Although electrocardiograms (ECGs) can help predict cardiac emergencies as much as several months before a potentially life-threatening episode, this usually requires being hooked up to an ECG machine for a period of time at a doctor's office or hospital. A new sensor belt prototype allows an ECG to be recorded around the clock for up to six months, increasing the chances a problem will be discovered and treated before an emergency strikes.
Electrocardiograms (ECGs) non-invasively measure the heart's electrical conduction system using electrodes attached to the skin. In this way, they are able to measure heartbeat rate and regularity over time. The sensor belt, developed by researchers at the Karlsruhe Institute of Technology (KIT) in Germany, is able to do this continuously over a very long period and also measures breathing frequency and activity.
The system consists of a device roughly the size and weight of a mobile phone that houses all the measurement electronics that is strapped to a patient's chest with a belt. There are mobile ECG measurement devices available that are used to record data for up to a week, however these rely on conductive pastes to be applied to the electrodes that can cause irritation or dry out over time. They also require the electrodes to be precisely positioned by medical staff. High-risk patients can also have a measuring device implanted by an operation.
The KIT system avoids these problems by having four dry electrodes embedded in the sensor belt. Not only does this prevent skin irritation, but it also makes it easy for the patient to apply the device on their own. The device records over 1 GB of data over a period of a week, at which time the memory card is read out and the accumulator is recharged.
"The belt resembles known pulse monitors for joggers and also looks similar," says Malte Kirst, one of the developers at KIT. "However, it records far more data. Due to the special design and data evaluation, a usable ECG is recorded for about 99 percent of the time even when single electrodes fail as a result of body movement, for instance."
KIT, the Karlsruhe Municipal Hospital, and the University Hospital of Tübingen conducted a long-term usability test of the sensor belt involving about 50 test subjects who wore the device for an average of two weeks. However, one test subject was continuously monitored for a period of six months, which the researchers say is a world record for a non-invasive ECG recording.
The team says the device could also be used to rule out heart problems in the diagnosis of atrial fibrillation and spontaneous losses of consciousness (so-called "syncopes"), which affect about 400,000 patients in Germany alone. Work is underway to develop the sensor belt prototype into a medical product for this application.
The belt was presented at the Medica trade fair in Düsseldorf last month.