IMEC improves wireless ECG patch for cardiac monitoring

Jul 14 2008

In the framework of Holst Centre, IMEC has further extended the functionality of its wireless ECG patch for cardiac monitoring. It added wave analysis software locally on the patch node.

The algorithm achieves excellent results for sensitivity and predictivity, and covers a broad range of wave morphologies. The innovative ECG patch is intended to monitor single-lead ECG in daily-life conditions, opening new perspectives for cardiovascular disease management. Besides technological advancements, IMEC also announces National Semiconductor, a specialist in energy-efficient analog integrated circuits, as a new partner within its Human++ program.

IMEC's wireless ECG patch is a wearable, wire-free system easy to set-up. It removes disturbances and discomfort caused by current cardiac monitoring systems. The hybrid system combines electronic assembly on flexible polyimide substrate and integration in textile. This enables flexibility in one dimension and stretchability in the other, which is required for optimal personal comfort. The patch features IMEC's proprietary ultralow-power biopotential ASIC (application specific integrated circuit) to extract the bio-potential signals produced during the ECG measurements, a commercial microcontroller and a 2.4GHz radio link. The patch can continuously monitor the patient's heart at a sample rate of up to 1KHz. It sends the results directly to the receiver, or it can analyze the signals locally before sending them. Local analysis reduces the use of the radio, improving the autonomy of the patch. The current autonomy with local delineation is 10 days of continuous monitoring.

The algorithm embedded in the system performs the delineation of the ECG signal, i.e. the detection of the important electrical waves from the heart. The delineator is able to identify P,Q, R, S, and T wave peaks and boundaries. Since the intervals and amplitudes of these waves contain most of the useful information of the ECG, this delineation will provide quick and useful information to the healthcare provider. The delineator on the ECG patch has been validated over all the recordings in the MIT QT database (a database developed by MIT which includes ECGs chosen to represent a wide variety of QRS and ST-T morphologies, in order to challenge QT detection algorithms with real-world variability). IMEC's ECG patch achieves a 99.93% sensitivity and a 98.28% positive predictivity for QRS detection on 86994 beats. For delineation over 3623 beats, it reaches a 99.83% sensitivity and a 95.08% positive predictivity.

IMEC's Human++ program develops technology for wireless autonomous sensor systems that can be used for health and wellness monitoring. Such systems will for example enable analysis of people with sleep apnea from home or monitor epilepsy patients in an ambulatory setting. The program was launched in 2002 and got a considerable boost in 2005 when IMEC decided to house it in Holst Centre, a new research center set up together with the Dutch research institute TNO under impulse of the Dutch government.

National Semiconductor recently joined the Human++ program. Other Holst Centre partners include Alcatel-Lucent, ASML, Bekaert, NXP, Philips, Target Compiler Technologies and Texas Instruments.

Bert Gyselinckx, Human++ program director: "We see that the Human++ technical progress is reflected in a growing industrial interest. Our physiological monitoring systems are based on ultra-low power wireless communication and start to make use of innovative energy harvesting technology. They are finding applications in sleep staging analysis, cardiac arrhythmia detection and epilepsy monitoring. The growing interest from industry worldwide is proven by new partnerships."