Background: One of the most frequent diagnostic pitfalls in cerebrovascular ultrasound is the evaluation of the vertebrobasilar system in the case of vertebral artery (VA) hypoplasia because the diagnostic findings are sometimes suggestive of significant pathologies, but may be completely normal as well. The Venturi effect is a phenomenon of hydrodynamics which describes a drop in hydrostatic pressure along areas of high flow velocities. Method: We review the physical background of the Venturi effect and describe how it can explain both physiological and pathological flow phenomena encountered during cerebrovascular ultrasound investigations. We focused on flow phenomena at the vertebrobasilar junction by theoretically calculating conditions with different influx angles and flow velocities on two-dimensional digital subtraction angiography images. In the discussion, we also address other areas of cerebrovascular ultrasound, where the Venturi effect is of particular interest. Results and Conclusions: The blood flow velocity within the VAs and the angle between a hypoplastic VA and the basilar artery (BA) are important determinants of the intraluminal pressures of these arteries and thus their resistances. In the case of angles below 90° between the distal VA and the BA, abnormal extracranial flow profiles may suggest downstream VA stenosis or occlusion, whereas in the case of angles above 90°, a diagnosis of an AV fistula downstream to the V4 segment may be assumed. Furthermore, various hemodynamic effects at the site of a stenosis of the brain supplying arteries can also be explained by a transstenotic pressure drop created by the Venturi effect, particularly the generation of musical murmurs. The systolic dip (‘systolic deceleration’) at the origin of the VA due to subclavian artery stenosis is also a consequence of the Venturi effect.

1.
DeToni GB: GB Venturi; in Mieli A (ed): Gli scienziati italiani. Roma, Nardecchia, 1923, pp 376–382.
2.
Krayenbühl H, Yasaragil MG: Die vaskulären Erkrankungen im Gebiet der A. vertebralis und A. basilaris. Eine anatomische und pathologische, klinische und neuroradiologische Studie. Stuttgart, Thieme, 1957.
3.
Delcker A, Diener HC: Die verschiedenen Ultraschallmethoden zur Untersuchung der A. vertebralis – eine vergleichende Wertung. Ultraschall in Med 1992;13:213–220.
4.
Hademenos G: The biophysics of stroke. Treatment advances may depend on understanding how blood flows around a blockage. Am Sci 1997;85:226–235. Accessed on 1/22/01 at www.amsci.org/amsci/articles/97articles/hademenos.html
5.
Faccenda F, Usui Y, Spencer MP: Doppler measurement of the pressure drop caused by arterial stenosis: An experimental study: A case report. Angiology 1985;36:899–905.
6.
Aaslid R, Nornes H: Musical murmurs in human cerebral arteries after subarachnoid hemorrhage. J Neurosurg 1984;60:32–36.
7.
von Reutern GM, Pourcelot L: Cardiac cycle-dependent alternating flow in vertebral arteries with subclavian artery stenoses. Stroke 1978;9:229–236.
8.
Hess OM, Buchi M, Kirkeeide R, Niederer P, Anliker M, Gould KL, Krayenbühl HP: Potential role of coronary vasoconstriction in ischaemic heart disease: Effect of exercise. Eur Heart J 1990;11(suppl B):58–64.
9.
Aaslid R: Hemodynamics of cerebrovascular spasm. Acta Neurochir Suppl 1999;72:47–57.
10.
Kliewer MA, Hertzberg BS, Kim DH, Bowie JD, Courneya DL, Carroll BA: Vertebral artery Doppler waveform changes indicating subclavian steal physiology. AJR Am J Roentgenol 2000;174:815–819.
11.
Choo MH, Mah PK, Chia BL, Tan NC, Cho LM: Musical murmur and cardiac shudder. Chest 1985;87:836–837.
12.
Kohno K, Hiroki T, Arakawa K: Aortic regurgitation with dove-coo murmur with special references to the mechanism of its generation using dual echocardiography. Jpn Heart J 1981;22:861–869.
13.
Miyahara K, Amitani S, Sohara H, Kurose M, Iwamura H, Toyohira H, Taira A: Chaotic musical murmur in aortic regurgitation. Jpn Circ J 1996;60:993–997.
14.
Pennestri F, Boccardi L, Minardi G, Di Segni M, Pucci E, Biasucci LM, Ferrari O, Lombardo A, Giovannini E, Loperfido F: Doppler study of precordial musical murmurs. Am J Cardiol 1989;63:1390–1394.
15.
Foreman JEK, Hutchinson KJ: Arterial wall vibration distal to stenoses in isolated arteries of dog and man. Circ Res 1970;26:583–590.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.