Fig. 1.

A brief synopsis of pulsatile hemodynamics. A: a simple model of the arterial system with a single dominant reflecting site at the interface between aorta and muscular arteries. When the forward wave (P_f) encounters the reflecting site, a portion is reflected (P_b) and most is transmitted (P_t). B: when the aorta stiffens (denoted by a thicker wall), impedance mismatch is reduced, the reflecting site shifts distally, a smaller fraction of P_f is reflected, and therefore more is transmitted into the microcirculation, which may trigger hypertrophic remodeling. C: the input flow wave interacts with input impedance (Z_i) to produce the resulting pressure wave. The forward-flow wave (Q_f) interacts with characteristic impedance (Z_c) to produce P_f. Wave reflection and overlap between P_f and P_b creates late systolic augmentation (P_aug), which contributes to central pulse pressure (CPP). The timings of wave reflection (t_i) and systolic ejection (t_es) are noted, and considerable overlap between P_f and P_b is evident (t_i < t_es). Total arterial compliance (TAC) can be computed by analyzing the pressure decay in diastole. PPP, peripheral pulse pressure. D: representative carotid (dark) and brachial (light) waveforms in a young healthy person. Note substantial amplification (Amp) of the pulse pressure with distal propagation. E: similar waveforms in an older individual with prominent central augmentation (Aug), which obscures normal peripheral amplification (Amp) of the forward-wave peak. [A and B reproduced with permission from Vyas et al. (96).]