Pseudocoarctation of the aorta: An unusual variant with coarctation

Pseudocoarctation

of the Aorta:

Variant

with

An Unusual

Coarctation*

NORMAN LAWN, M.D., SATCHIDAMANDMEHTA, M.D., MIRIAM LIBERSON, JEAN MAURICE

POUGET,

Chicago,

M.D. and

M.D., F.A.C.C.

Illinois

A case of pseudocoarctation associated with probable coarctation, hypoplasia of the left vertebral artery, aneurysmal dilatation of the left subclavian artery and a previously undescribed anomaly of the descending thoracic aorta is reported. Based on the concept of aortic arch derivatives, a hypothesis is advanced to explain the development of this additional anomaly.

A

N ANOMALY OF THE AORTIC

known

as pseudocoarctation

case with a complex of developmental anomalies of the aortic arch and descending thoracic aorta not previously described and consisting of pseudocoarctation, probable coarctation, aneurysmal dilatation of the origin of the left subclavian artery, hypoplasia of the left vertebral artery and corkscrew-like deformity of the descending thoracic aorta; (2) to review the significant literature on pseudocoarctation; and (3) to offer some embryologic postulations based on the concept of aortic arch derivatives in order to explain the development of the “corkscrew” deformity.

ARCH COlnmOnly was

first

de-

independently by Dotter and Steinberg,’ Robb* and Souders et aL3 in 1951. Souders et al. discussed 3 cases in which a sumediastinal mass on roentgenogram perior subsequently proved to be a vascular anomaly of the aortic isthmus. One of these patients was initially thought to have Hodgkins disease with involvement of the left superior mediastinal nodes. The lack of response to irradiation resulted in exploratory thoracotomy, at which time the aortic arch deformity was found. Since then, approximately 50 cases have been reported, variously listed as pseudocoarctation, subclinical coarctation, kinking or buckling of the aortic arch.2-14 Despite the relative paucity of reported cases, pseudocoarctation is not a rare entity. One of us (J.M.P.) has seen at least 4 well documented cases that were never reported. Pseudocoarctation can be defined as an elongation and kinking of the aortic isthmus which differs from true coarctation primarily by the absence of any real narrowing of the aortic lumen and by the absence of aortic pressure gradients and collateral circulation. Although the entity appears to be well defined, there is considerable confusion about the mechanism and significance of the lesion and the appropriate terminology. The purpose of this paper is (1) to report a scribed

CASE HISTORY A 49 year old Puerto Rican man was admitted for evaluation of a left superior mediastinal mass discovered on routine chest x-ray examination. The patient was asymptomatic with no past history of venereal disease, heart disease, or other serious illnesses. There was no familial history of congenital 01 acquired heart disease. While in the armed services in 1942, he was hospitalized in Puerto Rico for an ear infection, and was told at that time that he had hypertension; no medication was administered and there were no further follow-up studies. On physical examination the patient was alert, well developed, and well nourished. He was 5 ft., 5% in. in height and weighed 129 lb. ; there were no characteristics suggestive of Marfan’s syndrome. The pulse rate was 92 and regular. Auscultatory measurements of blood pressure were as follows: 146/90 mm. Hg in the right arm; 142/85 in the left arm; 132/80 in the right leg; 130/80 in the left leg. A thrill was felt in the left

* From the Cardiovascular Research Laboratory, Veterans Administration, West Side Hospital and Department of Medicine, University of Illinois College of Medicine, Chicago, Ill. Manuscript received October 1, 1968, accepted March 31, 1969. .4ddress for reprints: Jean Maurice Pouget, M.D., Cardiovascular Research Laboratory, Veterans Administration, West Side Hospital, 820 South Damen .4ve., Chicago, 111. 60612. 584

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Pseudocoarctation supraclavicular fossa in the region of the subclavian artery. A loud bruit was heard in the same location with radiation to the left interscapular region. The ocular fundi revealed no changes suggestive of arteriosclerosis, hypertension, or diabetes mellitus. The lungs were clear to percussion and auscultation. No deformities were noted in the thoracic cage. The maximal cardiac impulse was palpable in the fifth intercostal space, 10.0 cm. to the left of the midsternal line. The apex was not hyperdynamic and there were no thrills or heaves. The first heart sound was normal. The second heart sound was normally split, with the aortic component being slightly louder than the pulmonic component. A grade Z/6 short systolic ejection murmur was heard along the left sternal border. A soft, probably physiologic third heart sound and an intermittent fourth heart sound were heard at the apex. No diastolic murmur was heard. The chest roentgenogram (Fig. 1) showed a small density, smooth and round in contour, in the left upper paramediastinal area. Lung and cardiovascular structures appeared otherwise normal. Routine laboratory studies, including serology, blood sugar and urea nitrogen and a thyroid scan were within normal limits. The electrocardiogram was also normal. Arterial Catheterization Studies: No. 18 gauge Cournand needles were placed in the right and left brachial arteries and in the left femoral artery. Intravascular pressures were then simultaneously recorded with equisensitive gauges (Statham P23GB) on an Electronics for Medicine recorder. All pressures were measured from the same base line and the same zero reference level. Subsequently a No. 8F NIH catheter was advanced to the aortic root by way of a cutdown on the right brachial artery, and angiograms were obtained in the posteroanterior and left anterior oblique

of Aorta

positions after injections of GO cc. ol 75 per cent Hypaque@ at the aortic root. There was a consistent systolic pressure gradient. ot 36 mm. Hg hetvveen the simultaneously recorded left brachial and left femoral artery pressures. A smaller pressure difference of 18 to 20 mm. Hg was detected hehveen the right and the left brachial artery. the right brachial artery pressure being consistently slightly higher than the left (Fig. 3). The systolic pressure gradient hetween the right brachial and the left femoral artery measured 52 mm. Hg (Fig.

j! I

w

1

1I

I I j 1I I I I I I

I

mm 200 150 100

SO 0 Figure 2. Simultaneous recordings of right and left brachial artery pressures showing that the right brachial artery (RBA) pressure is slightly higher than the left (LB-A) (18 mm. Hg) which also shows a slight delay. VOLUME

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Lavin et al.

586

H¶

mm 200 150 100 50 0 Figure 3. systolic

Simultaneousrecordingsof right brachialand leftfmoralartery (LFA) pre~mre~ showing

gradient

of 52 mm.

Hg. The

left femoral

3).-The left brachial artery pressure exhibited a slight delay of 0.02 sec. when compared with the right. A greater delay of 0.04 sec. was noted in the femoral artery tracing. All systolic pressures during this study were in the hypertensive range. Aortography: Two representative views of the aortogram are shown in Figure 4. The aortic arch is elongated and extends higher and farther laterally than usual. There is a sharp kink at the level of the aortic isthmus between the origin of the left subclavian artery and the ductus arteriosus. The ductus is not patent and is not visualized in these studies. The descending thoracic aorta appears hypoplastic and is more markedly reduced in caliber than normal. Approximately at the mid-thoracic level the descending aorta exhibits a pronounced S-shaped deformity with an appearance not unlike that of a corkscrew. In these pictures aneurysmal dilatation of the initial segment of the left subclavian artery can be well appreciated. Hypoplasia of the left vertebral artery which was also quite evident on the angiogram does not show up as well in these pictures. Later films in the angiographic sequence showed delayed clearing of the dye with complete and fairly dense opacification of the isthmus and descending thoracic aorta above the corkscrew deformity up to 6 seconds after the dye injection. Although a marked gradient was demonstrated between the pressures in the upper and lower limbs, strongly suggesting the presence of a true coarctation, the angiograms failed to reveal a circumscribed or sharply localized ridge or diaphragm in the aortic lumen.

DISCUSSION The characteristic roentgenographic appearance of pseudocoarctation is an elongation and kinking of the aortic isthmus. The term pseudocoarctation was applied because of certain roentgenologic similarities with true coarctation of the aorta. Other terms were used in subsequent reports, such as kinking or buckling of the thoracic

artery

pressure

exhibits

also a delay of 0.04

a marked sec.

aorta. Proximal to the isthmic deformity, the aortic arch rises unusually high in the mediastinum before curving downward and angulating sharply forward. The left superior mediastinal with which these patients typically “mass” present is actually the high elongated arch extending further laterally than usual. The denser shadow often noted below the apparent mass is the end-on view of the buckled descending aortic arch. The radiographic appearance may resemble true coarctation but lacks the associated findings, such as rib notching. The clinical significance of this anomaly is that it resembles a tumor radiographically and must be considered in the differential diagnosis of left superior mediastinal masses. The angiographic studies in our patient show that his aorta conforms to this description. In addition, aneurysmal dilatation of the left subclavian artery, hypoplasia of the left vertebral artery (this is not well seen on the reproduction of the x-ray pictures) and hypoplasia and corkscrew-like deformity of the descending thoracic aorta can be noted. Pseudocoarctation vs. Coarctation: Souders et a1.3 and Bruwer and Burchellg believed the cause of pseudocoarctation to be a short ductus arteriosus, but Souders et al. found that after sectioning the ductus there was no change in the abnormal contour of the aorta. A short ligamentum arteriosum is not a common feature of true coarctation. l6 According to Hagstrom and Steinbergi pseudocoarctation results from extension to the wall of the aorta of the same process that causes functional obliteration of the ductus arteriosus (Skodiac theory of coarctation). They believe also that true coarctation and pseudocoarctation are closely related since THE

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Pseudocoarctation

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Figure 4. Aortic root angiograms showing the typical configuration of the aortic arch as described in pseudocoarctaCon. A, posteroanterior view; B, left anterior oblique view. The actual kink is not well seen because of positioning. .\neurysmal dilatation of the left subclavian artery and hypoplasia with S-shaped deformity of the descending midrhoracic aorta can be well noted. Hvpoplasia of the left vertebral artery, which was also present, dots not show up :is well in these pictures. I_

.

they represent different results of an abnormal growth of the aortic wall. Some authors regard pseudocoarctation as a subclinical form of coarctation caused by eccentric pulling of a fibrosing ductus arteriosus with resulting deformity in contour and they USC both terms indiscriminatelyg-‘*. Edmunds et a1.,17 on the other hand, believed that subclinical coarctation must be clearly differentiated from pseudocoarctation. Subclinical coarctation is characterized by a sharply demarcated and well circumscribed anatomic constriction of the aorta which is not severe enough to cause a decrease in distal blood pressure. By contrast, in pseudocoarctation, the aortic isthmus is elongated and twisted, but there is no significant or localized intraluminal narrowing. Furthermore, both entities may coexist in the same patient.17 Likewise, the combination of a significant true coarctation and pseudocoarctation has recently been reported.‘* The existence of a pressure gradient in certain cases of pseudocoarctation has not been adequately documented. In cases in which a VOLUME

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small gradient was thought to be present, the possibility of an associated true coarctation was not completely excluded. In our case, however, a marked and highly significant pressure difference was demonstrated between the upper and lower limbs. A smaller gradient was also evident between the right and the left brachial arterial pressures, the right one being slightly higher than the left. With these findings the presence of a true coarctation of the aorta as an associated lesion must be suspected. The coarctation was not visualized in the angiograms probably because of the anomalous course of this portion of the aorta and failure of the chosen views to display adequately a tangential cut of the involved segment. In our patient three main areas of involvement can be identified on the angiograms. First, the aortic isthmus exhibits greater than usual narrowing with the sharp kink and angulation customary in cases of pseudocoarctation. Second, the mid-descending thoracic aorta is somewhat hypoplastic, and its diameter as measured on the angiogram is less than 50 per cent of that of

588

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the ascending aorta. Third, at the mid-chest level, the descending thoracic aorta shows a very sharp S-shaped curve, the appearance of which we have compared to that of a corkscrew. The prolonged and dense opacification of this segment of the aorta after the dye had cleared from the ascending aorta is further supportive evidence of a significant obstruction at the aortic isthmus. Embryologic Basis of Aortic Arch Anomalies: Basic to an understanding of congenital aortic arch anomalies is an acquaintance with the embryologic formation of this vascular structure which has been well described by Barry.rg Of special importance in this regard is the cephalic shift of the-origin of the left subclavian artery which takes place in an early stage of development. During the second month of gestation the heart migrates caudally, progressively elongating the arteries that extend between the outlet of the heart and the cervical and upper reaches of the body. As this process takes place, certain segments of the original arterial pattern regress and others enlarge correspondingly. In addition to the alteration in the length and diameter of the arteries, changes occur in their relationship to one another. A branch of the seventh dorsal intersegmental artery, which supplies initially the anterior appendage bud, during subsequent development persists and enlarges to become the left subclavian artery. Concurrently with the cephalic shift of this structure, there is associated compression and fusion of the third through tenth segments of the dorsa1 aortic roots and of the Ieft fourth arch segment.19 It is widely believed that failure of compression of these segments results in an abnormally long aortic arch which twists at the point of insertion of the ligamentum arteriosum. This would explain the kinking of the aortic isthmus, that is, the segment between the left subclavian artery and the ductus arteriosus, which is the primary area of involvement in all reported cases of pseudocoarctation thus far. As can be seen in Figure 4 in our case, in addition to a deformity of the aortic isthmus, the descending thoracic aorta is hypoplastic and there is a marked S-shaped curve quite distal to the point of insertion of the ligamentum arteriosum, an area of involvement which has not previously been reported. This new anomaly may perhaps partly be explained by a more extensive failure of compression of the dorsal root segments as described for pseudocoarctation. One may, however, advance the following hypothesis as

et al. an alternative explanation. Normally the eighth segment of the right dorsal aortic root becomes atretic and regresses completely. It is conccivabie that only the cephalad end of the right eighth segment may become atretic and disappear whereas the caudad end of this structure remains attached to the left eighth and ninth aortic root segments, becoming subsequently incorporated into the descending thoracic aorta (Fig. 5). This could result in a contour deformity somewhat similar to that observed in our patient. Daugherty et ali2 and Dotter and Steinberg’ have reported on the combination of pseudocoarctation and subclavian arterial aneurysm. Aneurysmal dilatation of the initial portion of the left subclavian artery can be noted in our patient. Since the left subclavian artery originates from the junction of the seventh and eighth dorsal aortic root segments, aneurysmal dilatation in many of these patients could perhaps be explained by a mechanical effect consequent to the elongation of the adjacent segments seven and eight. It is not, however, necessary to resort to an embryologic explanation for this lesion. Some degree of post-stenotic dilatation is quite commonly present in both coarctation and pseudocoarctation and the causes of this phenomenon have been extensively debated. Holman20 and Robicsek et a1.21 have shown experimentally that post-stenotic dilatation can be produced by hydraulic forces. These authors emphasize the hemodynamic genesis of poststenotic dilatation and contend that a sharply circumscribed area of narrowing may cause turbulence phenomena, rapid conversion of kinetic energy to potential energy and produce fluctuating lateral pressure waves with subsequent damage to the elastic fibers of the aortic wall. Steinberg, l4 however, concludes not without logic that since significant aortic narrowing is absent in pseudocoarctation, the presence of post-stenotic dilatation distal to the lesion suggests that such a malformation is probably an associated anomaly rather than a resulting lesion. Clinical Features of Pseudocoarctation: Patients with pseudocoarctation are generally asympto matic with specific reference to the vascular anomaly. The significant finding in these patients is a systolic ejection murmur most prominent at the upper left sternal border. Bruwer and Burchellg observed this murmur in 9 of 10 patients in their series. They attributed the murmur to turbulence of blood flow in the THE AMERICANJOURNAL

0~ CARDIOLOGY

Pseudocoarctation

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u IO II

a

b

Figure 5. Diagrammatic representation of the embryologicdevelopmentof the nortic arch (a) and postulated secmence to explain the S-shaoed deformitv of the descending thoracic arch (b and c) L.D.A.R = left do;sal aortic root; R.D.A.R. = right dorsal aortic root; IV A. Seg = fourth arch segment; R.S. = right subclavian artery.

tortuous lumen. This is not inconsistent with the lack of pressure gradients in these patients since it has been shown experimentally and it is a common clinical observation that a murmur can occur before demonstrable differences in pressure. Nasser and Helmen” reported on 8 patients, of whom 4 had chest pain and 3 had episodes of paroxysmal atria1 tachycardia. All 8 patients had a systolic ejection murmur. The chest pain and arrhythmia in this series can only be interpreted as implying other and probably unrelated underlying disease. Pseudocoarctation occurs equally in male and female and 5 isolated cases have been reported in children.11-22 There is no evidence that pseudocoarctation or coarctation is inherited as a Mendelian character. Sporadic occurrences of these anomalies in siblings have, however, been reported.23 Associated anomalies have been described with pseudocoarctation, primarily patent ductus VOLUME 24, OCTOBER

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arteriosus, ventricular septal defect, bicuspid aortic valves and congenital aortic stenosis.3-14 Because of the possibility of associated bicuspid aortic valves Steinberg and Hagstrom have recommended prophylactic antibiotic therapy in these patients whenever dental or other minor surgical procedures are contemplated. Sqical correction is not generally thought to be indicated in isolated cases of pseudocoarctation. In our patient, however, because of the significant pressure gradient, moderate systemic hypertension and S-shaped anomaly of the descending thoracic aorta, surgical treatment was offered but refused by the patient. REFERENCES 1. DOTTER, C. and STEINBERG, I. Angiocardiography, p. 181. New York, 1951. Paul B. Hoeber. 2. ROBB, G. P. An Atlas of Angiography prepared for the American Registry of Pathology, Armed Forces Institute of Pathology (American Registry

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7. 8. 9.

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11.

12.

13.

14.

of Pathology, National Research Council). Washington, D. C., 1951. SOUDERS, C. R., PEARSON,C. M. and .\DAMS,H. D. i\n aortic deformity simulating mediastinal tumor: .i subclinical form of coarctation. Dis. Chest, 20: 35, 1951. VAUGHN B. F m mg of aortic arch. Brit. J. R a dial.’ 29:5;6 %5:.’ STEVENS, G. M. ’ Buckling of the aorta. Radiology, 70:67, 1958. PATTINSON,J. N. and GRAINGER,R. G. Congenital kinking of the aortic arch. Brit. Heart J., 21:555, 1959. GRIFFIN, J. F. Congenital kinking of the aorta. New England J. Med., 271~726, 1964. BERRY, R. E., GRIFFITH, J. R. and TEMPLETON,J. Y. Kinking of the aorta. Am. Surgeon, 29:65, 1963. BRUWER, A. J. and BURCHELL, H. B. Kinking of aortic arch (pseudocoarctation, subclinical coarctation). J.A.M.A., 162:1445, 1956. SHAW, V. V., SHAH, K. D., DASTUR, K. N. and SHAH, R. L. Kinking of aortic arch with aneurysma1 dilatation. Dis. Chest, 50:101, 1966. NASSER, W. K. and HELMEN, C. Kinking of the aortic arch (pseudocoarctation). Ann. Znt. Med., 64:971, 1966. DAUGHERTY, H. K., SANGER, P. W., ROBICSEK,F., SMITH, D. R. and SHARIFF, K. Pseudocoarctation associated with aneurysm of the aortic arch. Angiologr, 17:719, 1966. DIGUGLIELMO,L. and GATTADAURO,M. Kinking of the aorta: Report of two cases. Acta. radial., 44:121, 1955. STEINBERG,I. Anomalies (pseudocoarctation) of the

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arch of the aorta. Am. J. Roentgenof., 88:73, 1962. CAMPBELL,M. and POLANI, P. E. Etiological factors in coarctation of the aorta. Lancet, 1 :463, 1961. HAGSTROM,.I. W. C. and STEINBERG,I. Pathologic lesion in pseudocoarctation of the arch of the aorta. Circulation, 26 ~726, 1962. EDMUNDS,L. H., JR., MCCLENATHAN, J. E. and HUFNAGLE, C. ‘1. Subclinical coarctation of the aorta. Ann. Surg., 156:180, 1962. ACEVEDO, R. E., THILENIUS,0. G., MOULDER, P. V. and CASSELS,D. E. Kinking of the aorta (pseudocoarctation) with coarctation. Am. J. Cardiol., 21: 442, 1968. BARRY, A. The aortic arch derivatives in the human adult. Amt. Rec., 111~221, 1951. HOLMAN,E. The obscure physiology of post-stenotic dilatation: Its relation to the development of aneurysms. J. Thoracic Surg., 28:109, 1954. ROBICSEK,F., SANDER,P. W., TAYLOR, F. H., MAGISTRO, R. and FOTI, E. Pathogenesis and significance of post-stenotic dilatation in great vessels. Ann. Surg., 147:835, 1958. GUDBJERG,C. E. and PETERSON,0. Coarctation of the aorta: Relation between roentgenographic and hemodynamic findings. Rndiologv, 75:399, 1960. KELLER, H. I. and CHEITLIN,M. D. The occurrence of mild coarctation of the aorta (pseudocoarctation) and coarctation in one family. Am. Heart J., 70:115, 1965. STEINBERG,I. and HAGSTROM,J. W. C. Congenital aortic valvular stenosis and pseudocoarctation (kinking, buckling) of the arch of the aorta. Circulation, 25 1545, 1962.

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