When Kristen came to Children's Hospital Boston for open-heart surgery, a nurse marked a doll's chest to show the little girl where doctors would make the incision. "I felt bad for the little doll," Kristin wrote in her online diary. "I don't think she liked those marks on her."
But Kristen's atrial septal defect (ASD), a hole in the wall dividing her heart's upper chambers, could be fixed no other way. Using classic open-heart techniques, her surgeons split her chest, stopped her heart, emptied it of blood and opened it up. They hooked Kristin up to a cardiopulmonary bypass machine that acted as her heart and lungs. Then they sewed a patch over the hole.
Kristin survived, as do 97 percent of patients who have open-heart surgery at Children's. But the procedure's invasiveness is something Pedro del Nido, MD, chief of Cardiac Surgery at Children's, would like to avoid. "It's a sledgehammer," del Nido says.
The large incisions can scar the heart and disrupt its rhythm, occasionally requiring a pacemaker. Opening the heart invites serious infection, and air bubbles can slip into the bloodstream and damage the brain. As blood travels over the unfamiliar surfaces of the bypass machine, immune cells sensing an "invasion" may launch an inflammatory response, damaging organs throughout the body. And even in uncomplicated open-heart surgeries, recovery times are weeks to months.
About a decade ago, del Nido resolved to reinvent the way heart surgery is done. Keeping the chest closed, he would fix every child's heart while it was still beating—without the need for bypass.
Some defects, like tears in the vessels attached to the heart, can already be fixed while the heart beats. But fixing defects inside a beating heart is much harder, especially in small children. Simply navigating around moving parts to reach the defect is difficult, and even simple repairs can be dangerous. Clear images and the right instruments—sophisticated enough to sew sutures, but small enough to fit inside a newborn's heart—simply didn't exist.
Del Nido was convinced these problems could be overcome. He was used to rising above others' doubts. In high school, his teachers had tried to steer him toward a career in auto mechanics. But he always knew he would be a surgeon—and earlier this decade became the world's first surgeon to operate on a child's open heart with robots, whose precise, remotely-guided motions allow for smaller, less invasive incisions.
To fix beating hearts, however, del Nido knew robots would not be enough. He began assembling a team, enlisting engineers at MIT, Boston University, Harvard University, Philips Medical Systems and Microfabrica, Inc., to work with his surgical group.
"We look at some very unusual cardiac anatomy," he says. "Half the battle is figuring out what the structure is without opening up the heart."
Del Nido's first task was to enhance surgeons' sight, so they could clearly see the heart's working parts and their own tools, without the distraction of blood. They would need fast, real-time images, since the heart beats anywhere from 60 to 160 times a minute, and its tiny valves flutter even faster. And they would need to see depth.
Three-dimensional ultrasound, with its real-time images, seemed the place to start. Philips Medical Systems donated its most advanced machine, then used only for research. But the images were fuzzy, with little indication of depth. Nikolay Vasilyev, MD, del Nido's associate and a heart surgeon, tried to navigate a tool inside an animal's beating heart guided by the images, and became disoriented.
What they needed, del Nido realized, was stereoscopic vision. Watching the flat picture on the computer screen was like watching a baseball game on TV. "It's good enough to follow what's happening in the game," he says, "but you could never grab a ball in mid-flight."
Robert Gross, MD, performs the world's first successful surgical procedure to correct a congenital cardiovascular defect.
Robert Gross, MD, develops the first successful surgical closure of an atrial septal defect, a hole in the wall between the heart's two upper chambers.
William Norwood, MD, develops the first successful surgical intervention for hypoplastic left heart syndrome (HLHS), a previously fatal defect in which an infant is born without a left ventricle.
The FDA approves the use of CardioSEAL, a catheter-implanted device designed by James Lock, MD, to seal holes in the heart.
Children's interventional cardiologists, echocardiographers and fetal surgeons team up with Brigham and Women's Hospital to perform the world's first successful fetal intervention for HLHS, resulting in the birth of a baby with a healthy heart.
Pedro del Nido, MD, becomes the first to use the da Vinci surgical robot to fix a defect in a child's heart, using child-sized tools of his own design.
Virna Sales, MD, and John Mayer, MD, create heart valves through tissue engineering, offering hope that children can receive replacement heart structures that grow with them, avoiding repeat operations.
So collaborator Robert Howe, PhD, of Harvard University, plucked a solution from video games—splitting computer images in two and cocking them at slightly different angles. By donning gamers' flickering glasses, Vasilyev could now see ultrasound images of the beating heart as a hologram. He navigated his instrument inside the research animal's heart quickly and unerringly.
"You definitely have depth perception," says Vasilyev, who watched his first open-heart surgery as a high-school student in Moscow. "You feel like you're inside the heart chamber."
But del Nido still needed better instruments. He first aimed to design tools for simple hole repair. Holes in the heart's inner walls, like Kristen's ASD, can sometimes be plugged using catheters—thin tubes that can be snaked into the heart through blood vessels, carrying tools in their tip. But newborns' blood vessels are too small for catheters and their payloads, and the plugs don't fit in large or irregularly shaped holes.
Del Nido wanted to be able to use patches, as in open-heart surgery, but catheters are too "floppy" and too limited in their maneuvers to sew a patch. So del Nido probed for ideas at cardiology conferences around the world, searching for a way to fasten a patch in a beating heart.
He found what he was looking for in Germany, where cardiologist and engineer Franz Freudenthal, MD, was eager to help. "No idea is too crazy," del Nido told him. Freudenthal proposed rivets, like those that fasten pockets onto blue jeans. Del Nido thought of the collapsible anchors that climbers use to "fasten" themselves to rocks. Freudenthal saw the potential. Emails traveled across continents; prototypes were airmailed.
Two years later, what emerged was a long-handled patcher that slips through a keyhole made in the heart's side and holds a patch over the hole, while another tool drives in anchors to secure it. Using the patcher under stereoscopic vision, Vasilyev successfully closed a hole in the atrial wall of a pig's beating heart. Clinical trials of beating-heart surgery with this patching system could begin in patients with ASDs this year.
Vasilyev next attempted a more difficult maneuver—patching holes in the heart's ventricles. Introducing plugs with a catheter is risky, because these chambers contract more forcefully than the atria, and because the catheter's entryway is blocked by muscles that open and close the valves. But del Nido's patcher can enter the heart from anywhere, avoiding moving parts. Vasilyev slipped it in the left side of the pig's beating heart, and the patches held without complication.
Del Nido has his sights on even more difficult operations. Defective heart valves, the second most common congenital heart defect, would seem impossible to fix on a beating heart: The valves' tiny flaps flutter at least 200 times per second, five times the speed of human perception.
But Howe's students are writing computer algorithms—again adapted from video games—that track the heart's motion and spin tiny motors on a surgeon's instrument so it moves in synchrony with the beating heart. With imaging tricks, surgeons see a picture that stands still. Meanwhile, Vasilyev is conducting animal tests of a mitral valve "clip" that snatches valve flaps in mid-flight and folds back excess tissue, allowing them to close properly.
The ultimate test of beating-heart surgery would be to perform it before a baby is even born, when the heart is no larger than an olive. The danger is great, but fetal procedures offer the possibility of preventing heart defects before they develop. A single stuck valve in the fetus, for example, can create an anatomic defect too severe to undo after birth.
Children's cardiologists have successfully fixed some defects using balloon catheters, but success rates need to be improved, and del Nido's team is advancing the challenge. He is working with Microfabrica's engineers to design tiny machines, like a chainsaw-like "nibbler" that shaves away extra tissue. Pierre Dupont, PhD, of Boston University, is prototyping a needle-thin robot, controllable with a joystick, to guide these instruments through the womb and into the fetal heart.
"If a child is born missing one side of the heart, we can't give him a second side," says del Nido. "We do a series of operations to reroute the blood so it goes where it's supposed to go, but that heart is still not normal. A fetus's ability to regrow tissue is far greater than an infant's. If you can get the ventricle to grow in the womb, then you could be talking about a child born with a normal heart."