.ANOMALIES OF AORTOPULMONARY SEPTATION: PERSISTENT TRUNCUS ARTERIOSUS, AORTOPULMONARY SEPTAL DEFECT, AND HEMITRUNCUS ARTERIOSUS

R.M. Freedom

Persistent Truncus Arteriosus Incidence

Persistent truncus arteriosus, also called com• The Report of the New England Regional Infant mon aorticopulmonary trunk, is that anomaly Cardiac Program indicated that 33 of the 2251 where a single arterial trunk supported by the infants with disease or 1.4% had truncus ventricular mass gives origin to the coronary arteriosus [28]. The data also provided pre• arteries, pulmonary trunk, and the brachio• valence at livebirth of 0.030 per 1000 livebirths cephalic arteries [2, 9, 13, 14, 16, 17, 18, 52, 57, for this lesion. The prevalence at livebirth data 60, 69, 71, 72, 73, 74]. With very rare exception from the more current Baltimore-Washington a ventricular septal defect is present [14, 15]. Infant study was 0.056 per 1000 livebirths [25] Untreated, this condition carries a very high and the prevalence of this specific lesion is not mortality, with many babies dying in the neona• stated in the survey conducted by the Alberta tal period or early infancy in congestive heart Heritage Pediatric Cardiology Program [30]. failure, often with an ischemic myocardium. Data from The Hospital for Sick Children in About 65% of patients treated medically fail to Toronto gave an incidence for truncus arterio• survive beyond 6 months of life, and more than sus of 0.7% of congenital heart disease. 90% die before one year of age [14, 28, 34, 41, 47, 74]. Data from Butto et al. [13], Collett and Edwards [17] and Van Praagh and Van Praagh [74] summarized by Stanger [66] suggest that of 100 babies born with truncus and surgically Morphology and Morphogenesis untreated, 20 will die in the first week and at least 86 will have died by a year of age. A rare patient will survive with pulmonary vascular Three hypotheses have been used to explain the obstructive disease into the fourth decade of life development of this lesion: 1) This defect or beyond. represents partial or total absence of the aortico-

R. M. Freedom et al., Neonatal Heart Disease © Springer-Verlag London Limited 1992 430 NEONATAL HEART DISEASE

Fig. 26.1. Classification of truncus·arteriosus [17]. A single arterial trunk is supported by the ventricular mass, and this trunk gives origin to the coronary arteries, the pulmonary arteries, and the brachiocephalic arteries. With rare exception a ventricular septal defect is present. The bottom right is so-called truncus, Type 4, and there is discussion whether this is a true entity. TR = truncal root; AO = ascending aortic portion of truncus; PA = pulmonary artery; c = collaterols. Not shown is the form with coarctation or interruption. pulmonary septum, complete absence of fusion ate entirely above the right ventricle [3, 9, 14, of the truncal swellings and the conal ridges 16, 17, 18, 56, 60, 69, 71, 73, 74]. which normally join to form the arterial valves and the distal infundibulum. 2) Van Praagh and his colleagues consider truncus arteriosus to be Classification of truncus arteriosus closely related to and thus truncus arteriosus represents absence or severe The classification proposed by Collett and Ed• attenuation of the distal pulmonary infundibu• wards in 1949 [17] has been widely accepted, lum, with defects of the aortopulmonary sep• although in the past 15 years some modifica• tum and ventricular septum. Anderson and tions have been suggested. Calder and her Thiene [1] take issue with the view espoused colleagues have made a classification focusing by Van Praagh [73a] that tetralogy and com• both on the presence of a ventricular septal· mon arterial trunk are morphologically closely defect (Type A) or its absence (Type B), as well related. 3) This defect represents the absence of as on the site of origin of the pulmonary arteries a common arterial vessel downstream from the [14] (Fig. 26.1). Type Al has a partially separate semilunar valve [14, 57, 72, 73, 74]. main pulmonary trunk because of the presence of an incompletely formed aortopulmonary sep• tum (Fig. 26.2). In Type A2, the aortopulmonary Segmental Analysis septum is absent and the pulmonary arteries originate separately from the truncus. Type A3 exhibiting persistent truncus arteriosus is characterized by absence of either the right or are usually left-sided and the atrial situs is left pulmonary artery. The "absent" pulmonary sotitus. With rare exception, the hearts are artery will originate from either a ductus arter• biventricular, the atrioventricular connections iosus or a major aortopulmonary collateral [9, are concordant, and there is fibrous continuity 17, 56, 60, 71, 74]. Those patients with truncus between the and the truncal valve. arteriosus and either interruption of the aortic Occasionally, the single arterial root will origin- arch, atresia of the aortic arch, preductal coarc- ANOMALIES OF AORTOPULMONARY SEPTATION: PERSISTENT TRUNCUS ARTERIOSUS 431

A B

C D

Fig. 26.2. A Truncus (TRU) with its typical ventricular septal defect (white') viewed from the right ventricle. Note the short main pulmonary trunk bifurcating (arrows) into right and left pulmonary arteries. B Same heart seen from left ventricle. C Separate origins of pulmonary arteries (black'). D Truncus with interruption of aortic arch. The ascending aorta (asc ao) component of the truncus is relatively small. The ventricular septal defect is large (white') and there are separate origins of the pulmonary arteries (black'). The ductus arteriosus (') has constricted and is in continuity with the descending aorta.

tation of the aortic arch, or severe diffuse pid, and hexacuspid valves are very uncom• hypoplasia of the aortic arch are classified as mon. Amongst the 54 cases reported from the Type A4 (Fig. 26.1). United Hospital in Minneapolis, 42% had a tricuspid truncal valve, 30% a bicuspid valve, and 24% a quadricuspid valve [13]. Calder and The Truncal Valve her colleagues [14] from Boston Children's Hospital reported that 61% had a tricuspid The truncal valve can theoretically possess one truncal valve, 31 % a quadricuspid valve, and to six cusps, but the unicommissural, pentacus- 8% a bicuspid valve. 432 NEONATAL HEART DISEASE

septal defect results from absence of the infun• dibular septum and is found in the limbs of the trabecula septomarginalis (Fig. 26.4). Ventricu• lar septal defects may be present remote from this area but are uncommon. The infundibular ventricular septal defect is usually large but may be potentially restrictive, especially in those instances where the truncus originates almost entirely above the right ventricle [55].

Pulmonary Stenosis

Most patients with persistent truncus arteriosus have excessive pulmonary blood flow and, when untreated, die in congestive heart failure. In about 10% of patients with truncus arter• A iosus, the pulmonary blood flow is restrictive. In most of these patients the mechanism res• ponsible for limiting the pulmonary blood flow is ostial stenosis resulting from an obstructive truncal leaflet [9, 13, 14, 56, 73, 74] .

The Coronary Arterial Circulation

The coronary arteries exhibit a variable pattern of origin independent of the number of truncal valve leaflets [la, 21a, 61, 69, 74]. Abnormally high origin of a coronary artery, usually the right, has been observed in this disorder. Frank myocardial ischemia is usually the result of the disordered hemodynamics with a torrential pulmonary blood flow, a volume loaded left ventricle, and a low aortic diastolic or coronary artery driving pressure. Rarely, a coronary B ostium will be congenitally stenotic and this will Fig. 26.3. A and B Severely stenotic, quadricuspid truncal promote an ischemic myocardium. Uncommon• valve in two different patients. Little commissural fusion is ly, the coronary ostium will be just superior to present. the truncal valve commissure, and a bulky fleshy truncal valve leaflet may obstruct the coronary ostium, resulting in coronary insuf• The truncal valve may guard the ventricu• ficiency. loarterial junction normally, or the valve may be stenotic or regurgitant, or both. Truncal valve leaflet thickening may be mild, moderate, or Laterality of the Aortic Arch severe (Fig. 26.3). In this last group the truncal valve may be nodular, polypoid and myxoma• A right-sided aortic arch is present in 20%-30% tous [7, 12, 13, 14, 22, 29, 37, 38,48, 74]. Severe of patients with truncus arteriosus [13, 14, 69, truncal valve regurgitation has been reported as 74] . An occasional patient has a double aortic a very serious complication [21]. arch.

The Ventricular Septal Defect Obstructive Anomalies of the Aortic Arch

With very rare exception a ventricular septal Coarctation of the aorta, aortic arch atresia, and defect is present [9, 14, 15]. This ventricular interruption of the aortic arch, usually Type B, ANOMALIES OF AORTOPULMONARY SEPTATION: PERSISTENT TRUNCUS ARTERIOSUS 433

B

A

Fig. 26.4. Ventricular septal defect in truncus arteriosus (TRU). ALarge ventricular septal defect (white') cradled in limbs of trabecular septum in a baby with associated interruption of aortic arch. B Slightly smaller ventricular septal defect (white'). Note the thickened, fleshy, truncal valve (black'); pa = pulmonary artery. C Same specimen as in B viewed from the left ventricle; mv = mitral valve. C

can complicate the basic morphologic expres• 13, 14]. Crossed pulmonary arteries have been sion of truncus arteriosus. In this setting, the described in truncus arteriosus, usually but not ductus arteriosus is usually present [9, 13, 14, invariably with associated interruption of the 17, 18, 19, 46, 57, 68, 72, 74]. aortic arch [6, 36, 78].

Uncommon Lesions Clinical Features Persistent truncus arteriosus has been described in patients with associated complete form of atrioventricular septal defect, , Many patients with truncus arteriosus present single ventricle, hypoplastic left ventricle, and with features of congestive heart failure or mild total anomalous pulmonary venous return [9, cyanosis, or both, in the newborn period. 434 NEONATAL HEART DISEASE

A B Fig. 26.5. A and B Chest radiographs of two babies with truncus arteriosus. The cardiac silhouettes are large; the pulmonary vascular markings are increased; the left heart border may be straight; and a right aortic arch is present in about 20% -30% of patients.

Unless there is particularly severe obstruction to ing into the carotid arterial pulses, and associ• pulmonary blood flow, indeed an uncommon ated with a precordial and suprasternal thrill. If finding, cyanosis is not particularly severe. an obstructive anomaly of the aortic arch is Those babies with a severely obstructed aortic present, close examination of the caliber of the arch may present with "coarctation-like" arterial pulses and blood pressure recordings findings as well. may demonstrate the exact site of the obstruc• Cardiac findings include a hyperdynamic tion. precordium and in the absence of an obstructive anomaly of the aortic arch, all pulses are brisk, sometimes frankly collapsing. The first heart The Chest Radiograph sound is loud and crisp, and a conspicuous aortic ejection click is usually audible at the The chest radiograph usually shows a signi• cardiac apex [14, 54, 58, 76]. The second heart ficant degree of cardiac enlargement, and the sound is usually single, remembering that there pulmonary arterial markings are increased (Fig. is only a solitary arterial outlet. A split second 26.5). In the setting of severe congestive heart heart sound has been noted by some. Whether failure, hyperinflation of the lungs and pulmon• this represents asynchronous closure of a multi• ary edema may be conspicuous. A right-sided cusped truncal valve is uncertain (or incorrect aortic arch is present in about 20%-30% of interpretation of auscultatory findings). A blow• patients with truncus arteriosus. The heart will ing systolic ejection murmur is best appreciated appear very much enlarged in those patients at the left sternal border. A soft early diastolic with severe truncal valve regurgitation or severe murmur, high-pitched, is often present at the truncal valve stenosis. Bronchial compression left sternal edge as well, representing mild has been observed in the young infant produc• truncal valve incompetence. When the truncal ing severe respiratory distress [31]. valve is grossly regurgitant, then the diastolic murmur is very conspicuous and this murmur may persist throughout most of diastole. An The Electrocardiogram apical mid-diastolic murmur is indicative of a large pulmonary blood flow, and similarly S3 Electrocardiograms obtained from patients with gallop sounds are indicative of a volume loaded truncus arteriosus can exhibit a wide range in and stressed ventricle. The presence of severe frontal QRS axis. However, the majority of truncal valve stenosis may be heralded by a affected babies show a frontal QRS axis between loud coarse systolic ejection murmur, conduct- +60° and +180°. Right, left, or combined ven- ANOMALIES OF AORTOPULMONARY SEPTATION: PERSISTENT TRUNCUS ARTERIOSUS 435 tricular hypertrophy may be evident. ST -T wave dimension can be evaluated, along with a gen• abnormalities are common, especially amongst eral impression about the presence or absence those babies in severe congestive heart failure of stenosis. The latter however, is best achieved and in those with severe associated truncal through Doppler interrogation (Figs. 26.6C and valve stenosis or regurgitation [14, 77]. D). The presence of regurgitation is also evalu• ated from these views, through the use of color flow Doppler techniques (Figs. 26.6E and 26.7 A). Differential Diagnosis Pulmonary artery size and origin(s) are also assessed from these views, in conjunction with Before the application of cross-sectional echo• the suprasternal approach (Figs. 26.7B and C). cardiographic imaging, the differential diag• Again Doppler interrogation is useful if the question of stenosis is entertained. Absence of nosis of a acyanotic or mildly cyanotic neonate either the left or right pulmonary artery can also with brisk pulses would include the patient with be determined from this approach. pulmonary atresia, ventricular septal defect, Aortic arch pathology must be excluded in and multiple major aortopulmonary collaterals; each case (Fig. 26.70), in particular interruption origin of one pulmonary artery from the ascend• ing aorta (so-called hemitruncus arteriosus); distal to the left carotid artery [64]. Finally, an aortopulmonary septal defect; normal truncal attempt should be made to identify the origin of septation with either separate pulmonary arter• both coronary arteries, which may occasionally ies originating from ascending aorta or with arise from the pulmonary arteries. Further evaluation by angiography is indicated if it is lungs supplied by segmental arteries originating from the descending aorta; aorto-Ieft ventricular not possible to identify a central left or right tunnel; patent ductus arteriosus; tetralogy with pulmonary artery. absent pulmonary valve; and major arterio• venous fistula (i.e., vein of Galen type, etc.) [8, 11]. Hemodynamics and Angiocardiography

Neonates and infants with truncus arteriosus do The Echocardiogram not tolerate extensive catheter manipulation and contrast media (reflecting the brittleness of As with many other forms of neonatal heart the myocardium of these babies), although disease, the mode of investigation of this lesion admittedly with low ionic contrast there seems has altered since the introduction of echocar• to be less risk for these patients [58]. Thus for diography [20, 51, 53, 59, 63, 75]. In the majority more than a decade our institution has relied on of cases this technique provides all of the data derived from echocardiographic examina• information that is necessary to form a decision tion to confirm the clinical diagnosis of truncus regarding the optimal surgical approach. arteriosus, assess the form and function of the The classical appearance is that of an over• truncal valve, determine the topography of the riding great artery as seen in the precordial and pulmonary arteries relative to the truncus, and subcostal long axis views (Fig. 26.6A). The to define the normality of the aortic arch or the subarterial ventricular septal defect is also well presence of an obstructive anomaly of the aortic imaged from these cuts. It is important to arch. With these data in hand, we have felt exclude associated muscular ventricular septal comfortable in advocating surgery without a defects, which can be achieved with a combina• hemodynamic or angiocardiographic investiga• tion of high resolution imaging and color flow tion. Clearly, and without any hesitation, a Doppler techniques. In general, the remainder complete cardiac catheterization would be con• of the intracardiac anatomy is uncomplicated in ducted if there were confounding or inconsis• the majority of cases. The major focus in this tent features. lesion is on the truncal valve, the pulmonary The hemodynamic investigation of the neon• arteries and the aortic arch, as abnormalities of ate with truncus arteriosus reveals a systemic any of these have a significant impact on the arterial oxygen saturation that varies from the eventual outcome. low 80s to low 90s. A step-up in oxygen The truncal valve is best imaged from the saturation at right atrial level usually indicates precordial long and short axis views (Fig. left-to-right shunting through a patent foramen 26.6B). The number of cusps and the annular ovale. 436 NEONATAL HEART DISEASE

A .. _---c Fig. 26.6. A Precordial and subcostal long axis views demonstrating an overriding truncal root. Ao = aorta, LA = left atrium, LV = left ventricle, RV = right ventricle, TR = truncal root. B Precordial short axis view showing a quadricuspid truncal valve. c = cusp, TRU = truncus. C Doppler spectral trace in truncus arteriosus and associated truncal valve stenosis. o Suprasternal view in truncal valve stenosis demonstrating variance from the stenotic valve. AT = ascending trunc, DA = descending aorta, LPA = left pulmonary artery. E Precordial view in truncus and associated regurgitation of the truncal valve, as demonstrated by the variance. Note the regurgitant jet is directed towards the right ventricle. LV = left ventricle, REG = regurgitation, RV = right ventricle.

continued ANOMALIES OF AORTOPULMONARY SEPTATION: PERSISTENT TRUNCUS ARTERIOSUS 437

Fig. 26.6. continued

D

Fig. 26.6.

Fig. 26.7.

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....-... - '-----...-- ...... --- ,j~------,.j----

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A

Fig. 26.7. A Continuous wave Doppler spectral trace in truncal valve stenosis and regurgitation. B Subcostal view with right anterior oblique angulation showing the pulmonary arteries arising from the ascending trunk. at = ascending trunc, Ipa = left pulmonary artery, ra = right atrium, rpa = right pulmonary artery, rv = right ventricle. continued overleaf B 438 NEONATAL HEART DISEASE

Fig. 26.7. continued Fixed pulmonary vascular obstructive disease is not a realistic consideration at this age. The arterial oxygen saturation may reflect the matur• ity of the pulmonary vascular bed. Both ventri• cles are at systemic pressures, and the end diastolic pressures may be elevated reflecting a jeopardized and stressed endomyocardium. In the presence of truncal valve stenosis, both ventricular pressures will be higher than press• ure recorded ' in the truncus arteriosus. The pulmonary artery pressure is usually at syste• mic level or within 10-15 mmHg of systemic level. In the presence of branch or ostial pulmonary stenosis, the recorded pulmonary arterial pressure may be considerably lower than systemic. The truncal or arterial pressure usually demonstrates a wide pulse pressure, and in the presence of significant truncal valve regurgitation, diastolic pressure is frequently less than 30 mmHg. The ventricular anatomy is remarkably con• stant in truncus arteriosus. Biplane right and left ventricular angiocardiography should de• monstrate the intracardiac anatomy, although as stated earlier, this is rarely required [14, 16, 26, 33, 40, 46] . Angiography performed in the truncus should demonstrate the morphology and functional competence of the truncal valve, the disposition of the coronary arteries and their epicardial distribution, the integrity of the aortic arch, and the topography of the pulmonary arteries (Fig. 26.8). If only one pulmonary artery c is visualized by aortography performed in the ascending portion of the truncus or in the descending thoracic aorta, pulmonary vein wedge angiography may be necessary to de• monstrate the caliber of the hilar pulmonary artery [70]. An excellent review of the angiog• raphic features of truncus arteriosus was recent• ly published by Yoshizato and Julsrud [79] .

Medical Therapy

Most patients will benefit from anticongestive therapy but this disorder is relentless, resulting in severe and progressive congestive heart D failure, and the ST-T wave changes reflect Fig. 26.7. continued C Suprasternal views showing the subendocardial ischemia. For those babies pre• right and left pulmonary arteries. ao = aorta. D Supra• senting as ill neonates, medical anticongestive sternal view showing an unobstructed aortic arch in therapy has the same, possibly briefer effect, as truncus arteriosus. ao = ascending aorta, da = descending the little Dutch boy with his finger in the aorta, pa = pulmonary artery. crumbling dyke. Medical therapy cannot post• pone the inevitable. Babies with associated ANOMALIES OF AORTOPULMONARY SEPTATION: PERSISTENT TRUNCUS ARTERIOSUS 439

A B

C D Fig. 26.8. Truncal root angiography will demonstrate the morphology of the truncal valve, give a visual image ot the severity of truncal valve regurgitation, provide the site of origin of the pulmonary and coronary arteries, and will image the transverse aortic arch and isthmus. A Type 1 truncus with short pulmonary trunk and flow into both (arrows) pulmonary arteries. B Truncus arteriosus with interruption of the aortic arch; the large ductus (arrow) conducts blood to the descending aorta. C Truncus arteriosus (TRU) with multiple ventricular septal defects. Left ventricular (LV) angiogram in right axial oblique projection demonstrates the juxtatruncal ventricular septal defect (arrow) and the multiple, anterior trabecular defects (0). D and E Truncus with non-confluent pulmonary arteries imaged with digital subtraction technique. D'Injection of contrast in the truncus (TRU) shows only the right pulmonary artery (rpa). The left pulmonary artery (0) is not imaged in this injection.

continued overleaf 440 NEONATAL HEART DISEASE

Fig. 26.8. continued adequate symmetrical protection of the lungs and because of the substantial cumulative mor• tality of banding followed by late repair. In many neonates the timing of surgical interven• tion is not in question because of the severe and relentless heart failure. Some babies can be seemingly stabilized on medical therapy, and one is tempted to try and defer surgery until the babies are at least 1 month old. If this is the approach, serial electrocardiograms should be reviewed for findings of myocardial ischemia and echocardiograms for worsening ventricular function. Attempts to temporize too long may jeopardize the integrity of the pulmonary vascu• lar bed. Patients with truncus arteriosus are at risk for pulmonary vascular obstructive disease. Juaneda and Haworth [35] examined pulmon• ary vascular structure in patients with truncus arteriosus from both lung biopsy and postmor• tem material. Of the patients younger than 1 year of age, all demonstrated abnormal exten• sion of muscle and an increase in pulmonary E arterial medial thickness. Some of the older Fig. 26.8. continued E The left pulmonary artery (arrow) infants even showed intimal proliferation but fills from the left ductus (pda). these abnormalities were considered reversible. Thus, consideration of advanced and fixed pulmonary vascular damage is not really ger• obstructive anomalies of aortic arch will benefit mane to the neonate. from administration of an E-type prostaglandin. For those patients with associated interrup• tion of the aortic arch or with absence of one pulmonary artery, the surgical mortality is understandably very high, with almost all such babies requiring surgical attention in the neo• Surgical Therapy natal period [19, 27]. Some have advocated staged repair addressing reconstitution of the aortic arch and banding of the pulmonary trunk It was only slightly more than 20 years ago that or arteries at the initial operation, with complete complete correction of truncus arteriosus in an repair at a later date for patients with associated older child using the Rastelli technique was interruption of the aortic arch. Others eschew achieved [43, 49]. Despite considerable progress this approach, still advocating complete repair in surgery, repair of truncus arteriosus remains as the initial surgical approach, accepting a very hazardous in the neonatal period. Complete high surgical mortality [44]. Remembering the repair includes closure of the ventricular septal association between truncus arteriosus, inter• defect, removal of the pulmonary arteries from ruption of the aortic arch, and the DiGeorge the ascending portion of the truncus, and syndrome, irradiated blood should probably be restoration of continuity between right ventricle used if cardiac surgery is contemplated before and pulmonary arteries with either a valved or resolution of the babies' immune status. Severe non-valved conduit [4, 10, 23, 24, 40, 47, 50, 60, truncal valve regurgitation will require valve 65, 67]. The approach to complete repair in this replacement. The severely dysplastic and center and others has evolved from palliative myxoid nature of the profoundly disturbed banding of either the main pulmonary trunk or truncal valve does not lend itself to conservative bilateral banding [23, 42, 62, 67]. Others advo• procedures. Thus when confronted by neonates cate pulmonary artery plication or creation of with truncus arteriosus and severe truncal valve pulmonary trunk ostial stenosis [39, 45, 80]. regurgitation, some feel these babies are really These palliative approaches have largely been inoperable by conservative means. Others will abandoned because of the difficulty in achieving advocate valve replacement at the initial sur- ANOMALIES OF AORTOPULMONARY SEPTATION: AORTOPULMONARY SEPTAL DEFECT 441 gical approach, while others recommend cardiac replacement as another alternative. While some have attempted balloon valvuloplasty for the patient with a severely stenotic truncal valve, this only rarely will provide acceptable pallia• tion as commissural fusion is not a conspicuous feature of these very disturbed valves [5] (see Fig. 26.3). When the output through a stenotic truncal valve is reduced by repair, sometimes the valve seems less stenotic than thought be• fore repair, and the hemodynamically-recorded gradient less impressive. In others, some form of surgical attention to the valve must be under• taken at the time of complete repair and, as with those with truncus and a severely regurgitant truncal valve, some feel these babies are really inoperable by conservative means. Others will advocate valve replacement at the initial sur• gical approach, while others recommend cardiac replacement as another alternative. For those babies in the neonatal period surviving surgery, Fig. 26.9. A large aortopulmonary window (*) viewed from virtually all will require further intervention to the right ventricle and enlarged pulmonary artery (PA). replace the valved or non-valved conduit. Some may require balloon dilatation of stenotic proxi• mal pulmonary arteries at the site of the distal surgical connection between the right ventricle and pulmonary arteries. and tetralogy of Fallot. Kutsche and Van Mierop [96] defined an incidence of this anomaly of 0.2% (13 of 6522 children with congenital heart disease). The incidence for this lesion from The Hospital for Sick Children in Toronto is 0.171 Aortopulmonary Septal Defect [94].

The aortopulmonary septal defect (window) [83] is an uncommon cardiac defect in which Morphology and Morphogenesis there is a communication, usually large, be• tween the ascending aorta and pulmonary trunk [82, 85, 96, 97, 102, 103, 107] (Fig. 26.9). Kutsche and Van Mierop [96] define three types While clinically related to truncus arteriosus of aortopulmonary septal defect. and located in the same area of the heart, there 1. A defect with a more or less circular border, is evidence, marshalled by Kutsche and Van located between the arterial valves and the Mierop, indicating that these two anomalies are bifurcation of the main pulmonary artery. pathogenetically unrelated [96]. 2. A similarly located fenestration in which the border represents a helix. 3. A large defect with no posterior or distal Prevalence border. These authors suggest a different pathogenesis for each of the three types. The first type may The New England Regional Infant Cardiac reflect non-fusion of the embryonic aortopul• Program identified only 7 of 2251 infants with monary and truncal septi. The second type an aortopulmonary septal defect [91]. Two of suggests malalignment of the embryoniC aorto• these occurred in isolation; three were in pa• pulmonary and truncal septi, while the third tients with associated interruption of the aortic type results from total absence of the embryonic arch; and one each with coarctation of the aorta aortopulmonary septum. 442 NEONATAL HEART DISEASE

Associated Malformations The cardiac findings in the neonatal period also reflect the associated lesions. It is particu• Data compiled by Kutsche and Van Mierop [96] larly important to record the caliber and blood reviewing 249 patients with aortopulmonary pressures in all four limbs because of the fre• septal defect (including 13 of their own) showed quently associated obstructive anomalies of the that about 48% of the patients whose informa• aortic arch. In the symptomatic neonate one tion was available had no other cardiac lesions, would anticipate a hypertensive pulmonary while 52% had associated cardiac malforma• artery, and thus the heart murmur will be tions. Perhaps the most commonly associated systolic and of ejection quality, rather than lesion was either Type A interruption of the continuous. As Rowe has pointed out, some aortic arch or severe preductal coarctation of associated anomalies such as tetralogy of Fallot the aorta. Other lesions included anomalous may be masked by the aortopulmonary septal origin of one or both coronary arteries from the defect [109]. pulmonary trunk; right pulmonary artery from the ascending aorta; tetralogy of Fallot; bicuspid ; ventricular septal defect; pulmon• Chest Radiograph ary atresia and ventricular septal defect; [84, 86, 87, 92, 98, 99, 100, 104, 107, There is and the visceral situs 112, 114, 115]. Rarely, aortic atresia has been appears normal. The symptomatic neonate will found in patients with an aortopulmonary show at least moderate cardiomegaly with septal defect [108]. heavy lung vascularity or frank pulmonary edema. A right aortic arch may be found, espe• cially in those patients with associated tetralogy Non-Association with DiGeorge Syndrome of Fallot. We have discussed in previous chapters the association between interruption of the aortic Electrocardiogram arch, Type B and truncus arteriosus with the DiGeorge syndrome. This association has not The EeG usually demonstrates sinus rhythm, been documented with aortopulmonary septal right axis deviation, and right ventricular hyper• defect [96]. trophy. Right or combined atrial enlargement is not uncommon as well.

Echocardiography Clinical Features In the newborn period while the pulmonary pressure is high, this lesion can be missed if the The timing of clinical presentation and findings echocardiographer relies solely on Doppler echo• may be in large part determined by the associ• cardiography. It is therefore imperative that a ated lesions [82, 85, 103]. Clearly those with thorough examination of the aortopulmonary associated interruption of the aortic arch or septum is performed. It is also important to severe preductal coarctation of the aorta will understand which lesions occur in association present early in the neonatal period. The defect with aortopulmonary window. Probably coarcta• is small in about 10% of all patients with tion or aortic interruption are the two most aortopulmonary septal defect, and thus these commonly associated lesions. Tetralogy and fortunate few would present considerably later, other lesions also have been observed. much like the child with a small-to-moderate The diagnosis of aortopulmonary window is sized patent ductus arteriosus in isolation. readily made by echocardiography when a com• Remembering that in most patients with this bination of subcostal precordial and supraster• anomaly of aortopulmonary septation, the de• nal views are employed [81, 83, 100, 106, 110, fect is large, one is not surprised when symp• 113]. From a subcostal right anterior oblique toms related to a large pulmonary blood flow view the aortopulmonary septum is well visual• and , tachypnea, dysp• ized (Fig. 26. lOA), such that visualization of nea, poor feeding, and diaphoresis are observed even those rare cases where the defect involves late in the first month of life coincident with only the right pulmonary artery is possible. The maturation of the fetal pulmonary vascular bed. precordial short axis view, with the transducer ANOMALIES OF AORTOPULMONARY SEPTATION: AORTOPULMONARY SEPTAL DEFECT 443

A

B

Fig. 26.10. A Subcostal view in aortopulmonary window. Note the window does not extend onto the right pulmonary artery. ao = aorta, mpa = main pulmonary artery, rpa = right pulmonary artery, rv = right ventricle, w = window. B Suprasternal view in aortopulmonary window. AO = aorta, APW = aortopulmonary window, LA = left atrium, LAA = left atrial appendage.

angled superiorly above the aortic valve also catheter would be advanced into the main images the area of the aortopulmonary septum, pulmonary trunk and then, to the operator's as does the suprasternal long axis cut (Fig. surprise, to the ascending aorta. The hemo• 26.10B). Once the window is imaged, Doppler dynamics reflect the presence of the associated echocardiography can be used to document the lesions, but in the patient with an isolated large pattern of flow. Finally every attempt should be fenestration, arterial oxygen saturation is nor• made to identify the coronary arteries which mal. Substantial left-to-right shunting at atrial may occasionally arise from the pulmonary level is not uncommon, reflecting a large pul• artery. monary blood flow and shunting through a patent foramen ovale. Pulmonary artery and right ventricular pressures are at systemic Hemodynamics and Angiocardiography levels. A higher pressure in the main pulmon• ary trunk than in the descending thoracic aorta Before the routine application of echocardiogra• is consistent with an obstructive anomaly of the phy, the first suggestion of an aortopulmonary aortic arch and a narrowed ductus arteriosus. septal defect was often an unusual catheter The role of cardiac angiography is to demons• course [82, 84, 89, 92, 102, 103, 115]. The venous trate the presence of the aortopulmonary win- 444 NEONATAL HEART DISEASE dow, and to demonstrate as well the presence, from the aorta of a pulmonary artery will have or to exclude, important associated anomalies a higher surgical risk. Surgical closure of an [90, 101]. Biplane right ventricular angiography aortopulmonary septal defect has been accom• with some craniocaudal angulation will demon• plished without cardiopulmonary bypass [111]. strate the origin of the main pulmonary trunk from the right ventricular infundibulum, and in the lateral projection, the main pulmonary trunk can be seen crossing in front of the aorta. Hemitruncus Arteriosus Selective injection of contrast into the ascending aorta will demonstrate the size and extent of the aortopulmonary septal defect, and with varying Aortic Origin of One Pulmonary Artery obliquity, one should be able to exclude aortic from the Ascending Aorta origin of a pulmonary artery. Aortography should also demonstrate the integrity of the Anomalous ori~in of one pulmonary artery aortic arch. Balloon occlusion aortography may from the ascendmg aorta or hemitruncus arter• be useful in imaging the coronary arteries. iosus is an uncommon disorder. At The Hospit• In a baby with interruption of the aortic arch al for Sick Children in Toronto, two or three and an apparently intact ventricular septum, new patients are seen annually with this dis• this situation is so uncommon that it is likely order [123, 125, 140]. that an aortopulmonary septal defect has gone unrecognized. Morphology and Morphogenesis Medical Therapy The pathologic anatomic features and associ• The use of prostaglandin is required in those ated cardiovascular anomalies of patients with neonates with an associated obstructive anoma• anomalous origin of one pulmonary artery from ly of the aortic arch. Anticongestive therapy will the ascending aorta have been reviewed by not prevent the need for surgery as these Kutsche an~ Van Mierop [132] and others [116, defects in the symptomatic neonate are large, 117, 118, 120, 122, 127, 128, 130, 134, 141]. From and the hemodynamic effects obvious once the the 99 cases in the literature and 9 from their diagnosis has been established. own institution, Kutsche and Van Mierop [132] conclude that anomalous origin of the right pulmonary artery from the ascending aorta was far more common (89) than origin of the left Surgical Intervention (19). The anomalous right pulmonary artery usually originated from the posterior aspect of the ascending aorta close to the aortic valve. The large aortopulmonary septal defect is a Occasionally, it arose from the lateral ascending surgical lesion, and some patients will require aorta just proximal to the innominate artery. operative repair as neonates [88, 89, 92, 93, 97, Aortopulmonary septal defect and patent duc• 105]. It is important to characterize fully the tus arteriosus are commonly associated with presence or absence of those complicating anomalous origin of the right pulmonary artery, associated lesions as they are often terribly while other cardiovascular anomalies are rare important in determining the outcome. We [117, 118, 125, 127, 132, 140]. Amongst patients have had experience in recognizing the pre• with anomalous origin of the left pulmonary sence of an aortopulmonary septal defect only artery from the ascending aorta, right aortic after repair of a severe preductal coarctation of arch and tetralogy of Fallot are common [125, the aorta where a preoperative cardiac 140]. catheterization with angiocardiography had not been performed. This diagnosis was reached in a baby who did not demonstrate significant Clinical Features clinical improvement after repair of the arch anomaly. Clearly the baby with associated interruption of the aortic arch, anomalies of Patients with anomalous origin of the right coronary arterial origin, or anomalous origin pulmonary artery from the ascending aorta in ANOMALIES OF AORTOPULMONARY SEPTATION: HEMITRUNCUS ARTERIOSUS 445 isolation may present in the neonatal period with tachypnea and feeding disorder [117, 125, 130, 140]. If this anomaly is complicated by coarctation of the aorta, a defect of the aortopul• monary septum, or frank interruption of the aortic arch, then findings of congestive heart failure may be conspicuous, and the physical findings may point to an obstructive anomaly of the aortic arch. It is unlikely that the diagnosis of ascending aortic origin of the pulmonary artery will be considered solely on the basis of the cardiac findings. A

Chest Radiograph

The chest radiograph usually demonstrates levocardia and visceral situs solitus. Modest cardiac enlargement may be apparent. Despite unilateral origin of one pulmonary artery from the ascending aorta, it is uncommon for the chest x-ray to demonstrate differential pulmon• ary markings. In the newborn, shunting at atrial level through a stretched foramen ovale will promote the radiographic appearance of in• creased pulmonary blood flow.

Pulmonary Perfusion Scan B A pulmonary perfusion scan performed from a peripheral vein should establish the diagnosis of an "absent" pulmonary artery in the usual sense [123, 125, 140]. The origin of the anoma• lously connected pulmonary trunk may be suggested from the levophase of the radionuc• lide injection.

Cross-sectional Echocardiography

King and Duncan and their respective coauthors and others have reported the cross• sectional echocardiographic diagnosis of ano• malous origin of one pulmonary artery from the ascending aorta utilizing suprasternal imaging c of the ascending aorta (Fig. 26.11) [117, 118, 123, Fig. 26.11. A Precordial long axis view in anomalous origin 131, 138, 142]. of the right pulmonary artery from the ascending aorta, in If a segmental approach, as outlined in the presence of an intact ventricular septum. AO = aorta, Chapter 10 is carried out on each new patient, LA = left atrium, LV = left ventricle, RV = right ventricle. B then this lesion should not be missed [129, 131, Subcostal view from the same patient. Note the right pulmonary artery arising from the ascending aorta. AO = 133, 136, 142]. Evaluation from the subcostal aorta, LA = left atrium, PA = pulmonary artery, RP A = and suprasternal views provides the best imag• right pulmonary artery, RA = right atrium, RV = right ing position. The precise origin of the pulmon• ventricle. C Suprasternal view demonstrating the left pul• ary artery from the ascending aorta can be monary artery arising from the ascending aorta. AA = ascending aorta, LP A = left pulmonary artery. clearly identified (Fig. 26.11). Origin of one 446 NEONATAL HEART DISEASE

A B

'. . , D '. "~1 '. , ~1 • c Fig. 26.12 Origin of right pulmonary artery from ascending aorta in an infant. A Injection of contrast into the main pulmonary trunk (mpa) opacifies only the left pulmonary artery. No (white') right pulmonary artery is seen. B The left ventriculogram (LV) clearly demonstrates aortic (ao) origin of the right pulmonary artery (rpa). C and D Distal ductal origin of the right pulmonary artery in isolation. The topography of the right pulmonary artery is very different from ascending aortic origin of the right pulmonary artery. C The left ventriculogram (LV) demonstrates the ductus diverticulum (') orig• inating from the base of the innominate artery. D The pulmonary vein wedge angiogram (pvwa) demonstrates the hilar right pulmonary artery (hrpa). ANOMALIES OF AORTOPULMONARY SEPTATION: HEMITRUNCUS ARTERIOSUS 447 pulmonary artery from the ascending aorta may Table 26.1. Differential diagnosis of anomalous origin of a occur in patients with tetralogy of Fallot or pulmonary artery from the ascending aorta pulmonary atresia and ventricular septal defect 1. Hypertensive patent ductus arteriosus (see Chapters 15 and 16). 2. Aortopulmonary septal defect 3. Pulmonary sequestration Hemodynamics 4. Truncus arteriosus 5. Normal truncal septation with origin of both pulmonary arteries from the ascending aorta The hemodynamics will of course reflect the nature of the serious associated intracardiac disturbances [125, 130, 139, 140]. In the absence of major associated anomalies, cardiac a patient with truncus arteriosus and so-called catheterization in the newborn will indicate a "absent" pulmonary artery. Finally, one must substantial left-to-right shunt. Pulmonary be aware of the situation of so-called normally hypertension of both the normally connected septated truncus arteriosus with aortic origin of pulmonary artery and the anomalously con• both pulmonary arteries. In this most peculiar nected pulmonary artery will be present. anomaly, the main pulmonary trunk is sup• ported by the right ventricular infundibulum and is in continuity with the descending thor• Angiocardiography acic aorta via the ductus arteriosus. Both branch pulmonary arteries originate anomalously from Selective injection of contrast into the main the ascending aorta (see Fig. 16.1). pulmonary trunk will fail to opacify the anoma• lously-connected pulmonary artery [125, 140]. The aortic origin of the right or left pulmonary Therapy artery can be demonstrated by contrast injection into either the left ventricle or the ascending aorta (Fig. 26.12). Medical therapy will not prevent the ravages Because of the association between anoma• of chronic congestive heart failure nor the pul• lous origin of the right pulmonary artery from monary vascular disease which will undoubt• the ascending aorta with a distal aortopulmon• ably occur [124]. Thus, while it is important to ary septal defect, and hypoplasia of the aortic treat the patient for congestive heart failure, the isthmus, it is important to clearly image the area therapy must include primary surgical repair, of the aortopulmonary septum and the trans• usually early in infancy. Surgery will separate verse aortic arch [116, 118, 125, 140]. the anomalously connected pulmonary artery from the aorta and re-establish its continuity with the main pulmonary trunk [135, 137]. Differential Diagnoses Penkoske and her colleagues [138] have re• ported repair of this malformation in three The physical findings in the seriously ill neonate babies 2-8 weeks of age. More recently, Fucci may point to an aortic-runoff lesion, with and his colleagues [126] have reported the findings of a hyperdynamic precordium, non• repair of this condition in three patients (aged specific systolic murmur, but bounding 12 days, 18 days, and 6 months) without the use peripheral pulses. The physical findings could of cardiopulmonary bypass. lead one to suspect a hypertensive ductus arteriosus, aortopulmonary septal defect, nor• mal truncal septation but with origin of branch Prognosis pulmonary arteries from the aorta, or sequestra• tion [119, 121, 125]. The ultimate prognosis without surgery is poor. The routine application and systematic Sudden death in the untreated baby has been approach of cross-sectional echocardiography reported, and for those escaping medical sur• should focus attention on aortic origin of one of veillance or diagnosis until late in infancy, the pulmonary arteries. Rarely, aortic origin of pulmonary vascular obstructive disease will one pulmonary artery may be associated with a exact its toll, not just on the anomalously ventricular septal defect. In this circumstance, connected lung, but frequently on the normally one must be certain that one is not dealing with connected one as well. 448 NEONATAL HEART DISEASE

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