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Calcified plaques in the brachiocephalic arteries: A concept of focal atherogenesis
416
JOURNAL OF ATHEROSCLEROSIS RESEARCH
CALCIFIED PLAQUES IN THE BRACHIOCEPHALIC ARTERIES: A CONCEPT OF FOCAL ATHEROGENESIS F. DALITH
AND
M. MOLHO
Manhattan Guild Institute of Cardio-Angio-Radiology, Department of Diagnostic Radiology, Government Hospital, Tel-Hashomer (Israel) (Received April 8th, 1962) Certainly, cholesterol in some form is a factor in atherosclerosis. But it may be well to be reminded, that so is the arterial wall. A. I. LANSING! INTRODUCTION
The preferential deposition of calcified plaques in the wall of the aorta at the levels of the origin of the left subclavian artery and the insertion of the ligamentum arteriosum has been described in previous publications 2 ,3. The hypothesis was advanced that these calcifications are intimately related to the sites of connection of the embryonic fifth and sixth left aortic arches with the left dorsal aortic root. Subsequently, the technique applied in these studies has been utilized in an investigation of the principal brachiocephalic arteries. Preferential sites of calcium deposition have also been found in these vessels. These observations, together with a new theory of the pathogenesis of atheromata at certain locations, form the subject of this communication. MATERIAL AND METHODS
Fifty specimens of the aortic arch and the brachiocephalic arteries were obtained from consecutive autopsies; the ages of the subjects ranged from 50 to 91 years. None of them had had signs of cerebrovascular insufficiency or brachial ischemia during life. The specimens were fixed in formalin and studied radiologically by plain radiography and after injection of barium suspension. The calcified areas and their adjacent segments were excised transversely, radiographed and sent for histological examination. Only 30 of the specimens were considered adequately extensive for inclusion in the study. OBSERVATIONS
In addition to the calcifications in the aortic arch at the levels of the origin of the left subclavian artery and the insertion of the ligamentum arteriosum, four further sites of preferential deposition of calcium have been observed (Figs. 1-3): ]. Atheroscler. Res., 2 (1962) 416-423
CALCIFIED PLAQUES IN BRACHIOCEPHALIC ARTERIES
417
Fig. 1. Radiogram of specimen of aortic arch and brachiocephalic arteries, showing preferential sites of calcium deposition. Inserts: radiograms of cross sections of internal and common carotid arteries, showing calcified atheromatous plaques and stenosis of internal carotid arteries.
(1) and (2) in both internal carotid arteries, immediately cranial to or at the origin from the common carotid artery; (3) in the right subclavian artery at its origin from the innominate artery; (4) at the angle between aorta and innominate artery. The remaining portions of the vessels were free from calcium deposition. Calcified plaques in the vertebral arteries at the origin from the subclavian arteries were seen with less frequency. The carotid calcification was almost always found in the dorsal part of the vessel wall and was semicircular in shape (Fig. 1, inserts). Atheromatous plaques of varying sizes and varying degrees of stenosis were present at this level (Fig. 2, A-D). The calcium deposit in the right subclavian artery was situated in its lateral wall within an atheromatous plaque (Fig. 2, E-I). The calcification at the aorto-innominate angle was found in either of the two vessels or extending from one to the other (Fig. 3,
f. Atheroscler. Res., 2 (1962) 416-423
418
F. DALITH, :VI. MOLHO
Fig. 2. Radiograms of specimens of brachiocephalic arteries. A -D: carotid arteries, right and left. Plain radiograms (A and C): calcification and thickening of the wall in the first part of the internal carotid artery. Angiograms (B and D): stenosis. E-1: origin of right subclavian artery from innominate artery. Photogram (E): atheromatous plaque. Radiogram (F): calcification. Plain (G) and cross section radiograms (H): calcification. Angiogram (1): stenosis.
A-D). Even when calcification was absent at these sites, atheromatous changes were invariably present. Histological examination confirmed the presence of atherosclerosis with fibrous intimal plaques, cholesterol clefts, foci of calcification and splitting and reduplication of the internal elastic lamina (Fig. 4). The incidence of the calcifications in the 30 specimens included in this report is shown in Fig. 5. DISCUSSION
The focal calcifications in the aortic arch, described previousl y 2,3, were related to the sites of connection of embryonic vascular structures. It is postulated that the isolated calcified foci in the first part of the internal carotid arteries, at the origin of the right subclavian artery and at the angle between aorta and innominate artery, described in the present study, are of similar genesis (Fig. 6). According to PATTEN4; "When in early embryonic life that portion of the dorsal aortic root which lies between the third and fourth aortic arch dwindles and drops out, the third arch is left, constituting the curved proximal part of the internal carotid artery". The site of calcium deposition in this area, in the ageing adult, may be assumed, therefore, to be identical with the site of connection of the dorsal aortic root with the third arch in the embryo. At the inner curvature of the right subclavian j. Atheroscler. Res., 2 (1962) 416-423
CALCIFIED PLAQUES IN BRACHIOCEPHALIC ARTERIES
419
Fig. 3. Radiograms of specimens of aorto-innominate junction, showing various sites of calcium deposition: A, aorta; B, aorto-innominate angle; C innominate artery; D, aortic part of atheromatous plaque which extends from aorta into innominate artery.
artery, between its origin from the innominate artery and the mouth of the vertebral artery, there exist in the embryo three areas of connection with disappearing vascular structures: the fifth arch, the lateral part of the sixth arch and the caudal part of the right dorsal aortic root. According to the present hypothesis, the site of calcium deposition at the origin of the right subclavian artery in the adult may be related to one, to two or to all three of these points of connection. The site of the calcification at the aorta-innominate junction may correspond to the origin of the fifth aortic arch (or arches) from the ventral aortic root. We suggest that the presence of a congenital locus minoris resistentiae in the arterial wall at the areas of connection of disappearing vascular structures plays an important role in the pathogenesis of the observed structural changes in the internal carotid arteries, in the right subclavian artery and at the aorta-innominate junction. It is possible that a developmental structural deficiency of the vessel wall at these points is the primary lesion, resulting in localized atheromatosis and calcification in the ageing adult (Table I,A). Atheromatous plaques tend to occur in arteries at points of stress, for instance at the mouths of vascular branches 5 (Table I,B I ). The constant pounding of the systolic thrust of the blood has been credited as a source of mechanical injury to the arterial wall at such areas. However, there is no evidence that the first part of the internal ]. Atheroscler. Res., 2 (1962) 416-423
420
F. DALITH, M. MOLHO
A
E
Fig. 4. Histological section of internal carotid artery at level of calcification. Elastica-Van Gieson stain. A, low power view (x 28) of fibrous intimal plaque. The dark stippled area within the plaque represents calcification. E, high power view (x 100) of the plaque and the underlying media. There is splitting and reduplication of the internal elastic lamina.
carotid arteries, the origin of the right subclavian artery and the aorto-innominate junction constitute such points of stress. An atheromatous plaque may also mark the site of impingement of a jet of blood on a vessel wall distal to a stenotic area, as in aortic valvular stenosis (Table I,Bl or in coarctation of the aorta 6 . However, at the sites under discussion no such factor is operative. Moreover, diffuse calcific
J.
Atheroscler. Res., 2 (1962) 416-423
421
CALCIFIED PLAQUES IN BRACHIOCEPHALIC ARTERIES TABLE I PRIMARY PATHOGENETIC FACTORS IN FOCAL ATHEROMATOSIS
Primary atherogenic factor
Vascular region
Hemodynamic condition
Origin of internal carotid artery from common carotid artery
A
Developmental structural deficiency of arterial wall
Flow parallels course of vessel
Origin of right subclavian artery from innominate artery Origin of innominate artery from aorta
Pounding thrust at mouth of vascular branch
(1) Origin of branch
B
Mechanical stress to normal arterial wall during life
(intercostal, mesenteric, renal, etc.) from descending aorta Impingement of jet opposite to stenotic valve
(2) Ascending aorta in aortic valvular stenosis
atherosclerosis can be ruled out in our material because of the localized occurrence of the calcified plaques. At the origin of the vertebral arteries no. known involutive embryological process occurs which could account for the localized predilection of atheroma. On the other hand, these arteries of relatively small calibre arise from vessels with a wide lumen. It is suggestive that the primary damage to the arterial wall which results in calcium deposition at the mouths of the vertebral arteries is mechanical stress during life, the same factor which is held responsible for structural changes occurring at the origin of intercostal, mesenteric or renal arteries. In order to test the validity of the above concept of the relation of localized atheromatosis in the adult to the disappearance of embryonic vascular structures, specimens of branchial artery derivatives from necropsies of younger subjects, from 30 years and under, are now being studied. ACKNOWLEDGEMENTS This work was supported by a grant from TEVA, Middle East Pharmaceutical and Chemical Works, Ltd., Jerusalem, Israel. We are indebted to Dr. M. 1. SACKS, Lecturer in Pathology, Hadassa University Hospital, Jerusalem, for the histological examination. We wish to acknowledge the assistance of J. SHENHAV in obtaining the radiographs. The photographs were taken by Mr. ]. AJDAN and the illustrations were prepared by Mr. 1. BASS. ]. Atheroscler. Res., 2 (1962) 416-423
422
F. DALITH, M. MOLHO
20
--------~---:;;: R/6HT INTERNAL
lEFT INfEQNAL
CARanO ARTERY
CAROTIO ARTER'I
::::::~-::::: 3
!
1l/6H7DORSAL : AORTlCIXIOr
5---
LEfT DORSAL
--AOiiTICROOT
~--2
18
14 --25 -~27
LEfT JUBClAV/l1N
AIiTERY
Fig. 5. Sites and incidence of calcified plaques in aortic arch and brachiocephalic arteries of 30 anatomic specimens (age of subjects 50-91 years).
Fig. 6. Scheme of embryonic aortic arches to show points of connection (black points) of disappearing vascular structures (dotted lines) which are concerned, most probably, with areas of calcium deposition and atheroma formation in the ageing adult.
SUMMARY
The proximal part of the internal carotid arteries, the origin of the right subclavian artery and the angle between aorta and innominate artery are sites of preferential deposition of calcium compounds in the ageing adult. These are additional to two sites of predilection in the aortic arch, at the levels of the origin of the left subclavian artery and the insertion of the ligamentum arteriosum, described in an earlier communication. It is postulated that the calcifications, located in atheromatous plaques, are late sequels of the disappearance of embryonic vascular structures. A developmental structural deficiency of the vessel wall at these points is suggested to be the primary lesion leading to localized atheromatosis and calcification. RESUME
La partie proximale des arteres carotides internes, l'origine de l'artere sous-claviere droite et l'angle que forment l'aorte et Ie tronc brachiocephalique sont les regions ou se deposent electivement les composes calciques chez l'adulte age. Ces zones s'ajoutent a deux autres, precedemment decrites, situees dans la crosse aortique, au niveau de ]. Atheroscler. Res., 2 (1962) 416--423
CALCIFIED PLAQUES IN BRACHIOCEPHALIC ARTERIES
423
l'origine de l'artere sous-claviere gauche et de l'insertion du ligament arteriel. II est postule que les calcifications situees dans les plaques atheromateuses sont des sequelles tardives de la disparition des structures vasculaires embryonnaires. La lesion primaire qui conduit a une atheromatose localisee et calciMe pourrait etre l'apparition en ces points de la paroi vasculaire au cours du developpement de deficiences structurelles. ZUSAMMENFASSUNG
Der proximale Teil der A. carotis interna, der Ursprung der rechten A. subclavia und der Winkel zwischen Aorta und A. innominata sind bei Erwachsenen mit fortschreitendem Alter bevorzugter Sitz von Calcium-Ablagerungen. Diese GeHissabschnitte kommen noch hinzu zu den zwei anderen Pradilektionsstellen im Aortenbogen (auf der Rohe des U rsprungs der linken A. subclavia und der Insertion des Lig. arteriosum), die in einer friiheren Mitteilung beschrieben wurden. Es wird postuliert, dass die Verkalkungen in den atheromatOsen Plaques Spatveranderungen sind, die mit dem Verschwinden von embryonalen Strukturen in den Gefassen zusammenhangen, und es wird angenommen, dass ein entwicklungsgeschichtlich bedingter Strukturdefekt der Gefasswand an diesen Stellen die primare Lasion darstellt, die zu lokalisierter Atheromatose und Calcifizierung fiihrt. REFERENCES
A. 1. LANSING, Circulation, 24 (1961) 1283. F. DALITH, Radiology, 76 (1961) 213. 3 F. DALITH, Acta Radiol., 57 (1962) 129. 4 B. M. PATTEN, Human Embryology, Blakiston Camp., Philadelphia, Toronto, 1946, p. 624. 5 S. L. ROBBINS, Textbook of Pathology, W. B. Saunders Camp., Philadelphia, London, 1957, p.506. 6 J. E. EDWARDS, N. A. CHRISTENSEN, O. T. CLAGETT AND McDoNALD JR., Proc. Staff Meetings Mayo Clin., 23 (1948) 324.
J.
Atheroscler. Res., 2 (1962) 416-423
JOURNAL OF ATHEROSCLEROSIS RESEARCH
CALCIFIED PLAQUES IN THE BRACHIOCEPHALIC ARTERIES: A CONCEPT OF FOCAL ATHEROGENESIS F. DALITH
AND
M. MOLHO
Manhattan Guild Institute of Cardio-Angio-Radiology, Department of Diagnostic Radiology, Government Hospital, Tel-Hashomer (Israel) (Received April 8th, 1962) Certainly, cholesterol in some form is a factor in atherosclerosis. But it may be well to be reminded, that so is the arterial wall. A. I. LANSING! INTRODUCTION
The preferential deposition of calcified plaques in the wall of the aorta at the levels of the origin of the left subclavian artery and the insertion of the ligamentum arteriosum has been described in previous publications 2 ,3. The hypothesis was advanced that these calcifications are intimately related to the sites of connection of the embryonic fifth and sixth left aortic arches with the left dorsal aortic root. Subsequently, the technique applied in these studies has been utilized in an investigation of the principal brachiocephalic arteries. Preferential sites of calcium deposition have also been found in these vessels. These observations, together with a new theory of the pathogenesis of atheromata at certain locations, form the subject of this communication. MATERIAL AND METHODS
Fifty specimens of the aortic arch and the brachiocephalic arteries were obtained from consecutive autopsies; the ages of the subjects ranged from 50 to 91 years. None of them had had signs of cerebrovascular insufficiency or brachial ischemia during life. The specimens were fixed in formalin and studied radiologically by plain radiography and after injection of barium suspension. The calcified areas and their adjacent segments were excised transversely, radiographed and sent for histological examination. Only 30 of the specimens were considered adequately extensive for inclusion in the study. OBSERVATIONS
In addition to the calcifications in the aortic arch at the levels of the origin of the left subclavian artery and the insertion of the ligamentum arteriosum, four further sites of preferential deposition of calcium have been observed (Figs. 1-3): ]. Atheroscler. Res., 2 (1962) 416-423
CALCIFIED PLAQUES IN BRACHIOCEPHALIC ARTERIES
417
Fig. 1. Radiogram of specimen of aortic arch and brachiocephalic arteries, showing preferential sites of calcium deposition. Inserts: radiograms of cross sections of internal and common carotid arteries, showing calcified atheromatous plaques and stenosis of internal carotid arteries.
(1) and (2) in both internal carotid arteries, immediately cranial to or at the origin from the common carotid artery; (3) in the right subclavian artery at its origin from the innominate artery; (4) at the angle between aorta and innominate artery. The remaining portions of the vessels were free from calcium deposition. Calcified plaques in the vertebral arteries at the origin from the subclavian arteries were seen with less frequency. The carotid calcification was almost always found in the dorsal part of the vessel wall and was semicircular in shape (Fig. 1, inserts). Atheromatous plaques of varying sizes and varying degrees of stenosis were present at this level (Fig. 2, A-D). The calcium deposit in the right subclavian artery was situated in its lateral wall within an atheromatous plaque (Fig. 2, E-I). The calcification at the aorto-innominate angle was found in either of the two vessels or extending from one to the other (Fig. 3,
f. Atheroscler. Res., 2 (1962) 416-423
418
F. DALITH, :VI. MOLHO
Fig. 2. Radiograms of specimens of brachiocephalic arteries. A -D: carotid arteries, right and left. Plain radiograms (A and C): calcification and thickening of the wall in the first part of the internal carotid artery. Angiograms (B and D): stenosis. E-1: origin of right subclavian artery from innominate artery. Photogram (E): atheromatous plaque. Radiogram (F): calcification. Plain (G) and cross section radiograms (H): calcification. Angiogram (1): stenosis.
A-D). Even when calcification was absent at these sites, atheromatous changes were invariably present. Histological examination confirmed the presence of atherosclerosis with fibrous intimal plaques, cholesterol clefts, foci of calcification and splitting and reduplication of the internal elastic lamina (Fig. 4). The incidence of the calcifications in the 30 specimens included in this report is shown in Fig. 5. DISCUSSION
The focal calcifications in the aortic arch, described previousl y 2,3, were related to the sites of connection of embryonic vascular structures. It is postulated that the isolated calcified foci in the first part of the internal carotid arteries, at the origin of the right subclavian artery and at the angle between aorta and innominate artery, described in the present study, are of similar genesis (Fig. 6). According to PATTEN4; "When in early embryonic life that portion of the dorsal aortic root which lies between the third and fourth aortic arch dwindles and drops out, the third arch is left, constituting the curved proximal part of the internal carotid artery". The site of calcium deposition in this area, in the ageing adult, may be assumed, therefore, to be identical with the site of connection of the dorsal aortic root with the third arch in the embryo. At the inner curvature of the right subclavian j. Atheroscler. Res., 2 (1962) 416-423
CALCIFIED PLAQUES IN BRACHIOCEPHALIC ARTERIES
419
Fig. 3. Radiograms of specimens of aorto-innominate junction, showing various sites of calcium deposition: A, aorta; B, aorto-innominate angle; C innominate artery; D, aortic part of atheromatous plaque which extends from aorta into innominate artery.
artery, between its origin from the innominate artery and the mouth of the vertebral artery, there exist in the embryo three areas of connection with disappearing vascular structures: the fifth arch, the lateral part of the sixth arch and the caudal part of the right dorsal aortic root. According to the present hypothesis, the site of calcium deposition at the origin of the right subclavian artery in the adult may be related to one, to two or to all three of these points of connection. The site of the calcification at the aorta-innominate junction may correspond to the origin of the fifth aortic arch (or arches) from the ventral aortic root. We suggest that the presence of a congenital locus minoris resistentiae in the arterial wall at the areas of connection of disappearing vascular structures plays an important role in the pathogenesis of the observed structural changes in the internal carotid arteries, in the right subclavian artery and at the aorta-innominate junction. It is possible that a developmental structural deficiency of the vessel wall at these points is the primary lesion, resulting in localized atheromatosis and calcification in the ageing adult (Table I,A). Atheromatous plaques tend to occur in arteries at points of stress, for instance at the mouths of vascular branches 5 (Table I,B I ). The constant pounding of the systolic thrust of the blood has been credited as a source of mechanical injury to the arterial wall at such areas. However, there is no evidence that the first part of the internal ]. Atheroscler. Res., 2 (1962) 416-423
420
F. DALITH, M. MOLHO
A
E
Fig. 4. Histological section of internal carotid artery at level of calcification. Elastica-Van Gieson stain. A, low power view (x 28) of fibrous intimal plaque. The dark stippled area within the plaque represents calcification. E, high power view (x 100) of the plaque and the underlying media. There is splitting and reduplication of the internal elastic lamina.
carotid arteries, the origin of the right subclavian artery and the aorto-innominate junction constitute such points of stress. An atheromatous plaque may also mark the site of impingement of a jet of blood on a vessel wall distal to a stenotic area, as in aortic valvular stenosis (Table I,Bl or in coarctation of the aorta 6 . However, at the sites under discussion no such factor is operative. Moreover, diffuse calcific
J.
Atheroscler. Res., 2 (1962) 416-423
421
CALCIFIED PLAQUES IN BRACHIOCEPHALIC ARTERIES TABLE I PRIMARY PATHOGENETIC FACTORS IN FOCAL ATHEROMATOSIS
Primary atherogenic factor
Vascular region
Hemodynamic condition
Origin of internal carotid artery from common carotid artery
A
Developmental structural deficiency of arterial wall
Flow parallels course of vessel
Origin of right subclavian artery from innominate artery Origin of innominate artery from aorta
Pounding thrust at mouth of vascular branch
(1) Origin of branch
B
Mechanical stress to normal arterial wall during life
(intercostal, mesenteric, renal, etc.) from descending aorta Impingement of jet opposite to stenotic valve
(2) Ascending aorta in aortic valvular stenosis
atherosclerosis can be ruled out in our material because of the localized occurrence of the calcified plaques. At the origin of the vertebral arteries no. known involutive embryological process occurs which could account for the localized predilection of atheroma. On the other hand, these arteries of relatively small calibre arise from vessels with a wide lumen. It is suggestive that the primary damage to the arterial wall which results in calcium deposition at the mouths of the vertebral arteries is mechanical stress during life, the same factor which is held responsible for structural changes occurring at the origin of intercostal, mesenteric or renal arteries. In order to test the validity of the above concept of the relation of localized atheromatosis in the adult to the disappearance of embryonic vascular structures, specimens of branchial artery derivatives from necropsies of younger subjects, from 30 years and under, are now being studied. ACKNOWLEDGEMENTS This work was supported by a grant from TEVA, Middle East Pharmaceutical and Chemical Works, Ltd., Jerusalem, Israel. We are indebted to Dr. M. 1. SACKS, Lecturer in Pathology, Hadassa University Hospital, Jerusalem, for the histological examination. We wish to acknowledge the assistance of J. SHENHAV in obtaining the radiographs. The photographs were taken by Mr. ]. AJDAN and the illustrations were prepared by Mr. 1. BASS. ]. Atheroscler. Res., 2 (1962) 416-423
422
F. DALITH, M. MOLHO
20
--------~---:;;: R/6HT INTERNAL
lEFT INfEQNAL
CARanO ARTERY
CAROTIO ARTER'I
::::::~-::::: 3
!
1l/6H7DORSAL : AORTlCIXIOr
5---
LEfT DORSAL
--AOiiTICROOT
~--2
18
14 --25 -~27
LEfT JUBClAV/l1N
AIiTERY
Fig. 5. Sites and incidence of calcified plaques in aortic arch and brachiocephalic arteries of 30 anatomic specimens (age of subjects 50-91 years).
Fig. 6. Scheme of embryonic aortic arches to show points of connection (black points) of disappearing vascular structures (dotted lines) which are concerned, most probably, with areas of calcium deposition and atheroma formation in the ageing adult.
SUMMARY
The proximal part of the internal carotid arteries, the origin of the right subclavian artery and the angle between aorta and innominate artery are sites of preferential deposition of calcium compounds in the ageing adult. These are additional to two sites of predilection in the aortic arch, at the levels of the origin of the left subclavian artery and the insertion of the ligamentum arteriosum, described in an earlier communication. It is postulated that the calcifications, located in atheromatous plaques, are late sequels of the disappearance of embryonic vascular structures. A developmental structural deficiency of the vessel wall at these points is suggested to be the primary lesion leading to localized atheromatosis and calcification. RESUME
La partie proximale des arteres carotides internes, l'origine de l'artere sous-claviere droite et l'angle que forment l'aorte et Ie tronc brachiocephalique sont les regions ou se deposent electivement les composes calciques chez l'adulte age. Ces zones s'ajoutent a deux autres, precedemment decrites, situees dans la crosse aortique, au niveau de ]. Atheroscler. Res., 2 (1962) 416--423
CALCIFIED PLAQUES IN BRACHIOCEPHALIC ARTERIES
423
l'origine de l'artere sous-claviere gauche et de l'insertion du ligament arteriel. II est postule que les calcifications situees dans les plaques atheromateuses sont des sequelles tardives de la disparition des structures vasculaires embryonnaires. La lesion primaire qui conduit a une atheromatose localisee et calciMe pourrait etre l'apparition en ces points de la paroi vasculaire au cours du developpement de deficiences structurelles. ZUSAMMENFASSUNG
Der proximale Teil der A. carotis interna, der Ursprung der rechten A. subclavia und der Winkel zwischen Aorta und A. innominata sind bei Erwachsenen mit fortschreitendem Alter bevorzugter Sitz von Calcium-Ablagerungen. Diese GeHissabschnitte kommen noch hinzu zu den zwei anderen Pradilektionsstellen im Aortenbogen (auf der Rohe des U rsprungs der linken A. subclavia und der Insertion des Lig. arteriosum), die in einer friiheren Mitteilung beschrieben wurden. Es wird postuliert, dass die Verkalkungen in den atheromatOsen Plaques Spatveranderungen sind, die mit dem Verschwinden von embryonalen Strukturen in den Gefassen zusammenhangen, und es wird angenommen, dass ein entwicklungsgeschichtlich bedingter Strukturdefekt der Gefasswand an diesen Stellen die primare Lasion darstellt, die zu lokalisierter Atheromatose und Calcifizierung fiihrt. REFERENCES
A. 1. LANSING, Circulation, 24 (1961) 1283. F. DALITH, Radiology, 76 (1961) 213. 3 F. DALITH, Acta Radiol., 57 (1962) 129. 4 B. M. PATTEN, Human Embryology, Blakiston Camp., Philadelphia, Toronto, 1946, p. 624. 5 S. L. ROBBINS, Textbook of Pathology, W. B. Saunders Camp., Philadelphia, London, 1957, p.506. 6 J. E. EDWARDS, N. A. CHRISTENSEN, O. T. CLAGETT AND McDoNALD JR., Proc. Staff Meetings Mayo Clin., 23 (1948) 324.
J.
Atheroscler. Res., 2 (1962) 416-423