Total anomalous pulmonary venous connection

AORN Journal,  March, 2007  by Patricia Stein

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Total anomalous pulmonary venous connection (TAPVC) is a congenital heart defect that occurs in 1.5% of infants with cardiovascular malformations. (1) In TAPVC, there is no connection between the pulmonary veins and the left atrium. Rather, the pulmonary veins establish an anomalous connection that delivers pulmonary venous blood to the right side of the heart rather than to the left side. The right atrium, therefore, receives not only the entire systemic venous return as it should but also receives the entire pulmonary venous return. As a result, the left atrium has no direct pulmonary venous supply. A patent foramen ovale or an atrial septal defect provides a right-to-left shunt so that an admixture of oxygenated and unoxygenated blood eventually reaches the left side of the heart. Without the right-to-left shunting of blood, the infant would die.

Depending on the type of venous connection, TAPVC may be either obstructed or nonobstructed. Immediate surgery is required if the venous connection is obstructed. This article describes

* normal embryology,

* abnormal embryology that results in TAPVC,

* types of anomalous connections,

* how TAPVC is diagnosed,

* surgical correction, and

* nursing Interventions when caring for patients with TAPVC and dealing with the concerns of their family members.

EMBRYOLOGY

The heart, which develops from the cardiogenic mesoderm, is one of the earliest differentiating and functioning organs during embryonic development. Vascular development occurs in many places but most obviously in early formation of the heart. (2)

The heart grows rapidly, creating a cardiac "bulge" seen in the early embryo. It forms initially in the embryonic disc as a simple paired tube inside the forming pericardial cavity. When this disc folds, the heart moves into the correct anatomical position within the chest cavity. (2)

Peripheral vasculature in the developing embryo can be categorized as three distinct aortic and venous circulatory systems:

* the placental (ie, umbilical) system;

* the embryonic system; and

* the vitelline system.

The placental system develops primarily in the extraembryonic mesoderm of the chorion. Its function is to remove embryonic waste and act as a conduit for maternal nutrition. This conduit is not present at birth. The embryonic system begins on both the right and left sides of the embryo and eventually matures into the fully developed cardiovascular system. The vitelline system covers the surface of the yolk sac and contributes to circulation between the gut (ie, embryonic digestive tube consisting of foregut, midgut, and hindgut) and liver. (2)

The lungs develop as outpouchings of the foregut and share the foregut's splanchnic vascular plexus. (3) At this point, there is no direct connection from the lungs to the heart. The paired common cardinal and umbilicovitelline veins connect the plexus to the primitive heart. (3)

At 25 to 27 days of gestation, the developing pulmonary venous plexus retains connections to the right superior vena cava, left superior vena cava, and portal system. No direct communication to the left atrium exists. (2)

At 27 to 29 days of gestation, the primitive pulmonary vein appears as an out-pouching from the left atrium that eventually makes contact with the primitive pulmonary venous system. (2) The right common cardinal system later evolves into the right sinus venosus, which in turn becomes the right superior vena cava and azygos vein. The left common cardinal vein evolves into the left sinus venosus; this becomes the left superior vena cava and coronary sinus. The umbilicovitelline system becomes the inferior vena cava, ductus venosus, and portal vein (Figure 1). (2)

[FIGURE 1 OMITTED]

Connection between the primitive pulmonary vein and pulmonary venous plexus occurs by 30 days of gestation. The common pulmonary vein incorporates into the back wall of the left atrium. Normally, the pulmonary venous portion of the splanchnic plexus gradually loses its connection with the cardinal and umbilicovitelline veins. (2,3)

ABNORMAL EMBRYONIC DEVELOPMENT

With the anomalous connection that occurs in TAPVC, the common pulmonary vein either does not connect with the pulmonary venous system or does not form at all. Right atrial and right ventricular enlargement occur because all pulmonary venous return connects to the systemic venous system. (3) Persistence of the right and left cardinal veins and the umbilicovitelline all create, at one junction or another, a total anomalous pulmonary venous connection. If neither pulmonary nor systemic connection is available to the lungs, then death will occur during the neonatal period (ie, the first 28 days of life). (4)

An atrial septal defect or patent foramen ovale serves a vital function in keeping these patients alive because it is the only way for the left ventricle to receive blood, albeit an admixture of both oxygenated and unoxygenated blood. A ductus arteriosus frequently accompanies this anomaly. (5) Seventy-five percent of patients with TAPVC have a widely patent connecting vein with no obstruction of venous return; (4) the remaining 25%, however, have narrowed and obstructed systemic venous blood flow. (4)