Creepy-crawly robot to mend a broken heart
A device that sounds like a 21st-century version of a medicinal leech may soon be set loose inside the chests of heart patients. Resembling a robotic caterpillar, it will crawl across the surface of their beating heart, delivering treatment without the need for major surgery.
The device, called HeartLander, can be inserted using minimally invasive keyhole surgery. Once in place, it will attach itself to the heart and begin inching its way across the outside of the organ, injecting drugs or attaching medical devices. In tests on live pigs, the HeartLander has fitted pacemaker leads and injected dye into the heart. This video shows the latest prototype creeping over the surface of a beating model heart (2.1MB, mpg format).
The 20-millimetre-long robot has two suckers for feet, each pierced with 20 holes connected to a vacuum line, which hold it onto the outside of the heart. By moving its two body segments back and forth relative to one another it can crawl across the heart at up to 18 centimetres per minute. This back-and-forth movement is generated by pushing and pulling wires that run back to motors outside the patient’s body. The robot is being developed by Cameron Riviere and colleagues at Carnegie Mellon University in Pittsburgh, Pennsylvania.
The plan is to insert the HeartLander through an incision below the ribcage, and pass it through a further incision in the membrane that encloses the heart. Surgeons keep track of the device using X-ray video or a magnetic tracker, and control its movements via a joystick.
Traditional open-heart surgery requires a massive incision, and the heart usually has to be stopped to make it easier to operate safely. Though minimally invasive procedures on a beating heart are sometimes possible, some areas of the heart are out of reach to instruments inserted through the keyhole incisions, and the limited space in the chest cavity makes operating difficult.
"HeartLander can reach all parts of the heart’s surface," Riviere says. And because it is stationary relative to the heart’s surface, there is no need to interfere with the organ’s movement.
Entering the body from a single small incision could even allow some heart procedures to be performed without a general anaesthetic, he says. "It avoids having to disturb the ribcage, or to deflate the left lung to access the heart."
"This device is certainly like nothing else I’ve seen," says Andrew Rankin, a cardiologist at the University of Glasgow in the UK. Many procedures can be performed by passing instruments into the heart through blood vessels, but this is not possible where damaged or diseased tissue is close to the heart’s surface. "This device could be useful in those cases," Rankin says.
He suggests it might come into its own for future treatments such as stem cell therapies to encourage regeneration of heart tissue. "You can imagine this device moving around the surface of a scarred heart to deliver treatments."
The researchers are now working on adding a radio-frequency probe to the device, to treat arrhythmias by selectively killing malfunctioning heart tissue. They also plan to add a camera.
A helping hand for keyhole surgeons
Minimally invasive keyhole surgery can reduce the trauma of an operation and shorten a patient’s stay in hospital by limiting wound size and cutting the risk of infection. It may not, however, be an option when large organs such as the liver are in the way, as instruments thin enough to pass through a keyhole incision might cause damage when used to move such organs aside.
To tackle this problem, Toshio Takayama and colleagues at the Tokyo Institute of Technology in Japan have developed a three-fingered steel hand for grasping organs. The hand is only assembled after its component parts have been inserted into the patient through two small incisions.
The biggest component is a hollow arm 30 centimetres long and 16 millimetres in diameter. After this has been inserted through one of the incisions, surgeons pass the 5-centimetre-long fingers part-way through a nearby keyhole and snap them into place on the arm. Stiff wires along the arm move the fingers to make them grasp organs.
In experiments inside a dummy body cavity, Takayama says the hand proved adept at "grasping large and slippery objects like internal organs". The device was unveiled at a conference in Rome, Italy, last week, which included discussion of surgical robotics.
Ara Darzi, a surgeon at St Mary’s Hospital in London, says that until now surgical toolmakers have focused on making instruments for keyhole surgery smarter and more articulated. "Assembling tools inside the body is a novel idea," he says.
Paul Marks
Scientist 