Fig. 1

Simultaneously measured ECG, carotid and radial arterial pulse waveforms (CAPW and RAPW). The detected R-wave peaks are indicated by closed circle, and the starting points of CAPW and RAPW signals are indicated by "upward triangles and downward triangles", respectively. The heart-carotid pulse transit time (PTT) is the interval from the R-wave peak to the starting point of the CAPW signal; the heart-radial PTT is from the R-wave peak to the starting point of RAPW signal; the carotid-radial PTT is between the starting points of CAPW and RAPW signals