Hemodynamic correlates of late systolic flow velocity augmentation in the carotid artery

Background. The contour of the common carotid artery (CCA) blood flow velocity waveform changes with age; CCA flow velocity increases during late systole, and this may contribute to cerebrovascular disease. Late systolic flow velocity augmentation can be quantified using the flow augmentation index (FAIx). We examined hemodynamic correlates of FAIx to gain insight into determinants of CCA flow patterns. Methods. CCA Doppler ultrasound and wave intensity analysis (WIA) were used to assess regional hemodynamics in 18 young healthy men (age 22 ± 1 years). Forward waves (W1) and backward waves (negative area, NA) were measured and used to calculate the reflection index (NA/W1 = RIx). Additional parameters included W2 which is a forward travelling expansion/decompression wave of myocardial origin that produces suction, CCA single-point pulse wave velocity (PWV) as a measure of arterial stiffness, and CCA pressure augmentation index (AIx). Results. Primary correlates of FAIx included W2 (r = -0.52, P<0.05), _logRIx (r = 0.56, P<0.05), and AIx (r = 0.60, P<0.05). FAIx was not associated with CCA stiffness (P>0.05). Conclusions. FAIx is a complex ventricular-vascular coupling parameter that is associated with both increased expansion wave magnitude (increased suction from the left ventricle) and increased pressure from wave reflections.