A new wireless cardiac “patch” could allow doctors to continuously monitor patients’ hearts and record electrocardiograms (EKGs) while they are on the go. Such highly portable continuous monitors could help doctors treat cardiac patients, and they may soon become crucial tools in diagnosing conditions in otherwise healthy people, say the device’s developers.
Developed by researchers at the Interuniversity Micro-Electronic Centre (IMEC), an independent nanotechnology research institute in Eindhoven, the Netherlands, the flexible stick-on device is a variation of a Holter monitor, a portable EKG tool currently used by cardiologists to help assess and diagnose their patients. But Holter monitors require a number of electrodes to be stuck to the body and connected, via a tangle of wires, to a bulky recording device worn at the hip.
In contrast, the new device just sticks onto the patient’s chest and wirelessly sends electrical signals detected from the heart to a credit-card-like receiver. These signals can be analyzed and used to sound an alarm as an early warning when dangerous heart rhythms, or arrhythmias, are detected, says Bert Gyselinckx, the director of IMEC’s Wireless Autonomous Transducer Solutions program. For example, the device could be used to alert emergency services to problems suffered by elderly cardiac patients who live alone.
The new device consists of a flexible circuit board just 60 millimeters long and 20 millimeters wide that contains all the circuitry to detect and transmit the EKG signal up to 10 meters. The flexible board slips into a Lycra patch with three sticky points of contact that act as the EKG electrodes. Short wires within the pouch connect the contact points to the circuit board via snap-on sockets. “This makes it easier to attach the electrodes,” says Gyselinckx.
The signal is sent to the receiver using an off-the-shelf wireless transmitter, which uses technology similar to Bluetooth but at much lower power, says Gyselinckx. The receiver is a smart card–a pocket-sized card with an integrated circuit embedded in it–that also incorporates a thin battery. “It looks and feels like a credit card,” Gyselinckx says. The card can store the EKG data on an embedded two-gigabyte flash-memory device, or it can be hooked up to a handheld computer or cell phone to relay the data to a clinic.
There is a general trend to make heart-monitoring devices wireless because they are so much easier to use, says Mike Kingsley, director of exercise-physiology laboratories at Swansea University, in Wales.
Already, consumer products are available that monitor the heart and send the signal wirelessly to a watch. But these products only detect heart rate, in terms of beats per minute, says Kingsley. “An EKG gives you a lot more information about the way the electrical current is traveling through the heart,” he says. A cardiologist can use this data to determine the morphology and behavior of the heart, both of which are vital to making a diagnosis.
Many hospitals have started installing wireless EKG patient-tracking systems, says Gyselinckx, as a way of keeping tabs on their patients and locating them if they get into trouble. But such systems amount to little more than Holter monitors hooked up to a central hospital tracking system that monitors the patients’ whereabouts and EKGs.
The IMEC device does have limitations: in its current form, it can’t record as much of the heart’s electrical activity as a clinical EKG can. “It doesn’t give you an overall picture of the heart–only a snapshot,” Kingsley says.
Even so, it is still very useful because it allows all arrhythmic events to be detected, says Hans Stromeyer, chief medical officer of Monebo, in Austin, TX, which has developed a wireless EKG device that is worn like a belt. “And continuous monitoring can pick up events that the patient will not be aware of,” he says. This has huge potential in preventative medicine because it can help doctors detect and treat serious heart conditions before they progress and cause irreparable damage.
Indeed, the IMEC team is developing the heart patch as part of a larger project, called Human++, aimed at designing telemedicine technologies for preventative health. Continuously monitoring the vital signs of otherwise healthy people in the general population could make it possible for doctors to preempt a variety of serious illnesses through early detection, Gyselinckx says.
Wireless home-based monitoring and diagnosis is already beginning to happen, says Stromeyer. It has demonstrated its usefulness in long-term recovery and is much cheaper than hospital rehabilitation.
There is also a lot of interest in using portable heart monitors to assist in drug trials. This is because one section of the EKG trace, known as the QT segment, has been shown to be a good indicator of changes in heart activity caused by drug toxicity, says Stromeyer. Highly portable monitors such as the IMEC device could be particularly useful in such an application.
But for now the IMEC team is working to enable the device to record as much data as a clinical EKG can. The team is also working to make the patch more pliable with a combination of flexible organic electronics and thin-film silicon electronics, with the aim of licensing the technology.