Volumetric Carotid Flow Characteristics in Doppler Ultrasonography in Healthy Population Over 65 Years Old

Abstract

Background: Carotid flow velocity criteria are well established, with age being a factor influencing measurements. However, there are no volumetric standards for the flow in extracranial arteries. The aim of the study was related to volumetric flow assessment of extracranial arteries in a healthy population >65 years old.

Methods: Doppler volumetric measurements of internal carotid (ICA), external carotid (ECA) and vertebral arteries (VA) were performed in 123 healthy volunteers >65 years old and compared with 56 healthy volunteers <65 years old.

Results: The continuous decline in cerebral blood flow (CBF) volume was observed (p < 0.00001). Volumetric reference values were established in study groups: 1., 65-69 years: 898.5 ± 119.1; 2., 70-74 years: 838.5 ± 148.9; 3., 75-79 years: 805.1 ± 99.3; 4., >80 years: 685.7 ± 112.3 (mL/min). Significant differences were observed between groups: 1 and 3.4, as well as 3 and 4 (p = 0.0295, < 0.000001, 0.00446 respectively). CBF volume decreases gradually with age: 28-64 years-6.2 mL/year (p = 0.0019), 65-75 years-11.4 mL/year (p = 0.0121) and >75 years-14.3 mL/year (p = 0.0074). This is a consequence of flow volume decline in ICA (p = 0.00001) and to lesser extent ECA (p = 0.0011). The decrease of peak systolic (p = 0.002) and end diastolic (p = < 0.00001) velocities in ICA and peak systolic velocity in ECA (p = 0.0017) were observed.

Conclusions: CBF decreases with ageing. Volumetric assessment of CBF may play an important additional role in diagnostics of patients with carotid stenosis. Doppler assessment of cerebral flow volume may create an interesting tool for identifying patients with diminished cerebrovascular reserve and higher risk of ischemic symptoms occurrence.

Keywords: carotid flow volume; extracranial arteries; volumetric assessment.

Figure 1

Regression analysis of cerebral blood flow volume—sum of flow volumes in the internal carotid artery (ICA), external carotid (ECA) and vertebral artery (VA). (A) Statistically significant decrease of 7.6 mL/min in whole study group (p < 0.00001, r = −0.6231, r² = 0.3882). (B) Smaller decline of 6.2 mL/year in the group aged below 65 years (p = 0.0019, r = −0.4052, r² = 0.1642). (C) More prominent with age and in the group aged 65–75 reaching 11.4 mL/year (p = 0.0121, r = −0.2759, r² = 0.0761). (D) Increase to 14.35 mL/year above 75 years old. (p = 0.0074, r = −0.4222, r² = 0.1782).

Figure 2

The gradual decline of cerebral flow volume in patients over 65 years old. (A) Statistically significant volumetric differences between the groups aged: 65–69 and 75–80 years (p = 0.0295), 65–69 and >80 years old (p < 0.000001), 70–74 and >80 years old (p = 0.00446). (B) Statistically significant ICA flow volume decline (p = 0.00001, r = −0.3933, r² = 0.1547). (C) Less prominent ECA flow volume decline (p = 0.0011, r = −0.2916, r² = 0.0851). (D) No statistically significant flow volume changes in vertebral arteries with age (p > 0.07).

Figure 3

Flow velocity changes in internal and external carotid arteries. (A) The significant decrease of peak systolic velocity (PSV) (p = 0.002, r = −0.2392, r² = 0.0572). (B) The significant decrease of end-diastolic velocity (EDV) (p = <0.00001, r = −0.4112, r² = 0.1691) in ICA. ICA EDV decrease is relatively more prominent. (C) The significant decrease of PSV in ECA (p = 0.0017, r = −0.2612, r² = 0.0682).