Congenital anomalies of the thoracic aorta and main pulmonary arteries
Patent ductus arteriosus and coarctation of the aorta are among the most common congenital cardiovascular defects. However, other anomalies of the great vessels, such as aortopulmonary window or pulmonary artery sling, are very rare (Table 1) 497. Most defects of the aorta or main pulmonary arteries present, or are detectable, in infancy when successful surgical correction is feasible. Delayed intervention risks the development of irreversible or inoperable systemic or pulmonary hypertension.
INTERRUPTED AORTIC ARCH
This rare defect is characterized by a total lack of continuity between the aortic arch and the descending aorta (Fig. 1) 1726. Sometimes there may be an atretic fibrous connection without a lumen. The most common site of the interruption is between the left common carotid and subclavian arteries (Type B, 55 per cent of cases. Obstruction occurs distal to the left subclavian (Type A) in 45 per cent and between the innominate artery and left carotid (Type C) in 5 per cent. In these patients a large patent ductus arteriosus supplies the lower half of the body with desaturated blood from the right ventricle, whereas the arch vessels are supplied with oxygenated blood from the left ventricle. Interrupted aortic arch is commonly associated with other defects, including large ventricular septal defect (in 95 per cent of patients), single ventricle, truncus arteriosus, aortopulmonary window, and transposition of the great arteries.
Presentation is with severe heart failure in the neonatal period (Table 3) 499 and survival beyond infancy is uncommon (Table 4) 500. Unoperated the median age at death is 10 days, with an 80 per cent mortality rate within the first 4 weeks of life. Rarely, when the ductus remains widely patent and intracardiac lesions are not complex, presentation is delayed in a manner similar to that of coarctation. When the ductus arteriosus begins to close and pulmonary vascular resistance falls, severe congestive cardiac failure develops, with pulmonary plethora and hypoperfusion of the lower half of the body. The femoral pulses are decreased or absent, and metabolic acidosis, anuria, and renal failure develop rapidly. Echocardiography and cardiac catheterization are used to define the anatomy of the aortic arch and determine the nature and extent of associated intracardiac lesions. When the diagnosis is established administration of prostaglandin E&sub1; maintains patency of the ductus arteriosus until surgical treatment can be undertaken.
The type of surgical procedure performed depends on the site of interruption and the presence of associated cardiac anomalies, particularly left ventricular outflow tract obstruction. For patients with interruption distal to the left subclavian artery (type A) the situation is similar to that in preductal coarctation. The descending aorta and aortic isthmus are mobilized, and ductus ligated and divided, and direct end-to-end anastomosis is performed between the transverse and descending segments of aorta. When the distance between the two segments does not permit anastomosis, continuity can be established by disconnecting the left subclavian artery and turning this down on to the descending aorta.
Interruption between the left carotid and left subclavian arteries (type B), or rarely between the innominate and left carotid arteries (type C), is repaired using sternotomy rather than thoracotomy, and cardiopulmonary bypass with profound hypothermia and total circulatory arrest. With the circulation arrested the proximal descending aorta is mobilized using the ductus arteriosus for traction, until a direct anastomosis between the ascending and descending aorta can be made. Friable ductal tissue must be excised. With this technique associated cardiac defects, particularly ventricular septal defect, are repaired simultaneously.
Correction of the interrupted aortic arch carries a high risk of mortality. Whether associated cardiac defects are repaired at the same operation or secondarily, hospital mortality may be as high as 80 to 100 per cent. The best series report early mortality of about 30 per cent, though late complications such as subaortic stenosis, aortic anastomotic narrowing, or tube graft gradients cause additional mortality in childhood.
PERSISTENT TRUNCUS ARTERIOSUS
Persistent truncus arteriosus is an uncommon anomaly, comprising only 2 to 3 per cent of congenital cardiac defects. The defect consists of a single common outflow trunk arising from the base of both ventricles and giving rise to the systemic, pulmonary, and coronary arterial circulations ( Fig. 3 1728,1729 (a, b)). The truncus straddles an obligatory malalignment-type ventricular septal defect, which is usually large. The truncal annulus and valve are larger than the normal aortic annulus. About 65 per cent of patients have a tricuspid truncal valve, 25 per cent have four cusps, and the remainder are either bicuspid or pentacuspid valves (Fig. 4) 1730. Different morphological classifications have been proposed according to the anatomical configuration of the pulmonary arteries. The widely accepted classification is that of Collett and Edwards (Fig. 5) 1731. In Type 1 a single pulmonary trunk arises near the base of the truncus and divides into right and left branches; in Type 2 the right and left pulmonary arteries arise separately but close together usually from the posterior aspect of the truncus; in Type 3 one or both pulmonary arteries arise independently and more laterally from either side of the truncus; and in Type 4 there is absence of true pulmonary arteries with the pulmonary supply via large bronchial arteries. Currently, patients with Type 4 truncus in which the lungs are supplied by systemic arteries are grouped with patients having pulmonary atresia and ventricular septal defect. This defect is commonly referred to as ‘pseudotruncus’. Abnormal location of the coronary ostia, often with one or other main coronary artery arising from the non-coronary sinus of Valsalva, is found in approximately 50 per cent of patients. A degree of truncal valve incompetence is present in 50 per cent of patients. Truncal valve stenosis occurs infrequently, but may be severe. Arch anomalies such as coarctation, hypoplasia, or interruption may be found in association, and approximately 30 per cent of patients have a right-sided aortic arch. In a small proportion of patients the right pulmonary artery arises from the truncus and the left pulmonary artery from a persistent patent ductus arteriosus outside the pericardium (Fig. 6) 1732.
The haemodynamics in truncus arteriosus are determined by the differential resistance to flow in the systemic and pulmonary vascular beds. Equal systolic pressures exist in both ventricles and the truncus and blood from both ventricles is ejected directly into the common trunk where mixing occurs. Pulmonary blood flow and the development of pulmonary hypertension are influenced by the size of the pulmonary arteries, obstruction in these vessels, and by pulmonary arterial resistance. Systemic arterial saturation is always reduced and is influenced by the volume of pulmonary blood flow. In the neonate, pulmonary blood flow is initially restricted by high pulmonary vascular resistance. When this falls cardiac failure may occur because of large pulmonary blood flow and left ventricular volume overload. High pulmonary arterial pressure and flow eventually results in obstructive pulmonary vascular disease, which may appear within the first 6 months of life.
Unoperated, 90 per cent of patients die of heart failure during early infancy. Approximately 5 per cent of patients with moderate stenosis at the origin of both pulmonary arteries survive for many years with near normal function (natural pulmonary artery banding). In general only 10 per cent of patients survive past the age of 1 year. After this age mortality is determined by the severity of pulmonary vascular disease, which may allow survival to adolescent or adult life.
The clinical presentation is determined primarily by the status of the pulmonary vascular bed. Infants with pulmonary stenosis are often cyanotic in the neonatal period and present with symptoms of hypoxia. Patients with large pulmonary arteries develop congestive heart failure as early as the first week of life, though more often this is delayed until the second or third week. These patients are minimally cyanotic. In more than two-thirds of patients there is the harsh systolic murmur of ventricular septal defect, together with a systolic thrill at the second or third left interspace (Table 5) 501. Stenotic pulmonary arteries may result in a continuous murmur extending over both sides of the upper chest. Excessive pulmonary blood flow may result in a diastolic rumble due to augmented flow across the mitral valve. In most cases the chest radiograph shows cardiomegaly with increased pulmonary vascular markings. The cardiac pedicle is particularly narrow. Two-dimensional echocardiography with Doppler studies confirm the diagnosis and identify associated lesions such as additional ventricular septal defects, coarctation, or interrupted aortic arch. Although the diagnosis is made by non-invasive means, accurate haemodynamic and detailed anatomical evaluation is required before surgical treatment.
Cardiac catheterization is performed with right and left heart studies and angiography. Usually the catheter readily enters the truncus from the right ventricle. Injection of contrast into the proximal portion of the truncus defines the abnormal origin of the pulmonary vessels and on the basis of these findings surgical correction can be planned. The presence and magnitude of truncal valve regurgitation is noted. Truncal and pulmonary artery saturations are equal and high in infants presenting with heart failure secondary to high pulmonary blood flow. Truncal saturation less than 80 per cent usually suggests the presence of severe pulmonary vascular disease.
Indications of surgery
Infants presenting with severe heart failure uncontrolled by medical therapy require urgent surgical correction. Prior to satisfactory results from complete correction, pulmonary artery banding was generally undertaken, but this has now been abandoned since mortality exceeded 50 per cent and often failed to protect against pulmonary vascular disease. Nevertheless, some survivors of banding are suitable for correction in adolescent life if distortion of the pulmonary vessels has not rendered them inoperable. For those infants initially stabilized by medical treatment, corrective surgery is usually recommended at the age of 5 to 6 months of age. Delay beyond 6 months increasingly risks development of intractable pulmonary vascular disease. Patients with a pulmonary vascular resistance greater than 10 units/m² are generally regarded as inoperable.
The corrective procedure involves detachment of the pulmonary arteries from the truncus followed by closure of the defect in the aorta. The ventricular septal defect is then repaired through a right ventriculotomy which, in turn, will be used as the new right ventricular outflow. Continuity between the pulmonary arteries and the right ventricle is then established by a valved conduit. In Oxford, the operation is undertaken using profound hypothermia and total circulatory arrest. Carefully selected paediatric aorta homografts are used to create the new main pulmonary artery. Excess homograft aorta is used to close the defect in the truncus (neo-aorta) after mobilization of the pulmonary arteries. A Dacron or Gore-tex patch is used to close the ventricular septal defect. For patients with a single pulmonary artery arising from the truncus, continuity of the extra pericardial left pulmonary artery has been established using a bifurcated pulmonary arterial homograft (Fig. 6) 1732. Proprietary conduits of Dacron containing a porcine valve prosthesis are also used for correction but have a high late incidence of dysfunction secondary to endothelial overgrowth and valve calcification.
ANOMALIES OF THE AORTIC ARCH
Embryologically the aortic arch and its major intrathoracic branches, together with the main pulmonary arteries and ductus arteriosus, arise from six pairs of vascular arches which connect paired right and left dorsal aorti with the unpaired ventral vessel (Fig. 7) 1733. The normal left-sided aortic arch results from regression of the eighth segment of the right dorsal aorta. The normal aortic arch passes to the left of the trachea, giving rise to the innominate, left common carotid, and left subclavian arteries. The ductus arteriosus connects the arch just distal to the subclavian artery with the pulmonary artery. However, abnormalities in development present the theoretical potential for bilateral aortic arches, and alterations in the normal sequence of development give rise to numerous variations in the anatomy of the aortic arch and brachiocephalic branches.
In practice, most vascular rings result from lack of regression of the eighth segment of the right dorsal aortic arch or an abnormal regression of other segments. The abnormal vessels form a ring which may completely encircle the mediastinal structures. Symptoms arise due to compression of the trachea, oesophagus, or both. Tracheal compression produces inspiratory stridor or intermittent lower respiratory tract infections, whereas oesophageal compression may cause dysphagia. Double aortic arch is the most common symptomatic anomaly, though vascular rings also occur with malformations of both left and persistent right aortic arch systems.
Double aortic arch
This results from failure of regression of the eighth segment of the right dorsal aorta with persistence of both right and left dorsal aortic arches. The ascending aorta bifurcates in front of the trachea to give two separate arches which surround the trachea and oesophagus (Fig. 8) 1734. In 75 per cent of patients the right arch is larger and crosses behind the mediastinal structures, giving rise to a left-sided descending aorta. The carotid and subclavian vessels arise separately, two from each arch. The ductus arteriosus is most commonly left-sided and may contribute to the vascular ring by drawing the pulmonary artery backwards on to the anterior aspect of the trachea.
Most infants with double aortic arch show signs of severe respiratory distress within the first 6 months of life. A high index of suspicion is required to make the diagnosis. Dysphagia or feeding difficulties may accompany respiratory distress. The plain chest radiograph may show double aortic arches, and there may be visible evidence of tracheal compression. Barium instilled into the oesophagus may confirm the impression of vascular ring and allow the major (larger) arch to be identified. If barium swallow is not conclusive aortography may be required.
Surgical division of the smaller arch with mobilization of the mediastinal structures is required for babies with significant symptoms. When the left arch is smaller the mediastinum is approached through a left thoracotomy and the arch is divided just distal to the left subclavian artery. Since chronic compression of the trachea produces atretic cartilages, airways obstruction may require weeks or months to resolve.
Malformations associated with right aortic arch
A right-sided aortic arch occurs almost exclusively in association with vascular ring or a separate congenital heart defect (Fig. 9) 1735. A right aortic arch with a left innominate artery followed by right carotid and right subclavian artery, is associated with 98 per cent of patients with cyanotic congenital heart disease (often tetralogy of Fallot or persistent truncus arteriosus). In these patients the ductus arteriosus connects the innominate artery to the left pulmonary artery and there is no vascular ring. In contrast, in right-sided aortic arch with aberrant left subclavian artery, the left subclavian arises as the most distal brachiocephalic vessel, and passes posterior to the oesophagus to reach the left arm (Fig. 10) 1736. The ductus arteriosus then connects the left subclavian artery with the left pulmonary artery, completing the vascular ring. Concomitant cardiac defects occur in only 10 to 15 per cent of patients and symptoms of compression arise in approximately 20 per cent: these are less severe than in those with double aortic arch. Clinical presentation occurs between the ages of 6 months and 2 years. The proximal portion of the left subclavian artery develops embryologically from the eighth segment of the left dorsal aorta and is consequently greatly dilated. This produces a large posterior oesophageal indentation. When symptoms are significant surgical correction is by division of the ductus arteriosus or ligamentum with mobilization of the ring away from the trachea and oesophagus.
In a rare condition known as cervical aortic arch a right-sided aortic arch is elongated to extend into the neck above the clavicle. Apart from the abnormal location of the arch, the anomaly is identical to right arch with aberrant left subclavian artery. The ductus or ligamentum on the left completes the ring. Presentation is often with a pulsatile mass in the supraclavicular fossa, though symptoms may relate to mediastinal compression. Barium swallow shows findings similar to the previous lesions except for more cranial location. Because of the rarity of this lesion, angiography is usually employed for precise identification.
MALFORMATIONS ASSOCIATED WITH LEFT ARCH
Vascular rings are seldom found with a left aortic arch, although mirror image equivalents of right arch anomalies are occasionally encountered. The most common anomaly is aberrant right subclavian artery, resulting from regression of the right fourth arch, and persistence of the right eighth dorsal segment. The right subclavian arises distal to the left and passes behind the oesophagus to the right arm. Because the ductus is usually normally sited no ring is formed and dysphagia rarely, if ever, occurs. Presentation is almost exclusively in adult life when barium swallow may demonstrate an oblique posterior indentation sited between T2 and T4. Rarely, when significant dysphagia is proven, division of the aberrant vessel and mobilization away from the posterior aspect of the aorta will provide symptomatic relief. The surgical approach is by left thoracotomy and care must be taken to oversew the divided right subclavian artery which retracts away behind the oesophagus into the left hemithorax. In one Oxford patient the condition was associated with congenital tracheo-oesophageal fistula.
ANOMALIES OF THE BRACHIOCEPHALIC VESSELS
Variations in origin of the innominate or left carotid arteries are common and usually asymptomatic. Origin of the left carotid artery from the innominate artery may cause anterior tracheal compression and origin of the innominate artery unusually distal on the arch may produce upper airways obstruction as the vessel passes from left to right. Symptoms are usually investigated by bronchoscopy when exaggerated pulsation is evident on the anterior tracheal wall, or the brachial pulse is eliminated by internal pressure from the bronchoscope. Airways obstruction is seldom severe enough to warrant surgery.
Mid-arch coarctation of the aorta with narrowing of the arch vessels, and congenital septation of the aortic arch with carotid stenosis have been described in Oxford. In both cases aortic arch replacement with reimplantation of the arch vessels was undertaken during circulatory arrest at 18 C.
Pulmonary artery sling
This rare but clinically important anomaly occurs when the left pulmonary artery arises from the right pulmonary artery, extrapericardially, or from an elongated main pulmonary artery. The vessel then traverses to the right, crossing the superior aspect of the right main stem bronchus and lower trachea before turning acutely to the left and passing between the trachea and oesophagus to reach the hilum of the left lung (Fig. 13) 1742. Pulmonary artery sling is associated with developmental abnormalities of the tracheal cartilages (complete rings) or tracheobronchial compression with tracheomalacia, resulting in respiratory obstruction. The anomaly is thought to originate from failure of the proximal left sixth aortic arch to connect with the plexus of vessels developing in the primitive lung. It is more common in males and usually produces symptoms in the first weeks of life. Expiratory wheeze and hyperexpansion of the right lung result from compression of the tracheobronchial angle. Secondary infection of the affected lung occurs frequently, and death in misdiagnosed cases often occurs in the first 6 months. Wheezing may be confused with asthma, and clinical diagnosis is rarely made prior to investigation of an abnormal chest radiograph showing hyperinflation of the right lung and left shift of the mediastinum. Barium swallow shows anterior indentation of the oesophagus at the level of the carina, and is pathognomonic. Pulmonary angiography is usually carried out for clarification since the defect is rare and requires surgical correction.
Left thoracotomy is usually used for division and reimplantation of the left pulmonary artery, as described by Potts in 1954. The ligamentum arteriosum or persistent ductus arteriosus is divided and the left pulmonary artery mobilized between the trachea and oesophagus. After heparinization the left pulmonary artery is divided as close as possible to the right pulmonary artery, and the proximal end oversewn. The main pulmonary artery is then approached through a pericardial window in front of the left phrenic nerve. A partial occlusion clamp is used to isolate a portion of the main pulmonary artery into which the left pulmonary artery is implanted in an end-to-side manner. Often the surgical procedure is well tolerated, though tracheobronchial obstruction persists, and may require long-term intubation or tracheoplasty. Some centres prefer a median sternotomy approach and perform the procedure with the patient on cardiopulmonary bypass. The hospital mortality rate, predominantly due to airway complications, is 40 to 50 per cent. Diffuse anatomical tracheal stenosis with complete cartilaginous rings and severe stridor has a particularly poor outlook. Late thrombosis of the reimplanted pulmonary artery is common.
Aneurysm of the sinus of Valsalva
Aneurysm of the sinus of Valsalva is a thin-walled windsock-type out pouching, usually found in the right coronary sinus or adjacent part of the non coronary sinus. The tubular out-pouching from the wall of the sinus takes an intracardiac course, protruding into the right atrium or right ventricle. Symptoms occur when acute rupture of the sinus causes an aortocardiac fistula, though this rarely occurs in infancy or childhood.
The aneurysm occurs at a site of thinning of the wall of the aortic sinus just above the annulus, and is associated with absence of normal elastic and muscular tissue in this area. The sinus of origin determines the direction of protrusion and site and chamber into which rupture occurs. Very rarely aneurysms arise from the left coronary sinus or the posterior portion of the non-coronary sinus and rupture into the adjacent pericardium or left atrium. Other congenital cardiac defects are present in the majority of patients with aneurysm of the sinus of Valsalva. The most common are ventricular septal defects, aortic valve anomalies, and pulmonary stenosis. Coarctation of the aorta, patent ductus arteriosus, atrial septal defects, subaortic stenosis, and tetralogy of Fallot also occur.
Rupture of the aneurysm causes acute symptoms of breathlessness and precordial pain simulating myocardial infarction in 35 per cent of patients. In about 45 per cent of patients the only symptom is effort dyspnoea, and in 20 per cent rupture occurs without symptoms. Rupture may be precipitated by physical exertion or rarely by automobile accidents, bacterial endocarditis, or cardiac catheterization. The characteristic physical findings at this stage are those of aortic regurgitation and often tricuspid regurgitation, an otherwise unusual combination. The characteristic murmur is loud, harsh, superficial, and continuous, with either systolic or diastolic accentuation (Table 6) 502. An elevated jugular venous pressure with prominent V waves occurs through right heart failure or direct entrance of the fistula into the right atrium. Liver enlargement with pulsation and often epigastric pain is progressive.
The diagnosis is usually made on clinical grounds in patients with acute severe symptoms. Two-dimensional echocardiography and cardiac catheterization with angiocardiography are used to confirm the diagnosis and identify the sites of origin and rupture. Associated cardiac lesions, including ventricular septal defect, valvular aortic regurgitation, and pulmonary stenosis are also identified. The magnitude of left-to-right shunt through the fistulous communication can be measured, together with the pulmonary vascular resistance. The natural history of aneurysm of the sinus Valsalva is difficult to determine since many aneurysms fail to rupture during the patient's lifespan. Eighty per cent of patients with aneurysm of the sinus of Valsalva are male and in patients under going surgery rupture occurs predominantly in the third or fourth decade of life. Mean survival time after rupture is approximately 4 years, though in patients with a large shunt death may occur in less than 4 weeks from congestive heart failure. In unoperated patients, endocarditis complicates the syndrome in about 8 per cent.
Surgical correction is recommended for all patients. This is undertaken on cardiopulmonary bypass with cold cardioplegic arrest. The approach to the sinus is from both the aortic root as for aortic valve replacement, and through the right atrium, where the windsock and site of rupture can be identified within the right atrium or right ventricle. The dual approach allows accurate repair and avoids damage to the aortic valve. The most common associated anomaly, ventricular septal defect, can also be closed through the right atriotomy. Even if unsuspected, a ventricular septal defect should be sought: in one Oxford patient this remained undiagnosed during investigation through prolapse of an aortic valve cusp. The windsock is opened widely and excised, leaving a margin with which closure can be secured by direct suture or by Dacron patch. Operative mortality is extremely low and the late results excellent.
Aortopulmonary window is a rare malformation caused by incomplete formation of the septum in the developing truncus arteriosis. The result is an abnormal communication between the aorta and the pulmonary artery distal to their semilunar valves. Symptoms and signs are of congestive heart failure in the newborn. Pulses are bounding and pulse pressure may be wide. The heart is enlarged clinically and on chest radiography the lung fields are plethoric. The differential diagnosis of aortopulmonary window is persistent ductus arteriosis, persistent truncus arteriosis, and ventricular septal defect. Two-dimensional echocardiography will provide the diagnosis by demonstrating two separate semilunar valves related to the two great arteries.
Infants in severe heart failure are operated upon as soon as the diagnosis is established. Those whose heart failure is controlled medically should be operated upon before pulmonary vascular obstructive disease develops. The heart is approached through a midline sternotomy. Using cardiopulmonary bypass, often with deep hypothermia and circulatory arrest, the aorta is opened and the aortopulmonary window closed with a Dacron patch. Care is taken to visualize the left coronary artery to avoid inclusion in the suture line. Associated lesions such as patent ductus arteriosus or ventricular septal defect are closed simultaneously. Long-term outlook is good when surgery is performed before onset of pulmonary vascular disease.
Aortic left ventricular tunnel is a rare defect which presents at birth with severe congestive heart failure and signs of torrential aortic regurgitation. The aortic orifice is usually sited anteriorly and separated from the right sinus of Valsalva by a prominent transverse supravalvar ridge. The tunnel passes downwards to communicate with the left ventricle and is usually visible externally as an extracardiac bulge. The morphology is distinct from aneurysm of the sinus of Valsalva. Aortic right ventricular tunnel is rare. In this case the tunnel communicates with the infundibulum of the right ventricle rather than with the left ventricle.
Infants presenting with aortoventricular tunnel are investigated by two-dimensional and pulsed Doppler echocardiography to elucidate signs of suspected massive aortic regurgitation. The principal differential diagnosis in this age group is congenital coronary artery fistula. Cardiac catheterization and cineangiography are used to confirm the diagnosis. Urgent surgical treatment, consisting of patch closure of the aortic defect, is then required. There have been multiple reports of successful closure of aortic left ventricular tunnel, though late development of aortic regurgitation has marred the long-term result, possibly due to aortic cusp retraction following direct suture of the defect. Patch closure should avoid this complication. The first successful closure of an aortic right ventricular tunnel was by Westaby in 1990.
Origin of the right or left pulmonary artery from the ascending aorta
In this rare anomaly, usually the right but occasionally the left pulmonary artery arises from the ascending aorta in the presence of separate aortic and pulmonary valves and without interposition of the ductus arteriosus. Rarely, both right and left pulmonary arteries arise from the ascending aorta, but in the presence of separate aortic and pulmonary valves: the condition does not constitute truncus arteriosus.
Although less than 100 patients with this anomaly have been described, 70 per cent of untreated patients die before the age of 6 months, and 80 per cent are dead by 1 year. Patients who survive beyond the first months of life develop pulmonary vascular disease in both lungs. The development of pulmonary hypertension in the normally connected left lung is consistent with the finding that experimental ligation of a single pulmonary artery in calves within 24 h of birth results in severe pulmonary hypertension in the opposite lung within 8 weeks. In 80 per cent of patients aortic origin of the right pulmonary artery occurs in conjunction with another anomaly: patent ductus arteriosus is present in about 50 per cent of patients. Less common associations are with tetralogy of Fallot, ventricular septal defect, coarctation of the aorta, interrupted aortic arch, aortopulmonary window, and atrial septal defect. Clinical presentation occurs in early infancy, with respiratory distress and congestive heart failure. Cyanosis may occur because of venous admixture in the lungs or due to reversed shunting through a patent formaen ovale or ductus arteriosus. Bounding peripheral pulses are obtained through rapid run-off from the aorta into the right lung and left-to-right shunting.
The plain chest radiograph shows cardiomegaly with a globular shaped heart and pulmonary plethora often equal on both sides. Diagnosis is established by two-dimensional echocardiography and confirmed by cardiac catheterization, when pulmonary vascular resistance is calculated as a guide to operability.
Surgical correction is undertaken with profound hypothermia with total circulatory arrest. The anomalous right pulmonary artery is mobilized beneath the superior vena cava and disconnected from the ascending aorta. The resulting defect may be closed directly or with a patch. The aorta is then lifted and pulled leftward to give access to the right side of the main pulmonary artery, into which the mobilized right pulmonary artery is implanted. Surgical results in the absence of associated anomalies are good when reimplantation is performed prior to the development of severe pulmonary vascular disease. Normal late pulmonary artery pressures are obtained presumably with normal life expectancy.
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