This report presents a design proposal for a multi-lead electrocardiograph (ECG) wearable for heart monitoring during physical exercise. The problem: individuals with or at risk of cardiovascular disease (CVD) lack a reliable method to accurately monitor their heart during exercise and continuously for more than forty-eight hours, due to the wearability constraints of traditional ECG systems.
The general analysis finds that monitoring heart activity across multiple leads during exercise and over extended periods supports early detection of CVD. This approach is particularly useful for identifying silent arrhythmias in at-risk individuals, as irregular heartbeats may not appear at rest and occur infrequently during exercise. Traditional ECG systems are limited due to wearability constraints and signal noise resulting from motion artefacts and skin-electrode impedance. To address these challenges, the project focuses on the research, development, and integration of three main components: the dry electrode, the garment, and the conductor.
The dry electrode R&D aims to develop dry electrodes capable of delivering ECG signal quality comparable to wet electrodes. Two designs are developed: a silver screen-printed electrode (SPE) and a silver-plated fabric electrode, both incorporating a foam substrate and silicone skin interface. The SPE proves more viable, as the fabric electrode tends to lose conductivity more rapidly over time.
The garment R&D aims to achieve ECG signal quality comparable to wet electrodes using SPEs across multiple leads, while ensuring comfort and fit for diverse male and female body types. This leads to a design intended for the six-lead standard limb lead configuration, selected for its diagnostic capability, electrode placement, and opportunity to incorporate precordial chest leads. User testing shows that a garment based on a hiking backpack strap system has the potential to meet these requirements.
The conductor R&D aims to achieve low-noise signal transmission comparable to a 2.5 mm coaxial cable, with seamless garment integration. Single-lead testing shows similar signal quality for both shielded and unshielded silver-plated copper wires. However, a 1.13 mm coaxial cable is ultimately selected, supported by literature highlighting the benefits of shielding.
The design integration combines the beforementioned components, resulting in a six-lead garment with a detachable recorder and dry electrodes, and integrated coaxial cables. While adjustable in size, the design still requires at least six sizes.
Design validation shows varying ECG signal quality across participants, depending on fit. Even when tightly fitted, it does not match the ECG signal quality of wet electrodes. The garment is perceived as mildly uncomfortable and unsuited for all-day wear.