Paper - Coarctation of the aorta 1942
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Cauldwell EW. and Anson BJ. Stapes, fissula ante fenestram and associated structures in man III. from embryos 6.7 to 50 mm in length. (1942) Arch. Otolaryng. 36: 891-925.
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Coarctation of the Aorta
By A. D. Irvine
May 1942, Edmonton
Brief review of the development of the vascular system as outlined in any standard textbook of anatomy or embryology is an excellent approach to the subject of coarctation of the aorta.
The first stage in the development of the heart and great vessels is the appearance of two tubular spaces, one on each side of the midline in the pericardial area of the embryo. These run back as separate vessels but later fuse to form the thoracic and abdominal aorte.
As the embryo increases in size there is flexion and anterior growth of the vascular tubes so that the pericardial area and these vessels become folded under the head, and end by lying on the ventral aspect of the fore-gut. As a result each of these vessels now consists of a dorsal and a ventral portion, the two joined anteriorly by an arch. At this stage they are called primitive aorte and the anterior connecting portions are designated the first aortic arches. Five additional arches very soon develop on each side behind the first ones, so that at one stage six pairs of aortic arches are present. These aortic arches in the fish pass through the gills where the blood is aerated. In the human only a few of the arches persist, forming the major vessels as shown in Fig. 1.
In the pericardial area the two ventral primitive aorte fuse to form a fish-like twochambered heart. By a succession of rotations and flexions the adult heart develops from this primitive beginning.
During intrauterine life the lungs of the fetus are not functioning and only a very small part of the blood in the pulmonary artery goes to them. Most of it is shunted through the ductus arteriosus to the upper part of the descending aorta to be carried to the trunk, lower extremities, and placenta. The blood pumped by the left heart supplies chiefly the head and arms. Thus there is no great blood flow through that part of the descending arch between the origin of the left subclavian artery and the opening of the ductus arteriosus. Therefore this part is narrowed and is known as the fetal isthmus.
Very soon after birth when the lungs are functioning the ductus no longer is of use and degenerates to a fibrous band, the ligamentum arteriosum.
Definition and Classification
Coarctation of the aorta is defined as a partial or complete stenosis of the aorta at, or close to, the level of insertion of the ductus arteriosus.
The condition is further differentiated into the so-called infantile and adult types. The infantile type is characterized by a varying degree of narrowing of the vessel lumen between the origin of the left subclavian artery and the site of insertion of the ligamentum arteriosum, that is, in the region of the fetal isthmus. This form of coarctation seems to be a persistence or exaggeration of the condition obtaining during intrauterine life when the pulmonary artery carried the blood for the lower trunk and: legs to the descending aorta through the ductus. This type of coarctation is described only to complete the discussion and will not be mentioned further.
In the adult type of coarctation there is a partial or complete obliteration of the aortic arch adjacent to the opening of the ductus arteriosus (Fig. 2).
Morgagni is said by Evans*® to have first recognized the condition in a dissected cadaver in 1760. It is admittedly rare, and, judging by the reported cases, seldom diagnosed during life. In 1928 Abbott’s classical article on the subject appeared’ in which she collected all the reported cases up to that time. These, together with her own, numbered only 200. In addition she mentions 5 others known to her which came to autopsy but had not been reported. Of the 200 cases only 28 were diagnosed ante mortem.
Benkwitz and Hunter? summarized 75 cases that were reported between 1928 and 1935. Apparently as the condition became better known, largely because of Abbott’s comprehensive paper, it was recognized more frequently,
The rarity of the condition is emphasized by the following table compiled by Goodson.5
|Series||Number of autopsies||Cases of coarctation|
|Jaffe and Sternberg||4,500||1|
|Massachusetts General Hospital||5,000||2|
Probable incidence per 100,000 autopsies 77.
This would make a probable 77 cases per 100,000 autopsies.
The cause of this anomaly is not known. Earlier writers for the most part accepted the Skodaic theory, which was first offered by Craigie in 1841, and later popularized by Skoda. This hypothesis assumes that in these cases there is an extension into the adjacent wall of the aorta of the type of tissue making up the walls of the ductus arteriosus. Then when obliteration of the ductus occurs the same fibrosis and contraction takes place in the tissue in the aortic wall, causing a constriction. But such an extension of ‘‘peculiar tissue’’ has never been demonstrated microscopically. A more likely cause is the mechanical drag of the ligamentum arteriosum, producing a kinking at this level. This traction in some cases is strong enough to produce a tent-shaped traction aneurysm at the point of attachment.
More recent writers believe that the condition is usually an anomaly of development involving the left ventral aorta and fourth, fifth and sixth aortic arches on this side. In support of this they cite the anomalous vessels frequently reported in this region. These appear to be due to aortic arches which have persisted instead of disappearing in the usual manner. The presence of valves or folds, lined with normal intima, producing stenosis also is regarded as evidence of unusual development of the embryonic arterial wall. Frequent associated anomalies of the heart and aortic valves further support this theory.
Changes in the Circulatory System Resulting from Coarctation
The congenital anomalies of heart and great vessels frequently: associated with zoarctation will not be considered. They are concomitants rather than secondary results.
The most striking change is the development of a collateral circulation to link the proximal aortic segment with the trunk and lower extremities (Fig. 3). The extent of this collateral system is governed by the degree of stenosis present in the aorta. In approximately a quarter of the reported cases complete atresia was present. In these a high degree of efficiency must be present in the collateral compensatory system if life is to be sustained.
The connecting vessels are most prominent in the upper thoracic area as a rule. Usually the superior intercostal arteries, arising from the subelavians, develop powerful anastomoses with the first intercostals which arise from the aorta just below the level of constriction. Then, too, the posterior scapular, interscapular, and subscapular arteries run through from behind to pierce the intercostal muscles and their usually insignificant connections open up to form large vessels communicating with the second to about the fourth intercostal arteries. The intercostal arteries also communicate anteriorly with the internal mammary arteries which are receiving blood from the proximal aortic segment by way of the subclavians. As a result of the large volume of blood carried under high pressure the collateral arteries dilate and become large, turgid, tortuous vessels rather than the small, insignificant ones seen in the normal individual (Fig. 4). The mass of dilated, engorged arteries in the supraclavicular, scapular, and intercostal areas are of the greatest importance in ante mortem diagnosis as will be seen later.
A less frequent compensating mechanism is between the internal mammary vessels and the epigastric branches of the external iliacs over the abdominal wall.
Cardiac enlargement is another change frequently, but not always, found in the circulatory system. The work of the heart is very much increased by the necessity of forcing the blood through a collateral system instead of through a normal patent aorta. In order to ensure an adequate flow of blood to the trunk and lower limbs a marked. increase in blood pressure in the proximal aorta and upper extremity is necessary.
If the heart has no congenital lesion and the heart muscle is normal no hypertrophy may be apparent for years. But as time goes on the cardiac reserve is likely to lessen, due to intercurrent infection or continued excessive muscular activity. In about three quarters of the reported cases the heart had suffered from the abnormally high demands imposed on it and indicated this by hypertrophy.
Dilatation of the aorta proximal to the atresia is a very frequent finding in coarctation. This is secondary to the hypertension present in the aortic lumen. The dilatation may be so great as to form a large saccular aneurysm. Some writers have pointed out that in many cases of coarctation there is a congenital weakness of the middle coat of the aortic wall. This allows the intravascular pressure to produce a more marked dilatation than if the media were of normal thickness and quality. This congenital weakness is given as a probable contributory cause for the frequent rupture of the aorta in this region and the large number of dissecting aneurysms reported associated with coarctation.
The condition, although present through infaney and childhood, usually does not become apparent till adolescence or early adult life. A chart showing the average age at death in Abbott’s cases throws into clear relief the high mortality in the second, third, and fourth decades.
Excessive activity or an infection by its toxic effect on the myocardium, may lessen the cardiac reserve and make manifest for the first time the symptoms of dyspnea and palpitation on exertion. In these cases cardiac failure develops progressively, and brings about the patient’s death. In other cases, rupture of the proximal aorta or a dissecting aneurysm may be the dramatic cause of death without premonitory symptoms,
Approximately three times as many males as females are reported with coarctation. One hundred and forty-seven were males and 48 were females in the 195 cases in Abbott’s series in which the sex was known. In Benkwitz and Hunter’s review 55 were males, 16 were females, and in two the sex was not given. No one has offered a satisfactory explanation for the predilection for males shown by this congenital anomaly. Evans’ states that there is no such difference of sex incidence but he has little support in the literature. ,
The clinical findings in coarctation of the aorta are vascular rather than cardiac. Due to the obstruction to free flow of blood to the trunks and lower limbs there is an abundant supply to the upper part of the body and head.
This may be indicated by visible pulsations in the suprasternal notch, in the supraclavicular fosse, the scapular areas or even in the intercostal spaces. Palpation in these areas may disclose pulsating tortuous vessels even if they are not visible. Auscultation also may demonstrate a loud bruit above the sternum, in the root of the neck, about the scapule, or even over the greater part of the posterior thorax. It will be remembered that these are the areas in which most of the large anastomosing arteries forming the collateral circulation have developed.
Some writers have described their patients as being muscular and well developed in the upper trunk and arms and of unusually high intelligence due to the hyperemia of these parts and the brain. The lower trunk and legs on the other hand were underdeveloped. Cases with such marked differences between upper and lower development are probably rare, or many more patients would have been diagnosed ante mortem.
The difference in blood supply between the upper and lower extremities gives one a clinical finding which is diagnostic, namely, a marked difference between the blood pressures taken in the arm and in the leg. The usual difference between the brachial and popliteal pressures with the patient recumbent is said to be 20 to 40 mm. Hg. A greater variation than this is evidence of obstruction to the free flow of the blood through the aorta. An absent, diminished, or retarded pulse in the lower extremities with an increased palpable pulse in the upper is merely another manifestation of the difference in tension and is also diagnostic. There also may be a great difference in the quality of the pulse and blood pressure in the two arms. This is to be expected if there is an aneurysm or dilatation of the proximal segment of the aorta or the bases of the great vessels.
The pathognomonic radiological sign of coarctation of the aorta is a notching or scalloping of the inferior surfaces of some of the ribs. The presence of these is known as Rosler’s sign, after the writer who first recognized them and reported the finding in 1928. They are bilateral and have smooth well-defined edges. They are pressure defects caused by the dilated, tortuous, intercostal arteries which form part of the collateral circulation connecting the proximal and distal portions of the May 1942]
aorta. These defects are more numerous in the upper ribs due to the greater part of the collateral circulation being effected by the upper intercostal arteries. These markings are not present in all cases of coarctation; but when present are regarded as diagnostic.
Another common x-ray finding is cardiac enlargement, for, as noted above, most cases eventually develop hypertrophy of at least the left ventricle. This finding is not diagnostic, but merely supporting evidence. It is said that the actual constriction in the aorta may be visualized fluoroscopically or radiographically in certain cases when the patient is placed in the left oblique position. There can also be seen the dilatation of the ascending aorta and arch if such be present. Absence of the aortic knob would be expected in a typical case of coarctation, but many cases show a prominent bulb, due presumably to dilatation of the aorta just proximal to the constriction.
Direct visualization of the site of stenosis and the anastomosing collaterals have been reported by the use of arteriography. This cannot be regarded as beyond the experimental stage and is not a practical procedure for many radiologists.
Fig. 182. — A scheme of the aortic arches and their transformations. (Moditied from Kollmann.) External carotid
Tight subclavian Right pulmonary artery
Trunk of pulmonary artery
Left pulmonary artery
Fig. 1—Scheme of the aortic arches and their transformations.
Fig. 2.—Drawing to show a case of coarctation of the aorta with almost complete atresia
of adult type and infantile constriction immediately above.
(Benkwitz and Hunter).
Fig. 3.—Diagram to illustrate paths of collateral blood flow in coarctation. (Gitlow and Sommer). Fig. 4.—Drawing to show the marked arterial collateral anastomoses and the
extreme size and tortuosity of the intercostal arteries.
(Meckel’s case from Abbott).
REPORT OF CASES
Within one year I have had the good fortune to see two patients with this condition. In addition to these my confrére, Dr. P. H. Malcolmson, has kindly lent me the data on a case diagnosed by him during the same period.
W.L., age 32 years, a white male of English descent, who was a foreman at a meat packing plant. He was admitted to the Edmonton General Hospital on March 7, 1940, by Dr. F. A. Keillor because of cough and dyspnea for ten days with blood-streaked sputum. The functional inquiry elicited a history of severe pain in his chest four weeks before admission while lifting. This seemed to shoot from the centre of his back towards the front. There was also an indefinite history of other pains in the chest some time prior to admission. These were regarded as being due to strained dorsal muscles. The patient had always been a hard worker and had taken part in strenuous athletics, There had been no dyspneea till onset of present illness. The routine examination of the chest by a house surgeon disclosed rales over most of the chest and the vessels of the neck seemed to pulsate in an exaggerated manner. An x-ray examination of the chest was requested and the report reads in part (Figs. 5 and 6): ‘The left portion of the cardiac shadow is somewhat prominent. Numerous ribs show well-defined defects in relation to their inferior borders. These defects are supposed to be pathognomonic of coarctation of the aorta. In the right lung some increase in density is present in the perihilar and infrahilar areas. This presents the appearance of a right-sided central pneumonia.’’
The progress notes indicate that following x-ray report a further examination of the chest disclosed a souffle in the supraclavicular fosse on both sides and a systolic murmur at the base transmitted to the axilla and left side of the chest. The pressure is recorded as 165/110 but was
The hypertension in the upper extremity, the exaggerated pulsations in the neck vessels, the souffle noted over the collateral arteries and the left-sided cardiac hypertrophy are all further supporting evidence of coarctation.
H.H., a white male army recruit, age 36, from rural Alberta had a chest film taken on February 8, 1941, as a routine part of his medical examination before enlistment (Figs. 7 and 8).
The transverse diameter of the heart was 15.0 cm. as compared with a transverse diameter of the chest of 29.8 em. The x-ray report read: ‘‘The lungs are clear. Many of the ribs show areas of pressure erosion on their inferior aspects. Radiologically this is characteristic of the findings seen in coarctation of the aorta, the pressure defects being due to enlargement of the intercostal
taken only in the arm.
This patient made an uneventful recovery from his pneumonia and was discharged in 23 days with no symptoms. Dr. Keillor was kind enough to send the patient to my office for a recheck film. This showed the same rib defects and satisfactory resolution of the bronchopneumonia previously present.
Comment. — This appears to be a case of coarctation detected during routine x-ray chest examination, the diagnosis being made on the pathognomonic finding of pressure defects in the inferior surfaces of some of the ribs. The symptoms that brought him under medical attention were due to a bronchopneumonia and when this resolved he had no other complaints. The history of pain in his chest some weeks before admission may or may not have been related to the coarctation. If so, pain had disappeared before he was admitted and was not present at a time when his cardiac reserve should have suffered from toxemia and anoxemic secondary to the bronchopneumonia.
arteries. The cardiac enlargement is presumably secondary to the hypertension present in this condition.
Fig. 5.— Radiograph of the chest, Case 1.
Fig. 6. — More detailed view of Fig. 5 to show rib defects. Radiograph of the chest, Case 2. Rosler’s sign also can be seen in ribs. Fig. 8. — More detailed view of Fig. 7 to show rib defects.
Note rib notchings.
The prospective recruit was examined by Lt.-Col. Walter H. Scott, the medical consultant for the Edmonton district, and I am indebted to him for the following copy of his notes: ‘‘No history of illness. Has done hard work all his life making ties. Examination shows forcible pulsations visible and palpable in neck and arms. Whole neck pulsates. Cardiac enlargement. Systolic murmur at all valves but faint at apex, tricuspid and aorta, and long and louder at pulmonic cartilage. Blood pressure: left arm 185/100; left leg 120/100; right arm 200/120; right leg 115/100. Systolic murmur well heard at apices of both lungs posteriorly. Summary. Coarctation of the aorta. Unfit.’’
Comment. — Case 2 is almost a repetition of Case 1. The condition was accidentally found during an x-ray examination of the chest done with no thought of coarctation being present. The diagnosis was based in Résler’s sign of erosion of the ribs. A clinical examination done later confirmed the x-ray diagnosis by discovering visible and palpable pulsations due to the dilated collateral anastomosis, hypertension in the upper extremity and disparity between the blood pressures of the brachial and femoral arteries.
The roentgenogram of this. case shows a prominent bulb.
The case report supplied by Dr. Malcolmson was also of a recruit. He showed the pathognomonic rib defects in the roentgenogram and had secondary cardiac enlargement. Physical examination discovered marked hypertension in both arms with a much lower tension in the femoral arteries. Bruit was easily detected over the anastomosing branches in the scapular and upper thoracic areas.
This case is almost a duplicate of Case 2 above.
The condition had been overlooked in the first routine medical examination upon application.
- Coarctation of the aorta is one of the more rare anomalies of the cardiovascular system. Although present during infancy and childhood it usually does not become manifest till adolescence or early adult life.
- The most important change occurring in the vascular system is the development of a collateral circulation between the proximal and distal aortic segments. This is chiefly by the scapular, mammary and intercostal arteries.
- Clinically, the condition is diagnosed by the hypertension in the upper portions of the body contrasted with hypotension in the lower, coupled with evidence of dilated collateral arteries.
- Radiologically, the findings of smooth notching in the inferior surfaces of the ribs is pathognomonic. This so-called Rosler’s sign is not present in all cases. It is due to the dilated tortuous intercostal arteries which take part in the collateral circulation.
- Three cases of coarctation of the aorta discovered accidentally and confirmed by subsequent clinical examination are reported.
1. ApBoTT, M. E.: Coarctation of the aorta of the adult type, Am. Heart J., 1928, 3: 392, 574.
2. BENKWITzZ, KARL B. AND HUNTER, W. C.: Combined infantile and adult coarctation of aorta, Am. J. Path., 1937, 13: 289
3. Evans, W.: Congenital stenosis (coarctation), atresia, and interruption of the aortic arch, Quart. J. Med., Jan. 1, 1933, 2: (new series).
4. GITLow, S. AND SOMMER, R. I.: Complete coarctation of the aorta, Am. Heart J., 1940, 20: 106.
5. GoopDson, W. H.: Coarctation of the aorta, New Eng. J. Med., 1937, 216: 339.
Cite this page: Hill, M.A. (2023, November 28) Embryology Paper - Coarctation of the aorta 1942. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_Coarctation_of_the_aorta_1942
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