Professor Igor Efimov working with PhD candidate Sarah Gutbrod on the team's heart monitor

3D printing enables custom-built heart monitors

A cardiac monitor can now be custom-built to fit the hearts of patients suffering life-threatening disorders thanks to 3D printing.

An international team of biomedical engineers and materials scientists have created an elastic membrane made of a soft, flexible, silicon material that can be precisely shaped to match each patient’s epicardium – the outer layer of the wall of the heart.

The researchers use an MRI or CT scan to create a model of the patient’s heart using a 3D printer, before printing tiny sensors onto the membrane that can precisely measure temperature, mechanical strain and pH, among other markers.

Those sensors can assist physicians with determining the health of the heart and even to predict an impending heart attack before a patient exhibits any physical signs, as well as allowing them to deliver treatment in the form of an electric pulse for cases of arrhythmia – an irregular heartbeat.

Current technology is two-dimensional and cannot cover the full surface of the epicardium or maintain reliable contact for continual use without sutures or adhesives.

"Each heart is a different shape, and current devices are one-size-fits-all and don't at all conform to the geometry of a patient's heart," said Professor Igor Efimov of Washington University in St Louis, who is corresponding author of a paper published online in Nature Communications yesterday.

"With this application, we image the patient's heart through MRI or CT scan then computationally extract the image to build a 3D model that we can print on a 3D printer. We then mould the shape of the membrane that will constitute the base of the device deployed on the surface of the heart."

Ultimately, the membrane could be used to treat diseases of the ventricles in the lower chambers of the heart or could be inserted inside the heart to treat a variety of disorders, including atrial fibrillation, which affects three to five million patients in the USA.

 

"Currently, medical devices to treat heart rhythm diseases are essentially based on two electrodes inserted through the veins and deployed inside the chambers," Efimov said.

"Contact with the tissue is only at one or two points, and it is at a very low resolution. What we want to create is an approach that will allow you to have numerous points of contact and to correct the problem with high-definition diagnostics and high-definition therapy."

Co-leading the team with Efimov is Professor John Rogers from the University of Illinois at Urbana-Champaign, who developed the transfer printing technique and developed the sensors using semiconductor materials including silicon, gallium arsenide and gallium nitride, along with metals, metal oxides and polymers.

Efimov says the membrane developed is similar to the contact lens embedded with sensors designed to monitor glucose levels in diabetics, announced by Google in January, though much more sophisticated.

"Because this is implantable, it will allow physicians to monitor vital functions in different organs and intervene when necessary to provide therapy," he said. "In the case of heart rhythm disorders, it could be used to stimulate cardiac muscle or the brain, or in renal disorders, it would monitor ionic concentrations of calcium, potassium and sodium."

Efimov says the membrane could even hold a sensor to measure troponin, a protein expressed in heart cells and a hallmark of a heart attack, and he hopes that ultimately, such devices will be combined with ventricular assist devices – mechanical devices used to assist weakened ventricles in failing hearts.

"This is just the beginning," he said. "Previous devices have shown huge promise and have saved millions of lives. Now we can take the next step and tackle some arrhythmia issues that we don't know how to treat."

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