Abstract 12309: Relationship Between Pressure and Flow Waveforms in Cerebral Arteries of 1020 Subjects: Establishing Normal Values
In order to obtain new information on diagnosis and monitoring of cerebrovascular disease, it is desirable to know normal values and change with age of cerebral artery pressure and flow waves. Such information does not presently exist.
Flow waveforms (transcranial Doppler) were measured in 1020 normal subjects undergoing 24-hour BP monitoring to exclude diagnosis of hypertension at Ruijin Hospital, Shanghai. Central aortic pressure wave was generated using validated SphygmoCor generalized transfer function (K002742) from the radial artery wave measured at the wrist by applanation tonometry, and taken as a surrogate of pressure at entry into the carotid canal. Relationship were described in the time domain as Flow Augmentation Index (FAIx) vs Pressure AIx (PAIx). Relationship in the frequency domain was described as impedance. FAIx was flow augmentation ÷ flow wave amplitude and PAIx was pressure augmentation ÷ pressure wave amplitude.
Flow waves were similar in cerebral arteries, with flow velocity positive throughout diastole in all subjects and with no backflow. Peak flow velocity (45-85 cm/s) was similar to that in the carotid and other systemic arteries. Amplitude of pressure waves and PAIx increased with age. Amplitude of flow waves did not increase with age, but FAIx did, with linear relationship to PAIx. Cerebral vascular impedance was low and phase difference small, with fluctuations indicative of Wave Reflection, but with reflection magnitude <40%, and less than other vascular beds excepting the kidney and lungs. As with AIx relationship in the time domain, there was little or no change in impedance with age, and little or no gender difference.
Findings provide normal values against which measurements in disease states can be compared. Findings are consistent with those in vascular beds in lungs and kidney, but do not show aging changes as described in the ascending aorta for the whole systemic circulation.
Author Disclosures: M. Kim: None. Y. Li: None. F. Wei: None. J. Wang: None. M.F. O’Rourke: Ownership Interest; Significant; AtCor Medical. A. Avolio: None.
- © 2014 by American Heart Association, Inc.