It's the violence of it that surprises him, the angry vigor of the beats in contrast to the gentle rhythm in the chest. Nick Patronik stares into the red tunnel the surgeon has opened in the pig's ribs. He has never seen a beating heart before. He turns to a nearby clinician observing the cardiac procedure and says, "It moves a lot more than I thought it would."
The clinician replies, "And you're going to land a lunar module on that thing? Good luck."
Patronik looks back at the heart, wondering if the clinician's skepticism might be warranted. The lunar module is a metaphor, a reference to a project Patronik, a PhD candidate at Carnegie Mellon's Robotics Institute, has undertaken. He's observing this operation to get a sense of the challenge he's in for. His mentor at Carnegie Mellon, Cameron Riviere, has him working on a concept that would stretch the imagination of computer scientists everywhere, ultimately taking the field of surgical robotics to a new frontier: the pulsing surface of the heart itself.
The pig's heart beats defiantly, as if issuing a dare.
Six years later, Patronik wheels a cart through the hallways of Pittsburgh's UPMC Presbyterian Hospital. Bristling with electronics, the cart is the mothership for an explorer that today will attempt a remarkable mission. Resting on top of the cart, shorter than a paperclip and tethered to the mothership by a bundle of flexible wires, is HeartLander.
HeartLander is the brainchild of Riviere, associate research professor at the Robotics Institute, who has long been interested in problems of motion. Namely, differentiating between desired motion and undesired motion—and neutralizing the latter. As a PhD candidate in mechanical engineering, Riviere began developing a filtering system for undesired motion that allows people with movement disorders such as Parkinson's disease to operate computer applications using a joystick. While constructing algorithms that take into account pathological tremor, he became interested in the problem natural, physiological tremor presents for surgeons. Surgeons are known for having steady hands, but they, too, experience small-amplitude shakiness when moving. This isn't problematic when stitching a wound, but for surgeons performing delicate eye surgery, for example, unwanted motion can sabotage a procedure. At Carnegie Mellon, Riviere created Micron, a hand-held, microsurgical tool that constantly adjusts its tip during surgery to negate the surgeon's hand tremor. While testing and improving Micron's design, he began to wonder whether algorithms, similar to Micron's, could help overcome a formidable surgical hurdle when it comes to the heart.
In open-heart surgery, for procedures such as bypass, surgeons cut through the sternum and pull back the ribcage to reach the heart. In some cases, minimally-invasive closed-heart surgery is now an option, in which surgeons operate through small incisions in the chest, all while the heart is still beating. This endoscopic technique eliminates the risk of having to stop the heartbeat and then circulate the patient's blood via a bypass machine, which is what occurs during bypass surgery.
Although the closed-heart approach is an improvement, Riviere knew its constraints. Endoscopic surgical tools, inserted through stiff metal tubes, have only a limited range of access—imagine poking a drinking straw through the side of a Styrofoam cup and moving it around. As a result, multiple entry ports into the chest cavity are often required. Then there's the problem of the left lung: To reach the heart, the lung needs to be deflated. This requires the patient to be attached to an artificial respirator and placed under general anesthesia, which means at least an overnight hospital stay and a greater possibility of dangerous complications.
In the fall of 2001, Riviere, thinking robotics could make heart surgery less traumatic, approached Marco Zenati, professor of surgery at the University of Pittsburgh School of Medicine and adjunct professor at the Robotics Institute. Zenati was well aware of the uses and limitations of surgical robotics: A year before, he performed the first robot-assisted, beating-heart coronary bypass surgery in the United States.
Riviere and Zenati began a series of discussions about developing a robot capable of navigating and working on a beating heart. In approaching the problem of operating on an unstable surface, Riviere studied the existing technique for immobilizing areas of the beating heart. Surgeons would employ small braces that stabilize a portion of the heart. Although the technique was effective, anything that touches the heart, including the braces, causes some disruption to its rhythm.
To gain additional perspective on cardiac surgery, Riviere became a frequent visitor to Zenati's operating room. Observing procedures there sparked in him a research analogy. Rather than a robotic arm or hand-held device trying to impose its will on the beating heart, why not inconspicuously land a robot directly on the heart's surface just like a lunar module landing on the unpredictable surface of the moon? Hence, HeartLander.
His initial HeartLander concept was a two-piece robot linked by a spring. Using suction-cup feet, the robot could, in theory, be instructed by a surgeon to crawl inchworm-style to any point on the epicardium—the heart's surface. (Riviere's daughters dubbed it "Heart Slinky" because of its resemblance to Slinky Dog from the movie Toy Story.) HeartLander would adhere to the epicardium and be stationary, relative to the heart's movement, allowing it to perform precise surgical procedures while riding the heartbeats. And because no part of the heart would be immobilized, the tiny robot wouldn't disrupt the organ's rhythm.
Zenati understood the value and potential of robotic assistance in the OR. The most up-to-date technology for performing cardiac surgery is the Intuitive da Vinci Surgical System, a multi-armed robot controlled by the surgeon using an interface module about the size of an ATM. Zenati had performed his groundbreaking beating-heart procedure using the Computer Motion Zeus system, da Vinci's precursor. Da Vinci allows a surgeon to operate with great precision, but necessitates the use of endoscopic tools, which incurs all of the related undesirables: multiple entry ports, difficulty accessing all areas of the heart, deflation of the left lung. Zenati believed HeartLander would be a dramatic improvement: "We needed a new paradigm: single port procedures."
To allow HeartLander entry into the chest cavity, he developed a single-entry incision approach just below the sternum. Through this technique, HeartLander avoids the lungs. With an additional incision in the pericardium—the membrane that envelops the heart—the surgeon can place HeartLander, by hand, on the heart's apex.
Once Zenati's operative approach and Riviere's HeartLander concept were in place, Riviere and Zenati, in 2002, joined Patronik with bringing HeartLander to life. Starting with his observations of a pig's defiantly beating heart, Patronik spent the next six years working on a mechanical design small enough to fit beneath the pericardium, yet tough enough to not be ripped apart by the heartbeat.
Patronik began by concentrating on HeartLander's inchworm locomotion, in early tests creeping the robot over the surface of a heart substitute—a balloon filled with gel. Lacking motors small or reliable enough to power HeartLander's deliberate movements on the epicardium, he developed a design in which the robot is tethered to its mothership by a supple tail. Running through the tail are the robot's lifelines. Air tubes create the suction for HeartLander's feet. An injection tube supplies an on-board needle for surgical treatments. And drive wires, powered by motors on the mothership, create the robot's steps by extending and contracting the distance between HeartLander's front and rear bodies while the feet adhere and release unbeknownst to the heart. The surgeon can manipulate the drive wires to turn the robot, moving it across the heart in a sidewinding motion.
Patronik produced multiple versions of HeartLander, each one progressively smaller as tests continually resulted in the robot getting stuck between the heart and its protective pericardium, which fits the heart like a latex glove. Finally, Patronik was able to miniaturize HeartLander to around the size of a battery, close to half the size of the first prototype. Guided by the mothership, this miniaturized version nosed its way between the surface of the heart and the pericardium with ease.
After six years of robotics innovation, with funding from the Pittsburgh Foundation and the National Institute of Health, HeartLander is ready for a journey to the dark side of the heart. Patronik wheels the mothership into the OR at UPMC Presby. Takeyoshi Ota, cardiothoracic surgery research associate at the University of Pittsburgh and the fourth member of the HeartLander team, preps the porcine patient.
Patronik wants to provide validation of HeartLander's mastery of the heart. The back side of the heart has always been a difficult region for surgeons to access. HeartLander is already the first robot to successfully navigate the surface of the heart, but if it can successfully perform a test procedure on the heart's posterior, it could be a particularly impressive feat in the eyes of the surgical community. For HeartLander, this task requires it to crawl upside down, the weight of the heart pressing the robot against the spine.
Ota establishes an itinerary, and Patronik programs the robot to move independently to a series of predetermined points on the epicardium, all while the pair tracks its progress on a magnetically generated 3D map of the pig's heart. As planned, HeartLander rounds the backside of the pig's heart, accomplishes its task, and returns without difficulty.
Later, Patronik reviews the video. He sees the pig's chest open, the throbbing heart revealed. Ota's gloved hand then gently lifts and turns the organ. There, on the exposed epicardium, is a circular tattoo of dye marks—HeartLander's version of the American flag thrust into the lunar soil.
While HeartLander's sci-fi appeal has helped attract media attention from the likes of The New York Times, Business Week, and BBC News, it's the robot's practical applications that have surgeons buzzing:
- A recent test demonstrated that HeartLander is capable of placing pacemaker electrodes anywhere on the epicardium—a far greater range than existing techniques allow.
- Riviere notes that the robot could be outfitted with a probe to allow surgeons to treat arrhythmia by ablating(medical-speak for "zapping") damaged or malfunctioning cardiac tissue. Nearly 550,000 ablation and electrode placement procedures are done each year.
- Multiple tests, including HeartLander's journey to the dark side of the heart, have shown HeartLander to beeffective in delivering myocardial injections using its on-board needle. Riviere predicts it could deliver therapy like stem cell treatments to regenerate damaged heart muscle.
- Because the minimally-invasive HeartLander surgeries don't require lung deflation, they could be performedunder local, rather than general, anesthesia. The phrase Zenati utters to explain what that means seems incongruous yet conceivable: "Outpatient heart surgery."
The robot would be significantly cheaper than other current devices for these kinds of procedures, Riviere points out, possibly becoming disposable, like a syringe. Patronik adds that HeartLander could be used in situations when a surgeon must treat a patient remotely—even to the extreme of a patient not being on Earth—which is why NASA awarded Patronik (CS'08) a fellowship to support HeartLander work.
Robert Poston, chief of cardiac surgery and co-director of the Cardiovascular Center at Boston Medical Center, is by no means a skeptic of HeartLander's possibilities. He observed it in action during a recent physicians' seminar organized by HeartLander Surgical, Inc., a Carnegie Mellon spinoff company that is commercializing the robot.
"I was impressed by how far along they are with their technology," he says. "Right now, there's nothing like this device. It's totally novel. I think it has the potential to make a big impact on cardiology."
The inventors of HeartLander say there is more testing to be done; Riviere estimates in another three to eight years the robot will be used in humans.
Bo Schwerin is a science writer for NASA and an award-winning freelance writer. He is a regular contributor to this magazine.
