Figure 1: Sample ensemble-averaged radial pressure waveform. Systolic augmentation index (sAIx) was calculated as the ratio of amplitude of the late systolic shoulder ( ) the primary wave pressure peak ( ) expressed as a percentage ( ). Diastolic augmentation index (dAIx) was calculated as . is the peak diastolic pressure in diastole associated with the dicrotic notch. corresponds to a point on a straight line passing through the onset of the incisura of the dicrotic notch and tangential to the natural monoexponential decay of the late diastolic waveform. / was taken as the slope (maximal first derivative) of the maximum rate of pressure rise in systolic pressure per unit time. The slope of the late diastolic decay ( , tau) was calculated as the final two-thirds of the diastolic time interval/(lnESP − lnDP).