The soft robotic models are patient-specific and could help clinicians zero in on the best implant for an individual.:
From: Massachusetts Institute of Technology
February 22, 2023 -- Engineers
developed a procedure to 3D print a soft and flexible replica of a patient's
heart. These models could help doctors tailor treatments, such as aortic
valves, to an individual patient.
No two hearts beat
alike. The size and shape of the heart can vary from one person to the next.
These differences can be particularly pronounced for people living with heart
disease, as their hearts and major vessels work harder to overcome any
compromised function.
MIT engineers are
hoping to help doctors tailor treatments to patients' specific heart form and
function, with a custom robotic heart. The team has developed a procedure to 3D
print a soft and flexible replica of a patient's heart. They can then control
the replica's action to mimic that patient's blood-pumping ability.
The procedure involves
first converting medical images of a patient's heart into a three-dimensional
computer model, which the researchers can then 3D print using a polymer-based
ink. The result is a soft, flexible shell in the exact shape of the patient's
own heart. The team can also use this approach to print a patient's aorta --
the major artery that carries blood out of the heart to the rest of the body.
To mimic the heart's
pumping action, the team has fabricated sleeves similar to blood pressure cuffs
that wrap around a printed heart and aorta. The underside of each sleeve
resembles precisely patterned bubble wrap. When the sleeve is connected to a
pneumatic system, researchers can tune the outflowing air to rhythmically
inflate the sleeve's bubbles and contract the heart, mimicking its pumping
action.
The researchers can
also inflate a separate sleeve surrounding a printed aorta to constrict the
vessel. This constriction, they say, can be tuned to mimic aortic stenosis -- a
condition in which the aortic valve narrows, causing the heart to work harder
to force blood through the body.
Doctors commonly treat
aortic stenosis by surgically implanting a synthetic valve designed to widen
the aorta's natural valve. In the future, the team says that doctors could
potentially use their new procedure to first print a patient's heart and aorta,
then implant a variety of valves into the printed model to see which design
results in the best function and fit for that particular patient. The heart replicas
could also be used by research labs and the medical device industry as
realistic platforms for testing therapies for various types of heart disease.
"All hearts are
different," says Luca Rosalia, a graduate student in the MIT-Harvard
Program in Health Sciences and Technology. "There are massive variations,
especially when patients are sick. The advantage of our system is that we can
recreate not just the form of a patient's heart, but also its function in both
physiology and disease."
Rosalia and his
colleagues report their results in a study appearing today in Science
Robotics. MIT co-authors include Caglar Ozturk, Debkalpa Goswami, Jean
Bonnemain, Sophie Wang, and Ellen Roche, along with Benjamin Bonner of
Massachusetts General Hospital, James Weaver of Harvard University, and
Christopher Nguyen, Rishi Puri, and Samir Kapadia at the Cleveland Clinic in
Ohio.
Print and pump
In January 2020, team
members, led by mechanical engineering professor Ellen Roche, developed a
"biorobotic hybrid heart" -- a general replica of a heart, made from
synthetic muscle containing small, inflatable cylinders, which they could control
to mimic the contractions of a real beating heart.
Shortly after those
efforts, the Covid-19 pandemic forced Roche's lab, along with most others on
campus, to temporarily close. Undeterred, Rosalia continued tweaking the
heart-pumping design at home.
"I recreated the
whole system in my dorm room that March," Rosalia recalls.
Months later, the lab
reopened, and the team continued where it left off, working to improve the
control of the heart-pumping sleeve, which they tested in animal and
computational models. They then expanded their approach to develop sleeves and
heart replicas that are specific to individual patients. For this, they turned
to 3D printing.
"There is a lot of
interest in the medical field in using 3D printing technology to accurately
recreate patient anatomy for use in preprocedural planning and training,"
notes Wang, who is a vascular surgery resident at Beth Israel Deaconess Medical
Center in Boston.
An inclusive design
In the new study, the
team took advantage of 3D printing to produce custom replicas of actual
patients' hearts. They used a polymer-based ink that, once printed and cured,
can squeeze and stretch, similarly to a real beating heart.
As their source
material, the researchers used medical scans of 15 patients diagnosed with
aortic stenosis. The team converted each patient's images into a
three-dimensional computer model of the patient's left ventricle (the main
pumping chamber of the heart) and aorta. They fed this model into a 3D printer
to generate a soft, anatomically accurate shell of both the ventricle and
vessel.
The team also
fabricated sleeves to wrap around the printed forms. They tailored each
sleeve's pockets such that, when wrapped around their respective forms and
connected to a small air pumping system, the sleeves could be tuned separately
to realistically contract and constrict the printed models.
The researchers showed
that for each model heart, they could accurately recreate the same
heart-pumping pressures and flows that were previously measured in each
respective patient.
"Being able to
match the patients' flows and pressures was very encouraging," Roche says.
"We're not only printing the heart's anatomy, but also replicating its
mechanics and physiology. That's the part that we get excited about."
Going a step further, the
team aimed to replicate some of the interventions that a handful of the
patients underwent, to see whether the printed heart and vessel responded in
the same way. Some patients had received valve implants designed to widen the
aorta. Roche and her colleagues implanted similar valves in the printed aortas
modeled after each patient. When they activated the printed heart to pump, they
observed that the implanted valve produced similarly improved flows as in
actual patients following their surgical implants.
Finally, the team used
an actuated printed heart to compare implants of different sizes, to see which
would result in the best fit and flow -- something they envision clinicians
could potentially do for their patients in the future.
"Patients would
get their imaging done, which they do anyway, and we would use that to make
this system, ideally within the day," says co-author Nyugen. "Once
it's up and running, clinicians could test different valve types and sizes and
see which works best, then use that to implant."
Ultimately, Roche says
the patient-specific replicas could help develop and identify ideal treatments
for individuals with unique and challenging cardiac geometries.
"Designing
inclusively for a large range of anatomies, and testing interventions across
this range, may increase the addressable target population for minimally
invasive procedures," Roche says.
This research was
supported, in part, by the National Science Foundation, the National Institutes
of Health, and the National Heart Lung Blood Institute.
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