Figure 1.

Pressure waveforms and characteristics in patients with high and low arterial stiffness. In increased arterial stiffness, increased velocity of the pulse wave results in earlier return of the wave to the aorta, i.e., during systole instead of diastole. Thus, it is added and increases SBP (augmentation pressure), while DBP is decreased. CKD, chronic kidney disease; Tr, arrival time of reflected waves at central aorta from the onset of left ventricular ejection (T0) to inflection point A; AP = P1–P2 the augmentation of aortic systolic pressure induced by the return of the reflected wave, where P1 is the pressure at the first inflection point A and P2 is the pressure at the second inflection point B; Augmentation index (AI) (%) is defined by the formula: AI = 100 × AP/PP, where PP is the aortic pulse pressure (systolic minus diastolic pressure); Ts, period from start to the end of systole (ejection duration).