Background: Bipolar ECG leads derived from sensors within a comfortable wearable-band on the left upper-arm, can provide ECG signals of sufficient quality after signal-enhancement treatment, and reliable heart rhythm analysis can be provided for long-term ECG-monitoring and heart-rhythms clinical interpretation. We have developed and preliminary tested a cable-free arm-ECG recorder wearable band system-device for dual orthogonal arm-ECG (WAMECG2) recording and wireless data-transfer.
Methods: The WAMECG2 system-device functionalities: acquiring, storing, visualising and transmitting, high-quality far-field ECGs were assessed. The system integrates skin-surface dry-electrodes (Sintered-Ag-AgCl), dual-channel front-end amplifiers, analogue and digital signal conditioning filters, flash memory and wireless communication capability. These were integrated into a comfortable, easy to wear, and ergonomically designed arm-band ECG sensor system; which can acquire two bipolar ECG signals from the upper-arm of the user over a period of 72 hours. The small-amplitude bipolar arm-ECG signals are sensed and digitally captured using a programmable sampling rate in the range of 125-500Hz, and transmitted via Wi-Fi.
Results: The 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 sensibility was 99.66% and 94.64%, while the positive predictive value 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.
Conclusions: 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.