Tricuspid atresia: analysis of coronary artery distribution and ventricular morphology

Coronary Arteries in Childhood Heart Disease: Implications for Management of Young Adults

Survival of patients with congenital heart defects has improved dramatically. Many will undergo interventional catheter or surgical procedures later in life. Others will develop atherosclerotic or post-surgical coronary heart disease. The coronary artery anatomy in patients with congenital heart disease differs substantially from that seen in the structurally normal heart. This has implications for diagnostic procedures as well as interventions. The unique epicardial course seen in some defects could impair interpretation of coronary angiograms. Interventional procedures, especially at the base of the heart, risk injuring unusually placed coronary arteries so that coronary artery anatomy must be delineated thoroughly prior to the procedure. In this review, we will describe the variants of coronary artery anatomy and their implications for interventional and surgical treatment and for sudden death during late follow-up in several types of congenital heart defects including: tetralogy of Fallot, truncus arteriosus, transposition of the great arteries, double outlet right ventricle, congenitally corrected transposition of the great arteries and defects with functionally one ventricle. We will also discuss the coronary abnormalities seen in Kawasaki disease.

The anatomy of hearts with double inlet ventricle

In the past, hearts with double inlet ventricle have been amongst the most contentious of congenital cardiac malformations. This is because, although most examples found with this particular atrioventricular connection have one big and one small chamber within the ventricular mass, for many years the variant most frequently encountered, with a dominant left ventricle, was usually described as exhibiting a single ventricle.1With the recognition that, in this particular variant, the small chamber is an incomplete right ventricle, and is never capable of supporting independently the pulmonary circulation, the anatomic situation has now been clarified, as explained in the previous review,2by recognising that the arrangement produces a functionally single ventricle, and that almost always patients with this lesion, if treated surgically, will be converted to the Fontan circulation. Even though, nonetheless, most patients with all variants of double inlet ventricle will likely end up with the Fontan circulation, it remains necessary to identify the functionally significant variants, namely those to be found in ventricular morphology, atrioventricular valvar morphology, ventriculo-arterial connections, and associated malformations.3

Nomenclature of the functionally univentricular heart

Hearts which, at first sight, seem to have a solitary chamber within their ventricular mass have long been the subject of controversy. As difficult as it is to manage these cardiac malformations medically and surgically, it has been at least as challenging, to date, merely to describe and classify them. Even the most commonly used terms, “single ventricle” and “univentricular heart”, spark heated debate. In distant times, when congenitally malformed hearts were pathological curiosities, these entities were described as “cor triloculare biatriale”. Therein lies the beginning of the problem, since when hearts of this type were examined by more enlightened pathologists, such as the great Maude Abbott,1it became plain that the apparently solitary ventricular mass in reality possessed a second, albeit much smaller, chamber. Abbott described this second structure as the “outlet chamber”. This convention of describing a “single ventricle”, albeit with a co-existing “outlet chamber”, that presumably lacked ventricular status, continued throughout the first half of the twentieth century, although it had been recognised by then that hearts could rarely be found with truly solitary ventricles, and these were typically deemed to be common structures. Van Praagh et al.2neatly summarised the problem with this approach when they pointed out that the so-called “single ventricle” possessed two ventricular chambers, whilst the “common ventricle” described the truly solitary arrangement. In their seminal investigation of 1964, Van Praagh et al.2analysed only those hearts unified because of double inlet atrioventricular connection, or alignment. They excluded arbitrarily from their investigation all hearts with atrioventricular valvar atresia, despite the similarity in morphology between many of these latter lesions and the hearts with double inlet.3

The pathology of subaortic obstruction

BACKGROUND

In hearts having the atriums connected only to a dominant left ventricle, typified by double-inlet left ventricle but seen also in lesions such as tricuspid atresia, subaortic obstruction, when it exists, is usually found at the level of the ventricular septal defect when the aorta is supported by the rudimentary right ventricle.

METHODS

Heart specimens were examined to determine the nature and position of the ventricular septal defect existing between dominant left and rudimentary right ventricles when the ventriculoarterial connections are discordant.

RESULTS

Most commonly, the ventricular septal defect is positioned between the muscular apical trabecular septum and the muscular outlet septum. This type of defect is found not only in double-inlet left ventricle, but also in hearts with absence of either the right or left atrioventricular connection when the other atrium is connected to a dominant left ventricle, irrespective of the position of the rudimentary and incomplete right ventricle. Obstructive lesions within the aortic arch are commonly associated with restriction at the site of the ventricular septal defect. The atrioventricular conduction bundle takes a constant course relative to the margin of the septal defect.

CONCLUSIONS

Because subaortic obstruction is almost always caused by a restrictive ventricular septal defect, relief of the obstruction can be achieved by surgical enlargement of the septal defect, bearing in mind the course of the atrioventricular conduction system.

What is a ventricle?

BACKGROUND

The concept of "one and a half" ventricular repair is to use "half" a ventricle to support the pulmonary circulation. The component makeup of any ventricle needs clarification for us to understand the nature of the so-called half ventricle.

METHODS

The components of normal and abnormal ventricles are reviewed.

RESULTS

Normal ventricles possess an inlet, an apical trabecular component, and an outlet. This tripartite approach is also logical in the description of congenitally malformed ventricles. Rudimentary and incomplete ventricles lack one or more of its component parts, and are usually hypoplastic. The location and morphology of the rudimentary ventricles correlate with the disposition of the atrioventricular conduction system.

CONCLUSIONS

Recognition of the ventricular components permits determination of ventricular morphology and guidelines for the location of the atrioventricular conduction axis.

Pathologic substrates for 1 1/2 ventricular repair

BACKGROUND

The concept of "one and a half ventricular repair" relates to situations where one ventricle is capable of pumping one half of the circulation while the other ventricle is deemed inadequate and requires off-loading by means of a shunt. The inadequate ventricle is usually assigned the role of pumping the pulmonary circulation. The majority of hearts potentially amenable to this repair will have one large ventricle associated with a smaller and more-or-less rudimentary ventricle.

METHODS

In this review, we focused on hearts in which the morphologically left ventricle will continue to support the systemic circulation.

RESULTS

Among the hearts with univentricular atrioventricular connections, a few cases of classic tricuspid atresia and cases of double-inlet left ventricle coexisting with concordant ventriculoarterial connections would be suitable for incorporating the right ventricle into the pulmonary circulation. This procedure may be feasible in some cases of straddling and overriding tricuspid valve. Hearts with pulmonary atresia and intact ventricular septum display a wide range of sizes of the right ventricular cavity. Although biventricular repair is an option for those with good-sized cavities, patients with hypoplastic right ventricles may be candidates for one and a half ventricular repair.

CONCLUSIONS

For the lesions reviewed, and many others, one and a half ventricular repair can be an option.

Cardiac anatomy in patients undergoing the Fontan procedure

BACKGROUND

Controversies in nomenclature, especially of hearts with "single ventricle," have clouded discussion and understanding of the anatomy. Many patients with such malformations are submitted to the Fontan procedure as definitive surgical palliation. The spectrum of anatomy among these patients is wide and deserves analysis in an effort to provide a simple framework for description and to eliminate confusion.

METHODS

We reviewed 138 successive patients undergoing the Fontan operation at one institution to demonstrate the variability in pathology.

RESULTS

Only 89 patients (65%) had a univentricular type of atrioventricular connection. All but 5 patients had two ventricular chambers. Among the 49 patients with biventricular atrioventricular connections, 43 had a hypoplastic ventricle that precluded a biventricular repair.

CONCLUSIONS

Full understanding of the malformations that may preclude a "biventricular" repair and hence necessitate a Fontan procedure requires knowledge of the different forms of univentricular atrioventricular connection that, although usually associated with two ventricular chambers, are seldom amenable to a "two-pump repair." Understanding of those types of "biventricular heart" that preclude a two-pump repair (eg, severe hypoplasia of the left ventricle or the right ventricle) or are associated with high risks (eg, straddling atrioventricular valve) is also important.

Echocardiographic-morphologic correlations in tricuspid atresia

OBJECTIVES

Our aim was to clarify the anatomic substrate in hearts diagnosed as having tricuspid atresia by studying autopsy specimens and comparing the findings with those in two-dimensional echocardiograms.

BACKGROUND

Traditionally, tricuspid atresia was thought, and is still believed by some, to be due to an imperforate valvular membrane interposed between the floor of the blind-ending right atrium and the hypoplastic right ventricle. Others argued that the dimple, when present, pointed to the outflow tract of the left ventricle rather than to the right ventricle, making the lesion more akin to double-inlet left ventricle.

METHODS

We examined 39 autopsy specimens catalogued as having tricuspid atresia. We then studied 24 two-dimensional echocardiograms from patients with a primary diagnosis of tricuspid atresia.

RESULTS

Of the 39 specimens, 37 had a completely muscular floor to the right atrium (absent right atrioventricular [AV] connection). The dimple, when identified, was (except in one case) directed to the left ventricular outflow tract. Only two hearts had an imperforate tricuspid valve. Two-dimensional echocardiograms in all cases showed an echo-dense band, produced by the fibrofatty tissue of the AV groove and representing absence of the right AV connection, between the muscular floor of the morphologically right atrium and the ventricular mass.

CONCLUSIONS

Tricuspid atresia is usually, but not always, due to morphologic absence of one AV connection. In most cases, the ventricular mass then comprises a dominant left ventricle together with a rudimentary and incomplete right ventricle.

The surgical anatomy of ventricular septal defects with univentricular atrioventricular connection

Hearts that do not possess one-to-one connections at the segmental junctions almost always produce a univentricular atrioventricular connection. One ventricle is usually large and dominant and the other small, lacking one or two of its components. The ventricular septal deficiency forms part of the circulatory pathway. We take the stance that only hearts that possess a truly solitary ventricular chamber are univentricular. They cannot have a ventricular septal defect, and so are excluded from this study. This review, therefore, is concerned with the morphology of septal defects in hearts in which both atrioventricular junctions are connected exclusively to a dominant left or a dominant right ventricle, and those lacking one atrioventricular connection, where the remaining valve is connected to a dominant ventricle. This morphology in the absence of one atrioventricular connection can be modified when there is overriding of the solitary atrioventricular valve. The ventricular septal defects are analyzed and categorized for the various groups, and the position of the conduction axis is described for the well-recognized entities.

Tricuspid atresia. Microscopic findings in relation to "absence" of the atrioventricular connexion

In 10 out of 31 cases of tricuspid atresia (absent atrioventricular connexion), gross examination of the morphologically right ventricle suggested the presence of a tiny inlet portion in addition to the trabecular portion. Serial sections of two of these hearts have proven this diagnosis: a fibrous remnant in continuity with the central fibrous body was present not only above the left ventricle but also above the right ventricle. We interpreted this as a remnant of the atrioventricular valve and we also observed that the ventricle had a hypoplastic inlet portion. This inlet portion was bounded by a microscopically small septomarginal trabeculation containing the right bundle branch. Therefore, the diagnosis of absent connexion, which after clinical or gross anatomical investigation remains an appropriate one, cannot always be maintained after microscopical study if it is considered that the fibrous remnant represents evidence of a connexion initially present between the right ventricle and the right atrium.

Variable morphology of ventricular septal defect in double inlet left ventricle

The morphologic characteristics of ventricular septal defect (VSD) relative to the disposition of the atrioventricular conduction axis were studied (as far as was possible from gross observation) in 33 hearts with double inlet left ventricle. The hearts were separated into 4 groups. The hearts had either right-sided or left-sided rudimentary right ventricles (RV) coexisting with either ventriculoarterial (VA) concordance or discordance, respectively. Significant differences were noted in the morphology of the VSD according to these patterns. With right-sided rudimentary RV and VA concordance the anatomy was similar to that of classic tricuspid atresia, with an extensive outlet septum in the roof of the defect. With left-sided rudimentary RV and VA concordance, 2 further patterns were seen. In 1 pattern the arrangement was similar to that found with VA discordance. In the other, there was a pinhole VSD, a grossly hypoplastic right ventricle and a complete subaortic infundibulum in the dominant left ventricle. With VA discordance the morphology was broadly similar be the rudimentary RV right-sided or left-sided. The outlet septum was much less extensive than in the arrangement with right-sided RV and VA concordance. Minimal differences related to the formation of the right margin of the defect, which always carried the conduction axis on its left ventricular aspect. These differences dictated the "safest margins" of the defect should its excision be required during life. Basically, the left margin of the apical trabecular septum can most safely be excised.

Tricuspid atresia with overriding imperforate tricuspid membrane: an anatomic variant

An anatomical study of 34 specimens presenting with tricuspid atresia, in which particular emphasis was devoted to the atrioventricular junctional area, revealed 5 cases with an imperforate valve. In 1 heart the valve was completely committed to the right ventricle. In the other 4, however, the membrane was related not only to the right ventricle but also to the left ventricle. A hypoplastic right ventricular inlet portion was found in these 4 specimens. In 2 cases the tricuspid membrane overrode an inconspicuous inlet septal defect. In the other 2 hearts, as studied macroscopically, no defect was present underneath the membrane, which was connected to both right and left ventricles. These 4 specimens also had other ventricular septal defects. In classical tricuspid atresia, characterized by absence of the inlet portion of the right ventricle, the inlet septum is absent. In contrast, these 4 hearts did have an hypoplastic inlet septum.

The univentricular atrioventricular connection: getting to the root of a thorny problem

Most hearts described as "single ventricle" or "univentricular heart" possess 2 ventricular chambers, even though 1 is usually described as an "outlet chamber." This stems from the wide acceptance that the criterion of a single ventricle is the presence of a double-inlet atrioventricular (AV) connection. In recent years, using this criterion, an attempt was made to show how hearts with double-inlet right ventricle or "classic tricuspid atresia" were (in terms of ventricular morphology) just as univentricular as "single ventricle with outlet chamber." This attempt brought still further confusion to an already contentious topic. The root of the problem clearly is the injudicious use of the adjective "single" or "univentricular." Conventionally it is used to describe the ventricular mass. In most hearts with double-inlet connection it is not the ventricles that are univentricular; it is the AV connection. The concept of a univentricular AV connection, then, appropriately groups hearts with double-inlet along with those having absence of 1 AV connection. It distinguishes this entire group from those other hearts with biventricular AV connections (each atrium connected to its own ventricle). The term "univentricular AV connection" is thus a collective one for all those hearts in which the atria connect to only 1 ventricle. Confusion will be completely removed if individual hearts are described for what they are in terms of AV connection and ventricular morphology (for example, double-inlet left ventricle with rudimentary right ventricle rather than single ventricle with outlet chamber).

Mitral atresia. Morphological details

The morphological characteristics of mitral atresia were studied in 30 hearts to determine the presence or absence of a morphological rudiment of the atretic valve and the relation of this rudiment, if found, to any chamber in the ventricular mass. All the hearts showed atrial situs solitus and no ventricular inversion; consequently all had left atrioventricular atresia. In all instances dense fibrous tissue connected the floor of the left atrium to the left ventricle. This connective tissue is considered to be the morphological rudiment of the atretic mitral valve. In several hearts the intervening fibrous tissue varied from a thick fibrous membrane to a tiny fibrous cord; it is impossible to detect these variations clinically. It is, therefore, more practical to classify those hearts which have a detectable fibrous membrane macroscopically as having an "imperforate membrane" and those with a fibrous strand detectable only microscopically as having an "absent atrioventricular connection."