Common arterial trunk (truncus arteriosus) is a congenital malformation in which a single arterial trunk arises from the heart, overrides the interventricular septum, and supplies the systemic, pulmonary, and coronary circulations. With common arterial trunk (CAT) there are no remnants of a separate pulmonary valve or ventricular to pulmonary artery continuity, and thus this lesion can be distinguished from the severe forms of tetralogy of Fallot with pulmonary atresia. CAT is relatively uncommon, representing 0.21–0.34% of patients with congenital heart disease [1–4]. This chapter will use the American English nomenclature, common arterial trunk, instead of the Latin version, truncus arteriosus. Where historical significance requires the Latin version, it will be retained.

Embryologic and Anatomic Features

During embryonic life, the outflow tract of the developing heart, which extends from the distal extent of the developing right ventricle to the margins of the pericardial cavity, possesses a common lumen. It is subsequently divided into the ventricular outflow tracts and the arterial components. Its distal part, however, which becomes transformed into the intrapericardial arterial trunks, is divided into the aortic and pulmonary components by the growth intrapericardially of a protrusion from the dorsal wall of the aortic sac, which becomes the aortopulmonary septum [5]. It is failure of fusion of the outflow cushions that results in persistence of the common ventriculo‐arterial junction [6], this being the essential phenotypic feature of CAT (Figure 18.1).

The extent of growth of the aortopulmonary septum, and remodeling of the extrapericardial pharyngeal arch arteries, then accounts for the variation in formation of the intrapericardial branches of the common trunk (Figure 18.2), with these changes forming the basis of historical approaches to clinical classification, as already discussed. Experimental studies in chick embryos showed that ablation of the neural crest prevents fusion of the outflow cushions, and hence results in persistence of a common ventriculo‐arterial junction [7, 8]. The cells migrating from the neural crest also populate the pharyngeal pouches, and thence the thymus and parathyroid glands. This association explains the prevalence of CAT with DiGeorge syndrome [9, 10].

It is the presence of the common ventriculo‐arterial junction, therefore, which is the phenotypic feature of CAT. In this setting, there is a solitary arterial trunk arising from the heart, which gives rise directly to the aortic, pulmonary, and coronary arterial branches [11]. In most instances, the arterial trunk overrides the ventricular septum, being dominantly positioned over the right ventricle in around two‐fifths of cases, the left ventricle in one‐fifth, and balanced between the ventricle in two‐fifths [12].

Clinical classifications have traditionally been based on the intrapericardial arrangement of the pulmonary arteries arising from the common trunk (Figure 18.3).

Collett and Edwards [11] suggested four subcategories (Figure 18.3, upper row). Their classification, although helpful, did not account for the variants with hypoplasia of the aortic pathways. The importance of aortic hypoplasia was emphasized in the modification of the classification provided by Van Praagh and Van Praagh (Figure 18.3, middle row) [13]. In this classification, the Van Praaghs also described a “type A3” variant, which had discontinuous intrapericardial pulmonary arteries, with one, usually the right, taking origin through a persistently patent arterial duct. The most important modification provided by Van Praagh and Van Praagh, nonetheless, was to emphasize the significance of aortic hypoplasia, particularly in association with severe coarctation or interruption of the aortic arch. They accounted for this variant as their type A4 [13]. They subsequently modified their system still further, by combining their A1 and A2 categories (Figure 18.3, bottom row), recognizing that, in most instances, the pulmonary arteries arise together from the leftward and posterior aspect of the common trunk. Their system was potentially confusing, since Collett and Edwards had also described a “type IV” variant (Figure 18.3, upper row). This variant is now recognized as a solitary arterial trunk in the setting of tetralogy with pulmonary atresia. The different use of “type 4” in the subcategorizations, nonetheless, highlights the shortcomings of alphanumeric categorizations. In their initial account, Van Praagh and Van Praagh had suggested that the branching of the common trunk could also be addressed in terms of aortic as opposed to pulmonary dominance. This is the feature we now recommend for subcategorization (Figure 18.4), recognizing that there can sometimes also be a balanced division of the common trunk into its aortic and pulmonary components [14]. Examples of anatomic specimens with aortic dominance versus pulmonary dominance are shown in Figure 18.5.

Other features of the intrapericardial pulmonary arteries are also of surgical significance, such as origin of the pulmonary component from a truncal valvar sinus or crossing of the origins of the pulmonary arteries as they exit from the common trunk. It was the categorization suggested by Van Praagh and Van Praagh, nonetheless, that was expanded to provide a stepwise hierarchical system suitable for computerized classification of all the anatomic variants and associated anomalies of CAT [15]. If further modified to account for the variants of aortic or pulmonary dominance [16], this system can now be used to monitor incidence, document surgical results, and develop models for risk stratification.

The truncal valve is often insufficient owing to abnormally thickened and deformed leaflets, and, in some instances, the valve can also be stenotic. It is trifoliate in 60% of cases, quadrifoliate in 25%, and bifoliate in 5%. The aortic arch is right‐sided in up to one‐third of patients and is then usually associated with mirror‐image branching of the brachiocephalic arteries. In very rare circumstances, when the common trunk arises exclusively from the right ventricle, the ventricular septum can be intact. Almost always, however, there is an interventricular communication, which is directly juxtaarterial (Figure 18.6). It opens to the right ventricle between the limbs of the septomarginal trabeculation. In the majority of cases, the caudal limb of the trabeculation then fuses with the inner heart curvature, producing a postero‐inferior muscular rim to the defect that protects the atrioventricular conduction axis. In a minority of cases, the defect extends to the region of the membranous septum, meaning that the conduction axis is at risk postero‐inferiorly. In the latter setting, greater care is required during patch closure to avoid surgical heart block. Examples of anatomic specimens illustrating the difference in ventricular septal defect morphology and the impact on the conduction system are shown in Figure 18.7. There is no “standard” pattern for the coronary arteries, although typically they arise from opposite valvar sinuses in the setting of a quadrifoliate truncal valve [17]. Solitary coronary arterial origin is frequent, as is abnormally high takeoff above the sinuses of Valsalva. These variations indicate that it is essential to identify and then preserve the coronary arteries during surgical neoaortic construction subsequent to removal of the pulmonary component of the common trunk [18].

Historical Perspectives

The historical accounts of CAT (truncus arteriosus) anatomy, classification, and initial application of surgical therapy are well chronicled [19]. The first well described autopsy case of truncus arteriosus was recorded in 1798 by Wilson [20]. In 1864, Buchanan reported the anatomic details of a 6‐month‐old infant [21]. Similarities associated with single arterial trunk and anomalous pulmonary arteries were clarified by Vievordt, as noted by Victorica [22] regarding some of the characteristic features of these anomalies. In 1930, Shapiro distinguished truncus arteriosus from hearts with aortic and pulmonary atresia [23]. In 1942, Lev and Saphir offered the basic morphologic criteria that defined truncus arteriosus [24]. These anatomic inquiries established the basis for subsequent classification schemes reported by Collett and Edwards (1949) [11], Van Praagh and Van Praagh [13], and Anderson [5] (Figures 18.3 and 18.4) [14, 25].

Surgical treatment strategies were introduced in the early 1960s and were based on palliative therapy using pulmonary artery banding techniques [26–28], with suboptimal results. The first successful intracardiac repair was performed by Herbert Sloan at the University of Michigan in 1962 using a nonvalved Teflon conduit [29].

The first report of truncus arteriosus repair using a valved conduit was by McGoon, Rastelli, and Ongley in 1968 [30–33]. Rastelli’s idea and research led to the repair of other disease entities using valved conduits such as transposition of the great arteries, ventricular septal defects, pulmonary stenosis, and ventricular septal defect with pulmonary atresia. Before long, any operation that employed an extracardiac ventricular to pulmonary artery valved conduit was termed a “Rastelli operation.”

In 1973, homograft conduits were not in great supply, prompting Hancock to develop a Dacron‐porcine valved conduit in association with Bowman and Malm, physicians from Columbia‐Presbyterian Hospital in New York [34]. They noted that total surgical repair of congenital heart lesions with pulmonary artery–right ventricular discontinuity required a valve‐containing conduit for optimum results. Follow‐up data of up to two years demonstrated this prosthesis to be satisfactory and perhaps a superior alternative to the aortic homograft for restoring pulmonary artery–right ventricular continuity [34].

At about the same time, Dr. Paul Ebert at Cornell University was applying this new technology to younger patients, made possible by the availability of the #12 Hancock conduit to be used in patients younger than 6 months of age. This represented the first application of this conduit to infants.

In 1976, Paul Ebert reported on 10 infants under 6 months of age with type 1 (n = 5) or type 2 truncus (n = 5); 5 had pulmonary atresia with some discontinuity between right and left pulmonary arteries [35]. Patients were managed with closure of the ventricular septal defect and placement of a valved conduit between the right ventricular outflow tract and pulmonary arteries. An aortic allograft valve or 12 mm Hancock was used to allow for adequate flow. Almost a decade later, Ebert reported on 106 truncus patients who underwent correction between 1974 and 1981. At the time of correction 100 patients were under 6 months of age, 6 died before operation, and there were 11 operative deaths. Of the 86 long‐term survivors, 55 returned for conduit change owing to somatic growth or pseudointimal conduit proliferation. There were no mortalities at this conduit change (26 valved conduits, 29 straight tubes between ventricle and pulmonary trunk) [36–38].

By 1984 John Kirklin had been convinced by Barratt‐Boyes that he needed to begin using homografts for complex congenital heart defects. This resulted in establishment of local tissue banks, which were expanded by the New England Organ Bank and Cryolife in cooperation with Richard Jonas [19]. These advances allowed surgeons to approach these patients with more certainty. Perioperative bleeding, which had been the focus of poor results, was now neutralized, leading to improved survival.

The most recent historical innovation with repair of CAT was by Edward Bove, who reasoned that application of cardiac repair in neonates with complex congenital heart disease before the onset of pulmonary hypertension would result in improved results [39–41]. In 1989, Bove et al. reported on 11 neonates and young infants (median age 21 days), 5 of whom also had major truncal valve insufficiency [41]. Two patients required valve replacement, and right ventricle to pulmonary artery continuity was established with porcine valved conduits in three and aortic or pulmonary homograft in eight patients. There was one operative and one late death. At publication, eight of nine late survivors were doing well, leading the team to recommend repair in the first month of life [41]. The traditional method of repairing the arch in truncus patients was often complicated by the presence of a small ascending aorta distal to the point where the pulmonary arteries originated. This left residual left ventricular outflow tract obstruction proximal to the arch repair and no doubt contributed to the historically poor results in that era. Augmenting the entire ascending aorta as one continuous structure, similar to the way they were performing the arch in hypoplastic left heart syndrome, not only simplified the operation but removed any potential systemic outflow tract obstruction following repair [39, 40].

It was clear that associated anomalies, especially truncal regurgitation during the repair of CAT, were significant risk factors for early and late mortality. Many techniques have been applied to neutralize these problems [42–47].

In 1999, Mee et al. reported 17 patients who had undergone repair of CAT with associated anomalies. There were no early deaths and one late death. Four patients had truncal insufficiency; three of these had annular valvuloplasty, with excellent results [48].

Mavroudis and associates studied eight patients with severe truncal valve insufficiency at primary repair (three patients) or in conjunction with conduit replacement (five patients) in 2000. One neonate had truncal valve replacement at initial repair; seven had truncal valve repair (three by valvar suture and four by leaflet excision and annular remodeling). There were seven survivors; truncal valve remodeling by leaflet excision and reduction annuloplasty was effective while valvar suture techniques were not [49].

Physiology and Clinical Findings

The overwhelming abnormal pathophysiologic feature of CAT is a large left‐to‐right shunt that increases after the neonatal period as the pulmonary vascular resistance falls. Truncal valve regurgitation is present in about 50% of patients and may cause pressure overload to the already volume‐overloaded ventricles. Pulmonary vascular obstructive disease may develop as early as 6 months of age, leading to poor results after late surgical correction.

The clinical manifestations of CAT usually become apparent within the first weeks of life because of a murmur, tachypnea, and costosternal retractions. The patients are sometimes cyanotic, but the progressive signs of congestive heart failure are most prominent, including tachypnea, hepatomegaly, sweating with feeding, failure to thrive, bounding pulses, a pansystolic murmur at the left sternal border, and sometimes a diastolic murmur if significant truncal regurgitation is present. The second heart sound is predictably single.

The electrocardiogram shows sinus rhythm and biventricular hypertrophy. Left ventricular forces may predominate in the case of large pulmonary flow, while right ventricular forces may predominate if pulmonary vascular obstructive disease develops. The chest roentgenogram shows cardiomegaly, increased pulmonary vascular markings, and an absent pulmonary artery segment. A right aortic arch can be appreciated in about one‐third of cases. Unequal vascularity may denote unilateral pulmonary artery atresia, while bilaterally decreased pulmonary markings often reflect long‐standing pulmonary vascular obstructive disease.

The various views of two‐dimensional echocardiography combined with pulsed Doppler or Doppler color‐flow mapping can usually provide sufficient information to determine the type of CAT, the origin of the coronary arteries and their proximity to the pulmonary trunk, the character of the truncal valve, and the degree of truncal insufficiency, if present (Figure 18.8). The newer and less invasive diagnostic methods of magnetic resonance imaging and computed tomography (Figure 18.9) have helped to provide more accurate anatomic details, such as coronary artery location and pulmonary artery origins, which can help in planning the operation and avoiding complications. Despite these advances in imaging techniques, cardiac catheterization is sometimes indicated to further evaluate truncal insufficiency, confirm anatomic details (Figures 18.10 and 18.11) [25], and measure pulmonary vascular resistance, especially in the case of late presentation.

Natural History

Untreated patients with CAT have a dismal prognosis, with a 65% 6‐month and 75% 1‐year mortality rate [11] despite treatment with anticongestive medications, which are the only medical therapeutic option. Occasionally some children will develop a mild degree of increased pulmonary vascular resistance to balance their systemic and pulmonary circulations and live to 10 years and more [50, 51]. The greater number, however, fall victim to congestive heart failure due to the large left‐to‐right shunt, or develop accelerated pulmonary vascular obstructive disease with progressive cyanosis. Surgeons now perform complete repair in the first 1–2 weeks of life, typically prior to hospital discharge, which has resulted in improved early and late survival.

Operative Technique

The operative techniques for repair of CAT have undergone evolutionary advances relating to cannulation and perfusion techniques, myocardial preservation, and types of extracardiac conduits [52–59]. In particular, improved results with transmediastinal interrupted aortic arch (IAA) reconstruction [60–69] and truncal valve repair [42, 48, 49, 70–75] have positively influenced perioperative survival and long‐term outcome. These techniques are discussed in this section.

Surgical Repair of Common Arterial Trunk

Repair of CAT is highly dependent on the peculiar anatomic details that have been mentioned. Figure 18.12 shows aortobicaval cardiopulmonary bypass and pulmonary artery trunk constriction, to prevent pulmonary overcirculation and systemic hypoperfusion during the initiation of systemic perfusion. We also place a left ventricular vent in the right superior pulmonary vein (not shown). The aortic cross‐clamp is applied and antegrade cardioplegia is administered. If significant truncal valve insufficiency is present, alternative administration techniques must be initiated, such as direct coronary infusion or retrograde cardioplegia. Figure 18.13 shows the next stages of the operation, which include pulmonary trunk separation, right ventriculotomy, and patch aortoplasty of the common trunk that is to become the aorta (Figure 18.13A). Not shown in this drawing is the important maneuver of separating the pulmonary trunk from the common trunk. CAT has numerous coronary anomalies, including high takeoff of the left main coronary artery. During separation of the pulmonary trunk from the common trunk, careful attention must be paid to the origin of all coronary arteries to prevent unwanted injury. For this reason, it is best to repair the moiety of the common trunk with a biologic or prosthetic patch, which will maintain the neoaortic configuration and guard against coronary artery obstruction from suture line distortion.

Some surgeons prefer to completely transect the CAT to visualize the orifice of the pulmonary arteries and the coronary arteries while excising the pulmonary artery. Figure 18.13B shows the technique of ventricular septal defect (VSD) closure using an interrupted suture technique for an outlet VSD (the more common type) through a ventriculotomy. Alternatively, many surgeons use a running suture technique for this patch placement. Once the VSD is closed, the aortic cross‐clamp can be removed, and systemic warming is begun. This maneuver is mildly controversial because the patent foramen ovale (PFO) is not closed, and it is likely that the heart will recover to sinus rhythm before the ventriculotomy is closed. We manage this problem of possible air in the ventricle by leaving the left ventricular vent on suction and discontinuing the assisted suction venous drainage in the right atrium, allowing a reservoir of right atrial volume and decreasing the possibility of air shifts to the left atrial and left ventricular cavities. Alternatively, the cross‐clamp can be left engaged until the ventricle is closed with the proximal conduit reconstruction. The PFO is generally left alone unless the interatrial communication is large. Leaving the PFO will help with the postoperative hemodynamics, since the right ventriculotomy often leads to temporary right ventricular dysfunction. The PFO can serve as a “pop‐off” to maintain cardiac output when decreased right ventricular compliance limits diastolic filling. The resultant right‐to‐left atrial shunt during these episodes maintains cardiac output, but causes an obligatory mild cyanosis that is usually well tolerated [76].

Establishing right ventricular to pulmonary artery continuity is achieved by a conduit. Various methods can be used for this portion of the operation, namely pulmonary or aortic homografts; Contegra^® grafts (bovine internal jugular vein grafts, Medtronic, Minneapolis, MN, USA); the porcine Dacron valved conduit; valveless polytetrafluoroethylene (PTFE) right ventricular to pulmonary artery graft; and direct pulmonary artery–right ventricle anastomosis.

Most surgeons prefer some type of valved conduit, although there have been no prospective studies on this issue. Some authors [45, 77] have extolled the benefits of nonvalved conduits and still others have introduced other creative techniques [78–80].

We prefer to use a valved conduit. Figure 18.14 shows our preferred technique of conduit placement. The distal pulmonary anastomosis is accomplished with running suture technique as an end‐to‐end configuration. Rarely, a left or right pulmonary artery incision is made to accommodate an enlarged conduit. The proximal conduit–ventricle anastomosis is performed directly to the superior portion of the ventriculotomy for about one‐third of the circumference in order to use the patch hood technique (Figure 18.14), which will align the conduit for a proper orientation. The hood technique is not necessary if a Contegra or Dacron valved graft is used, because the conduit can be cut on a bevel, which will achieve the same orientation as the homograft hood technique. If the homograft hood technique or the Contegra graft is used, the ventricular anastomosis usually does not require Dacron felt strips for reinforced suturing, but the porcine Dacron valved conduit is stiff, and suturing to the friable ventricular edge often requires Dacron felt to reinforce the anastomosis, especially in young infants undergoing their first surgery. The completed truncus repair using the hood technique is shown in Figure 18.15. We have also had success with direct anastomosis of the muscular cuff of a pulmonary homograft to the opening in the right ventricular outflow tract.

Surgical Repair of Anatomic Variants

In the early to middle 1970s, before the advent of the more accurate and more inclusive nomenclature classifications, surgeons often noted that the takeoff of the pulmonary artery trunk was not exactly Collett and Edwards type I and not exactly Collett and Edwards type II. In other words, the continuum between these two subtypes was characterized as somewhere in the middle of the anatomic descriptions, resulting in an informal type called type 1½. It turned out that this type was more common than types I and II. These patients do not have a distinct main pulmonary trunk that can be easily divided from the aortic component of the common trunk.

Figure 18.16 shows aortobicaval cardiopulmonary bypass preparations in a patient with CAT type 1½ or type II, depending on one’s subjective analysis. As mentioned earlier, complete transection of the arterial trunk leads to more accurate pulmonary orifice excision, coronary artery preservation, and safe proximal arterial trunk reconstruction. Figure 18.17 shows the aortic cross‐clamp in place and clear exposure of the pulmonary and coronary orifices, after partial transection of the CAT before the pulmonary artery is excised. Note that the left main coronary artery is very close to the orifice of the pulmonary artery. Also note that removal of the pulmonary artery without truncal transection can be associated with suboptimal exposure, which will place the coronary artery orifice in jeopardy. Figure 18.18 shows the fully transected CAT, which allows for proximal truncal reconstruction with a prosthetic/biologic patch while respecting the orifice of the coronary artery. Figure 18.19 shows the pulmonary artery homograft being sutured into the confluence of the pulmonary arteries and the aorta being reconstructed using an end‐to‐end technique. The operation is completed by closing the VSD through the right ventricular ventriculotomy and anastomosing the conduit to the right ventricular outflow tract opening, as shown in Figures 18.13 and 18.14.

Interrupted Aortic Arch

Surgical repair of CAT with IAA is a highly demanding operation requiring intricate management of cardiopulmonary bypass, myocardial preservation, and technical strategies. Figure 18.20 shows the cannulation technique for cardiopulmonary bypass. Most cardiopulmonary bypass techniques in patients with IAA are managed by dual arterial cannulation, with one catheter in the proximal aorta and one catheter in the arterial duct to perfuse the lower extremity during the cooling phase of bypass. Patients with CAT and IAA do not require this type of cannulation technique, however, because the proximal connection of the aortic and pulmonary artery trunks is part of the pathology, thereby allowing catheter flow to the ascending aorta and the descending aorta through the truncal connection and the arterial duct. One arterial catheter is sufficient to effect total body perfusion and cooling. Another option, recently adopted by some surgeons but not shown here (see Chapter 16), is to anastomose a PTFE graft to the innominate artery for the arterial cannulation and employ it for regional perfusion during the arch repair [81]. Once the perfusion strategy is chosen, cardiopulmonary bypass is commenced with separate snagging of the right and left pulmonary arteries to prevent pulmonary overcirculation and systemic hypoperfusion. A left ventricular vent is placed through the right superior pulmonary vein.

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