Tissue-Hugging Implant Maps Heart's Electrical Activity

A new type of implantable device for measuring the heart's electrical output in unprecedented detail represents the first use of flexible silicon technology for a medical application.

Researchers at the University of Pennsylvania (Penn; Philadelphia, USA) School of Medicine and School of Engineering and Applied Science developed the innovative device, which allows the measuring of cardiac electrical activity with greater resolution in both time and space. In a proof of concept experiment in an in vivo animal model, the researchers built a sensor system composed of 2,016 silicon nanomembrane transistors configured to record electrical activity directly from the curved, wet, surface of a beating porcine heart. The device sampled the transistor's activity with simultaneous submillimeter and submillisecond resolution through 288 amplified and multiplexed channels. The researchers thus succeeded in mapping the spread of spontaneous and paced ventricular depolarization on the epicardial surface in real time, and at high resolution.


For comparison, standard clinical systems usually use about five to 10 contacts and no active transistors, placed on a catheter that is moved in and around the heart and connected to rigid silicon circuits distant from the target tissue. Another focus of the ongoing work is to develop similar types of devices that are not only flexible, like a sheet of plastic, but fully stretchable, like a rubber band, so that they can fully conform and wrap around large areas of curved tissues. The researchers describe their proof-of-principle design and findings in the March 24, 2010, issue of Science Translational Medicine.

"The new devices bring electronic circuits right to the tissue, rather than having them located remotely inside a sealed can that is placed elsewhere in the body, such as under the collar bone or in the abdomen,” said cosenior author Brian Litt, M.D., an associate professor of neurology. "This enables the devices to process signals right at the tissues, which allows them to have a much higher number of electrodes for sensing or stimulation than is currently possible in medical devices.”

"We demonstrated high-density maps of electrical activity on the heart recorded from the device, during both natural and paced beats,” added coauthor David Callans, M.D., a professor of medicine at Penn. "We also plan to design advanced, ‘intelligent' pacemakers that can improve the pumping function of hearts weakened by heart attacks and other diseases.”

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