Acknowledgments
I am deeply indebted for the mentorship, comments, and editorial guidance given to me by Drs. Gary Webb and Charles Bullaboy. Furthermore, I am indebted to my wife and children for affording me the time away from them to write this chapter and the support to see it to completion. Lastly, I am grateful to Dr. Harold Litt for providing some of the CT and MR images.
Partial anomalous pulmonary venous connections (PAPVCs) refer to anomalies in which one or more (but not all) of the pulmonary veins connect to a location other than the left atrium. Often, the term denotes one or more pulmonary veins emptying into a systemic vein such as the superior or inferior vena cava (SVC or IVC) or a cardiac chamber such as the right atrium. Physiologically, it produces a left-to-right shunt, similar to an atrial septal defect, allowing already-oxygenated blood to recirculate into the lungs, resulting in excessive pulmonary blood flow. Of note, if all the pulmonary veins from both lungs drain to an anomalous site or in an abnormal fashion, the diagnosis is total anomalous pulmonary venous connection (TAPVC), a condition nearly universally diagnosed in childhood and always requiring surgical intervention. Although the initial diagnosis of TAPVC has been reported in patients older than 18 years, this is very unusual. Thus, for the purposes of this chapter on pulmonary venous anomalies in patients with adult congenital heart disease (ACHD), the discussion will be limited to PAPVC.
Definition and Morphology
When discussing anomalous vessels in this chapter, the term connection always denotes anomalous blood return or flow; however, anomalous drainage or return can occur without an anomalous connection. For example, with atrial septal abnormalities such as a common atrium or malposition of the atrial septum, the patient may have normal “return” of vessels in the sense that the veins return to the morphologic left atrium, but they functionally mix with the systemic venous return or are redirected to the right atrium. Thus, one cannot interchange the terms return or drainage with connection . Anomalous connections will therefore imply abnormal anatomic attachments.
Dr. J. Winslow initially described the lesion we now know as PAPVC in 1739 when he observed a right upper pulmonary vein (RUPV) anomalously draining to the SVC. Over time, it has been appreciated that there are many anatomic variants of pulmonary venous anomalies ( Box 34.1 ) and that the right-sided pulmonary veins are 10 times more common than abnormalities of the left veins. The most common anatomic variants are as follows:
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RUPV (± the right middle lobe pulmonary vein [RMPV]) to the SVC, azygos vein, or right atrium; often associated with a superior-type sinus venosus atrial septal defect (SV-ASD).
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Right pulmonary vein(s) to the IVC (usually via a single trunk draining caudally and connecting to the IVC near the diaphragm; also called the Scimitar syndrome)
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Left pulmonary vein(s) to the innominate vein via a vertical vein.
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Left pulmonary veins to the coronary sinus.
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Right upper and middle lobe pulmonary vein to the SVC or azygos vein
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Right upper and middle lobe pulmonary vein to the right atrium
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Right pulmonary vein(s) to the inferior vena cava
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Right lower pulmonary vein to the IVC with anomalous arterial blood supply to the right lower lobe and lung sequestration (Scimitar syndrome)
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Left upper or all left pulmonary vein(s) to the innominate vein via an anomalous left vertical or levoatriocardinal vein
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Left upper or lower pulmonary vein(s) to the coronary sinus
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Left lower pulmonary vein to the right atrium or inferior vena cava
IVC, Inferior vena cava; SVC, superior vena cava.
The most common associated lesion with PAPVC is an associated atrial septal defect, with up to 80% of pulmonary venous anomalies cooccurring with atrial septal defects (ASDs). Notably, a superior-type SV-ASD most frequently occurs with right-sided PAPVC, especially when the anomalous drainage enters the SVC ( Fig. 34.1 ). With superior-type SV-ASDs, there is a posterior defect in the atrial tissue by the junction of the right atrium and the SVC. Because the RUPV passes directly behind this area, an SV-ASD defect will often involve the RUPV and allow continuity of blood flow not only between the RUPV and the right atrium but also between the left atrium and the right atrium. A recent surgical series estimated that SV-ASDs occur in 87% of right-sided PAPVC cases. Ostium secundum ASDs are also found in association with pulmonary vein anomalies, but with a lower reported incidence of 2% to 10%.
In addition to ASDs, other cardiac lesions may occur in association with anomalies of the pulmonary veins, including conotruncal abnormalities such as tetralogy of Fallot or double-outlet right ventricle, and valvular abnormalities such as pulmonary stenosis, mitral or aortic stenosis/atresia, and aortic arch anomalies.
PAPVC may also occur in patients with the visceral heterotaxy syndrome, especially in association with a secundum ASD (see Chapter 57 ). Heterotaxy syndrome is characterized by various venous abnormalities, and malpositioned organs such as the heart, lungs, stomach, intestines, and liver that may be in nonstandard locations within the chest and abdomen. In the case of heterotaxy and PAPVC, the pulmonary veins lie in their normal position; however, there is leftward deviation of the septum primum and absence of the septum secundum, creating an ASD and physiologically committing the right-sided veins to the right atrium. Here, it is the “return” that is abnormal, not the “connection.” Other associated venous anomalies traditionally associated with heterotaxy syndrome may coexist, such as a persistent left SVC or an interrupted IVC with azygos continuation. In addition, patients may have asplenia (bilateral right sidedness) or polysplenia (bilateral left sidedness), depending on whether there is left- or right-sided isomerism. Regardless of type, these patients are often considered immunocompromised because they lack a functioning spleen, a condition that has immune ramifications even into adulthood (see Chapter 57 ).
Many adults with PAPVC will be diagnosed serendipitously by thoracic imaging carried out for some other indication, whether it be with a computed tomographic angiography (CTA) in an emergency department setting to rule out a pulmonary embolus, or during a cardiac catheterization for coronary intervention, or as part of a postradiofrequency catheter ablation evaluation such as was described by Selby et al. In one recent study the authors took advantage of these scans performed for another purpose and estimated the population prevalence of PAPVC in undiagnosed adults at 0.1%; of those patients, 42% had an associated SV-ASD. These numbers differ somewhat from the aforementioned pediatric data; furthermore, the left upper pulmonary vein (LUPV) was the most commonly anomalous vein in these otherwise-asymptomatic adults, a pattern that also differs from prior pediatric studies.
Scimitar Syndrome
PAPVC of the right lung to the IVC via a common venous trunk is known as the Scimitar syndrome. Rather than connecting to the left atrium, a descending trunk from the right pulmonary veins enters the IVC, creating a radiographic vascular lucency that is crescentic and mimics a Scimitar or a curved Turkish sword from the Ottoman Empire era. The pulmonary veins from various lobes of the right lung may be involved, ranging from only the right lower lobe to the entire right pulmonary venous system. Hypoplasia of the right lung may also occur along with pulmonary sequestration (a cystic lung lesion that does not communicate with the other lung tissue and may have a separate arterial blood source), or pulmonary vascular abnormalities such as additional collateral blood supply to the sequestered segment from the aorta or an arteriovenous malformation. Scimitar syndrome may be seen in some patients (<10%) with a secundum ASD, and in association with many other forms of CHD. This syndrome is more common in females, has been known to be hereditary, and is encountered more frequently in hearts with visceral heterotaxy. See Box 34.2 for additional information.
Scimitar syndrome is a constellation of anomalies including anomalous pulmonary venous connection from part or all of the right lung to the inferior vena cava, often associated with hypoplasia of the right pulmonary artery and the right lung itself. Furthermore, the lower portion of the right lung tends to receive its arterial supply through collateral vessels arising from the abdominal aorta. The name of the syndrome derives from the characteristic rounded venous appearance on a posteroanterior chest radiograph, showing the curvilinear shadow formed by the anomalous pulmonary venous connection with the IVC that resembles a curved Turkish sword, or Scimitar.
Associated lesions are seen in 25% of patients, the most common being atrial and ventricular septal defects, patent ductus arteriosus, coarctation of the aorta, and tetralogy of Fallot.
Presentation
Patients may present with:
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Systolic ejection murmur as a result of shunt flow or associated lesions.
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Coincidental abnormal cardiac shape or position on chest radiograph: heart in mesoposition or dextroposition because of right lung hypoplasia and curvilinear density with Scimitar vein. There may be some degree of right-sided heart dilatation.
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Exertional dyspnea and/or palpitations, depending on the degree of left-to-right shunting and the resultant hemodynamic effect.
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Frequent pulmonary infections with or without hemoptysis because of lung sequestration.
Diagnosis
Although the diagnosis may be evident on the chest radiograph, the following tests should be considered:
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Echocardiography is used to demonstrate fully the intracardiac anatomy, to evaluate for right-sided heart dilatation, and to estimate pulmonary arterial pressures (from tricuspid and pulmonary regurgitation). Aortopulmonary collateral vessels with continuous flow originating from the abdominal aorta may be seen supplying part of the right lung; transesophageal echocardiography may be required to delineate pulmonary venous return.
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Cardiac MRI/MRA are used to delineate the course of the Scimitar vein and the collateral vessels from the abdominal aorta to the right lung. Cardiac MRI can also demonstrate intracardiac anatomy, quantitate the magnitude of left-to-right shunting and right ventricular size, and establish the presence and degree of right pulmonary artery and right lung hypoplasia.
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CTA very clearly defines arterial and venous vascular anatomy, similar to MRI. CTA will not allow for measurement of physiologic parameters, but nicely demonstrates vasculature in relation to bony structures or other thoracic soft tissue structures such as the esophagus or trachea with high spatial resolution; it can be useful in evaluation of associated pulmonary pathology.
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Cardiac catheterization assesses pulmonary vascular resistance, the degree of right pulmonary artery hypoplasia, and the nature and course of right pulmonary venous return (both with selective right pulmonary angiography). Injection of a contrast agent in the abdominal aorta will demonstrate the presence and course of collateral vessels, which may be occluded with a variety of catheter devices as part of a management protocol addressing recurrent lung sequestration.
Management
Management of the adult patient with Scimitar syndrome depends on the following:
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Presence of associated lesions and determining the need for, and the nature of, intervention with respect to them.
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Degree of right-sided heart dilatation resulting from PAPVC. In cases of marked right pulmonary artery and right lung hypoplasia (reflected by loss of right lung volume on the chest radiograph and marked shift of the heart to the right), there is a lesser degree of effective left-to-right shunting and, therefore, few grounds for intervention on this indication alone. In contrast, patients with minimal right lung hypoplasia and total right pulmonary venous connection to the right atrium (via a Scimitar vein and the inferior caval vein) are likely to benefit from surgical repair, as discussed for patients with PAPVC.
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Presence and frequency of pulmonary complications: Patients with severe sequestration of the lung and recurrent pulmonary infections should be considered for resection of the sequestrated lung and ligation or catheter occlusion of the anomalous arterial blood supply to respective lung segment(s).
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Surgical approaches to repair of Scimitar syndrome are varied. One approach consists of direct anastomosis of the Scimitar vein into the left atrium. This series reports patent anastomoses and no deaths or reoperations in the short and midterm. Another approach has recently been proposed using a Gore-Tex graft rather than direct venoatrial anastomosis as a means of reducing the risk of kinking or stenosis.
CTA , Computed tomographic angiography; IVC , inferior vena cava; MRA , magnetic resonance angiography; MRI , magnetic resonance imaging; PAPVC , pulmonary venous connection.
Genetics and Epidemiology
Although most cases of PAPVC are spontaneous and isolated, there are likely genetic causes or links that have yet to be elucidated. However, it is known that cases of TAPVC and PAPVC can be clustered in families or associated with known genetic syndromes. As in Scimitar syndrome, reports of familial PAPVC often occur in the setting of the heterotaxy syndrome, with other venous anomalies. In addition, up to 13% of Turner syndrome patients have PAPVC.
The incidence of PAPVC differs between clinical and autopsy studies because many patients remain asymptomatic throughout life and therefore are undiagnosed. Thus, from autopsy studies, the incidence is estimated at approximately 0.7% of the general population but is noted to be considerably lower as an isolated form of CHD. There is no clear gender predilection, but females appear to be more commonly affected in adult studies. In contrast, pediatric studies indicate that PAPVC may be twice as common in males as females. Other age-related epidemiologic differences emerge when the diagnosis of PAPVC is delayed until adulthood. For example, in the pediatric PAPVC population, the anomalous vein is more frequently found arising from the right upper lobe (90%) than the left upper lobe (10%). This compares with an adult study that found that the left upper lobe (47%) was more commonly affected compared with the right upper lobe (38%).
Early Presentation and Management
As previously noted, many cases of PAPVC are discovered incidentally in otherwise asymptomatic patients ( Box 34.3 ). This is especially true in the current era of detailed chest imaging by CTA or magnetic resonance imaging (MRI) for other indications such as evaluating pulmonary nodules or in an emergency department for trauma or unrelated dyspnea or chest pain. Many patients remain asymptomatic through childhood and early adolescence. Physiologic cardiac changes depend on the magnitude of the left-to-right shunt, but may lead to substantial right-sided heart dilatation if the pulmonary-to-systemic ( Q p: Q s) shunt burden is greater than 2:1. The degree and the speed at which this occurs are determined by a number of variables, including the number of anomalously draining veins, their site of connection, the compliance of the pulmonary vascular bed, and the presence and size of an associated ASD or other forms of congenital heart disease. Overall, symptoms such as reduced exercise tolerance, dyspnea on exertion, or palpitations from atrial arrhythmias are similar to those of an isolated ASD. Later, pulmonary hypertension and right-sided heart failure may occur.
