Total Anomalous Pulmonary Venous Drainage (TAPVD)
In TAPVD, the pulmonary veins form a common collector behind the left atrium but do not empty into it. As a result, all arterial blood from the lungs mixes with venous return in the right heart chambers.
The patient's life with such a defect is impossible without a compensatory right-to-left shunt at the atrial level (via a patent foramen ovale or an atrial septal defect). Blood from the venous confluence is directed into the right atrium via one of four pathways:
- Supracardiac type (50%): shunting occurs via the ascending vein into the brachiocephalic vein (v. brachiocephalica) and further into the superior vena cava (SVC).
- Cardiac type (15%): the collector drains directly into the right atrium via the coronary sinus (coronary sinus).
- Infracardiac type (25%): the descending vein passes through the diaphragm and drains into the inferior vena cava (IVC) or the portal venous system (v. portae).
- Mixed type (10%): represents various combinations of the above pathways.
Features of the infracardiac type
This variant has the most severe clinical course. As the descending vein passes through the diaphragm, obstruction (vessel narrowing) frequently occurs. Severe pulmonary venous hypertension is added to the left-to-right shunt and blood mixing.
The clinical presentation unfolds rapidly (within the first 24–36 hours of life). The newborn exhibits cyanosis, tachypnea, tachycardia, hepatomegaly, and pronounced pulmonary edema with respiratory distress syndrome. Chest radiography reveals pulmonary edema—infracardiac TAPVD must be included in the differential diagnosis for such radiographic findings in an infant.
Partial Anomalous Pulmonary Venous Drainage (PAPVD)
In PAPVD, usually only a single pulmonary vein drains anomalously. This is an acyanotic defect whose pathophysiology is virtually identical to an atrial septal defect (ASD). The severity of symptoms and the magnitude of the shunt depend on the number of misconnected veins.
PAPVD is frequently associated with a sinus venosus ASD (sinus venosus ASD). This defect should be suspected in cases where measurements indicate the presence of a shunt, but no visible atrial or ventricular septal defect is identified.
Diagnostic radiology
Ultrasonography remains the primary imaging modality, but cardiac MRI (CMR) and CT serve as the gold standard for patients with a poor acoustic window. These modalities help avoid diagnostic catheterization.
Key objectives in TAPVD:
- Determine the anatomical type of connection.
- Identify any sites of pulmonary venous obstruction.
- Confirm the presence of the obligatory right-to-left shunt.
- Evaluate associated anomalies (e.g., atrial appendage isomerism).
MR angiography findings:
- In the supracardiac type: dilatation of the SVC and right-sided pulmonary veins.
- In the infracardiac type: clear visualization of vessel narrowing at the diaphragmatic hiatus.
Single Ventricle Concept
TAPVD is frequently associated with complex defects requiring the creation of a functionally "single ventricle" (e.g., hypoplastic left heart syndrome or valve atresia). The goal of treatment for such conditions is the complete separation of systemic and pulmonary circulations without the participation of a subpulmonary ventricular pump.
Palliative correction is performed in three stages:
- Systemic-to-pulmonary shunt (e.g., Blalock-Taussig shunt) for neonates with high pulmonary vascular resistance.
- Bidirectional Glenn shunt (BCPC): connection of the SVC to the right pulmonary artery.
- Fontan circulation (TCPC): creation of a conduit between the IVC and the pulmonary arteries.
At each stage, diagnostic imaging is critically important to rule out stenoses, assess systemic ventricular function, and search for undesirable collaterals.
Briefly: answers to topical questions
Which echocardiographic signs indicate the presence of total anomalous pulmonary venous drainage?
Ultrasonography visualizes the anomalous pulmonary venous connection directly and assesses associated hemodynamic abnormalities.
- Total anomalous pulmonary venous drainage (TAPVD) — visualization of supracardiac, cardiac, infracardiac, or mixed connection types.
- Obstruction — identification of pulmonary venous narrowing sites.
- Obligate shunt — confirmation of right-to-left blood shunting.
- Associated anomalies — detection of atrial appendage isomerism.
What long-term complications can occur after the Fontan procedure?
In the long term following the Fontan procedure, a severe condition known as a failing Fontan can develop, alongside a range of other structural abnormalities.
- Failing Fontan (failing Fontan) — a condition characterized by systemic venous hypertension and low cardiac output, leading to peripheral edema.
- Right atrial dilatation — a major complication of the classic procedure causing arrhythmias, thrombosis, or compression of the pulmonary veins.
- Specific syndromes — development of plastic bronchitis and protein-losing enteropathy.
Ultimately, these complications can lead to death or necessitate heart transplantation.
To memorize the anatomical variants of TAPVD, move from top to bottom: Supracardiac (shunting above the heart—into the SVC), Cardiac (into the heart itself—coronary sinus), Infracardiac (below the heart—through the diaphragm into the IVC system).
Class and exam questions
Why is an infant with total anomalous drainage viable at all after birth?
Viability is maintained exclusively through a compensatory right-to-left blood shunt at the atrial level (via an atrial septal defect or patent foramen ovale). This allows mixed blood to enter the systemic circulation.
How does the hemodynamics of PAPVD differ from TAPVD?
PAPVD is an acyanotic defect presenting with a left-to-right shunt (similar to an ASD). In TAPVD, complete mixing of arterial and venous blood occurs, leading to severe hypoxia and necessitating an obligate right-to-left shunt.
What is the main danger of infracardiac TAPVD?
Because the descending vein is compressed as it passes through the diaphragm. This causes severe obstruction, pulmonary venous hypertension, and rapidly developing pulmonary edema in the newborn.
What else to study on this topic
- Associated defects in TAPVD (isomerism, AVSD, hypoplastic left heart syndrome).
- Association of partial anomalous pulmonary drainage with Turner syndrome.
- Evaluation of collateral blood flow and fenestrations after the Fontan procedure (TCPC).
- Complications of the classic Fontan procedure (right atrial dilatation, thrombosis).
- Clinical presentation of the "failing Fontan" (plastic bronchitis, protein-losing enteropathy).
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