Silicone Robotic Heart Sleeve Offers Tailored Support
An age-old idiom cautions “don′t wear your heart on your sleeve„, but what about having your heart placed in a sleeve? Researchers show that encasing the heart in a robotic sleeve offers exciting therapeutic promise for end-stage heart failure patients awaiting transplants.
Heart failure affects more than 26 million patients worldwide, accounting for up to 2% of all healthcare expenditure in Europe and North America. The disease also places a considerable burden on hospitals with 1-2% of all hospital admissions in Europe and the United States associated with heart failure. For end-stage patients, the wait for a transplant can be extensive varying from between six months to two years or even beyond. Ventricular assist devices (VADs) can support patients during bridge-to-transplantation, but current devices are bulky and necessitate the use of anticoagulants.
However, a Boston research team from Harvard University and the Wyss Institute for Biologically Inspired Engineering has developed a new approach - a silicone robotic heart sleeve. Tested in vivo using a porcine model the innovation could be a significant alternative to current VADs. Investigator Ellen Roche, now a post-doctoral Research Fellow for the Royal College of Surgeons in Ireland and the National University of Ireland in Galway, explains that in addition to being less bulky, patients would not require anticoagulant therapy. “The advantage is that the patient wouldn′t have to be on blood thinners because the device doesn′t touch the blood there is less risk of clotting compared to other devices,„ she said.
Roche says that moulds are made using 3D printing technology and the heart sleeve is cast in silicone, an inexpensive material. Small artificial muscles then are embedded into the sleeve. “They are basically tiny air balloons surrounded by a mesh and when there is enough pressure they contract linearly. The way they are orientated follows the lines of the heart muscles. There′s a layer of circumferential muscles and a layer of helical muscles and because of their orientation, when they are pressurized you get a squeezing and twisting motion,„ she says. Using this combination of motion, the sleeve mimics the native motion of the heart. Roche details, “We can control the actual myocardium, we can actuate it. We can adjust the pattern from the bottom of the heart up or twist and then squeeze-do whatever patterns we want to mimic the motion of the heart.„
WE CAN CONTROL THE ACTUAL MYOCARDIUM, WE CAN ACTUATE IT. WE CAN ADJUST THE PATTERN FROM THE BOTTOM OF THE HEART UP OR TWIST AND THEN SQUEEZE-DO WHATEVER PATTERNS WE WANT TO MIMIC THE MOTION OF THE HEART.Ellen Roche
Rhythm can be highly fine-tuned and synchronized to the individual by software that reads data via a sensor placed on the heart. The data can then be sued to trigger an algorithm based on the patient′s electrocardiogram. These can include timing delays and actuation sequences. The physician could adjust rhythm as the patient recovers or if the activity level changes. While the current design features external controls designed to wear on a belt, so the patient can remain ambulatory, the hope is that in the future it would be completely implantable, remotely charged and programmable.
The silicone sleeve also could have developments. In the current iteration, the silicone sleeve is cast in a few general sizes and the surgeon adjusts it to the individual heart during the implantation procedure. Roche notes that 3D printing technology isn′t “quite there yet„ for the quality necessary to print a sleeve directly. She says in the future, “You definitely could scan patients beforehand and use that data to choose a size within a range of sizes. You could also tailor-make the device for unique anatomies or perhaps have a special arrangement of the artificial muscles, that would be possible as well. Especially if you are [3D] printing the whole device, then you would have a lot of flexibility.„
Other hoped for improvements are to deliver the heart sleeve using a less invasive surgical procedure. “Ideally, we would like to do it through a thoracotomy or even a mini-thoracotomy,„ she says.
The combination of flexible material and artificial muscles could lend itself to many other applications. While several cardiac indications are a natural fit, Roche suggests the technology could be adapted for external massage or stimulation of muscles, possibly for patients suffering from paralysis or muscular dystrophy.
Combining the technology with biologics is another avenue. Roche explains, “We′ve done some work with controlled release of biologics. We′re still working on that and one study should be published relatively soon on preliminary work. That′s definitely something that I′m interested in: combining mechanical assist with biological therapy.„ She believes that paracrine factor therapy and small molecule drugs are areas of interest. “Our hope, which is a hypothesis at the moment, is that we can use the device to almost train the heart or do some rehabilitation. That we could unload it temporarily and then deliver biologics. So that while it′s unloaded we could help it to repair itself. Then eventually we could wean the patient off the mechanical assist,„ she says.
Ellen Roche estimates it could be five to ten years before the device will enter human trials. “We need to do some work on miniaturizing controls and pumps so that they are wearable. Also, the robustness of the artificial muscle and the attachment to the heart. There are a number of things that we want improve on before considering human trials and then to get through regulatory approval would be quite a big task.„ However, in the future millions of heart failure patients may benefit from a robotic heart sleeve that could move many from the bridge-to-transplant category to bridge-to-recovery.