Characterization of volumetric flow rate waveforms at the carotid bifurcations of older adults

While it is widely appreciated that volumetric blood flow rate (VFR) dynamics change with age, there has been no detailed characterization of the typical shape of carotid bifurcation VFR waveforms of older adults. Toward this end, retrospectively gated phase contrast magnetic resonance imaging was used to measure time-resolved VFR waveforms proximal and distal to the carotid bifurcations of 94 older adults (age 68 +/- 8 years) with little or no carotid artery disease, recruited from the BLSA cohort of the VALIDATE study of factors in vascular aging. Timings and amplitudes of well-defined feature points from these waveforms were extracted automatically and averaged to produce representative common, internal and external carotid artery (CCA, ICA and ECA) waveform shapes. Relative to young adults, waveforms from older adults were found to exhibit a significantly augmented secondary peak during late systole, resulting in significantly higher resistance index (RI) and flow augmentation index (FAI). Cycle-averaged VFR at the CCA, ICA and ECA were 389 +/- 74, 245 +/- 61 and 125 +/- 49 mL min(-1), respectively, reflecting a significant cycle-averaged outflow deficit of 5%, which peaked at around 10% during systole. A small but significant mean delay of 13 ms between arrivals of ICA versus CCA/ECA peak VFR suggested differential compliance of these vessels. Sex and age differences in waveform shape were also noted. The characteristic waveforms presented here may serve as a convenient baseline for studies of VFR waveform dynamics or as suitable boundary conditions for models of blood flow in the carotid arteries of older adults.

[1]  D. Holdsworth,et al.  Characterization of volumetric flow rate waveforms in the normal internal carotid and vertebral arteries , 2005, Physiological measurement.

[2]  P. Scheel,et al.  Flow velocity and flow volume measurements in the extracranial carotid and vertebral arteries in healthy adults: reference data and the effects of age. , 2000, Ultrasound in medicine & biology.

[3]  M. Kaazempur-Mofrad,et al.  Hemodynamics and wall mechanics in human carotid bifurcation and its consequences for atherogenesis: investigation of inter-individual variation , 2004, Biomechanics and modeling in mechanobiology.

[4]  D. Holdsworth,et al.  Characterization of common carotid artery blood-flow waveforms in normal human subjects , 1999, Physiological measurement.

[5]  W. Nichols Clinical measurement of arterial stiffness obtained from noninvasive pressure waveforms. , 2005, American journal of hypertension.

[6]  S. Dowd,et al.  The Frequency Dependent Response of the Vascular Endothelium to Pulsatile Shear Stress , 2006, American journal of physiology. Heart and circulatory physiology.

[7]  Edward G Lakatta,et al.  Arterial aging: is it an immutable cardiovascular risk factor? , 2005, Hypertension.

[8]  Ian Marshall,et al.  Carotid flow rates and flow division at the bifurcation in healthy volunteers. , 2004, Physiological measurement.

[9]  B. Rutt,et al.  Frequency response of retrospectively gated phase‐contrast MR imaging: Effect of interpolation , 1993, Journal of magnetic resonance imaging : JMRI.

[10]  L. Ferrucci The Baltimore Longitudinal Study of Aging (BLSA): a 50-year-long journey and plans for the future. , 2008, The journals of gerontology. Series A, Biological sciences and medical sciences.

[11]  A D Hughes,et al.  Flow in carotid bifurcations: effect of the superior thyroid artery. , 1999, Medical engineering & physics.

[12]  Kozo Hirata,et al.  Age-Related Changes in Carotid Artery Flow and Pressure Pulses: Possible Implications for Cerebral Microvascular Disease , 2006, Stroke.

[13]  B. Rutt,et al.  Reconstruction of carotid bifurcation hemodynamics and wall thickness using computational fluid dynamics and MRI , 2002, Magnetic resonance in medicine.

[14]  D. Parker,et al.  Accuracy of phase‐contrast flow measurements in the presence of partial‐volume effects , 1993, Journal of magnetic resonance imaging : JMRI.

[15]  M. Lunt Accuracy and limitations of the ultrasonic Doppler blood velocimeter and zero crossing detector. , 1975, Ultrasound in medicine & biology.

[16]  L. Antiga,et al.  Geometry of the Carotid Bifurcation Predicts Its Exposure to Disturbed Flow , 2008, Stroke.