Pulmonary Venous Anomalies

Historical Note

Dr. John Craig, the senior author of this landmark paper, was my principal teacher of pediatric pathology at the Children’s Hospital Medical Center (as it was then called) in Boston, from 1956 to 1957. Dr. Bill Rothney was a Senior Resident in Pathology. I did not know Dr. Darling.

In 1962, when I was taking the oral part of the examination for the American Sub-board of Pediatric Cardiology, Dr. Abraham Rudolph asked me, “What is the embryologic basis of anomalous pulmonary venous drainage?” I replied by telling Dr. Rudolph the Darling, Rothney, and Craig classification of TAPVC, which seemed to satisfy him. Years later, I realized that my answer had been not wrong but certainly superficial, as will soon be seen.

Embryologically, TAPVC represents failure of development of the common pulmonary vein, as was appreciated by Lucas et al in 1962. As a consequence of failure of development of the common pulmonary vein, an anastomosis almost always persists and enlarges between the pulmonary venous plexus of the lung buds and the systemic veins.

As the classification of TAPVC indicates, such pulmonary venous–to–systemic venous anastomoses can occur at the supracardiac level between the lungs and the anterior cardinal veins ( Fig. 7.3 ), at the cardiac level between the lungs and the sinus venosus, at the infracardiac level between the lungs and the ductus venosus (see Fig. 7.3 ), or at several of the previously mentioned levels in the mixed form of TAPVC.

These normal anastomoses between the pulmonary venous plexus and the systemic venous plexus usually undergo involution after the development of the common pulmonary vein. But if the common pulmonary vein fails to develop, these pulmonary-systemic venous anastomoses can persist, resulting in TAPVC.

It will be seen that the previously mentioned classification of TAPVC is a very general classification. There are multiple different anatomic subtypes of supracardiac, cardiac, infracardiac, and mixed TAPVC (see Fig. 7.3 ).

TAPVC to RA

In TAPVC to the RA, there is no discrete horizontal vein that can be anastomosed to the LA in the usual way. The pulmonary veins connect directly with what has been interpreted in the past as the dorsal wall of the RA, without forming a horizontal vein. From the anatomic standpoint, one approach to surgical repair is atrial septectomy, followed by surgical construction of a new atrial septum that will direct the pulmonary venous return into the LA and/or to the physiologically appropriate atrioventricular (AV) valve.

In 1995, S. Van Praagh et al published a study of 36 patients, 21 with postmortem confirmation and 15 living patients, in which there was partially anomalous (44%) or totally anomalous (56%) pulmonary venous drainage into the RA because of displacement of the septum primum into the LA. Displacement of the septum primum—leftward in atrial situs solitus or rightward in atrial situs inversus—was present in all patients and appeared to be responsible for the anomalous pulmonary venous drainage.

For example, in visceroatrial situs solitus, when the septum primum was displaced to the left so that the atrial septum lay between the right and LPVs, this created the appearance known as ipsilateral pulmonary veins, which is characteristic of the polysplenia syndrome and has led to the (we think erroneous) interpretation of bilaterally left atria or left atrial isomerism ( Fig. 7.15 ) in visceral heterotaxy with polysplenia.

When the atrial septum is displaced even further to the left so that the septum primum lies to the left of all of the pulmonary veins, this creates the appearance generally known as TAPVC to the RA (see Fig. 7.1 ) (see Tables 7.1 to 7.3 ). The atrial septum can be displaced so far to the left that it resembles a supramitral membrane and can result physiologically in significant supramitral stenosis and LV hypoplasia. Surgically, such a markedly malpositioned atrial septum should be excised and replaced with a normally located atrial septum—currently fashioned from glutaraldehyde-fixed pericardium.

Does this mean that the conventional diagnosis of “TAPVC to the RA” is wrong? We now think that the answer is yes. This diagnosis should be modified to TAPVD to the RA. Accurately speaking, ipsilateral pulmonary veins have partially anomalous pulmonary venous drainage (not connection).

Whenever the pulmonary veins connect with the atria, within the “horseshoe” formed by the right and left horns of the sinus venosus (see Fig. 7.4 ), we think that the pulmonary veins are connected normally . However, the pulmonary venous drainage can be partially anomalous (see Fig. 7.15 ) or totally anomalous ( Fig. 7.16 ), depending on how malpositioned the septum primum is. In Figs. 7.1 and 7.15 , note how malpositioned the atrial septum is relative to the ventricular septum (which is normally located). Normally, the atrial septum is approximately parallel with the ventricular septum, not markedly angulated as it is in Figs. 7.1 and 7.15 . Displacement of septum primum into the LA often can be more obvious echocardiographically than it is anatomically.

From the right atrial view, the septum primum is much too easy to see, that is, much better seen from the right atrial perspective than normally is the case (see Fig. 7.16 ). (This intriguing fact was first pointed out to us by Dr. Luis Alday of Cordoba, Argentina.) Why is this so? We think that the answer is because the superior limbic band of the septum secundum, which normally covers the upper part of the septum primum, is poorly developed or absent. This is particularly true in patients with polysplenia and visceral heterotaxy. Rarely, this can also occur in patients with asplenia or with a normally formed spleen and visceral hetertoaxy.

Why can septum primum be displaced into the morphologically LA, resulting in partially or TAPVD? Our hypothesis is as follows: When the superior limbic band of the septum secundum is absent or very poorly formed, the upwardly growing septum primum has no septum secundum to attach to superiorly, and consequently systemic venous blood flow from the IVC and SVC can displace the unattached septum primum into the LA.

This new understanding of the role of malposition of the septum primum has several significant sequelae:

• 1.

  TAPVC and TAPVD are two different things. What was formerly thought to be TAPV C to the RA is now thought to be TAPV D to the RA, with normally pulmonary venous connections and malposition of the septum primum.

• 2.

  Septum primum malposition of the atrial septal defect (ASD) (see Fig. 7.1 ) is a newly recognized anatomic type of ASD that lies between the posterior margin of the malpositioned septum primum and the posterior wall of the LA.

• 3.

  This is a new understanding of TAPVC/D. The supracardiac and infracardiac forms of TAPVC do indeed appear to result from failure of development of the common pulmonary vein, almost always leading to the persistence of early embryonic anastomoses between the pulmonary and the systemic veins, as described earlier.

But what is TAPVC to the coronary sinus? The common pulmonary veins may have developed and connected abnormally with the left sinus horn, because of anomalous development of the common pulmonary vein, abnormal development of the left sinus horn (coronary sinus), or both. Does the common pulmonary vein grow out dorsally from the atrial wall to tap into the pulmonary venous plexus, as Fig. 7.4 suggests? Or does the common pulmonary vein grow in both directions (dorsally from the heart and ventrally from the developing lungs)? Are there species differences? All of these questions have been answered positively. Consequently, we think that definitive resolution of these questions embryologically may well help clarify the morphogenesis of TAPVC to the coronary sinus.

The pulmonary veins in TAPVC to the coronary sinus look like pulmonary veins, suggesting that the common pulmonary vein did not fail to develop. By contrast, the common pulmonary vein does appear to be absent in the supracardiac and infracardiac forms of TAPVC.

TAPVC to the Coronary Sinus

In TAPVC to the coronary sinus, there is no discrete horizontal vein. However, the coronary sinus can function as a horizontal vein from the surgical standpoint, and a large “window” can readily be made between the coronary sinus and the LA (see Figs. 7.10 and 7.17 ). The operative steps are as follows (see Fig. 7.17 ).

The RA is opened horizontally, from the right atrial appendage anteriorly and extending the incision posteriorly, stopping anterior to the sulcus terminalis to avoid injury to the tail of the sinoatrial (SA) node and to the posterior internodal tract or preferential internodal pathway. From the surgeon’s perspective in the operating room, the SVC is to the left, the IVC is to the right, and the right atriotomy incision appears to be in a longitudinal or vertical direction, as opposed to a latitudinal or horizontal direction. This opening incision avoids both the SA node lateral to the entry of the SVC and the sulcus terminalis and crista terminalis where the posterior internodal tract or preferential pathway runs (see Figs. 7.10 and 7.17A ). The aim of this careful placement of the right atriotomy is to avoid sick sinus syndrome or other atrial arrhythmias postoperatively.

The coronary sinus is relatively huge and has a cornucopia-like shape. A right-angle clamp is inserted into the markedly enlarged coronary sinus (see Figs. 7.17A and 7.17B ). The apposed (conjoined) anterior wall of the coronary sinus and the posterior wall of the LA are then pushed up with the tip of the clamp so that the conjoined wall is displaced and can be seen through the patent foramen ovale (see Fig. 7.17B ).

This tented-up wall is then grasped with toothed forceps and a piece is cut out, leaving an opening of at least 15 mm in diameter (see Fig. 7.17C ). In this manner, a wide and sutureless opening is created between the coronary sinus posteriorly and the LA anteriorly (see Fig. 7.17D ). This opening is made well within the coronary sinus, to the left of the orifice of the coronary sinus, so as not to injure the posterior internodal pathway or preferential tract that courses near the ostium of the coronary sinus (see Fig. 7.10 ).

The ostium of the coronary sinus is then closed with a running horizontal mattress stitch, placing the sutures at least 4 to 5 mm inside the ostium (see Fig. 7.17E ), to avoid injury to the AV node and the internodal preferential conduction pathways (see Fig. 7.10 ). Alternatively, the coronary sinus ostium may be closed using a patch, placed well inside the large coronary sinus, to avoid any distortion of the surgically created coronary sinus septal defect—the “window” between the coronary sinus posteriorly and the LA anteriorly.

The patent foramen ovale is then sutured closed (see Fig 7.17F ), placing the sutures through the left side of the superior limbic band of septum secundum to spare the middle internodal preferential conduction pathway that runs along the right side of the superior limbic band of septum secundum.

Parenthetically, it should be added that whether the internodal tracts shown in Fig. 7.10 actually exist as anatomically discrete internodal tracts or alternatively are preferential internodal conduction pathways (but not anatomically discrete tracts) remains controversial. This is why we have referred to them both as internodal tracts and as internodal preferential conduction pathways . Within either interpretation, these internodal regions are thought to be electrophysiologically important and hence should not be inadvertently damaged surgically.

The foregoing operation for the correction of TAPVC to the coronary sinus ( Fig. 7.17 ) is now known as the Van Praagh procedure. This operation was “born” in the Cardiac Registry of Children’s Hospital Boston. The surgeon had attempted to redirect the coronary sinus blood flow through a surgically enlarged patent foramen ovale using a large U-shaped conduit between the coronary sinus ostium below and enlarged patent foramen ovale above. Autopsy revealed that the large U -shaped conduit had obstructed the IVC blood stream almost totally, leading to the death of the patient. The operation described previously was designed (1) to avoid vena caval obstruction, (2) to avoid pulmonary venous obstruction, and (3) to avoid interruption of the preferential internodal electrophysiologyic pathways between the SA and AV nodes.

On March 17, 1971, Dr. Robert E. Gross, the legendary pioneer of congenital heart surgery who first ligated a PDA in Lorraine Sweeney on August 26, 1938, sent me the following note ( Fig. 7.18 ):

Dr. Van Praagh. Richard! Hail! Your operation is simply superb. It went just like fine clockwork. There was no difficulty making the window between the coronary sinus and the left auricle. There is another aspect to this—it greatly increases the volume of the left auricle. And the coronary sinus was so huge there was no trouble at all moving around inside of it and closing it off. There is no A-V block. Many thanks. REG

Mixed Type of TAPVC

In the mixed type of TAPVC, occasionally there is no horizontal vein for the surgeon to suture to the LA. In the study by Delisle et al, this situation was found in only 1 of 5 cases of mixed TAPVC (20%): the left lung drained via a snowman connection, and the right lung drained into the coronary sinus.

Agenesis of the right lung with anomalous pulmonary venous connection of the left lung merits mention. There were two such patients in the study by Delisle et al : a snowman connection in one, and a coronary sinus connection in the other. However, the reason that this situation is noteworthy is that it can mimic a vascular ring . Agenesis of the right lung resulted in extrinsic dextrocardia. Because the heart was abnormally right sided, the normal left aortic arch compressed the tracheobronchial tree anteriorly and superiorly. To make matters worse, the large LPA was posterior to the left bronchus. (Normally, the LPA is anterior to the left bronchus.) Hence, the large LPA compressed the left bronchus posteriorly and inferiorly. The ligamentum arteriosum, and in one case an aberrant right subclavian artery, facilitated the external tracheobronchial compression.

From the surgical standpoint, in addition to correction of the anomalous pulmonary venous connection, steps to relieve the vascular tracheobronchial compression also may well be necessary, such as:

• 1.

  division of the ligamentum arteriosum, and

• 2.

  division of an aberrant right subclavian artery, if present, and aortopexy—attaching the aorta anteriorly in a subcostal or substernal location to reduce or eliminate the anteroposterior tracheobronchial compression.

Thus, with agenesis of the right lung, tracheobronchial compression appeared to be as important as the TAPVC, suggesting that both problems should be managed surgically.

With the exception of the aforementioned new morphogenetic understanding (three different mechanisms), the foregoing is essentially what we knew before undertaking the present study for this book. That which follows is what we have learned very recently by reviewing all of our data.

Conclusions

TAPVC to the LIV (snowman type) was common in visceroatrial situs solitus (38; see Table 7.7 ), but rare in heterotaxy with asplenia (1.7%; see Table 7.8 ), and was not observed in small series of heterotaxy with polysplenia (see Table 7.9 ), heterotaxy with normally formed spleen (see Table 7.10 ) or in visceroatrial situs inversus (see Table 7.11 ).

By contrast, the prevalence of TAPVC to the ductus venosus was approximately the same in visceroatrial situs solitus (25.4%; see Table 7.7 ) and visceral heterotaxy with asplenia (27.6%; see Table 7.8 ). TAPVC to the ductus venosus was not observed in heterotaxy with polysplenia (see Table 7.9 ) or in heterotaxy with a normally formed spleen (see Table 7.10 ), but did occur in visceroatrial situs inversus (25%; see Table 7.11 ).

The data suggest that TAPVC to the ductus venosus is approximately equally as frequent in solitus and nonsolitus visceroatrial situs.

TAPVC to the coronary sinus occurred only in visceroatrial situs solitus (19%; see Table 7.7 ) but not in visceral heterotaxy (see Tables 7.8 to 7.10 ) and not in situs inversus (see Table 7.11 ) ( p < .0001).

TAPVC to the coronary sinus occurred only in visceroatrial situs solitus.

The mixed type of TAPVC occurred both in visceroatrial situs solitus (10.3%; see Table 7.7 ) and in heterotaxy with asplenia (5.2%; see Table 7.8 ) and polysplenia (12.5%; see Table 7.9 ), but not in visceroatrial situs inversus (see Table 7.11 ) ( p = NS, i.e., 0.25).

The prevalence of the mixed type of TAPVC in visceroatrial situs solitus and in visceroatrial situs nonsolitus (heterotaxy and situs inversus) was not significantly different.

TAPVC to SVC occurred in visceroatrial situs solitus (9.5%; see Table 7.7 ) but was much more common in heterotaxy with asplenia (53.5%; see Table 7.8 ), heterotaxy with polysplenia (25%; see Table 7.9 ), heterotaxy with a normally formed spleen (50%; see Table 7.10 ), and visceroatrial situs inversus (50%; see Table 7.11 ). Indeed, TAPVC to SVC (right or left) was by far the most common type of TAPVC in visceral heterotaxy (34/68, i.e., 50%; see Tables 7.8 through 7.10 ). These differences in the prevalence of TAPVC to SVC in visceroatrial situs solitus and in visceroatrial situs nonsolitus are very highly statistically significant ( p < .0001, x ² = 38.62).

TAPVC to the SVC is common in visceral heterotaxy and in situs inversus (see Tables 7.8 to 7.11 ) but is much less frequent in visceroatrial situs solitus (see Table 7.7 ).

TAPVC/D to the RA is infrequent in visceroatrial situs solitus (4%; see Table 7.7 ), but is more common in visceral heterotaxy with asplenia (10%; see Table 7.8 ), in heterotaxy with polysplenia (62.5%; see Table 7.9 ), in heterotaxy with a normally formed spleen (50%; see Table 7.10 ), and in visceroatrial situs inversus (25%; see Table 7.11 ). In our earlier study of 93 postmortem cases with Dr. Georges Delisle et al in 1976, we never found TAPVC/D to the RA in the isolated form with visceroatrial situs solitus (see Table 7.3 ). Consequently, we concluded that TAPVC/D to the RA is characteristic of the nonisolated form, typically with visceral heterotaxy and asplenia or polysplenia.

The present larger study of 198 (of a total of 204) autopsied cases of TAPVC/D shows that it is indeed possible to have TAPVC to the RA in visceroatrial situs solitus, that is, without visceral heterotaxy or situs inversus (3.97%; see Table 7.7 ). Nonetheless, the prevalence of TAPVC/D to the RA in visceroatrial situs nonsolitus (13/72, i.e., 18.05%) (see Tables 7.8 to 7.11 ) remains a statistically highly significant difference ( p < .001, x ² = 10.98) compared with the findings in visceroatrial situs solitus (see Table 7.7 ).

TAPVC/D to the RA is significantly more frequent in visceral heterotaxy (with asplenia, or polysplenia, or with a normal spleen) and in visceroatrial situs inversus than in visceroatrial situs solitus.

To summarize, TAPVC/D more frequently found in visceroatrial situs solitus includes:

• 1.

  TAPVC to the LIV (snowman type) ( p < .0001) and

• 2.

  TAPVC to the coronary sinus ( p < .0001).

TAPVC/D more frequently found in visceral heterotaxy and in situs inversus includes:

• 1.

  TAPVC to a SVC ( p < .0001) and

• 2.

  TAPVC/D to the RA ( p < .001).

TAPVC/D with prevalences that were not significantly different in visceroatrial situs solitus and nonsolitus (heterotaxy with asplenia, heterotaxy with polysplenia, heterotaxy with normal spleen, and visceroatrial situs inversus) include:

• 1.

  mixed TAPVC/D ( p = .25, i.e., NS) and

• 2.

  TAPVC to the ductus venosus ( p = .78, i.e., NS).

In Visceroatrial Situs Solitus (n = 126)

• 1.

  TAPVC to the LIV (snowman type). Obstruction was present in 9 of 38 cases (23.7%). Agenesis of the right lung was observed in 1 patient, and agenesis of the left lung in another case.

• 2.

  TAPVC to the ductus venosus. Atresia of the anomalous pulmonary venous pathway was present in 3 of 32 patients (9.4%). A conjoined twin was present in 3 other cases (9.4%), and multiple congenital anomalies (MCAs) were found in 2 patients (6.25%).

• 3.

  TAPVC to the coronary sinus. Obstruction of the anomalous pulmonary venous pathway was observed in 1 patient (A76-008), who had agenesis of the LPVs. Where the right pulmonary veins (RPVs) joined the coronary sinus, the junction was obstructive. This patient also had DORV {S,D,D}, with the DiGeorge syndrome and MCAs. This case proves that it is indeed possible to have TAPVC to the coronary sinus with congenital obstruction (stenosis or atresia), unrelated to prior surgery. Prior to this patient, we had thought (erroneously) that congenital obstruction did not occur with TAPVC to the coronary sinus.

• 4.

  Mixed TAPVC. MCAs were present in 2 of these 13 patients (15.4%).

• 5.

  TAPVC to the RSVC. Obstruction was present in 3 of these 11 patients (27.3%). MCAs were found in 2 other patients (18.2%).

• 6.

  TAPVD to the RA. Of these 5 patients, 2 (40%) had MCAs, 1 of which had the Ellis-van Creveld syndrome.

• 7.

  TAPVC to the azygos vein. Both of these patients had severe stenosis of the anomalous pulmonary venous pathway (100%).

In Visceral Heterotaxy With Asplenia (n = 58)

• 1.

  TAPVC to the RSVC. Obstruction was present in 6 of these 20 patients (30%).

• 2.

  TAPVC to the LSVC. Obstruction was present in 4 of these 11 patients (36.4%).

In these 31 cases with TAPVC to a right or left SVC, obstruction was present in a total of 10 patients (32.3%).

• 3.

  TAPVC to the ductus venosus. Although some degree of obstruction may well have been present in all 16 cases (100%), it was particularly marked in 2 (12.5%).

Situs Solitus of the Viscera and Atria (Present in 122 of 198 Cases of TAPVC/D [61.6%])

• 1.

  Normal systemic veins were present in 97 of 122 patients (79.5%). Abnormalities of the systemic veins were found in 25 cases (20.5%).

• 2.

  Persistent LSVC to the coronary sinus to the RA was present in 18 of 122 patients (14.75%). Although an abnormality, this anomaly led to no physiologic derangement because all of the systemic venous blood did indeed return to the morphologically RA.

• 3.

  Interruption of the IVC was found in 2 of these 122 patients with visceroatrial situs solitus (1.6%). The interrupted IVC was right-sided in 1 patient and left-sided in the other.

• 4.

  Bilateral SVC with unroofing of the coronary sinus was present in 1 patient (0.8%). Because of the large coronary sinus septal defect (unroofing of the coronary sinus), the blood of the left SVC drained into the LA.

• 5.

  Bilateral SVC with hypoplasia of the right SVC was found in 1 patient (0.8%). Bilateral SVC was observed in 2 of 122 patients with situs solitus of the viscera and atria (1.6%).

• 6.

  Left SVC to LA, absence of an identifiable coronary sinus, and atresia of the right SVC were present in 1 patient (0.8%). Unroofing of the coronary sinus explains why the left SVC drained into the LA and why a discrete coronary sinus was not found.

• 7.

  Absence of the coronary sinus was observed in 1 patient (0.8%) with visceroatrial situs solitus and TAPVC/D.

• 8.

  Absence of the ductus venosus was noted in 1 patient (0.8%).

• 9.

  A small arteriovenous fistula between the descending aorta and the IVC was present in 1 patient (0.8%).

Systemic Veins in Visceroatrial Heterotaxy With Asplenia

Of the 198 patients with TAPVC in which the data were suitable for analysis, visceral heterotaxy with asplenia was present in 59 cases (29.8%). The complexity of the systemic venous anatomy is so great that it almost defies brief summary. Of these 59 cases with heterotaxy and asplenia, 1 patient was excluded because the systemic veins were not well described. Hence, the following is an analysis of 58 patients with TAPVC, heterotaxy, and asplenia.

In how many of these 58 cases of the asplenia syndrome did we think we could identify the anatomic type of atrial situs? The answer is in 46 of 58 patients (79.3%). We were not able to diagnose the atrial situs with confidence in 12 of 58 cases (20.7%).

The key to the understanding of the systemic veins in these patients is to diagnose, when possible, the basic anatomic type of visceroatrial situs that is present, despite the coexistence of visceral heterotaxy (anomalies of lateralization or asymmetry). The anatomic pattern of the systemic veins is linked to the visceroatrial situs and indeed is an expression of the visceroatrial situs.

What is (are) the basic type (s) of visceroatrial situs in the heterotaxy syndrome with asplenia? This is one of the mysteries of contemporary pediatric cardiology. Let us see what these cases suggest:

The atrial situs was diagnosed in 46 patients:

• 1.

  basically situs solitus of the atria, that is, {A(S,-,-}, in 26 of 46 cases (56.52%); and

• 2.

  basically situs inversus of the atria, that is, {A(I),-,-}, in 20 of 46 patients (43.48%).

• This ratio of the proportions of atrial situs solitus to atrial situs inversus suggests an almost random distribution:

Now let us look at the 12 cases in which the atrial situs was not diagnosed but was recorded as situs ambiguus, not otherwise qualified, that is, {A,-,-}. The sidedness of the IVC was recorded in 9 patients:

• 1.

  left-sided IVC6

• 2.

  right-sided IVC3

If one accepts that the sidedness of the IVC strongly suggests the basic type of visceroatrial situs that is present (right-sided IVC = probable situs solitus, and left-sided IVC = probable situs inversus), the findings become:

Hence, the ratio of the proportions of situs solitus/situs inversus in this sample of the asplenia syndrome becomes 1 · 115, that is., quite close to 1:1, a randomized distribution of atrial situs. Thus, these findings suggest that in visceroatrial heterotaxy with asplenia, the basic types of situs are approximately 1 to 1, or 50/50 (in percentages), that is, essentially randomized.

If the aforementioned data are representative and the inferences are valid, this means that visceroatrial situs ambiguus with asplenia is much less ambiguous than it used to be just a few years ago. However, it is also noteworthy that there are some cases of the asplenia syndrome in which we were not able to diagnose the basic type of atrial situs with confidence, that is, {A,-,-} = 12/58 (20.7%).

The systemic venous anomalies found within each group, that is, {A(S),-,-}, {A(I),-,-}, and {A,-,-} are summarized in Tables 7.12, 7.13, and 7.14 , respectively.

Systemic Veins in Visceroatrial Heterotaxy With Polysplenia

In 198 well-documented cases of TAPVC, 9 had visceral heterotaxy with polysplenia (4.5%). The atrial situs was solitus, that is, {A(S),-,-}, in 6 patients (66.7%) and was inversus, or {A(I),-,-}, in 3 cases (33.3%). Although atrial situs solitus was more predominant in polysplenia (66.7%) than in asplenia (56.5%), this difference was not statistically significant ( p = .25, NS, Fisher’s exact test).

Thus, in this sample of visceral heterotaxy, patients with asplenia and patients with polysplenia both had atrial situs solitus and atrial situs inversus. The status of the spleen (asplenia versus polysplenia) cannot be used to infer the type of atrial situs present.

It is noteworthy that in this small series of patients with polysplenia, the atrial situs was always diagnosed with confidence. This is a characteristic difference between polysplenia (atrial situs can be diagnosed with confidence always, or almost always) and asplenia (atrial situs may not be diagnosed with confidence in ≈ 20% of cases). It also should be understood that because the concept of atrial isomerism is erroneous, it is therefore possible to diagnose the atrial situs of polysplenia patients almost always and to diagnose the atrial situs of asplenic patients usually (≈ 80%).

The salient associated systemic venous anomalies in the 6 patients with TAPVC, heterotaxy with polysplenia, and atrial situs solitus were as follows:

• 1.

  LSVC to coronary sinus, to RA, 4 of 6 (66.7%);

• 2.

  interruption of the IVC, 2 of 6 (33.3%); and

• 3.

  bilateral superior venae cava, 1 of 6 (16.7%).

One of these patients with polysplenia and visceroatrial situs solitus did not have heterotaxy. Polysplenia without visceroatrial heterotaxy is noteworthy and rare.

The salient associated systemic venous anomalies in the 3 patients with TAPVC, heterotaxy with polysplenia, and atrial situs inversus were as follows:

• 1.

  interruption of the IVC in all 3 (100%),

• 2.

  RSVC to coronary sinus to left-sided RA in 2 (66.7%),

• 3.

  bilateral SVC in 1 (33.3%), and

• 4.

  hepatic veins draining into the morphologically LA in 1 patient (33.3%).

Interruption of the IVC with an enlarged azygos vein to a SVC was observed in 5 of these 9 polysplenic patients (56%).

Systemic Veins in Visceral Situs Inversus

In 198 well-documented cases of TAPVC, situs inversus of the viscera was present in 6 patients (3.03%). The salient visceroatrial findings were the following:

• 1.

  The atrial situs was inversus in 5 of 6 patients (83%), just as one would expect.

• 2.

  In 1 patient, a 3-day-old boy, the IVC was left-sided, as expected, but it switched from left to right at the level of the liver to connect with a right-sided morphologically RA. In other words, there was visceroatrial situs discordance of the {I(S),-,-} type. The segmental anatomy was DORV {I(S),D,D}. The patient had a RSVC, with nonobstructive TAPVC to the RSVC, bilaterally trilobed lungs, a normally formed right-sided spleen, common gastrointestinal mesentery, common atrium, common AV valve opening into a single morphologically RV, absent morphologically LV, bilateral conus, pulmonary outflow tract atresia, absent left anterior descending coronary artery, left aortic arch (abnormal for visceral situs inversus), and a PDA (3 mm). This case is recorded in detail because of its rarity.

• 3.

  A persistent RSVC, resulting in bilateral SVCs, was found in 2 patients (33.3%).

• 4.

  Congenital complete heart block was observed in 1 patient (16.7%).

Systemic Veins in Visceral Heterotaxy With a Normally Formed Spleen

Of 198 well-documented cases of TAPVC, 2 (1.01%) had visceral heterotaxy with a normally formed spleen. The salient features of these 2 rare cases were as follows.

One was a 6-month-old girl with dextrocardia. The segmental anatomy was {A(I),D,I}, i.e., isolated ventricular noninversion. The IVC was right-sided, but it switched from right to left at the level of the liver and connected with the left-sided morphologically RA. The stomach and normally formed spleen were left sided. The SVC was left-sided and the coronary sinus was absent. There was TAPVC to the left-sided morphologically RA. The lobation of the lungs was solitus. A common atrium was present in association with completely common AV canal, type A of Rastelli. A single LV was present due to absence of the right ventricular sinus. Common-inlet LV was present. From the infundibular outlet chamber an atretic pulmonary artery originated. The aortic arch was right-sided, but the descending thoracic aorta was left-sided. A left-sided PDA connected the LPA and the left innominate artery (left PDA being inappropriate for situs inversus).

The other patient was a 7 4/12–year-old boy with dextrocardia and DORV {A(I),D,D}. The right-sided IVC switched from right to left at the liver and connected with the left-sided morphologically RA. The stomach and normally formed spleen were left-sided (echocardiographic observations, the autopsy being limited to heart and lungs). The coronary sinus was absent and there were bilateral SVCs. There was TAPVC to the junction of the LSVC with the left-sided morphologically RA, without obstruction. The right lung had 4 lobes and the left lung had 3. There was a partially common AV canal with an ostium primum type of ASD. The tricuspid component of the common AV valve was large and regurgitant. The mitral component of the common AV valve was adherent to the crest of the ventricular septum and was atretic. There was no VSD. The patient had a functionally single morphologically RV. The morphologically LV was minute, with neither inlet nor outlet. There was a subaortic conus, pulmonary atresia, and a left aortic arch.

Thus, visceral heterotaxy rarely does occur with a normally formed spleen, as these two cases of complex congenital heart disease illustrate.

Left-Sided Scimitar Syndrome

Our findings in what may be called the left-sided scimitar syndrome involved a 3-day-old female infant and may be summarized as follows. A scimitar vein draining all of the left pulmonary venous blood passed through the diaphragm and into a hepatic venous confluence on the superior surface of the liver. From there, the anomalous left pulmonary venous pathway traveled rightward and joined the suprahepatic segment of the IVC via a stenotic orifice that was 3 mm in diameter. A single RPV connected with the LA. Numerous small pulmonary venous collaterals bilaterally connected with the intercostals veins.

Two relatively large systemic arteries from the abdominal aorta above the celiac axis penetrated the diaphragm and supplied the lower portions of the left lung and the right lung. Other smaller systemic collateral arteries from the descending thoracic aorta supplied the lungs bilaterally; that is, major aortopulmonary collateral arteries (MAPCAs) were present both from above and below the diaphragm.

The RPA and LPA branches were strikingly hypoplastic and serpentine, we thought because of the major systemic arterial collateral blood supply to both lungs.

The IVC was interrupted, with absence of its renal-to-hepatic venous segment. An enlarged right-sided azygos vein connected with the RSVC. The spleen was normally located and normally formed.

We reported this rare case in 1979 because it represented a most unusual basis for persistence of the fetal pattern of the circulation. At autopsy, the PDA was small and appeared to be closing.

What Really Is the Scimitar Syndrome?

As Table 7.16 shows, the scimitar syndrome typically is an anomaly of the right lung that almost always has a scimitar vein draining into the IVC (in 11 of 12 patients, 92%; see Table 7.16 ). The one exception had an anomalous RPV draining into the RA. In this case, the hypoplastic right lung received four moderately large systemic arteries from the celiac axis below the diaphragm that supplied 60% to 70% of the arterial blood supply of the hypoplastic right lung. Dextrocardia was present, secondary to the right pulmonary hypoplasia. The normally related great arteries produced severe tracheal compression anteriorly (treated with aortopexy), again secondary to the right pulmonary hypoplasia and the secondary dextrocardia. In view of all of the previously mentioned findings, we thought that this case should be regarded as a closely related variant of the scimitar syndrome, even though the signature finding—the scimitar vein—was not present in this rare case.

Thus, the main point is that the scimitar syndrome really is an anomaly typically of the right lung, with characteristic malformations of the systemic veins, and often with anomalous systemic arterial blood supply (in 58% of these cases; see Table 7.16 ).

The next point is that both lungs can be abnormal, as in 33% of our cases of right-sided scimitar syndrome (see Table 7.16 ) and as in our patient with left-sided scimitar syndrome.

Rarely is it possible to have a scimitar vein with a normal ipsilateral lung. Our case had a left-sided scimitar vein that ran behind the LA and then passed through the diaphragm and connected with the suprahepatic segment of the right-sided IVC. This patient (whom we are currently in the process of reporting) had elective surgical closure of a secundum ASD at 10 years of age. At 22 years of age, she had side-to-side anastomosis of the left pulmonary venous confluence with the LA, with ligation and division of the left-sided scimitar vein to the right of the anastomosis. Six years postoperatively, cardiac magnetic resonance imaging (MRI) showed that the anastomosis was widely patent. Ten years postoperatively, the patient remains asymptomatic. (This is a living and currently unpublished patient.)

Pulmonary pathologists regard typical scimitar syndrome as a special form of intralobar sequestration . We made the diagnosis of sequestration of the right lung—meaning that the right lung did not communicate normally with the right bronchus (hence the right lung was sequestered or separated from its bronchus)—in only 1 case (8%).

Familial congenital anomalies were noted in 1 of these patients (8%) and consanguinity (first cousin marriage) was recorded in 1 case (8%).

Although one usually thinks of the scimitar syndrome as occurring in isolation, it is noteworthy that other forms of congenital heart disease frequently coexisted (see Table 7.16 ): secundum type of ASD in 5 patients (42%); persistent LSVC to the coronary sinus in 4 (33%); preductal coarctation of the aorta in 3 (25%); muscular VSD in 3 (25%); conoventricular type of VSD in 2 (17%); mitral atresia in 2 (17%); polysplenia in 2 (17%), without visceral heterotaxy in 1 (8%); and truncus arteriosus, aberrant left coronary artery, right aortic arch Wolff-Parkiknson-White syndrome, and absent RPA in 1 case each (8%).

Perhaps even more impressive, MCAs, that is, malformations involving not only the cardiovascular system but also one or more additional systems, were present in more than half of these patients with the scimitar syndrome (58%; see Table 7.16 ).

RUPV to RSVC

The right upper pulmonary vein (RUPV) draining anomalously into the RSVC was the second most common form of PAPVC that was encountered in the present series: 12 of 45 patients (27%; see Table 7.15 ).

In RUPV to RSVC (see Fig. 7.19 ), only one pulmonary vein drains anomalously. Consequently, RUPV to RSVC is a less severe form of PAPVC than is the scimitar syndrome, in which typically all RPVs drain anomalously.

Other differences from the scimitar syndrome are as follows: RUPV to RSVC typically is not associated with an abnormal right lung, right pulmonary hypoplasia, secondary dextrocardia, or anomalous systemic arterial blood supply.

What, then, is typical of RUPV to RSVC? It often is not the main diagnosis and consequently may be overlooked diagnostically and surgically. Prominent “main” diagnoses associated with RUPV to RSVC are presented in Table 7.17 .

Thus, RULPV to RSVC was overshadowed by other more important diagnoses in 7 of these 11 cases (64%; see Table 7.17 ).

In addition to these seven major forms of congenital heart disease (see Table 7.17 ), other cardiovascular anomalies also coexisted with RULPV to RSVC ( Table 7.18 ).

These 11 patients with RUPV to RSVC were associated with additional interesting data:

• 1.

  Abnormal lobation of the lungs was present in 3 cases (27%). In 1 case, both lungs had abnormal lobation. These findings indicate that RULPV to RSVC can be associated with abnormal lungs.

• 2.

  One of these patients was an identical twin; the co-twin was normal.

• 3.

  Familial congenital heart disease was present in 2 patients (18%). One had a brother with VSD and mild pulmonary stenosis. The other had a brother with tetralogy of Fallot (TOF) and pulmonary atresia.

What is the anatomic difference between RULPV to the RSVC, and sinus venosus defect of the SVC type? In RULPV to RSVC, the RULPV is anomalously connected to the RSVC typically at approximately the level of the azygos vein, and there is usually no interatrial communication. Indeed, an interatrial communication typically must be created by the surgeon to permit the RUPV blood to reach the LA.

By contrast, in sinus venosus defect of the SVC type, the right upper and often the right middle lobe pulmonary veins open somewhat lower into the RSVC, and there is a characteristic interatrial communication. This interatrial communication is the orifice of the RPVs into the LA. From the right atrial aspect, this interatrial communication is located above and behind the foramen ovale (or fossa ovalis, when the foramen ovale is sealed). From the left atrial aspect, this interatrial communication is just behind and somewhat above the septum primum. In sinus venosus defect, the pulmonary veins are thought to be normally connected with the LA. But the right upper and right middle pulmonary veins drain anomalously into the RSVC because of absence of the partition that normally separates the RPVs posteriorly from the RSVC anteriorly. In other words, the RPVs are “unroofed” into the RSVC because of absence of the partition that normally separates them.

Thus, RUPV to RSVC is characterized by anomalous pulmonary venous connection and drainage, whereas a sinus venosus defect has anomalous pulmonary venous drainage with normal pulmonary venous connection .

Diagnostically and surgically, these differences are of critical importance. Generations of pediatric and adult cardiologists and cardiac surgeons have been erroneously taught that the interatrial communication is the sinus venosus ASD. In fact, this interatrial communication is the normal opening of the RPVs into the LA. The partition that the surgeon creates to baffle the right pulmonary venous blood through the interatrial communication, which may or may not need enlarging, into the LA repairs the real sinus venosus defect. The surgeon “re-roofs” the unroofed RPVs, thereby repairing the real sinus venosus defect between the RPVs posteriorly and the RSVC (or RA) anteriorly.

To summarize this point concerning differential diagnosis, if there is an interatrial communication posterosuperior to the foramen ovale (or fossa ovalis or septum primum), one is dealing with a sinus venosus unroofing defect of the RPV(s). However, if there is no characteristically located interatrial communication, one is dealing with RUPV to RSVC, which is the persistence of a normal embryonic connection of the right pulmonary venous plexus with the systemic venous system. Why such normal embryonic venous connections persist abnormally into the postnatal period remains unknown.

LUPV to the LVV to the LIV to the RSVC to the RA

This was the third most common anatomic type of PAPVC/drainage, occurring in 6 of these 45 patients (13%; see Table 7.15 ).

An LUPV connected anomalously with a LVV ( Fig. 7.20 ). What is the LVV? Developmentally, it is the left anterior cardinal vein. Then why do we not call the LVV the LSVC? Dr. Jesse Edwards and colleagues thought that this vein should not be called the LSVC because it does not return to the heart the way the LSVC does. In other words, below the connection of the LUPV, this left anterior cardinal vein typically has undergone involution and is consequently either absent or atretic. So this is the understanding that lies behind the designation LVV.

The left innominate vein is a strange name, if one thinks about it. Innominate of course mean “nameless,” or “no name.” (If we can have a No-Name Restaurant, why not a no-name vein or artery?) The other name for the LIV is the left brachiocephalic vein.

The LULPV blood returns to the heart via the snowman pathway. Why is the LIV to the LIV to the RSVC to the RA called the snowman pathway ? This term was coined for the typical form of supracardiac TAPVC. As mentioned previously, by about 4 months of age, this supracardiac anomalous pulmonary venous pathway becomes visible on the plain posteroanterior chest x-ray film. Then, with a little imagination, the cardiovascular shadow resembles a snowman, the heart shadow forming the body and the supracardiac venous shadow forming the head of the snowman.

The salient anatomic findings associated with LUPV to LVV to LIV to RSVC to RA are summarized in Table 7.19 . Table 7.19 should be self-explanatory, with perhaps several exceptions.

What is TGA {S,D,L}? Just as the segmental anatomy suggests, there is AV concordance {S,D,-} and VA discordance—this being the definition of TGA. But the interesting and unusual feature is that the aortic valve is anterior and to the left relative to the pulmonary valve, that is, TGA {S,D, L } ( Fig. 7.21 )

The question is why is the transposed aortic valve to the left of the transposed pulmonary valve? The answer appears to be because the bulboventricular loop is malpositioned—not just the conus, but also the ventricles.

TGA {S,D,L} is a recently recognized distinctive form of complete or physiologically uncorrected TGA that is characterized by six additional interrelated anomalies : (1) VSD, usually conoventricular, in 96%; (2) malalignment of the conal septum, typically leftward and posteriorly, in 80%; (3) right ventricular hypoplasia, in 50%; (4) pulmonary outflow tract stenosis, in 27%; (5) ventricular malposition, such as superoinferior ventricles, in 23%; and (6) absent left coronary ostium resulting in “single” right coronary artery, in 23%. Each of these six interrelated anomalies was associated significantly more frequently with TGA {S,D,L} than with the classic form of TGA {S,D,D} ( p < .01 to < .02). These characteristics associated malformations largely determined the surgical management of patients with TGA {S,D,L}.

Mixed PAPVC was encountered in 2 of these patients (see Table 7.19 ). In addition to the LULPV to LVV to LIV to RSVC to RA pathway (the “snowman” pathway), 1 patient also had an anomalous RPV to the RSVC. Another patient also had a diminutive vein from the LVV to the coronary sinus.

Before reviewing these cases (see Table 7.19 ), we thought that the mixed type of anomalous pulmonary venous connection applied only to TAPVC. But these cases indicate that it is indeed possible for PAPVCs to be multiple and to occur at different sites.

The second case, mentioned previously, also very strongly suggests that the LVV in this anatomic type of PAPVC is indeed the LSVC, because the LVV connects with the coronary sinus (via a diminutive vein), just as a persistent LSVC does.

You will note that there were 2 cases of mitral atresia (33%; see Table 7.19 ). But 1 of these patients had left atrial outlet atresia, not really mitral atresia (see Table 7.19 ).

What is left atrial outlet atresia with a large morphologically LV and a small morphologically right ventricular sinus? We think that this rare entity is different from typical mitral atresia that has a diminutive LV. In this case of left atrial outlet atresia (that resembles mitral atresia), the LA is located above the LV free wall; consequently the left atrial outlet is blind. Pulmonary venous blood passed from LA to the RA (atrial septum was found to be surgically excised at autopsy). The RA opened into the large LV via an AV valve that was mitral in morphology. (This is why we think that mitral atresia really is not present.) The right ventricular sinus was small (not absent) and received no entering AV valve or tensor apparatus. This patient, a 4-month-old boy, also had TGA {S,D,L}, stenosis of the left atrial ostium of the common pulmonary vein, and diffuse hypoplasia of all pulmonary veins, without evidence of acquired pathological conditions. This patient also had mixed PAPVC: LUPV to LVV, and a diminutive vein from the LVV to the coronary sinus with an obstructive right atrial ostium of the coronary sinus.

So, what is left atrial outlet atresia with a large LV? Based on the previously mentioned anatomic description, we think that from the developmental standpoint, this entity represents rightward malalignment of a very abnormal bulboventricular loop relative to the atria. The result of rightward ventricular malalignment relative to the atria is that the outlet of the LA is blind because it is located above the left ventricular free wall. The AV valve opening from the RA into the LV is of mitral morphology; hence, our disinclination to make the conventional diagnosis of mitral atresia in this situation (with a large LV and an AV valve of mitral morphology). Why the bulboventricular loop is malaligned to the right relative to the atria remains unknown.

This entity was first reported, to our knowledge, by Quero. In his case, the right ventricular sinus was absent, resulting in the arresting combination of “mitral atresia” with single LV, infundibular outlet chamber, and TGA, that is, TGA {S,D,D}. Quero wanted to convince the medical world (and he certainly did) that single ventricle could indeed coexist with AV valve atresia. Single or common ventricle used to be defined as follows : both AV valves or a common AV valve opens entirely or predominantly into one ventricle ( Fig. 7.22 ) This old premorphologic definition of single ventricle tacitly excludes AV valve atresia. Quero’s point was that this old definition of single ventricle is unsatisfactory in this respect (see Figure 7.22 )

We agree with Quero about this. Even if mitral atresia is not really present in this entity (as earlier), we now know that single ventricle should be diagnosed in terms of its ventricular myocardial morphology, not in terms of the AV valves. For example, Quero’s patient had single RV (because the RV sinus was absent), whereas our patient did not (because the RV sinus was merely hypoplastic). Both Quero’s case and the present patient had “mitral atresia” or left atrial outlet atresia. The latter diagnosis we think is more accurate, as suggested earlier. This entity is merely one example of the importance of ventriculoatrial malalignment.

Sinus Venosus Defect, Right Atrial Type

This was the fourth most frequent type of PAPVD, occurring in 4 of these 45 cases (9%) (see Table 7.15 ). As was indicated in Chapter 6 concerning systemic venous anomalies, sinus venosus defect is absence of the partition that normally separates the RPV posteriorly from the RA anteriorly (see Fig. 7.20 ). Consequently, the RUPV and right lower pulmonary vein (RLPV) drain anomalously into the RA. However, the RPVs are connected normally with the LA, the posterior wall of the RPVs connecting normally with the posterior wall of the morphologically LA, as is also true in the SVC type of sinus venosus defect ( Fig. 7.23 ). The interatrial communication is the ostium of the RPVs, which is located posteriorly and superiorly relative to the foramen ovale and septum primum.

This interatrial communication plus the absence of the intervenous partition between the RPVs posteriorly and the SVC and/or RA anteriorly combine to function like an ASD, typically permitting left-to-right shunting at the atrial level.

Surgical repair of sinus venosus defect involves the prosthetic creation of the missing intervenous partition, thereby closing the sinus venosus defect, with or without enlargement of the right pulmonary venous ostium where it enters the LA (the interatrial communication). The right pulmonary venous ostium into the LA may be smaller than normal apparently because of extensive left-to-right shunting from the RPVs into the RSVC and/or RA.

The foregoing is a relatively new understanding of sinus venosus defect. Previously it was thought that the interatrial communication was the sinus venosus “ASD.” We now understand that this interatrial communication is not an atrial septal defect. Instead, it is a normal opening posterosuperior to the septum primum (see Fig. 7.20B ); that is, it is the normal opening of the RPVs where they connect with, and open into, the LA.

It is the unroofing of the RPVs (the absence of the intervenous partition) that makes this normal right pulmonary venous ostium function like an ASD.

A sinus venosus defect is the right-sided venous unroofing defect. Unroofing of the coronary sinus, including the Raghib syndrome, is the left-sided unroofing defect, that is, absence of the partition between the coronary sinus posteriorly and the LA anteriorly. The characteristic large, low, posterior interatrial communication of the Raghib syndrome again is not an ASD. Instead, it is an interatrial communication, that is, the ostium of the unroofed coronary sinus.

Thus, there are two venous unroofing defects: right-sided (sinus venosus defect) and left-sided (unroofing of the coronary sinus).

Finally, it should be understood that the so-called inferior vena caval type of sinus venosus defect is an error. The real problem here is absence of septum primum. Hence, the interatrial communication is very large and extends very caudally—right down to the IVC—because the septum primum is absent ( Fig. 7.24 ). Thus, the so-called IVC type of sinus venosus defect is really a large ostium secundum type of ASD, due to absence of the septum primum. None of the RPVs are unroofed. The RPVs may well drain anomalously into the RA because of the absence of the septum primum.

Sinus venosus defects of the SVC and/or right atrial type have partially anomalous pulmonary venous drainage of the RPVs into the RA, but with normal pulmonary venous connections of the RPVs with the LA—and hence the characteristic posterosuperior interatrial communication (i.e., the right pulmonary venous ostium into the LA).

Sinus venosus defects are also considered in detail in Chapter 6 concerning systemic venous anomalies, because sinus venosus defects are both systemic venous anomalies ( Chapter 6 ) and pulmonary venous anomalies (this chapter).

The salient anomalies associated with sinus venosus defect of the right atrial type (n = 4) are summarized in Table 7.20 . Sinus venosus defects may be regarded as nonisolated (associated with other clinically significant congenital heart disease) or as isolated (not associated with other clinically significant congenital heart disease).

Thus, sinus venosus defect of the right atrial type usually was nonisolated (75%; see Table 7.20 ).

Sinus Venosus Defect, Superior Vena Caval Type

Of these 45 patients with PAPVC/D, 1 had a sinus venosus defect of the SVC type (2%; see Table 7.15 ). The RUPV was unroofed into the RSVC–right atrial junction ( Fig. 7.25A ). The posterior wall of this RUPV connected normally with the LA and limited the interatrial communication posteriorly (see Fig. 7.25B ). The foramen ovale was probe patent but functionally closed (see Fig. 7.25B ). All of the other pulmonary veins connected normally with the LA (see Fig. 7.25B ). This 10 10/12-year-old girl had a sinus venosus defect of the SVC type that was otherwise isolated (no other clinically significant cardiac or noncardiac anomalies). Note that in the normal LA, the normally located RUPV—the largest of the three ostia adjacent to the septum primum (S1°; see Fig 7.25C )—is in the exact location of the interatrial communication in sinus venous defects (see Figs. 7.20B and 7.25B ).

The total incidence of sinus venosus defect, that is, of the SVC type and of the right atrial type, was 5 of 46 patients (11%; see Table 7.15 ).

Ipsilateral Pulmonary Veins

In this series of 45 patients with PAPVC/D, 2 had ipsilateral pulmonary veins (4%; see Table 7.15 ). Ipsilateral is derived from ipse meaning “self” (Latin), plus lateralis from latus meaning “side” (Latin). Thus, the designation ipsilateral pulmonary veins means that the pulmonary veins drain into the atrium of the same side: right-sided pulmonary veins drain into the right-sided atrium, and left-sided pulmonary veins drain into the left-sided atrium ( Fig. 7.26 ).

Both of these patients had visceral heterotaxy with the polysplenia syndrome. One was a 3-month-old girl with the segmental anatomic set of {A,D,S}, bilateral SVC, interrupted IVC, left-sided azygos vein to the LSVC, and suprahepatic IVC to the right-sided atrium. The morphology of the atrial septum was bizarre: neither septum primum nor septum secundum was clearly recognizable. It looked as though the septum primum and septum secundum were abnormally fused to each other, with both the right-sided and left-sided atrial septal surfaces being curiously featureless or “faceless.” Neither side displayed either a right atrial or a left atrial septal surface morphology. The completely common AV canal type A was present. The coronary sinus was absent. The cardiac veins had multiple openings into the left-sided atrium. Biventricular hypertrophy, widely patent pulmonary and aortic outflow tracts, left aortic arch, and a large PDA (5 mm, internal diameter) were present. Other findings included a symmetrical liver (right lobe slightly larger than the left), right-sided stomach, three right-sided splenuli (4/14 g; i.e., hyposplenia), common gastrointestinal mesentery, appendix in the right lower quadrant, and bilaterally bilobed lungs.

The other patient with ipsilateral pulmonary veins was a 3-day-old boy, also with visceral heterotaxy and the polysplenia syndrome. The segmental anatomy was {A(I,S),L,I}. This segmental situs set is fascinating. There was visceral heterotaxy with situs ambiguus: { A -,-,-}. The abdominal visceral situs was thought to be basically situs inversus: {A ( I ,-,-}. The liver was symmetrical with a left-sided gallbladder. The stomach and the polysplenia were right-sided.

The atrial situs was thought to be solitus: {A (I, S ),-,-}. The right-sided atrium had RA morphology, receiving the suprahepatic segment of the interrupted IVC, the RSVC (that received an enlarged azygos vein), the coronary sinus, and the RPVs. The left-sided atrium was small, had the morphologic appearance of a LA, and received only the LPVs. There was right-sided juxtaposition of the atrial appendages. The atrial septum was intact and malformed, with the septum primum and septum secundum being indistinct. Premature closure of the foramen ovale was present.

L-loop ventricles were present: {A(I,S), L ,-}. The great arteries were inverted and normally related: {A(I,S),L, I }. Hence, there was visceroatrial situs discordance, with abdominal situs inversus and atrial situs solitus. Isolated atrial noninversion was also present; only the atria were not inverted.

Superoinferior ventricles were also noted. The small RV was superior, left-sided and left-handed, whereas the large LV was inferior, right-sided, and right-handed. The lungs were bilaterally trilobed (not bilobed, which is more usual with the polysplenia syndrome).

Comment: Ipsilateral pulmonary veins are where the concept of bilateral left-sidedness or left atrial isomerism comes from. This was part of Dr. Jesse Edwards’ helpful teaching mnemonic that the polysplenia syndrome is characterized by “bilateral left-sidedness.” The ipsilateral pulmonary veins were supposed to suggest that a LA is present bilaterally—because pulmonary veins are reminiscent of the morphologically LA on both the right and the left sides.

Other features of “bilateral left-sidedness” typically found with the polysplenia syndrome include bilaterally bilobed lungs (not present in this case), absence of the gallbladder (not present in this case), and interruption or “absence” of the IVC (present in this case).

As mentioned elsewhere, we think that the concepts of “bilateral right-sidedness” in the asplenia syndrome and “bilateral left-sidedness” in the polysplenia syndrome are helpful memory aids that should not be regarded as accurate anatomy. In the heterotaxy syndromes with asplenia and polysplenia, there is a good deal of crossover or overlap of morphologic features, as the case just presented illustrates.

It is also noteworthy that right-sided juxtaposition of the atrial appendages (i.e., dextromalposition of the left atrial appendage in atrial situs solitus) often is associated with left-sided hypoplasia, as in the latter patient who had hypoplastic left-sided tricuspid valve and RV.

Conversely, left-sided juxtaposition of the atrial appendages (i.e., levomalposition of the right atrial appendage in atrial situs solitus) often is associated with hypoplasia of right-sided structures (AV valves and ventricles). ^,

Ipsilateral pulmonary veins are characteristic of visceral heterotaxy with polysplenia (see Chapter 29 ) and are underrepresented here.

From the developmental standpoint, S. Van Praagh et al presented the hypothesis that whenever pulmonary veins connect at the atrial level, above the coronary sinus and between the SVCs, they are connected normally. We think that malposition of the septum primum accounts for ipsilateral pulmonary veins. In the 2 patients presented earlier, the suprahepatic IVC was right-sided, leading to our diagnostic impression that the atria probably were basically in situs solitus.

In typical cases of the polysplenia syndrome ( Chapter 29 ), the superior limbic band of septum secundum is poorly developed or absent, which is important because the septum primum normally attaches to the left side of the superior limbic band. When the septum secundum is poorly developed or absent, the septum primum has nothing to attach to superiorly. Consequently, the septum primum can get blown into the LA by the IVC blood stream, displacing the septum primum to the left of the RPVs and resulting in ipsilateral pulmonary veins ( Figs. 7.15 and 7.26 ).

If our understanding of ipsilateral pulmonary veins is correct, this is a form of PAPVD (into the morphologically RA) with normal pulmonary venous connections because of malposition of the septum primum into the LA, to the left of the RPVs (in atrial situs solitus). Thus, PAPVC and PAPVD are two different concepts (not synonyms), as ipsilateral pulmonary venous drainage illustrates.