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Ann Thorac Surg 2000;69:S77-S82
© 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, 1989–1999.
Abstract
The extant nomenclature for tetralogy of Fallot (TOF) 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. The general categories of TOF are: classic TOF with varying degrees of pulmonary stenosis, TOF with common atrioventricular canal defect, and TOF with absent pulmonary valve. Although centers may choose to code a fourth general category, TOF with pulmonary atresia, this lesion will be grouped with pulmonary atresia-ventricular septal defect for multiinstitutional analysis. 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
Of the common cyanotic congenital heart malformations, tetralogy of Fallot (TOF) was among the first to be described anatomically [1] and the first to be addressed surgically [2]. But this long history of pathological study and surgical treatment has led to a more unified and simplified, rather than a more complicated, understanding of this malformation. The original anatomic description, composed of a "tetrad" of malformations, has given way to a unified developmental theory. Thus, the four anatomic features characteristic of the disease: (1) stenosis of the pulmonary artery, (2) ventricular septal defect (VSD), (3) deviation to the right of the origin of the aorta, and (4) hypertrophy of the right ventricle, are all elements of a "monology," the hallmark of which is hypoplasia of the subpulmonary infundibulum, which is sufficient to account for all four anatomic features. As proposed by Van Praagh and associates [3], the abnormal superior, anterior, and leftward position of the infundibular septum is the common developmental anomaly, which results in crowding of the right ventricular outflow tract, a nonrestrictive malalignment-type ventricular septal defect caused by nonocclusion of the infundibular septum with the left anterosuperior and right posteroinferior limbs of the septal band, varying degrees of overriding of the aorta, and ultimately secondary hypertrophy of the right ventricle. It is logical that so common a form of congenital heart disease would derive from one malformation with four facets or consequences rather than from the chance coexistence of four unrelated anomalies.
Thus, the consequences of hypoplasia of the subpulmonary infundibulum in hearts with normal segmental anatomy include (1) varying degrees of obstruction of the right ventricular outflow tract (infundibular, valvar, and supravalvar pulmonary stenosis), (2) a conoventricular type of ventricular septal defect with malalignment of the infundibular septum with respect to the true trabecular septum, (3) aortic override, and (4) right ventricular hypertrophy. Perhaps as a consequence of this unifying pathologic hypothesis, there have not evolved such elaborate systems of nomenclature with respect to TOF as has occurred with other common congenital cardiac malformations. In fact, the controversies in nomenclature relate more to the "language" chosen to name elements of cardiac structure than to subtypes of tetralogy itself. Thus, the debate as to whether to refer to the ventricular septal defect (VSD) as malalignment type, conoventricular type, or perimembranous type is of academic interest and has little bearing on the surgical repair. Likewise, the outcome of repair is oblivious to the choice of labels such as infundibular septum, conal septum, or parietal band to describe the anteriorly displaced outlet septum, which encroaches upon the right ventricular outflow tract. Thus, nomenclature per se becomes most important in describing anatomical variants of TOF or associated lesions. In this manuscript, we will consider "classic" TOF, or TOF with pulmonary stenosis, together with its variants. These include TOF with common atrioventricular canal defect, and TOF with absent pulmonary valve.
GUEST EDITORS’ NOTE: The proper location in the nomenclature system for lesions classified as "TOF with pulmonary atresia" or any subtypes of "TOF with pulmonary atresia" was debated extensively at the First International Nomenclature Conference for Pediatric Cardiac Surgery, Chicago, Illinois, September 19 to 20, 1998. Some feel strongly that these lesions should be grouped with TOF and others feel strongly that these lesions should be grouped with pulmonary atresia-VSD. These lesions may be entered into the hierarchical database either under TOF with pulmonary atresia or pulmonary atresia-VSD. Thus, any given center or surgeon may decide to group these lesions under either TOF with pulmonary atresia or pulmonary atresia-VSD.
Regardless of where in the database the lesion is entered, for our purposes of analysis, it was agreed that lesions coded as "TOF with pulmonary atresia" or any subtypes of "TOF with pulmonary atresia" will not be analyzed with TOF but instead will be analyzed with pulmonary atresia-VSD.
This definition was also debated extensively at the Third International Nomenclature Conference for Pediatric Cardiac Surgery, New Orleans, Louisiana, April 23, 1999. There, the decision was made that "TOF with pulmonary atresia" would not be considered a subtype of TOF on the short diagnosis list (see "Diagnosis and Procedure Short Lists"); "TOF with pulmonary atresia" would thus not be a choice on the short diagnosis list. "TOF with pulmonary atresia" would instead be coded under "pulmonary atresia-VSD" on the short diagnosis list. Although "TOF with pulmonary atresia" can be accessed via the TOF hierarchy in the hierarchical nomenclature system, it will not be analyzed with TOF but instead will be analyzed with pulmonary atresia-VSD.
This manuscript will discuss the simplest forms of TOF with pulmonary atresia, ie, that form characterized by confluent pulmonary arteries with a ductus arteriosus as the sole source of pulmonary blood flow and that form characterized by the left pulmonary artery arising from a ductus (not really pulmonary atresia if the right pulmonary artery still connects to the right ventricle). These lesions will be discussed further in the manuscript covering "pulmonary atresia-VSD." TOF with multiple aortopulmonary collaterals (also known as "pulmonary atresia-VSD, MAPCAs" or "pseudotruncus") is also discussed in the manuscript covering "pulmonary atresia-VSD."
Although most of the variability between cases of TOF concerns the levels and degree of hypoplasia of the right ventricular outflow tract and pulmonary arterial tree, some features of the intracardiac anatomy merit description. The VSD is typically large and physiologically nonrestrictive. It lies between the infundibular septum anterosuperiorly, and the two limbs of the septal band (trabecula septomarginalis) inferoposteriorly. Unlike the common form of perimembranous VSD in nontetralogy hearts, the VSD is not in the plane of the septum, but nearly perpendicular to it as a result of the anterior malalignment of the infundibular septum. When the posteroinferior limb of the septal band is attenuated, little or no muscle is interposed between the fibrous annulus of the tricuspid valve and that of the aortic valve. In some instances, hypoplasia of the infundibulum of the right ventricle involves extreme hypoplasia or virtual absence of the infundibular septum. In these instances, the VSD is subarterial and the aortic and pulmonary valves are separated by a thin band of fibrous tissue. In these instances, there is often hypoplasia of the pulmonary annulus. Approximately 3% to 4% of patients with TOF have a second VSD. These may be muscular and may occur in any portion of the septum, but are most often located anteriorly.
The VSD type(s) in TOF can be coded in hierarchical detail utilizing the coding system presented in the VSD manuscript of this publication. This hierarchical VSD coding can be entered into a comprehensive database as an additional or secondary diagnosis(es) under the primary TOF diagnosis. The most common VSD type in TOF is classified in the hierarchical nomenclature system as "VSD, type 2 (perimembranous) (paramembranous) (conoventricular), outlet, conal septal malalignment, TOF type."
II. Analysis: a unified TOF nomenclature system
Perhaps because the segmental anatomy of hearts with TOF is fundamentally similar to normal hearts, complex systems of nomenclature have not evolved with respect to this very common malformation. Thus, the majority of cases of TOF in which there are varying degrees of hypoplasia of the right ventricular infundibulum, but with physical continuity between the right ventricle and the central pulmonary arteries, are referred to as either simple tetralogy, classic tetralogy, or TOF with pulmonary stenosis. This is in contradistinction to those cases in which there is a complete physical obstruction or separation between the outflow portion of the right ventricle and the pulmonary arteries (TOF with pulmonary atresia). In its simplest form, TOF with pulmonary atresia is fundamentally similar to simple tetralogy, with the exception that the infundibulum either narrows to a blind end point, or terminates at an imperforate pulmonary valve plate, thus creating a complete physical separation between the right ventricle and the pulmonary arteries. In such cases, it is usually true that a ductus arteriosus is the sole source of flow into confluent pulmonary arteries. In general, the pulmonary vasculature in such cases is reasonably well developed. More complicated forms of TOF with pulmonary atresia are characterized by severe hypoplasia or absence of the central pulmonary arteries, and in general are associated with the presence of multiple aortopulmonary collaterals (considered in another manuscript). Rarely, TOF with pulmonary stenosis is associated with one or more major aortopulmonary collateral vessels.
The common physiologic characterization of TOF as either "cyanotic" or "acyanotic" is of limited utility, as it describes a condition of a patient at one point in time rather than a cardiac malformation per se. Thus, in the majority of instances, an infant with tetralogy and adequate or generous antegrade pulmonary blood flow will, over time, with the acquisition of right ventricular hypertrophy, develop either progressive or periodic cyanosis.
Several additional associated malformations can have an important impact on the physiology of TOF. These include absence of one branch pulmonary artery (generally the left), absence of the pulmonary valve, and association of complete common atrioventricular canal defect with TOF. TOF with absence of the left pulmonary artery may exist as a rare congenital anomaly, or may develop as a consequence of involution of the ductus arteriosus, which results in occlusion of the proximal left pulmonary artery. In general, there is entirely normal development of the right pulmonary artery, and the natural history and associated surgical risks for these patients differs very little from that of patients with uncomplicated TOF.
TOF with absent pulmonary valve is a variant that is associated with massive enlargement of the central pulmonary arteries, a malalignment-type VSD, and absence or extremely vestigial development of the pulmonary valve leaflets in association with varying degrees of hypoplasia of the pulmonary annulus. This is almost always associated with absence of the ductus arteriosus. The aneurysmal development of the central pulmonary arteries is attributed to the combination of absence of the ductus and free pulmonary regurgitation during fetal development. The spectrum of physiologic derangement in these cases is quite broad, but generally bimodal. In the most extreme forms, neonates present with severe respiratory distress due to compression of the central airways by the huge aneurysmal central pulmonary arteries and constitute a surgical emergency. At the other end of the spectrum are patients whose course and development are most similar to those with simple tetralogy with mild degrees of right ventricular outflow tract obstruction [3].
TOF with complete common atrioventricular canal defect is a rare but challenging variant of common atrioventricular canal defect with the associated conotruncal abnormality of TOF. The degree of cyanosis depends upon the degree of malalignment of the infundibular septum and the severity of consequent right ventricular outflow tract obstruction. The anatomy of the endocardial cushion defect is that of Rastelli type C (nondivided bridging superior leaflet), in virtually all cases [4].
Apart from the previously mentioned associated anomalies, abnormal patterns of origin and branching of the principal coronary arteries are numerous. The most common and surgically relevant coronary anomaly, which occurs in approximately 3% of patients [4], involves right coronary origin of the anterior descending coronary artery. This anomaly, as well as the less common single coronary artery with origin of the right coronary from a normally arising left coronary artery, may require specific modification of surgical technique to avoid the consequences of coronary artery injury. The coronary artery anomalies in TOF can be coded in hierarchical detail utilizing the coding system presented in the "Anomalies of the Coronary Arteries" manuscript of this publication. This hierarchical "coronary artery anomalies" coding also can be entered into a comprehensive database as an additional or secondary diagnosis under the primary TOF diagnosis.
One area of controversy centers on the differentiation between TOF and double-outlet right ventricle (DORV). DORV is discussed in detail in a separate manuscript in this publication. The distinction between DORV and TOF is controversial. Some authors use the term DORV when the pulmonary artery arises from the right ventricle and more than 50% of the aorta arises from the right ventricle [5, 6]. Other authors only use the term DORV when the pulmonary artery arises from the right ventricle and 90% or more of the aorta arises from the right ventricle [7]. Still others use the term DORV only when there is absence of fibrous continuity between the aortic and mitral valves [8]. In the "DORV" manuscript of this publication, DORV is defined as a type of ventriculoarterial connection in which both great vessels arise predominantly from the right ventricle. It is inescapable that some hearts will be called TOF at some centers and DORV at other centers.
A final area of TOF variation merits discussion: the variety of types of pulmonary artery or pulmonary branch stenoses. The detailed hierarchical nomenclature for all types of pulmonary artery or pulmonary branch stenoses is presented in the "RVOT Obstruction, Intact Ventricular Septum" manuscript of this publication. This hierarchical pulmonary artery and/or pulmonary branch stenoses coding also can be entered into a comprehensive database as an additional or secondary diagnosis under the primary TOF diagnosis.
The detailed consideration of pulmonary atresia with VSD (and multiple aortopulmonary collaterals) is presented in the "Pulmonary atresia-VSD" manuscript of this publication. This TOF manuscript thus analyzes and codes TOF with pulmonary stenosis (patency of the right ventricular tract), TOF with pulmonary atresia (and ductal origin of pulmonary blood flow [As stated above, these lesions may be entered into the hierarchical database either under TOF with pulmonary atresia or pulmonary atresia-VSD. Regardless of where in the database the lesion is entered, it will not be analyzed with TOF but instead will be analyzed with pulmonary atresia-VSD.]), TOF with absent pulmonary valve, and TOF with common atrioventricular canal defect. In each of these cases, the presence of associated anomalies such as additional VSD, atrial septal defect, right aortic arch, left superior vena cava, and coronary artery anomalies must be subspecified as an additional or secondary diagnosis under the primary TOF diagnosis.
TOF hierarchy level 1
TOF hierarchy level 2
Tetralogy of Fallot hierarchy level 3
Modifiers for tetralogy of Fallot pulmonary valvar stenosis
Many surgeons make decisions as to whether or not to perform a transannular patch based on the z-score of the pulmonary annulus. This section allows one to code the pulmonary valve annulus z-score.
Additional modifiers for tetralogy of Fallot hierarchy level 1
Additional modifiers for reoperative TOF surgery
Note: A large and ever-increasing number of patients S/P prior to TOF surgery are requiring additional interventions. The following diagnoses will assist in coding diagnoses for these patients.
III. Nomenclature for tetralogy of Fallot treatment options
In general, the surgical approach to Tetralogy of Fallot (TOF) involves either initial palliation by means of construction of a systemic to pulmonary artery shunt followed by definitive repair at a later date, or by one-stage definitive repair or "corrective surgery." Recently, in some instances initial palliation has been achieved by means of balloon angioplasty of the pulmonary valve. The essential features of any reparative operation for TOF include the elimination of intracardiac shunts by means of closure of the malalignment VSD, and relief of right ventricular outflow tract obstruction. Relief of right ventricular outflow tract obstruction is accomplished either by means of excision of obstructing tissues (muscular or valvar), by augmentation of the outflow tract (patching: infundibular, pulmonary artery, or transannular), or by some combination of both. Controversy exists as to the optimal approach to the VSD: either transatrial or transventricular. Although the classical method of repair generally involves an incision in the infundibulum of the right ventricle, closure of the VSD through the right ventricular approach, and relief of right ventricular outflow tract obstruction by means of a combination of resection and patching, more recently, there has been considerable enthusiasm for a combined transatrial and transpulmonary artery approach with a goal of avoiding an incision in the right ventricular outflow tract. It should be noted, however, that even when a predominantly transatrial and transpulmonary approach is utilized, if the main pulmonary artery incision is extended proximally through the pulmonary annulus, this must be considered a "transannular," and thus ventricular incision, though the length of the incision onto the ventricle itself, may be minimal.
Thus, an adequate description of operative repair of TOF must include an accurate description of the incisions made into cardiac tissue, be they atrial, right ventricular (infundibular) with or without transannular extension on to the main pulmonary artery, transatrial and transpulmonary artery (with or without proximal extension across the annulus onto the right ventricle), and whether the incision is extended out onto either or both branch pulmonary arteries. Likewise, the means of relief of right ventricular outflow tract obstruction must be described, including muscular resection and augmentation with patch material (infundibular, transannular, with or without extension onto the branch pulmonary arteries, or by means of a conduit with or without valve.)
A final area of TOF treatment merits discussion: the treatment of the variety of types of pulmonary artery or pulmonary branches stenoses with PA reconstruction (plasty) of the main, right, and left pulmonary arteries. The detailed hierarchical nomenclature for treatment of all types of pulmonary artery and/or pulmonary branch stenoses is presented in the "RVOT Obstruction, Intact Ventricular Septum" manuscript of this publication. This hierarchical coding of treatment of pulmonary artery or pulmonary branch stenoses also can be entered into a comprehensive database as additional or secondary procedures under the primary TOF procedure.
Tetralogy of Fallot treatment hierarchy level 1
Tetralogy of Fallot (TOF) treatment hierarchy level 2
Palliation, NOS
TOF repair, NOS
TOF repair, Other corrective
Tetralogy of Fallot (TOF) treatment hierarchy level 3
Palliation, NOS Palliation, Shunt, Systemic to pulmonary, NOS
Palliation, Shunt, Ligation and takedown Palliation, Valvuloplasty, Pulmonic, Valvotomy, NOS
TOF repair, NOS TOF repair, No ventriculotomy TOF repair, Ventriculotomy, nontransannular patch TOF repair, Ventriculotomy, Transannular patch TOF repair, Right ventricle-pulmonary artery conduit TOF/AVC (AVSD) repair TOF/absent pulmonary valve repair, NOS
TOF repair, Other corrective
Additional comments regarding therapeutics
In addition to the above basic treatment options for TOF, 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). Third, 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 biologic or prosthetic materials.
Procedures directed at associated lesions (thymectomy, closure of patent foramen ovale, closure of atrial septal defect, etc) can be coded as additional or secondary procedures under the primary TOF procedure.
Finally, details regarding management of cardiopulmonary bypass, myocardial protection, and associated issues will be recorded in another related and linked module of the database.
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. The operative risk factors may include history of hypercyanotic spells, severe cyanosis, prostaglandin dependence, ventilator dependence, inotrope or vasopressor dependence, and multiple organ dysfunction.
Anatomic variables potentially predictive of risk include pulmonary artery size (McGoon or Nakata index), multiple ventricular septal defects, and coronary artery anomalies. Associated noncardiac congenital anomalies, definite chromosomal anomalies, and DiGeorge’s syndrome should be considered. 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
TOF: inclusion criteria and allowable concomitant diagnoses
A case is included for TOF analysis if the primary diagnosis is TOF and concomitant cardiac diagnoses are none, left superior vena cava, PDA, atrial septal defect, VSD, aortic coarctation, pulmonary artery or pulmonary branch stenoses, coronary artery anomalies, or any combination of these.
If no TOF subtype is given, the TOF will be classified as TOF, NOS.
Outcome reports
1. Mortality (30-day and late) by:
Anatomic type
Age at surgery
Birth weight
Gestational age
Weight at surgery
Type of repair
2. Length of stay
Length of intubation
Length of intensive care unit stay
Length of hospital stay
3. Complications
A separate module of the database will allow for coding of perioperative complications.
Summary
More variability exists in the detailed methodology of the surgical approach to TOF than in the actual nomenclature and classification. A simple system of classification is proposed. The details of the surgical approach should be able to be described, enabling investigators to correlate outcome with surgical methodology.
References
This article has been cited by other articles:
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  G. Michielon, B. Marino, R. Formigari, G. Gargiulo, F. Picchio, M. C. Digilio, S. Anaclerio, G. Oricchio, S. P. Sanders, and R. M. Di Donato Genetic Syndromes and Outcome After Surgical Correction of Tetralogy of Fallot. Ann. Thorac. Surg., March 1, 2006; 81(3): 968 - 975. [Abstract] [Full Text] [PDF]
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B. Faidutti, J. T. Christenson, M. Beghetti, B. Friedli, and A. Kalangos How to diminish reoperation rates after initial repair of tetralogy of Fallot? Ann. Thorac. Surg., January 1, 2002; 73(1): 96 - 101. [Abstract] [Full Text] [PDF]
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