UNLABELLED: Sudden cardiac arrest during exercise can occur without prior warning signs at rest, highlighting the importance of monitoring for its prevention. To detect the signs of ischemic heart disease, including coronary artery anomalies, ST changes must be detected using three‑lead electrocardiograms (ECGs) corresponding to each region of the three coronary artery branches. We conducted ECG monitoring of five runners during a marathon using a wearable three‑lead ECG device (e-skin ECG; Xenoma Inc., Tokyo, Japan). Data without noise or artifacts were successfully collected for one of five runners during the entire marathon. Within the initial hour of the marathon, poor electrode adhesion to the skin hindered the data collection for the remaining four runners, which resulted in significantly decreased acquisition rate compared with the first hour (86.7 ± 13.4 % to 37.3 ± 36.9 %, p = 0.028). Couplets of premature ventricular contractions with clear ECG waveforms in the three leads were detected in one runner during the marathon. Further device improvements are necessary to enable marathon runners to obtain ECGs efficiently without affecting their performance. This study also demonstrated the potential applications of three‑lead wearable ECG monitoring for other short-duration sports and remote home-based cardiac rehabilitation. LEARNING OBJECTIVE: This is an initial trial of a three‑lead wearable electrocardiogram (ECG) monitoring device during a full marathon. ECG data were obtained with low noise and artifacts during the first hour of the marathon; however, the data acquisition rate decreased in the middle and late stages owing to poor electrode adhesion. This study demonstrated the possibility of applying wearable ECG monitoring during short-term exercise and cardiac rehabilitation to detect warning signs and prevent sudden cardiac arrest.
