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THE MEANING OF A MURMUR
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twelfth list2 has since appeared with 175 Unless an objection to a name is filed, it is forwarded to the member States ofW.H.O. with the request that it be recognised as the non-proprietary name of the substance, and that steps be taken to prevent the acquisition of proprietary rights in the name. Names to which some objection has been made also appear in the cumulative list, though they are still subject to negotiation and reconsideration. Publication of the nature of such objections might help to eliminate unnecessary ones. A high proportion of the Approved and Official Names of the British Pharmacopoeia Commission are also international non-proprietary names; but, as long as any names differ in the two systems, some sort of dictionary will be needed. A simple measure would be to indicate the international non-proprietary name for each entry in the lists of Approved Names.
in the venous sinuses may impart vibration the whole of the skull. part Normal cranial murmurs of no pathological significance are found in 60% of children at four years of age in 35% of young adults, but in only 9% of older adults.’e A murmur which is increased or made continuous by partial compression of the carotid artery on the same side implies stenosis of a major contributor to the circle of Willis. If contralateral carotid compression iricreases a murmur, all that can be concluded is that both common carotids are patent. Allen and Mustian hold that the value of a murmur in localising a vascular abnormality is limited; but Gilroy and Meyerstudied 50 cases of carotid murmur and concluded that the sound was always accompanied by stenosis in the ipsilateral-or, rarely, the contralateral-carotid artery. A murmur over the vertebral artery was associated with stenosis of the vertebral or subclavian artery in 8 cases out of 10. Allen and Mustian also point out that transitory murmurs can be heard for a few days after cerebral infarction. Moreover, orbital and carotid murmurs may be found in uncomplicated migraine when angiograms are normal. Other causes of murmur include fever, nervous exercise, tension, and anaemia with a packed cell volume below 25%. A rise in intracranial pressure may produce a murmur by kinking the intracranial segment of the ’internal carotid artery, but tortuosity of the cervical portion does not cause a murmur unless atherosclerosis is present besides. A murmur due to arteriovenous fistula is difficult to obliterate by compression of a single vessel, is often continuous, and is usually conducted by bone; characteristically, it is reduced or abolished by venous compression. But in only 50% of cases of arteriovenous fistula is any murmur produced.8 Venous hums are frequently found in children but have also been heard in fifty-year-old adults. The hum is usually confined to the right internal jugular vein low in the neck, but it may occur over the right subclavian vein or the left internal jugular. The sound is a deep continuous roar with diastolic accentuation; it is louder when the patient stands erect and is sometimes intensified by turning the head; it is abolished by light compression of the jugular vein above the point of auscultation. Thus, an audible murmur does not necessarily indicate localised disease of the underlying artery: the nature of the murmur, its site, timing, and response to vascular compression must be considered before definitive angiographic investigations are planned. After retrograde catheterisation from the brachial artery,9 10 all the vessels in the neck can be delineated by radiopaque material; intracranial vessels can be investigated by similar methods, supplemented on occasion by percutaneous left carotid injection. An X-ray of the abdomen taken after an appropriate interval then provides a pyelogram which can be useful in the investigation of these vascular diseases.l1 Total angiography is a method as yet comparatively little tried; until its advantages have been
together, and a
produced
more.
to
THE MEANING OF A MURMUR
AsKED what causes a vascular bruit, most doctors would probably mutter the word " turbulence ": but analysis of the physical factors leading to production of the sound suggests that their muttering is misguided. Allen and Mustian3 believe that, in causing a murmur, the importance of turbulence-i.e., chaotic movement of blood in irregular eddies with random direction of forceis doubtful. The necessary conditions for such turbulent flow4 are met in the carotid system at bends and bifurcations, and in some pathological states such as mild ansemia. Allen and Mustian found that turbulence led to the dissipation of energy as heat rather than as periodic vibrations; they therefore concluded that the intensity of sound from this source was low, its frequency spectrum broad, and any resulting murmur soft and without recognisable pitch. Since, on the other hand, the regular periodic swirling of blood in vortices produced sounds within a relatively narrow range of frequency, this movement could account for louder murmurs. They found vortices in the fluid wake created in the blood-stream by an interposed obstruction, in blood flowing through a narrow orifice, or in the region where a small and rapid stream encountered the sharp edge of a solid boundary. The forces induced were directed perpendicularly to the arterial wall and, under conditions obtaining in the human circulation, produced vibrations at the frequency of audible sound. The pitch of the sound varied directly with the velocity of flow. Where the velocity was very high, all the energy available could be in the form of kinetic energy and lateral pressure could fall so far that the vessel collapsed momentarily with the consequent arrest of flow, intravascular pressure rose again, and the vessel re-expanded. The oscillation so produced was called "flitter" and could cause sound. Allen and Mustian maintain that this mechanism may operate in the internal jugular vein when flow is rapid and posture erect, but they believe that it is unlikely to be relevant to arterial murmurs; in arteriovenous fistulae and vascular malformations, flitter may occur locally on the venous side. A murmur may be propagated along the vessel in the direction of flow; but, from the cranium, the sound emerges most easily from a hiatus such as an orbital foramen or a trephine hole. Intense murmurs or those 1. International Non-proprietary Names for Pharmaceutical Preparations: Cumulative List 1962. Geneva: World Health Organisation. 1962. Pp. 52. Obtainable from H.M. Stationery Office, P.O. box 569, London, S.E.1. 5s. 2. W.H.O. Chronicle, 1962, 16, 385. 3. Allen, N., Mustian, V. Medicine, Baltimore, 1962, 41, 227. 4. Reynolds, O. Phil. Trans. 1883, 174, 935.
or even
confirmed by general use, selective anteriography will still be favoured and clinical assessment of murmurs will still be important in the management of these cases. Prof. C. G. DOUGLAS, F.R.S., died at Oxford on March 23 at the age of 81. 5. 6. 7. 8. 9. 10. 11.
Wadia, N. H., Monckton, G. Brain, 1957, 80, 492. Crevasse, L. E., Logue, R. B. J. Amer. med. Ass. 1958, 167, 2177. Gilroy, J., Meyer, J. S. Circulation, 1962, 25, 300. Mackenzie, I. ’Brain, 1955, 78, 350. Sheehan, S., Bauer, R. B., Meyer, J. S. Neurology, 1960, 10, 968. Poser, C. M., Snodgrass, R. G. J. Amer. med. Ass. 1962, 182, 126. Shenkin, H. A., Tatsumi, T., Bantley, D. ibid. p. 132.
twelfth list2 has since appeared with 175 Unless an objection to a name is filed, it is forwarded to the member States ofW.H.O. with the request that it be recognised as the non-proprietary name of the substance, and that steps be taken to prevent the acquisition of proprietary rights in the name. Names to which some objection has been made also appear in the cumulative list, though they are still subject to negotiation and reconsideration. Publication of the nature of such objections might help to eliminate unnecessary ones. A high proportion of the Approved and Official Names of the British Pharmacopoeia Commission are also international non-proprietary names; but, as long as any names differ in the two systems, some sort of dictionary will be needed. A simple measure would be to indicate the international non-proprietary name for each entry in the lists of Approved Names.
in the venous sinuses may impart vibration the whole of the skull. part Normal cranial murmurs of no pathological significance are found in 60% of children at four years of age in 35% of young adults, but in only 9% of older adults.’e A murmur which is increased or made continuous by partial compression of the carotid artery on the same side implies stenosis of a major contributor to the circle of Willis. If contralateral carotid compression iricreases a murmur, all that can be concluded is that both common carotids are patent. Allen and Mustian hold that the value of a murmur in localising a vascular abnormality is limited; but Gilroy and Meyerstudied 50 cases of carotid murmur and concluded that the sound was always accompanied by stenosis in the ipsilateral-or, rarely, the contralateral-carotid artery. A murmur over the vertebral artery was associated with stenosis of the vertebral or subclavian artery in 8 cases out of 10. Allen and Mustian also point out that transitory murmurs can be heard for a few days after cerebral infarction. Moreover, orbital and carotid murmurs may be found in uncomplicated migraine when angiograms are normal. Other causes of murmur include fever, nervous exercise, tension, and anaemia with a packed cell volume below 25%. A rise in intracranial pressure may produce a murmur by kinking the intracranial segment of the ’internal carotid artery, but tortuosity of the cervical portion does not cause a murmur unless atherosclerosis is present besides. A murmur due to arteriovenous fistula is difficult to obliterate by compression of a single vessel, is often continuous, and is usually conducted by bone; characteristically, it is reduced or abolished by venous compression. But in only 50% of cases of arteriovenous fistula is any murmur produced.8 Venous hums are frequently found in children but have also been heard in fifty-year-old adults. The hum is usually confined to the right internal jugular vein low in the neck, but it may occur over the right subclavian vein or the left internal jugular. The sound is a deep continuous roar with diastolic accentuation; it is louder when the patient stands erect and is sometimes intensified by turning the head; it is abolished by light compression of the jugular vein above the point of auscultation. Thus, an audible murmur does not necessarily indicate localised disease of the underlying artery: the nature of the murmur, its site, timing, and response to vascular compression must be considered before definitive angiographic investigations are planned. After retrograde catheterisation from the brachial artery,9 10 all the vessels in the neck can be delineated by radiopaque material; intracranial vessels can be investigated by similar methods, supplemented on occasion by percutaneous left carotid injection. An X-ray of the abdomen taken after an appropriate interval then provides a pyelogram which can be useful in the investigation of these vascular diseases.l1 Total angiography is a method as yet comparatively little tried; until its advantages have been
together, and a
produced
more.
to
THE MEANING OF A MURMUR
AsKED what causes a vascular bruit, most doctors would probably mutter the word " turbulence ": but analysis of the physical factors leading to production of the sound suggests that their muttering is misguided. Allen and Mustian3 believe that, in causing a murmur, the importance of turbulence-i.e., chaotic movement of blood in irregular eddies with random direction of forceis doubtful. The necessary conditions for such turbulent flow4 are met in the carotid system at bends and bifurcations, and in some pathological states such as mild ansemia. Allen and Mustian found that turbulence led to the dissipation of energy as heat rather than as periodic vibrations; they therefore concluded that the intensity of sound from this source was low, its frequency spectrum broad, and any resulting murmur soft and without recognisable pitch. Since, on the other hand, the regular periodic swirling of blood in vortices produced sounds within a relatively narrow range of frequency, this movement could account for louder murmurs. They found vortices in the fluid wake created in the blood-stream by an interposed obstruction, in blood flowing through a narrow orifice, or in the region where a small and rapid stream encountered the sharp edge of a solid boundary. The forces induced were directed perpendicularly to the arterial wall and, under conditions obtaining in the human circulation, produced vibrations at the frequency of audible sound. The pitch of the sound varied directly with the velocity of flow. Where the velocity was very high, all the energy available could be in the form of kinetic energy and lateral pressure could fall so far that the vessel collapsed momentarily with the consequent arrest of flow, intravascular pressure rose again, and the vessel re-expanded. The oscillation so produced was called "flitter" and could cause sound. Allen and Mustian maintain that this mechanism may operate in the internal jugular vein when flow is rapid and posture erect, but they believe that it is unlikely to be relevant to arterial murmurs; in arteriovenous fistulae and vascular malformations, flitter may occur locally on the venous side. A murmur may be propagated along the vessel in the direction of flow; but, from the cranium, the sound emerges most easily from a hiatus such as an orbital foramen or a trephine hole. Intense murmurs or those 1. International Non-proprietary Names for Pharmaceutical Preparations: Cumulative List 1962. Geneva: World Health Organisation. 1962. Pp. 52. Obtainable from H.M. Stationery Office, P.O. box 569, London, S.E.1. 5s. 2. W.H.O. Chronicle, 1962, 16, 385. 3. Allen, N., Mustian, V. Medicine, Baltimore, 1962, 41, 227. 4. Reynolds, O. Phil. Trans. 1883, 174, 935.
or even
confirmed by general use, selective anteriography will still be favoured and clinical assessment of murmurs will still be important in the management of these cases. Prof. C. G. DOUGLAS, F.R.S., died at Oxford on March 23 at the age of 81. 5. 6. 7. 8. 9. 10. 11.
Wadia, N. H., Monckton, G. Brain, 1957, 80, 492. Crevasse, L. E., Logue, R. B. J. Amer. med. Ass. 1958, 167, 2177. Gilroy, J., Meyer, J. S. Circulation, 1962, 25, 300. Mackenzie, I. ’Brain, 1955, 78, 350. Sheehan, S., Bauer, R. B., Meyer, J. S. Neurology, 1960, 10, 968. Poser, C. M., Snodgrass, R. G. J. Amer. med. Ass. 1962, 182, 126. Shenkin, H. A., Tatsumi, T., Bantley, D. ibid. p. 132.