New medical instruments with integrated soft electronics could improve diagnosis and treatment of cardiac conditions. The surgical tools use soft materials that conform to the body’s tissue and permit a single catheter to combine diagnostic and therapeutic functions while providing real-time feedback and electrophysiological information. A “fully loaded” catheter could reduce the need for multiple catheters and repeated imaging during cardiac procedures, reducing time in surgery and improving outcomes.

The instruments were developed by engineers at the George Washington University in Washington, DC, and Northwestern University in Chicago and a paper on cardiac applications for catheters with the soft multilayer electronic array appeared in Nature Biomedical Engineering Sept. 7.

"We have taken new breakthrough materials and fabrication techniques typically employed by the semiconductor industry and applied them to the medical field, in this case cardiology, to advance a new class of medical instruments that will improve cardiac outcomes for patients and allow physicians to deliver better, safer and more patient-specific care,” said Igor Efimov, the Alisann and Terry Collins professor of biomedical engineering at the George Washington University.

The multipurpose tools will be particularly useful in cardiac ablation procedures for atrial fibrillation. Currently, physicians use one catheter to map the malfunctioning cells generating the irregular heartbeat and another to destroy those cells using radio frequency ablation, cryoablation, or electroporation ablation.

Soft electronics affixed to an inflated balloon catheter. Credit: John Rogers, Northwestern University

By integrating sensors and devices that permit measurement of temperature and quality of contact, as well as provide real-time feedback and enable either radio frequency or electroporation ablation, the new instrument can eliminate the need for two catheters.

The sophisticated tool can also dramatically reduce the amount of imaging required and exposure to radiation sustained by patients and physicians. Procedures to treat atrial fibrillation today recreate in a minimally invasive way the Cox Maze procedure developed in 1987, with physicians creating a series of lines using ablation instead of incisions to create scar tissue that interrupt the abnormal electrical signals underlying the condition.

“Leaving a gap in the line will lead to failure of the ablation procedure,” Efimov told BioWorld. But creating continuous lines in the right locations is challenging with typical catheter technology that requires drawing lines as a series of points, so “fluoroscopy is used to see each point, and that exposes both the patient and physician to X-rays,” he explained.

The integrated catheter allows the physician to use imaging once to ensure proper placement, then to draw a line through multiple electrodes, without having to continuously or repeatedly use X-rays. In addition, the rigidity of most catheters limits their ability to conform to heart tissue and achieve good contact, which is essential for well targeted delivery of the electrical current used in radiofrequency and irreversible electroporation ablation.

"Hard, rigid catheters cannot conform to the heart because the heart itself is not hard and rigid,” said John Rogers, the Louis A. Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery at Northwestern University. “We leveraged our advances in soft, stretchable and flexible electronics to develop medical devices that include elastic, interconnected arrays of sensors and actuators, capable of gently and softly conforming to tissue surfaces. The result improves the accuracy and precision of associated surgical processes, for faster, less risky and more effective treatments."

The technology

Efimov and Rogers have collaborated for years. They have developed a number of applications for Roger’s laboratory’s advances in material science, including the ability to transfer print electronic structures developed with traditional semiconductor industry methods onto soft plastic materials without exposing the materials to the acids and high heat that would otherwise destroy them, Efimov said. The current “Lego like” toolkit connects electrical circuitry such as electrodes and activators using serpentine structures that permit even metals to stretch to a significant degree.

The two researchers have already founded a new company, Nusera Biosystems Inc., to pursue commercialization of the technology for cardiology. Rogers is also working with collaborators on neurological and other applications.

“From my standpoint as a biomedical engineer, the high-level takeaway is that we have developed methods and materials approaches that allow us to integrate some of the most advanced electronic structures, formed using methods adapted from the semiconductor industry, onto balloon type substrates, in single or multilayer configurations,” Rogers told BioWorld. “The results open up new opportunities in the development of sophisticated, minimally invasive surgical instruments that address clinical needs in interventional cardiology and other areas.”

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