to the cardiac ICU, but despite every measure, the doctors were unable to get enough oxygen into his system. "He had a cardiac arrest within the first thirty minutes of life, so they crashed onto ECMO," Lock recounted. Again, ECMO stands for extracorporeal membrane oxygenation, the special heart-lung machine used only in the most dire circumstances. Shira Stein was headed for ECMO until she rallied. But unlike in Shira's case, there was no surprise turnaround. A large catheter was placed into Baby O'Connell's neck. The venous blood from his body, depleted of oxygen, would ordinarily go to the right side of the heart and be pumped to the lungs where it receives oxygen, but instead the spent blood entered the ECMO machine. Baby O'Connell's depleted blood passed over a broad porous membrane that allows the release of toxic wastes and carbon dioxide and the entry of much-needed oxygen. A pump moved his freshly oxygenated blood into a second catheter in his neck; this entered his aorta, and from his aorta the blood reached the tissues of his body.

ECMO can have dangerous side effects. The large catheters inserted in the baby's neck can provide a fertile field for infection, resulting in fatal sepsis. Friction from the pump and at the membrane surface can destroy fragile blood platelets, predisposing him to life-threatening hemorrhage. It was urgent to decipher his problem and get him off ECMO. But each time the doctors tried to detach Baby O'Connell from ECMO and give him oxygen via a respirator, they failed. Something was seriously wrong. But no one could pinpoint the precise problem.

In normal circulation, as we've seen, spent blood returns from the tissues and enters the right atrium, which pumps it into the right ventricle. The right ventricle then pumps the blood through the pulmonary arteries to the lungs, where fresh oxygen enters and toxic carbon dioxide is released. The newly oxygenated blood returns from the lungs via the pulmonary veins to the left atrium and then the left ventricle. The left ventricle pumps the oxygen-rich blood into the aorta and then through the arteries to the body.

"In a newborn, one cause of being very blue, indicating scant oxygen in the tissues," Lock explained, "is that the pulmonary veins are connected incorrectly—they go somewhere other than the left atrium, or they're blocked for some reason." In such cases, the oxygen-rich blood leaving the lungs can't enter the left heart and be pumped to the body. There is a backup in the system. "You get a blue child. Fluid seeps into his lungs—pulmonary edema."

Baby O'Connell was taken to the cardiac lab for further study. The lab has bright overhead lights, a movable table, a fluoroscope to obtain real-time x-rays. Catheters were threaded into his heart and vessels, and computerized monitors displayed their pressures. Dye was injected into the pulmonary artery. The dye should have passed through the artery into his lungs, then out via the pulmonary veins, and entered the left atrium. "Nothing is going through to the heart," Lock observed. Somewhere, there was an obstruction.

A catheter with a tiny balloon at its end was snaked into the pulmonary artery and inflated. The balloon opened up the artery. Again dye was injected. This time, the dye went through the pulmonary artery into the lungs and entered the pulmonary veins. An image appeared on the fluoroscopic screen that resembled the trunks of a tree with tapering branches. But the tree and its branches seemed suspended in the chest. "The pulmonary veins don't go anywhere," Lock said. "They don't connect to the left heart. They just stop."

For a long moment, there was silence. None of the doctors or nurses could figure out the path of Baby O'Connell's vessels. Lock moved his head back and forth in its radar sweep. Then he stopped. He pointed to a trickle of dye that had somehow made its way into the inferior vena cava, the large vessel that brings blood from the lower part of the body into the right heart. It made no sense: Why would a whiff of dye injected into the arteries of the lungs end up in the belly? "That's what he is trying to live on before he dies," Lock said, referring to the trickle. Again, silence filled the room. It seemed the baby would be lost.

"What doesn't belong here?" Lock asked himself. When he confronts an unknown, he thinks out loud. He manipulated the computer keyboard and called up the stored images onto the screen from the previous injections of dye. He flashed each in succession. No new clues. Then, with a rapid jerk of his arm, he pointed to a thin white line over the right side of the baby's chest. "What's that?" he demanded. No one on the team had any idea.

Lock traced the mysterious line on the screen, moving backward from the baby's chest, down to a tangle of images that represented the tubes and catheters that the doctors had inserted. "It's the umbilical catheter in the umbilical vein!" Lock yelled out. A catheter had been placed in the umbilical vessel that originally connected the mother to the fetus. "But where is that line ending now?" Lock asked. After a few seconds of intense concentration, he announced, "It's in the pulmonary vein!" A vessel in the abdomen was aberrantly connected to a vessel in the chest.

Lock and his colleagues had never encountered a case like this. Using the catheter in the umbilical vessel as a thread, he began to unravel the bizarre connections of Baby O'Connell's anatomy: the umbilical vein connected to the large portal vein in the child's belly, and the portal vein somehow was connected to the pulmonary vein in the chest. "When you have never seen anything before," Lock said to the team, "it becomes an opportunity to do something no one has ever done.

"Let's try to open up the pulmonary veins using the umbilical catheter." Lock took a long guide wire that resembled a straightened coat hanger. He threaded the wire through the umbilical catheter, up through the abdomen, into the chest and the pulmonary vein. Following this wire, Lock inserted a catheter with a balloon on its end. He inflated the balloon and expanded the pulmonary vein; then he injected dye. The dye flowed from the pulmonary vein in the chest into the portal vein in the belly and then began to slowly work its way back up into the baby's chest and into his heart.

"Why is it still only a slow trickle?" Lock asked. There must be a second obstruction. Lock located another vessel branching off the portal vein. He expanded this second vessel with a balloon catheter and threaded two metal stent devices and wedged them into the opening. He paused and moved a catheter into the pulmonary artery of the lungs and injected dye. "Look at the blood blasting out!" he exclaimed. Now blood flowed down from the pulmonary vein in the chest to the portal vein in the abdomen, then up via the stented vessel into the left side of the heart. Lock had created a path to get oxygen-rich blood from the lungs to the left side of the heart and out to the baby's tissues.

Baby O'Connell spent three more days on ECMO as his body gradually adapted to a jury-rigged circulation. Then the doctors placed him on a respirator; his oxygen levels held.

A few days later, I went to visit Baby O'Connell in the cardiac ICU with Jim Lock. The O'Connells warmly greeted him. Lock reviewed with them the procedures he had performed and emphasized they were temporary measures, but effective for now. Soon Baby O'Connell would undergo surgery to fully repair his circulation.

As we walked out of the ICU, I asked Lock how he thinks through these kinds of conundrums.

"When a case first arrives," he told me, "I don't want to hear anyone else's diagnosis. I look at the primary data." He avoids all biases or preconceptions; he tries to identify the key clinical features—pattern recognition—and frame the situation himself. "In this instance, the shadow just didn't belong there," he said, referring to the white line of the umbilical catheter. While everyone was concentrating on what he termed "the main event"—the blocked pulmonary vessels—he said he was able to see the entire picture at once, integrating each component into a coherent whole. And when one piece does not fit, he seizes on it as the key to unlock the mystery. "It's like that game Where's Waldo?" he said.

The surgery was a success. Baby O'Connell's pulmonary vein was attached to the back wall of his left atrium, so there was a robust flow of oxygen-rich blood from the lungs to the left heart, which pumped it out to the aorta. He'll be carefully monitored, and he may need further surgery as he grows, but there was no reason, Lock said, that he couldn't lead a normal life.

A week after we saw Baby O'Connell, I asked Lock about the times when his judgment was off target. "The mistakes that I remember...," he began, and then stopped in midsentence. I was struck by his pause. Studies show that most physicians are unaware of their cognitive errors. Lock's phrasing acknowledged this: there likely were instances when his judgment was wrong but he was yet to learn of them. Then he picked up the thread of his thoughts. "All my mistakes have the same thing in common."

Lock took a blank sheet of paper and began to rapidly sketch the outlines of the heart, its chambers and valves. There was a disorder called "common AV canal," he said, where the wall between the left and right sides of the heart does not fully form. This most often occurs in children with Down syndrome. "The central part of the heart is missing, and this can include the lower wall between the atria, part of the mitral valve and part of the tricuspid valve, and the upper wall between the ventricles—all don't form." Some of these children also have aortic stenosis, Lock explained, meaning partial closure of the aortic valve, or co-arctation of the aorta, meaning that the large vessel is narrowed. "When this happens, the left ventricle can be very small."