Age-related changes in carotid artery flow and pressure pulses: possible implications for cerebral microvascular disease.

BACKGROUND AND PURPOSE We sought to establish the relation between the pulsatile components of pressure and flow waveforms in the carotid artery and their change with age. METHODS Distention (pressure) and axial flow velocity waveforms were recorded noninvasively and simultaneously from the common carotid artery of 56 healthy subjects aged 20 to 72 years. RESULTS There was a close relation between the time intervals of pressure and flow waves: from foot to first shoulder or peak, to second shoulder or peak, and to incisura (r=0.97, P<0.0001 for each), which approximated the line of identity. The peak and nadir of flow velocity decreased with age, but late systolic flow augmentation increased substantially (1.6 times in the older group); this can be attributed to earlier wave reflection from the lower body. Pressure augmentation index (PAI) and flow augmentation index (FAI) increased similarly with age (PAI (%) = 0.84 x age - 26.6; FAI (%) = 0.75 x age + 11.9; both P<0.0001). CONCLUSIONS Arterial stiffening with aging increases carotid flow augmentation and can explain the increasing flow fluctuations in cerebral blood vessels. Measurement of carotid FAI may provide a gauge for risk of cerebral microvascular damage, just as PAI provides a gauge for risk of left ventricular hypertrophy and failure.