Characterization of common carotid artery blood-flow waveforms in normal human subjects

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Abstract
Knowledge of human blood-flow waveforms is required for in vitro investigations and numerical modelling. Parameters of interest include: velocity and flow waveform shapes, inter- and intra-subject variability and frequency content. We characterized the blood-velocity waveforms in the left and right common carotid arteries (CCAs) of 17 normal volunteers (24 to 34 years), analysing 3560 cardiac cycles in total. Instantaneous peak-velocity (Vpeak) measurements were obtained using pulsed-Doppler ultrasound with simultaneous collection of ECG data. An archetypal Vpeak waveform was created using velocity and timing parameters at waveform feature points. We report the following timing (post-R-wave) and peak-velocity parameters: cardiac interbeat interval (TRR) = 0.917 s (intra-subject standard deviation = ±0.045 s); cycle-averaged peak-velocity (VCYC) = 38.8 cm s-1 (±1.5 cm s-1); maximum systolic Vpeak = 108.2 cm s-1 (±3.8 cm s-1) at 0.152 s (±0.008 s); dicrotic notch Vpeak = 19.4 cm s-1 (±2.9 cm s-1) at 0.398 s (±0.007 s). Frequency components below 12 Hz constituted 95% of the amplitude spectrum. Flow waveforms were computed from Vpeak by analytical solution of Womersley flow conditions (derived mean flow = 6.0 ml s-1). We propose that realistic, pseudo-random flow waveform sequences can be generated for experimental studies by varying, from cycle to cycle, only TRR and VCYC of a single archetypal waveform.