1. Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
2. Department of Evidence-Based Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
3. Department of Clinical Physiology, Tohoku University Graduate School of Medicine, Sendai, Japan
4. Department of Electronic Engineering, Tohoku University Graduate School of Engineering, Sendai, Japan
5. Division of Biomedical Measurements and Diagnostics, Tohoku University Graduate School of Biomedical Engineering, Sendai, Japan