eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiothoracic Surgery

Partial and Total Anomalous Pulmonary Venous Connection, Surgical Treatment

Author: Jayme Scott Bennetts, MD, Fellow, Department of Cardiac and Thoracic Surgery, Flinders Medical Centre
Coauthor(s): Christopher A Caldarone, MD, Associate Professor, Department of Surgery, The Hospital for Sick Children, University of Toronto
Contributor Information and Disclosures

Updated: May 1, 2009

Introduction

Congenitally anomalous drainage of the pulmonary venous system results from in utero failure of the embryological pulmonary venous confluence to fuse with the forming left atrium (LA). The failure of fusion can be complete (ie, bilateral and involving all pulmonary veins) or partial, unilaterally or contralaterally involving only one or two veins per side. At least one vein is connected normally.

In the absence of a normal connection, an alternative pathway is formed to allow the egress of blood from the developing lung. This connection is usually to the right atrium (RA), or major systemic vein draining directly to the RA, creating a left-to-right shunt.

Patients with partial anomalous pulmonary venous drainage (PAPVD) most commonly have an associated atrial septal defect (ASD), usually of superior sinus venosus type associated with anomalous drainage of the right superior pulmonary vein. These patients often remain asymptomatic into adulthood.

Patients with total anomalous pulmonary venous drainage (TAPVD) usually present in the early neonatal period, often with profound cyanosis and shock. The pulmonary veins drain to an anomalous, usually single, connection to the systemic venous system. Less commonly, the pulmonary veins may drain to multiple sites (termed mixed pulmonary venous drainage). Supply of oxygenated blood to the systemic circulation relies on an intracardiac right to left shunt in these patients.^1,2

History of the Procedure

Wilson first described the analogy in 1798, which Brody reviewed in 1942 (37 cases in the literature). Muller performed the first surgical intervention in 1951, and the condition was first completely corrected with the use of cardiopulmonary bypass in 1956-1957.

Since then, various modifications of the technique have been proposed. For instance, free and in situ autologous tissue have been used to create a wide, unobstructed connection between the pulmonary venous confluence and the LA. Despite this technique, 10-15% of patients represent with stenosis after initial successful correction. Recurrent stenosis is often a progressive process, resulting in multiple representations requiring further procedures for correction, with an increasingly poor outcome at each representation.

Most recently, a technique to minimize the surgical trauma to the pulmonary vein intima was proposed to improve outcomes in patients with postrepair stenosis. At present, indications for using this technique are being extended to the correction of primary venous anomalies.

Problem

Total anomalous pulmonary venous drainage

In patients with TAPVD, all the venous blood returning from the lungs drains to the systemic venous system, creating a large left-to-right shunt. Supply of oxygenated blood to the systemic circulation requires intracardiac communication between the right and left sides of the heart to allow oxygenated blood to enter the left ventricle. This communication is usually through an ASD. The size of the communication determines the volume of blood able to cross to the left heart and, therefore, determines the cardiac output and systemic oxygenation.

Types of TAPVD are classified by the site of pulmonary venous drainage connection to the systemic circulation, and are listed as follows (with the percentage of occurrence):

• Supracardiac (45-55%): Pulmonary venous drainage courses through the pulmonary venous confluence behind the LA and then through a connecting vein (often termed a vertical vein) to connect with the systemic venous system at the innominate vein. Pulmonary outflow then courses, mixed with the systemic return, through the superior vena cava (SVC) to the RA. In rare cases, other sites of connection to the systemic venous system, such as direct drainage to the right-sided SVC, are seen.
• Cardiac (15-20%): In this group, the pulmonary venous confluence connects to the coronary sinus posteriorly. This connection results in excessive blood flow through the coronary sinus, producing an enlarged coronary sinus, as the returning pulmonary blood mixes with the lesser volume coronary venous blood. In uncommon cases, the confluence drains directly to the RA.
• Infracardiac (15-20%): The pulmonary-systemic venous connection lies inferior to the heart in a subdiaphragmatic position. Most commonly, a vertical vein lying posterior to the pericardium connects the pulmonary vein confluence with the portal vein, or the ductus venosus, after traversing the diaphragm. Blood then enters the RA via the inferior vena cava (IVC). The course of the connecting vein is often long and tortuous, resulting in a high incidence of obstruction to pulmonary venous outflow.
• Mixed (5-10%): Pulmonary venous drainage is through multiple connections to the systemic venous circulation by a combination of the supracardiac, cardiac, and/or infracardiac types.

Although obstruction to the pulmonary venous return is most common with infracardiac type connection, stenosis is possible in all types of anomalous connection, and at various sites along the pathway to the RA. This usually results in significant hemodynamic compromise and cyanosis. Restrictive flow across the intracardiac communication is uncommonly the cause of obstruction producing significant compromise of systemic cardiac output and oxygenation.

In a supracardiac type of connection, obstruction can occur in the ascending vertical vein connecting the pulmonary venous confluence to the innominate vein. Passage of the vertical vein between the pulmonary artery and the left bronchus can cause compression in the vertical vein. Because the egress of blood from the lungs is restricted, pulmonary arterial pressure rises, causing further distention of the pulmonary artery and obstruction and creating a repeating cycle of pulmonary artery distention and further obstruction.

With the infracardiac type of pathology, focal obstruction is commonly seen at the connection between the pulmonary venous confluence and the systemic vein. In addition, the connection between the pulmonary and systemic venous systems is often long and tortuous, producing a limitation of flow without any discrete stenosis. This is a common feature of infracardiac TAPVD.

Any restriction at the level of the ASD, reducing the volume of blood able to cross to the left heart, causes elevation of the RA pressure and functional obstruction of the pulmonary venous return.

Partial anomalous pulmonary venous drainage

PAPVD is characterized by a failure of one or more of the pulmonary veins to incorporated with the developing LA during fetal development. The superior right-sided pulmonary vein is typically affected and has abnormal connection to the SVC. In a few cases, both pulmonary veins on the right side are anomalous, and they directly connect to the IVC or the RA. The lesion commonly occurs in association with an ASD, usually a superior sinus venosus type, though it can be present with an intact atrial septum.

The most common pattern of PAPVD is an anomalous connection of the right superior pulmonary vein with the SVC, or the junction of the RA and SVC, in association with a superior sinus venosus ASD.

A second pattern of PAPVD is in patients with scimitar syndrome, in whom both the right pulmonary veins (superior and inferior) drain to the IVC via a descending vein coursing parallel to the right-heart border. This condition is commonly associated with right lung hypoplasia of variable degrees.

Frequency

TAPVD and PAPVD account for 1-2% of congenital heart defects.

Etiology

Normal embryologic development of the pulmonary venous system involves creation of a connection between the LA and the pulmonary venous plexus with subsequent regression of pulmonary-to-systemic venous connections. Any disruption of this process can result in anomalous pulmonary venous drainage.

The primitive lungs form as buds arising from the foregut. As a consequence, venous drainage of the lung buds occurs through the cardinal and umbilical-vitelline venous systems (systemic veins). As the embryo develops, the primordial pulmonary vein arises behind the developing atrium and fuses with the plexus draining the developing lung buds, forming a confluence of pulmonary venous connection. As the atrium enlarges an outpouching, or evagination, of the common atrium forms to the left of the developing septum primum. This structure fuses with the pulmonary venous confluence behind. It becomes increasingly incorporated into the LA wall as growth continues, completing the connection of the developing lung buds to the LA, and resulting in the 4 pulmonary vein orifices. The connections between the lung buds and the systemic venous system regress.

Anomalous pulmonary venous drainage can result from failure of fusion between the LA evagination and the pulmonary venous plexus, or from malposition of the relationship between the atrial evagination and the forming atrial septum.

If all of the pulmonary veins develop anomalous connections, the lesion is termed TAPVD. If 1-3 pulmonary veins drain by means of an anomalous pathway and if at least 1 pulmonary vein drains to the LA, the lesion is termed PAPVD.

Pathophysiology

Total anomalous pulmonary venous drainage

The hemodynamic abnormality in patients with TAPVD is related to the complete diversion of pulmonary venous blood away from the LA to a systemic vein. As a consequence, 2 anatomic factors determine the patient's clinical status.

• First, returning pulmonary venous (oxygenated) blood is mixed with systemic venous (unoxygenated) blood and cannot reach the left ventricle unless a right-to-left shunt is present. In most cases, a patent foramen ovale or ASD is present to allow blood to enter the LA and then the left ventricle to maintain systemic cardiac output. The patient's cardiac output and supply of oxygenated blood is limited by the amount of blood that can cross the atrial septum. Therefore, the characteristics of the necessary right-to-left shunt determine systemic cardiac output and oxygenation.
• Second, an obstruction may occur in the path of the pulmonary venous drainage from the lungs to the systemic venous system. If obstruction occurs, egress of blood from the lungs is limited. The consequences of obstruction are limitation of pulmonary blood flow, pulmonary venous congestion, impairment of oxygenation, and elevation of pulmonary artery pressures. These events lead to life-threatening cyanosis in neonates.

Partial anomalous pulmonary venous drainage

The hemodynamic abnormality is related to the left-to-right shunt imposed by pulmonary venous drainage into the RA. This anomalous drainage often is accompanied by an ASD. In a common scenario, the right upper pulmonary vein drains into the RA at the site of a superior sinus venosus ASD.

As a consequence, the return of oxygenated blood from the anomalous pulmonary venous connection produces a left-to-right shunt and increases the volume of blood returning to the RA. This increased amount of blood creates a volume load on the right ventricle and results in chronic dilatation of the right ventricle, hypertrophy, and eventual dysfunction. The addition of an ASD increases the left-to-right shunt as blood passes from the LA to the RA, further adding to the volume load on the right ventricle.

Although an associated ASD usually produces a left-to-right shunt, it adds the potential for right-to-left shunting with elevated pressures on the right side of the heart.

Presentation

Total anomalous pulmonary venous drainage

The degree of pulmonary venous obstruction largely determines the clinical presentation. Patients with high-grade obstruction present postnatally with profound cyanosis and shock, or in the neonatal period with cyanosis, respiratory distress, and poor growth. On examination, the infant is tachypneic and cyanotic and has poor perfusion of the extremities. The second heart sound is prominent and split as a result of pulmonary arterial hypertension.

In contrast, patients without clinically significant pulmonary venous obstruction present in infancy or early childhood with signs and symptoms related to a large left-to-right shunt and resulting right-heart volume overload. These patients have dyspnea, poor feeding, and poor growth. They may have cyanosis on examination, but this manifestation is usually mild. Other findings include a split second heart sound and a systolic flow murmur because of increased flow across the pulmonary valve, as well as elevated right-heart pressures.

Partial anomalous pulmonary venous drainage

Patients are often asymptomatic and present with a murmur as an incidental finding on routine examination. Some patients may present with primary arrhythmia, most commonly atrial fibrillation.

Subsequent workup demonstrates PAPVD and an associated sinus venosus ASD. Symptomatic patients present with the sequelae of a large left-to-right shunt. The symptoms are often decreased exercise tolerance or poor growth. On examination, patients are not cyanotic unless they have pulmonary hypertension, which can occur as a late manifestation of a large left-to-right shunt. A split and prominent second heart sound and a systolic murmur are often present as a result of increased flow across the pulmonary valve.

Indications

Obstruction in the pulmonary venous pathway constitutes a surgical emergency in patients with total anomalous pulmonary venous drainage (TAPVD). Medical measures to stabilize and resuscitate the patient are minimally effective and include intubation, ventilation with 100% oxygen, hyperventilation, prostaglandin infusion, correction of pH, and inotropic support. The therapeutic goal is relief of pulmonary venous obstruction, which can be accomplished with only surgical repair.

In the absence of obstruction, surgery can be performed on an elective basis after diagnosis. Excellent clinical results are reported in infants, suggesting that little is gained by delaying surgical repair until the patient reaches an arbitrary size, weight, or age.

Relevant Anatomy

See Introduction and Pathophysiology for relevant anatomy in patients with partial anomalous pulmonary venous drainage (PAPVD) or total anomalous pulmonary venous drainage (TAPVD).

Contraindications

Total anomalous pulmonary venous drainage

No specific contraindications are noted for the repair of total anomalous pulmonary venous drainage (TAPVD), though the surgical risk may be high in select groups of patients (eg, patients with TAPVD and pulmonary venous obstruction, a single ventricle, or heterotaxy syndromes).

Partial anomalous pulmonary venous drainage

In patients with partial anomalous pulmonary venous drainage (PAPVD) and an atrial septal defect (ASD), closure of the ASD may be inappropriate when pulmonary artery pressures are greater than two thirds the systemic pressure, without reversibility. Severe, fixed pulmonary hypertension with suprasystemic pressure (Eisenmenger syndrome) is associated with systemic cyanosis. The surgical risk in this group of patients may be prohibitive.

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