Aortic obstructions in infants and children

Aortic Obstructions in Infants and Children Pathophysiology

and Clinical Presentation of

Interrupted Aortic Arch

JAMES A. JOHNS, THOMAS P. GRAHAM,

M.D. JR., M.D.

Division of Pediatric Cardiology Department of Pediatrics Vanderbilt University Medical Center Nashville. Tennessee

ABSTRACT Interrupted aortic arch is an uncommon form of congenital heart disease in which there is almost always an associated ventricular septal defect or aorticopulmonary window. There may also be other cardiac abnormalities or DiGeorge anomaly. Presentation usually occurs as the ductus closes and is related to decreased perfusion to the lower body, left-to-right shunting, and increased left ventricular end-diastolic pressures. Diagnosis can generally be made by echocardiography, but catheterization may provide additional helpful data. Temporary palliation may be achieved with prostaglandin El infusion to maintain ductal patency, but urgent operation is required. Long-term results are good after repair of the arch and associated defects, but subaortic stenosis or restenosis at the site of the arch repair may occur. Keywords: interrupted aortic arch; pathophysiology; congenital heart disease Interrupted aortic arch, or the complete absence of luminal continuity between the ascending and descending aorta, comprises -0.5% to 1.5% of Address correspondence to James A. Johns, M.D., D-2220 Medical Center North, Vanderbilt University Medical Center, Nashville, TN 37232-2572.

congenital heart disease.’ The incidence of interrupted aortic arch has been reported as -1 in 20,000 to 1 in 50,000 live births2,j and is similar in boys and girls. Without therapy, interrupted aortic arch is usually fatal in the first month of life. Over the past 35 years, advances in preoperative, operative, and postoperative management have allowed the successful repair of many infants with interrupted aortic arch.‘+8 Celoria and Patton’ classified interrupted aortic arch by the location of the interruption. In type A the interruption is distal to the left subclavian artery, in type B it is between the left carotid and left subclavian arteries (Table), and in type C it is between the innominate and left carotid arteries. In most series, type B is slightly more common (45% to 70% of cases) than type A (30% to do%), and type C is much less common (<10%).5.6JoJ1

ASSOCIATED DEFECTS Virtually all patients have associated intracardiac anomalies. There is almost always a patent ductus arteriosus connecting the main pulmonary artery with the descending aorta. With rare exceptions, patients with interrupted aortic arch have either a ventricular septal defect (80% to 90% of cases) or an aorticopulmonary window (10% to 20%). The Prog Pediatr Cnrdio2 1994; 3(2):87-93 Copyright 0 1994 by Butterworth-Heinemann

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Classification of Interrupted Aortic Arch* Type A Percentage of total Male/female Ventricular septal defect Bicuspid aortic valve Anomalous subclavian artery Aorticopulmonary window Truncus arteriosus Transposition Single ventricle Right descending aorta DiGeorge syndrome

Type B

30-40 1.7 70-85 % 20% 2%

45-70 0.8 94% 40% 40%

10-15 %

Very rare

Very rare 20% 12% 20% Very rare (never?)

5-10% 3% 2% 10% Common

* See text for definitions of types A and B.

septal defect in interrupted aortic arch often involves the conal septum ( - 60% of cases), but it may be an inlet, muscular, or perimembranous defect (10% to 15% each).12 The ventricular septal defect is generally larger than the aortic orifice. Almost all of those patients who do not have a ventricular septal defect have an aorticopulmonary window. Aorticopulmonary windows are rarely seen in patients with type B or C interrupted aortic arch. Subaortic stenosis is common in patients with interrupted aortic arch.13J4 Even if it is not significant in the neonatal period, subaortic stenosis can progress after repair of the interrupted arch and ventricular septal defect. Sell et a1.6 have found that up to 40% of patients undergoing primary repair of interrupted arch in infancy may develop significant subaortic stenosis within 3 years after operation. It has been proposed that leftward displacement of the crista supraventricularis may produce subaortic stenosis and a malalignment ventricular septal defect, reducing in utero antegrade flow to the ascending aorta and allowing involution of the aortic arch.‘J5J6 Bicuspid aortic valve is also common in patients with interrupted arch.” Some patients with interrupted aortic arch have complex intracardiac defects, including truncus arteriosus, transposition of the great arteries, and single ventricle. Pulmonary outflow tract obstruction almost never occurs in association with interrupted aortic arch. Other abnormalities of the great arteries may occur, including a right aortic arch in - 5 % ventricular

and an aberrant right subclavian artery in up to 20% of cases (usually type B interruptions).” DiGeorge anomaly, an abnormality of the development of the pharyngeal pouches, is seen in up to 70% of patients with type B interrupted aortic arch.17J8 Patients with DiGeorge anomaly usually have hypocalcemia in the neonatal period because of parathyroid hypoplasia, and they have abnormal lymphocyte subsets because of failure of descent of the thymus. Only a minority have clinically significant immunodeficiency.18J9 DiGeorge anomaly is discussed in detail in another article in this issue (Buck et al., pp. 94-99).

PATHOPHYSIOLOCY With interrupted aortic arch, fetal left ventricular output is decreased and right ventricular output is increased. The pulmonary artery is large, and the ascending aorta is small. Usually, there is no hemodynamic compromise before birth. After delivery, the right ventricle supplies blood flow to the descending aorta through the patent ductus arteriosus, whereas the left ventricle supplies the ascending aorta. Because of the increased afterload on the left ventricle, there is left-to-right shunting across the ventricular septal defect or aorticopulmonary window. There may be differential cyanosis of the lower body compared with the upper body, but this is often subtle. In infants with coarctation of the aorta, the presence of a ductal diverticulum may allow flow around the area of coarctation, but infants with interruption of the aortic arch must have a patent ductal lumen to allow flow to the lower body. As the ductus arteriosus begins to constrict, flow to the descending aorta decreases, resulting in decreased perfusion to the lower body, including the kidneys. Urine output falls and acidosis occurs. With ductal constriction, left-to-right shunting across the ventricular septal defect or aorticopulmonary window increases, resulting in more pulmonary venous return to the left atrium. Left ventricular enddiastolic and left atria1 pressures increase, often leading to the left-to-right atria1 shunting across, an atria1 septal defect or stretched foramen ovale. Pulmonary edema occurs because of the increase in left atria1 and pulmonary venous pressures, thus making breathing difficult and causing respiratory distress.

Interrupted Aortic Arch

FIGURE 1. Suprastemal notch view of an echocardiogram of an infant with type A interrupted aortic arch. The ascending aorta (AAO) gives rise fo the innominate (INNOM), left common carotid (MICA), and left subcfavian fLSCA) arteries, but there is no continuity with the descending aorta.

PRESENTATION Infants with interrupted aortic arch usually are not symptomatic at birth, but they become symptomatic over the first 24 to 48 hours of life. Often there is a systolic murmur, either from the shunting across the ventricular septal defect or through the aorticopulmonary window, from left ventricular outflow tract obstruction or ductal flow. As the ductus begins to close, flow from the right ventricle to the descending aorta decreases, and pulses and perfusion in the lower extremities decline. Depending on whether the left subclavian artery is proximal (type A) or distal (types B and C) to the interruption, pulses in the left arm may be normal or decreased. If there is an aberrant right subclavian artery, both subclavian arteries may arise distal to the interruption, and pulses in all four extremities may be weak or absent. In this situation, the only palpable pulses may be those in the head and neck. With ductal constriction and the decrease in lower body perfusion, urine output decreases and acidosis develops. All patients develop congestive heart failure, and some have shock with circulatory collapse. Chest x-ray usually shows cardiomegaly, increased pulmonary blood flow, and pulmonary

edema. Electrocardiography may show right, left, or biventricular hypertrophy.20

ECHOCARDIOGRAPHY The diagnosis of interrupted aortic arch is usually made with echocardiography (Figure 1). Imaging of the aortic arch from the suprasternal notch shows the ascending aorta giving rise to the innominate artery. In types B and C interrupted aortic arch, the proximal arch is oriented in a cephalic direction without the normal curve toward the descending aorta. Type A interruption can usually be distinguished from a severe coarctation, but this can be difficult in some cases. The ductus is seen continuing to the descending aorta in all types of interrupted arch. The ventricular septal defect is easily seen, as are less commonly associated anomalies such as transposition, truncus arteriosus, and single ventricle. Care must be taken to look for an aorticopulmonary window, which may occasionally be mistaken for artifactual dropout of the aorticopulmonary septum. If there is no ventricular septal defect, there is almost always an aorticopulmonary window. An aberrant right subclavian

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90

FIGURE 2. Anterior-posterior with type A interrupted lary artery.

via the patent

ductus

projection

aortic arch.

The innominate,

mal to the interruption.

in Pediatric

of an ascending

The catheter

left carotid,

The descending arteriosus.

Cardiology

aortogram

was placed

and left subclavian

arteries

aorta is not seen because

The heart is enlarged

of an infant

via the right

axil-

arise proxi-

it filled only

and pulmonary

vascular

markings are increased.

artery may be difficult to visualize with echocardiography unless one is specifically looking for it. Often, echocardiography provides sufficient anatomic detail to allow surgical intervention without catheterization.

CATHETERIZATION Catheterization is reserved for those patients for whom additional anatomical or physiological data is needed before operation. Measurements generally demonstrate equal right and left ventricular pressures with elevated pulmonary artery pressures. It is difficult to enter the ascending aorta directly via the venous approach (right atrium-left atrium-left ventricle-ascending aorta) because the catheter preferentially passes from the left ventricle across the ventricular septal defect into the pulmonary artery. Thus, we usually do not measure the gradient from the left ventricle to the ascending aorta to determine the presence of aortic or subaortic stenosis. It is possible to determine such a gradi-

ent by comparing right-arm and left ventricular pressures (unless the right subclavian artery arises aberrantly), but Doppler echo estimation of the gradient is usually suficiently accurate. If the ductus is partially constricted, there may be a gradient from the right ventricle to the descending aorta. Oximetry reveals left-to-right shunting at the atria1 and ventricular levels, with right-to-left shunting through the ductus. The descending aortic oxygen saturation may be 80% to 90% if there is excessive pulmonary blood flow, which is often the case. Angiography can be very helpful in delineating the exact site of interruption, the size of the ascending aorta, the presence of an aorticopulmonary window, and the presence of an aberrant right subclavian artery. For the abovementioned reason, it is difficult to perform an ascending aortogram from the venous approach. A retrograde approach from the right brachial or axillary artery is possible (Figure 3, but this frequently results in decreased right-arm pulses, which makes follow-up with arm and leg blood pressures difficult. A left ventriculo-

Interrupted Aortic Arch

91

FIGURE 3. Anterior-posterior projection of a left ventriculogram and a descending aortogram in an infant with type B interrupted aortic arch and an aberrant right subclavian artery. (A) an early frame from the left ventriculogram shows filling of the right and left carotid arteries from the ascending aorta. The right subclavian artery is not seen. The pulmonary artery has filled via the ventricular septal defect. No patent ductus arteriosus is seen. (B) a descending aortogram. There is filling of the right and left subclavian arteries, There was washout of the contrast in the subclavian arteries by retrograde flow of uncontrasted blood down the vertebral arteries and into the subclavian arteries. Again, no patent ductus arteriosus is seen.

gram with straight anterior-posterior and lateral imaging often clearly shows the ascending aorta and site of interruption, although the interruption may be partially obscured by the large pulmonary artery filling through the ventricular septal defect or the aorticopulmonary window (Figure 3A). If there is a question that one or both of the subclavian arteries may arise distal to the interruption, a descending aortogram with the venous catheter through the ductus and with balloon occlusion of the distal aorta may fill any vessels that originate distal to the interruption (Figure 3B). One must be careful not to give too much contrast, because renal

dysfunction may occur from decreased perfusion and can be exacerbated with excessive contrast material .

MANAGEMENT

Initial management of infants with interruption of the aortic arch is directed at stabilization of the patient for surgical intervention. Prostaglandin E, infusion (0.05 pg. kg-’ - min-‘) usually will maintain ductal patency and allow the right ventricle to perfuse the descending aorta through the ductUs.21*22 Inotropic support with dobutamine at a rate

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of 5 to 10 pg*kg-‘emin-’ is helpful, along with low-dose dopamine (2 to 5 pg*kg-‘emin-‘) to improve renal perfusion. Diuretics may help maintain urine output and decrease ventricular filling pressures. Intubation and ventilation are helpful in minimizing the work of breathing, which is increased because of pulmonary edema. Ventilation with room air is desirable because supplemental oxygen may result in a decrease in the pulmonary resistance and a further increase in pulmonary blood flow, thus worsening the pulmonary edema. Relatively high end expiratory pressures may be required. All patients with type B interruption should be considered to have DiGeorge anomaly until proven otherwise. Blood should be drawn for determination of lymphocyte subsets before blood transfusions. If blood products are required, they should be irradiated to minimize the risk of graft-versushost disease. Calcium levels should be measured; if they are low, supplemental calcium should be given intravenously. Measurement of parathyroid hormone levels at the time of hypocalcemia can confirm the cause of the hypocalcemia. Beyond the newborn period, problems with hypocalcemia are less frequent,19 and clinically significant immunodeficiency is uncommon .18 Surgical management of interrupted aortic arch is discussed elsewhere in this issue. In a few patients with a small (
SUMMARY

Interrupted aortic arch is a relatively uncommon form of congenital heart disease that is nearly always associated with intracardiac defects. Infants with this condition present with decreased lower body perfusion, congestive heart failure, and sometimes shock. With appropriate medical and surgical

management, ing common.

survival

of these children

is becom-

REFERENCES 1. Van Praagh R, Bernhard WF, Rosenthal A, et al. Interrupted aortic arch: surgical treatment. Am 1 Cardiol. 1971;27:200-211. 2. Fyler DC, Buckley LP, Hellenbrand WE, et al. Report of the New England Regional Infant Cardiac Program. Pediatrics. 1980;65:376-461. 3. Martin ML, Adams MM, Mortensen ML. Descriptive epidemiology of selected malformations of the aorta, Atlanta, 1970-1983. Teratology. 1990;42:

273-283. 4. MerrilI DL, Webster CA, Sampson PC. Congenital absence of the aortic isthmus. ] Thorac Surg. 1957;

33:311-320. 5. Scott WA, Rocchini AI’, Bove EL, et al. Repair of interrupted aortic arch in infancy. 1 Thorac Cardiovast Surg. 1988;96:564-568. 6. Sell JE, Jonas RA, Mayer JE, Blackstone EH, Kirklin JW, Castaneda AR. The results of a surgical program for interrupted aortic arch. ] Thorac Cardiovasc Surg. 1988;96:864-877. 7. Irwin ED, Braunlin EA, Foker JE. Staged repair of interrupted aortic arch and ventricular septal defect in infancy. Ann Thorac Surg. 1991;52:632-639. 8. Karl TR, Sano S, Brawn W, Mee RBB. Repair of hypoplastic or interrupted aortic arch via sternotomy. 1 Thorac Cardiovasc Surg. 1992;104:688-695. 9. Celoria G, Patton RB. Congenital absence of the aortic arch. Am Heart 1. 1959;58:407-413. 10. Collins-Nakai RL, Dick M, Parisi-Buckley L, Fyler DC, Castaneda AR. Interrupted aortic arch in infancy. 1 Pediatr. 1976;88:959-962. 11. Menahem S, Rahayoe A, Brawn WJ, MeeRBB. Interrupted aortic arch in infancy: a lo-year experience. Pediatr Cardiol. 1992;13:214-221. 12. Freedom RM, Bain HH, Espligas E, Dische R, Rowe RD. Ventricular septal defect in interruption of the aortic arch. Am 1 Cardiol. 1977;39:572-582. 13. Ilbawi MN, Idriss FS, DeLeon SY, Muster AJ, Benson DW, Paul MH. Surgical management of patients with interrupted aortic arch and severe subaortic stenosis. Ann Thorac Surg. 1988;45:174-180. 14.Moller JH, Edwards JE. Interruption of aortic arch: anatomic patterns and associated cardiac malformations. Am 1 Roentgen01 Nuclear Med. 1965;95(3): 557-572. 15. Rudolph A, Heymann M, Spitznas U. Hemodynamic considerations in the development of narrowing of the aorta. Am 1 Cardiol. 1978;42:467-471.

16. Moore GW, Hutchins GM. Association

of inter-

Interrupted Aortic Arch

rupted aortic arch with malformations producing reduced blood flow to the fourth aortic arches. Am I Cardiol. 1978;42:467-472. 17. Van Mierop LHS, Kutsche LM. Cardiovascular anomalies in DiGeorge syndrome and importance of neural crest as a possible pathogenetic factor. Am 1 Cardiol. 1986;58:133-137. 18. Hong R. The DiGeorge anomaly. lmmunodefic Rev.

1991;3:1-14. 19. Conley ME, Beckwith JB, Mancer JFK, Tenckhoff L. The spectrum of the DiGeorge syndrome. J Pediatr.

1979;94:883-890. 20. Higgins CB, French JW, Silverman JF, Wexler L. Interruption of the aortic arch. Preoperative and postoperative clinical hemodynamic and angiographic features. Am J Cardiol. 1977;39:563-611. 21. Graham TP, Atwood GF, Boucek RJ. Use of prostaglandin E1 for emergency palliation of symptomatic coarctation of the aorta. Cathet Cardiouasc Diagn.

1978;4:97-102. 22. Heymann MA, Berman WB Jr, Rudolph AM, Whitman V. Dilation of the ductus arteriosus by prostaglandin E, in aortic arch abnormalities. Circulation.

93

1979;59:169-173. 23. Hammon JW, Merrill WH, Prager RL, Graham TP, Bender HW. Repair of interrupted aortic arch and associated malformations in infancy. Indications for complete or partial repair. Ann Thorac Surg. 1986;

42~17-20. 24. Schumacher G, Schreiber R, Meisner H, et al. Interrupted aortic arch: natural history and operative results. Pediatr Cardiol. 1986;7:89-93. 25. Foker J. Surgical repair of aortic arch interruption. Ann Thorac surg. 1992;53;369-370. 26. Griffin S, Richens D, Behl R. Early results of direct repair of aortic interruption by the lateral approach. Ann Thorac surg. 1992;53:430-434. 27. Cooper SG, Sullivan ID, Wren C. Treatment of recoarctation: balloon dilatation angioplasty. J Am Co11 Cardiol. 1989;14:413-419. 28. Hellenbrand WE, Allen HD, Golinko RJ, Hagler DJ, Lutin W, Kan J. Balloon angioplasty for aortic recoarctation: results of Valvuloplasty and Angioplasty of Congenital Anomalies Registry. Am I Cardiol.

1990;65:793-797.