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Ann Thorac Surg 2000;69:S50-S55
© 2000 The Society of Thoracic Surgeons
a Section of Cardiothoracic Surgery, St. Christopher’s Hospital for Children, Philadelphia, Pennsylvania, USA
Address reprint requests to Dr Jacobs, Section of Cardiothoracic Surgery, St. Christopher’s Hospital for Children, Erie Ave at Front St, Philadelphia, PA 19134-1095
Presented at the International Nomenclature and Database Conferences for Pediatric Cardiac Surgery, 1998–1999.
Abstract
The extant nomenclature for truncus arteriosus (TA) is reviewed for the purpose of establishing a unified reporting system. The subject was debated and reviewed by members of the STS-Congenital Heart Surgery Database Committee and representatives from the European Association for Cardiothoracic Surgery. All efforts were made to include all relevant nomenclature categories using synonyms where appropriate. A modified Van Praagh (VP) classification is proposed involving three main categories of TA: TA with confluent or near confluent pulmonary arteries (large aorta type, VP A1, A2), TA with absence of one pulmonary artery (VP A3), and TA with interrupted aortic arch or coarctation (large pulmonary artery type, VP A4). A comprehensive database set is presented that is based on a hierarchical scheme. Data are entered at various levels of complexity and detail that can be determined by the clinician. These data can lay the foundation for comprehensive risk stratification analyses. A minimum database set is also presented that will allow for data sharing and would lend itself to basic interpretation of trends. Outcome tables relating diagnoses, procedures, and various risk factors are presented.
I. Background
Truncus arteriosus is an uncommon congenital heart anomaly in which a single arterial trunk arises from the heart, giving origin to the coronary arteries, the pulmonary arteries, and the systemic arterial circulation. In the vast majority of instances, there is a ventricular septal defect (VSD) and a single semilunar valve. The infundibular septum is virtually absent superiorly. The single semilunar valve may contain two, three, four, or more leaflets, and is occasionally dysplastic. In most instances, the semilunar valve overrides the true interventricular septum, and thus both ventricles. Very rarely, there is not a VSD. In these instances, there are what appear to be separately formed but conjoined aortic and pulmonary semilunar valves. Also very rarely, the truncal valve may override the right ventricle entirely. If in such cases there is no VSD, then the left ventricle and mitral valve may be extremely hypoplastic.
The variable development of primitive arterial arches 4 through 6 in truncus arteriosus may result in hypoplasia or interruption of the aortic arch. In these instances, a large ductal arch exists between the common arterial trunk and the descending thoracic aorta. Conversely, when the aortic arch is fully developed, a ductus arteriosus is rare. Anomalies of origin and distribution of the coronary arteries are seen in patients with truncus arteriosus. As in tetralogy of Fallot, a surgically relevant variant of coronary anatomy involves right coronary origin of the left anterior descending coronary artery. Often, there is a rather high origin of the left coronary artery from the common arterial trunk. This may be surgically relevant because of proximity of the left coronary to the origin of a branch pulmonary artery, or because of ostial stenosis.
Two principle classification systems for truncus arteriosus have evolved. The classification scheme of Collett and Edwards [1] bases nomenclature upon the sites of origin of the pulmonary arteries (Fig 1). In type I, there is a partially formed aorticopulmonary septum, and thus a main pulmonary artery segment is present. In type II, the right and left branch pulmonary arteries originate adjacent to one another from the posterior aspect of the common arterial trunk. In type III, the right and left branch pulmonary arteries have their origins further from one another, on the right and left posterolateral aspects of the common arterial trunk. The Collett and Edwards classification also includes a type IV. In this instance, true branch pulmonary arteries are absent and pulmonary blood flow is derived from aorticopulmonary collaterals. Often referred to as pseudo-truncus, this is currently not thought by most to be a type of truncus arteriosus, but rather to represent a form of pulmonary atresia with VSD (tetralogy of Fallot with pulmonary atresia) [2].
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While both classifications have found wide application in clinical cardiology and cardiac surgery, each has its limitation. A natural history distinctly different from that of truncus arteriosus [4] has been recognized for pulmonary atresia with VSD and major aortopulmonary collaterals (tetralogy of Fallot with pulmonary atresia); as new and different treatment strategies are evolving for that group of patients, it seems important to classify them separately from those with truncus arteriosus [2]. Thus, the truncus type IV of Collett and Edwards is probably a misnomer. The utility of both classifications is limited by the fact that there are frequent inconsistencies between the description of origin of the right and left branch pulmonary arteries from the common arterial trunk as imaged by angiography and echocardiography, and the actual appearance at surgery. It is very often the case that imaging modalities suggest the presence of a partially formed aorticopulmonary septum, and thus the presence of a main pulmonary artery segment. At surgery, the branch pulmonary artery orifices may be found adjacent to one another in the left posterolateral aspect of the common arterial trunk. The surgeon may in fact be unable to excise a main pulmonary artery segment from the common arterial trunk though one was described by imaging, as it may in fact have no actual length to it. Thus, in the same sense, it is extremely rare, even when preoperative imaging studies suggest the presence of a partially formed aorticopulmonary septum, for the surgeon to be able to isolate and band a main pulmonary artery segment [5]. In common parlance, surgeons often refer to many cases as truncus arteriosus type 1
. This anatomy may in fact be quite often encountered at surgery, emphasizing one of the limitations of both the Collett and Edwards classification and the Van Praagh classification. Additionally, of the very few cases of truncus arteriosus type B (absence of a VSD) described or reviewed by Van Praagh, most have either conjoined aortic and pulmonary semilunar valves or a large pulmonary valve and aortic atresia. As such, it is debatable whether these truly are cases of truncus arteriosus, as opposed to large aorticopulmonary window on the one hand, or aortic atresia on the other.
A variety of associated cardiac anomalies may coexist with any one of the various subtypes of truncus arteriosus. Among these are right aortic arch, presence of persistent left superior vena cava draining to the coronary sinus, aberrant origin of the right subclavian artery from the descending thoracic aorta, patent foramen ovale or ostium secundum-type atrial septal defect, and others. These are all adequately described using standard nomenclature.
A complete surgical description of truncus arteriosus should include in addition to the principle classification the following elements: (1) the number of leaflets making up the truncal valve; (2) dysplasia of the truncal valve if present; (3) functional abnormality of the truncal valve including regurgitation or stenosis, specifying grade of the regurgitation (I, II, III, IV), and the gradient associated with stenosis if known; (4) alignment of the truncal valve with respect to the true ventricular septum; (5) associated hypoplasia of either ventricle if present; and (6) hypoplasia or absence of the thymus.
Two additional terms have often been utilized in the literature and merit discussion and definition: hemitruncus and pseudotruncus. Hemitruncus has often been used to describe a situation in which one pulmonary artery arises from the ascending aorta and the other pulmonary artery arises from the right ventricle. This defect is usually not associated with a VSD. Hemitruncus is not really a form of truncus arteriosus, and is best defined as ascending aortic origin of one pulmonary artery and right ventricular origin of the other pulmonary artery [6]. This definition distinguishes hemitruncus from Van Praagh type 3 truncus. Pseudotruncus has often been used as a synonym for Collett and Edwards type IV truncus. As discussed above, pseudotruncus is not really a form of truncus arteriosus, and is best defined as a form of pulmonary atresia with VSD with major aortopulmonary collaterals (MAPCAs) [7].
GUEST EDITORS’ NOTE: The term Hemitruncus is classified as "pulmonary artery origin from ascending aorta (hemitruncus)" in the "Aortopulmonary Window" article in this supplement by Jacobs J, and colleagues. This article further discusses the term hemitruncus as follows:
The term hemitruncus should be discouraged; hemitruncus is an inaccurate term because it implies that the anomalous vessel arises from a common persistent arterial trunk while it actually arises from the aorta. While we include this term in our hierarchy below, we discourage its use. If used, hemitruncus should be synonymous with "pulmonary artery origin from ascending aorta, left pulmonary artery" or "pulmonary artery origin from ascending aorta, right pulmonary artery" and not as a subtype of truncus arteriosus or aortopulmonary window.
The term Pseudotruncus is discussed in the "Pulmonary Atresia-Ventricular Septal Defect" article in this supplement by Tchervenkov and Roy as follows:
The term pseudotruncus was used by Bharati and associates in 1975 to describe patients with PA-VSD. The term pseudotruncus was subsequently felt to be inappropriate by Van Praagh and associates because of its vagueness and that it did not represent an entity. It has since fallen out of favor.
II. Analysis: a unified truncus arteriosus nomenclature system
While anatomists and embryologists have continued to debate the true nature of truncus arteriosus, and thus the ideal system of classification, it has become clear that a small variety of surgical approaches hold promise for salvage and satisfactory outcomes for the majority of neonates and infants with truncus arteriosus [8–12]. The anatomic features that more than any others determine the necessary surgical approach are those related to the virtually ever-present inverse developmental relationship between the derivatives of primitive arterial arches 4 and 6 (aortic isthmus and ductus arteriosus, respectively). In 1976, Van Praagh [13] revisited the controversy surrounding classification of types of truncus arteriosus, and introduced the new terms "large aortic type of truncus" and "large pulmonary artery type of truncus." The majority of cases are accounted for by the large aortic type of truncus, typified by a small or absent main pulmonary artery component and virtual absence of a ductus arteriosus. Anatomically, these cases are characterized by a large aortic trunk and confluent or near confluent pulmonary arteries arising there from. The descriptive term "truncus arteriosus with confluent or near confluent pulmonary arteries" combines Van Praagh types A1 and A2 as well as Collett types I, II, and III. This way, the adopted and often confusing term "truncus arteriosus type 1" need never be used again. Moreover, the term is descriptive and complies with the other forms of truncus arteriosus, which use modifiers such as: truncus arteriosus with interrupted aortic arch. Following through with this logic, the next category is "truncus arteriosus with absence of one pulmonary artery" or large aortic type of truncus with absence of pulmonary artery, which conforms to Van Praagh type A3. The third category involves cases of "truncus arteriosus with interrupted aortic arch or coarctation," alternatively described as large pulmonary artery type of truncus (Van Praagh, type A4). The descriptive term "truncus arteriosus with interrupted arch or coarctation" assumes no hidden knowledge, whereas the term "large pulmonary artery type of truncus" is less descriptive and assumes more knowledge of embryologic development than some might want to attain.
The few remaining (rare) cases fall into the categories of the intact ventricular septum type of truncus, and the complete muscular subtruncal infundibulum (or transposition) type of Truncus.
In general, the surgical approach to the truncus arteriosus with confluent or near confluent pulmonary arteries (large aortic type of truncus) consists of separation of the right and left branch pulmonary arteries from the arterial trunk, association of those branch pulmonary arteries with the right ventricle, which usually but not always requires some type of conduit, and closure of the defect in the ventricular septum. The surgical approach to truncus arteriosus with interrupted aortic arch or coarctation (large pulmonary artery type of truncus) consists of separation of the right and left branch pulmonary arteries from the arterial trunk, association of the branch pulmonary arteries with the right ventricle, association of the descending aorta with the arterial trunk and ascending aorta, and closure of the defect in the ventricular septum. In most [8, 14], but not all series [9, 12], the latter type has proved more challenging for survival.
Thus, with regard to the establishment of a system of nomenclature for use in a surgical database, the recognition of synonyms allows each institution to use either the proposed, or one of the classical systems, of nomenclature (Table 1).
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Truncus arteriosus hierarchy level 2
GUEST EDITORS’ NOTE: Absence of one PA in this case means absent origin of the PA from the common arterial trunk and not absence of the entire PA. The "absent PA" usually takes origin from the distal aorta or patent ductus arteriosus.
Truncus arteriosus hierarchy level 3
Important modifiers for truncus arteriosus: hierarchy level 1
Important modifiers for truncus arteriosus: hierarchy level 2
Definitions and guidelines to describe the "important modifiers" are difficult at best. Insufficient truncal valves are best evaluated by echocardiography. A subjective evaluation can usually be assessed by experienced clinicians. The same is true to describe truncal stenosis, because cardiac catheterization is not usually performed for these patients. Right or left ventricular hypoplasia similarly is a subjective diagnosis that could lead to biventricular or univentricular repair. These terms are included to identify patients who have smaller but "acceptable" ventricles for a biventricular repair, the idea being that future risk analysis might stimulate a more thorough evaluation of a problem. Coronary anomalies can be grouped together for this database and are present or not present. Furthermore, the coronary artery anomalies in truncus arteriosus can be coded in hierarchical detail utilizing the coding system presented in the "Anomalies of the Coronary Arteries" manuscript by Dodge-Khatami and colleagues in this supplement. This hierarchical "coronary artery anomalies" coding also can be entered into a comprehensive database as an additional or secondary diagnosis under the primary truncus arteriosus diagnosis.
The modifier "truncus arteriosus with intact ventricular septum" can be used for all cases of truncus without a VSD. For the vast majority of cases of Truncus with a VSD, the characteristics of the VSD should be described in hierarchical nomenclature like any other VSD, as an additional or secondary diagnosis. Although most (approximately 80% of) VSDs associated with truncus are "VSD, type 1 (subarterial) (supracristal) (conal septal defect) (infundibular)," some (the remaining 20%) are "VSD, type 2 (perimembranous), (paramembranous), (conoventricular), outlet," a type 2 VSD that extends toward the outlet portion of the septum. This type 2 VSD will require more careful surgical consideration to avoid heart block during patch closure [2, 12].
III. Nomenclature for truncus arteriosus treatment options
Truncus arteriosus treatment hierarchy level 1
Truncus arteriosus treatment hierarchy level 2
Additional comments regarding therapeutics
In addition to the above basic treatment options for truncus arteriosus, several other therapeutic issues must be addressed and coded in other areas of the database. First, a separate part of the database must allow for coding of incisions for this and all other diagnoses (median sternotomy, submammary incision, right thoracotomy, left thoracotomy, minimally invasive incisions [partial sternotomy, parasternal incision, "minithoracotomy"], etc). Second, a separate part of the database must allow for coding of cardiac incisions for this and all other diagnoses (aortotomy, pulmonary arteriotomy, right atriotomy, right ventriculotomy, left ventriculotomy, etc). Finally, a separate module of the database must permit coding of patch materials (Dacron, Gore-Tex, Bovine pericardium, autologous pericardium, gluteraldehyde fixated autologous pericardium, etc), conduit type, conduit materials, conduit size, and use of other biological or prosthetic materials.
IV. Diagnosis and procedure short lists
V. Potential diagnostic-related risk factors
Patient size (weight and body surface area) and gestational age are considered potential risk factors. As in other heart malformations associated with excessive pulmonary blood flow, preoperative risk factors include congestive heart failure, pulmonary artery hypertension, failure to thrive, multiple organ dysfunction, ventilator dependence, and inotrope dependence. Other variables potentially predictive of risk include truncal valve insufficiency and/or stenosis, right or left ventricular hypoplasia, aortic arch obstruction or interruption, and DiGeorge’s syndrome. Procedural risk factors are shared in common with other complex malformations whose management includes cardiopulmonary bypass with or without ischemic myocardial arrest and with or without hypothermic circulatory arrest.
VI. Database studies and outcome analysis
Truncus arteriosus: inclusion criteria and allowable concomitant diagnoses
A case is included for truncus arteriosus analysis if the primary diagnosis is truncus arteriosus and concomitant cardiac diagnoses are none, left superior vena cava, right aortic arch, aberrant origin of the right subclavian artery from the descending thoracic aorta, patent ductus arteriosus (PDA), patent foramen ovale (PFO), atrial septal defect, VSD, aortic coarctation, interrupted aortic arch, or any combination of these.
If no truncus arteriosus subtype is given, the truncus arteriosus will be classified as truncus arteriosus, NOS.
Outcome reports
I. Mortality (30 day and late) by:
Anatomic type
Age at surgery
Birth weight
Gestational age
Weight at surgery
Intervention directed at truncal valve
II. Length of stay
Length of intubation
Length of intensive care unit stay
Length of hospital stay
III. Complications
A separate module of the database will allow for coding of perioperative complications.
Summary
While debate continues regarding the embryology of truncus arteriosus, it is clear that there are anatomic features and associated physiologic consequences that impact on the timing and technique of operative management. A system of Nomenclature is proposed that is based upon a modification of Van Praagh’s classification and these observable features. Through the recognition of synonyms, it may be used interchangeably with either of the traditional classification systems.
References
This article has been cited by other articles:
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  I. Adachi, H. Uemura, K. P. McCarthy, A. Seale, and S. Y. Ho Relationship between orifices of pulmonary and coronary arteries in common arterial trunk Eur. J. Cardiothorac. Surg., April 1, 2009; 35(4): 594 - 599. [Abstract] [Full Text] [PDF]
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 C. M. Phelps, E. Da Cruz, T. Fagan, A. K. Younoszai, and C. Tissot Anterior Origin of the Main Pulmonary Artery From the Arterial Valvar Sinus: Unusual Truncus Arteriosus Circulation, February 3, 2009; 119(4): 624 - 627. [Full Text] [PDF]
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 F. Lacour-Gayet and S. Goldberg Surgical repair of truncus arteriosus associated with interrupted aortic arch MMCTS, March 28, 2008; 2008(0328): 2451. [Abstract] [Full Text] [PDF]
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 M. Nathan, D. Rimmer, G. Piercey, P. J. del Nido, J. E. Mayer, E. A. Bacha, and F. A. Pigula Early repair of hemitruncus: Excellent early and late outcomes J. Thorac. Cardiovasc. Surg., May 1, 2007; 133(5): 1329 - 1335. [Abstract] [Full Text] [PDF]
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 S. Leschka, E. Oechslin, L. Husmann, L. Desbiolles, B. Marincek, M. Genoni, R. Pretre, R. Jenni, S. Wildermuth, and H. Alkadhi Pre- and Postoperative Evaluation of Congenital Heart Disease in Children and Adults with 64-Section CT RadioGraphics, May 1, 2007; 27(3): 829 - 846. [Abstract] [Full Text] [PDF]
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T. M. Bashore Adult Congenital Heart Disease: Right Ventricular Outflow Tract Lesions Circulation, April 10, 2007; 115(14): 1933 - 1947. [Full Text] [PDF]
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 W. Liu, J. Selever, D. Wang, M.-F. Lu, K. A. Moses, R. J. Schwartz, and J. F. Martin Bmp4 signaling is required for outflow-tract septation and branchial-arch artery remodeling PNAS, March 30, 2004; 101(13): 4489 - 4494. [Abstract] [Full Text] [PDF]
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