Abstract
This article presents the devising, development, prototyping and assessment of a wearable arm-ECG sensor system (WAMECG1) for long-term non-invasive heart rhythm monitoring, and functionalities for acquiring, storing, visualizing and transmitting high-quality far-field electrocardiographic signals. The system integrates the main building blocks present in a typical ECG monitoring device such as the skin surface electrodes, front-end amplifiers, analog and digital signal conditioning filters, flash memory and wireless communication capability. These are integrated into a comfortable, easy to wear, and ergonomically designed arm-band ECG sensor system which can acquire a bipolar ECG signal from the upper arm of the user over a period of 72 h. The small-amplitude bipolar arm-ECG signal is sensed by a reusable, long-lasting, Ag–AgCl based dry electrode pair, then digitized using a programmable sampling rate in the range of 125 to 500 Hz and transmitted via Wi-Fi. The prototype comparative performance assessment results showed a cross-correlation value of 99.7% and an error of less than 0.75% when compared to a reference high-resolution medical-grade ECG system. Also, the quality of the recorded far-field bipolar arm-ECG signal was validated in a pilot trial with volunteer subjects from within the research team, by wearing the prototype device while: (a) resting in a chair; and (b) doing minor physical activities. The R-peak detection average sensibilities were 99.66% and 94.64%, while the positive predictive values achieved 99.1% and 92.68%, respectively. Without using any additional algorithm for signal enhancement, the average signal-to-noise ratio (SNR) values were 21.71 and 18.25 for physical activity conditions (a) and (b) respectively. Therefore, the performance assessment results suggest that the wearable arm-band prototype device is a suitable, self-contained, unobtrusive platform for comfortable cardiac electrical activity and heart rhythm logging and monitoring.
Highlights
Despite the overall decrease in cardiovascular mortality in recent decades, sudden cardiac death, usually caused by lethal arrhythmias, accounts for 50% of heart disease-related deaths and occurs among patients never diagnosed or previously classified as at low cardiovascular risk [1].Different paroxysmal arrhythmias only manifest sporadic symptoms requiring long-term cardiac monitoring for correct diagnosis [2]
The total number of manually counted R-peaks was 3104, while the system detected 3163 (a false R-peak physical activity to a low level, as requested (TP is the number of true R-peaks detected)
Discussion and Conclusions physical activity to a low level, as requested (TP is the number of true R-peaks detected)
Summary
Despite the overall decrease in cardiovascular mortality in recent decades, sudden cardiac death, usually caused by lethal arrhythmias, accounts for 50% of heart disease-related deaths and occurs among patients never diagnosed or previously classified as at low cardiovascular risk [1]. Different paroxysmal arrhythmias only manifest sporadic symptoms requiring long-term cardiac monitoring for correct diagnosis [2]. In such cases, implantable loop recorders (ILRs) are currently becoming more common and are considered as an important tool by clinicians; their use requires costly surgical procedures and carries infection risks [3]. A variety of experimental wearable smart devices have been developed for ECG monitoring; they include T-shirts or vests [7,8], belts [9,10], adhesive patches [11,12]
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