Attenuation of blood flow pulsatility along the Atlas slope: a physiologic property of the distal vertebral artery?
OBJECTIVE
Physiologic and pathologic arterial tortuosity may attenuate blood flow pulsatility. The aim of this prospective study was to assess a potential effect of the curved V3 segment (Atlas slope) of the vertebral artery on arterial flow pulsatility. The pulsatility index and resistance index were used to assess blood flow pulsatility.


METHODS
Twenty-one healthy volunteers (17 men, 4 women; mean age, 32 years) were examined with a 3T MR imaging system. Blood velocities were measured at 2 locations below (I and II) and at 1 location above the V3 segment (III) of the vertebral artery by using a high-resolution 2D-phase-contrast sequence with multidirectional velocity-encoding.


RESULTS
Pulsatility and resistance indices decreased along all measurement locations from proximal to distal. The pulsatility index decreased significantly from location II to III and from I to II. However, the decrease was more pronounced along the Atlas slope than in the straight-vessel section below. The decrease of the resistance index was highly significant along the Atlas slope (location II to III). The decrease from location I to II was small and not significant.


CONCLUSIONS
The pronounced decrease in pulsatility and resistance indices along the interindividually uniformly bent V3 segment compared with a straight segment of the vertebral artery indicates a physiologic attenuating effect of the Atlas slope on arterial flow pulsatility. A similar effect has been described for the carotid siphon. A physiologic reduction of pulsatility in brain-supplying arteries would be in accordance with several recent publications reporting a correlation of increased arterial flow pulsatility with leukoencephalopathy and lacunar stroke.
From the Divisions of Neuroradiology (T.S., C.S., A.v.H.) Tilman.Schubert@usb.ch.
T
T
Schubert
Department of Radiology (M.P.), Bruderholz Cantonal Hospital, Basel, Switzerland.
M
M
Pansini
Radiological Physics (O.B., F.S.), Clinic of Radiology and Nuclear Medicine.
O
O
Bieri
From the Divisions of Neuroradiology (T.S., C.S., A.v.H.).
C
C
Stippich
Department of Neuroradiology (S.W.), Hirslanden Clinic, Zurich, Switzerland.
S
S
Wetzel
Clinical Trial Unit (S.S.), Basel University Hospital, Basel, Switzerland.
S
S
Schaedelin
From the Divisions of Neuroradiology (T.S., C.S., A.v.H.).
A
A
von Hessling
Radiological Physics (O.B., F.S.), Clinic of Radiology and Nuclear Medicine.
F
F
Santini
D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods; D008297:Male; D011446:Prospective Studies; D011673:Pulsatile Flow / Q000502:physiology*; D014655:Vascular Resistance; D014711:Vertebral Artery / Q000502:physiology*; D055815:Young Adult