What is Total Anomalous Pulmonary Venous Return (TAPVR)?

Total Anomalous Pulmonary Venous Return (TAPVR)

Total Anomalous Pulmonary Venous Return (TAPVR) is a congenital cardiovascular malformation in which none of the pulmonary veins connect to the morphological left atrium, instead draining into the right side of the heart or systemic veins, resulting in right heart volume overload and requiring surgical correction for survival. 1, 2

Definition and Pathophysiology

TAPVR is characterized by:

• Abnormal connection of all pulmonary veins to the systemic venous circulation rather than the left atrium
• Resulting mixing of oxygenated and deoxygenated blood in the right atrium
• Requirement for an atrial septal defect or patent foramen ovale for survival, allowing mixed blood to cross from right to left atrium
• Right heart volume overload due to recirculation of pulmonary blood flow

Classification

According to the American College of Cardiology, TAPVR is classified into four types based on the location of the anomalous connection 2:

1. Supracardiac (most common): Pulmonary veins connect to the superior vena cava or its tributaries
2. Cardiac: Pulmonary veins connect directly to the right atrium or coronary sinus
3. Infracardiac: Pulmonary veins connect to infradiaphragmatic structures (portal vein, hepatic veins)
4. Mixed: Combination of connections at different levels

Clinical Presentation

The severity of symptoms depends on:

• Presence of pulmonary venous obstruction
• Size of the interatrial communication
• Degree of pulmonary hypertension

Key clinical features:

• With obstruction: Severe cyanosis, respiratory distress, pulmonary edema (medical emergency)
• Without obstruction: Milder cyanosis, heart failure symptoms, failure to thrive
• Cyanosis is significantly more prevalent in patients with pulmonary venous obstruction (80% vs 30%) 3

Diagnosis

Diagnostic approach:

• Transthoracic echocardiography: Initial evaluation showing right-sided cardiac chamber dilation 2
• Cardiac MRI or CT: Methods of choice for detailed delineation of pulmonary venous connections 2
• Cardiac catheterization: Indicated in high-risk patients to measure pressures, quantify shunts, and evaluate pulmonary vascular resistance 2

Diagnostic challenges:

• Multiple echocardiograms may miss the diagnosis in some cases 4
• Classic "snowman" or "figure-of-8" appearance may be seen on chest radiograph in supracardiac TAPVR 5

Management

Surgical intervention is the definitive treatment:

• Emergency surgery: Required for obstructive TAPVR (especially infracardiac type) 2
• Early elective surgery: Recommended for non-obstructive cases 2
• Surgical approach: Creation of an anastomosis between the common pulmonary venous sinus and the left atrium 6

Postoperative considerations:

• Monitor for pulmonary venous obstruction (occurs in approximately 11% of cases) 2
• Assess for residual atrial shunting
• Manage pulmonary hypertension, which can compromise surgical outcomes 2, 7

Prognosis

Factors affecting outcomes:

• Timing of diagnosis and intervention
• Presence of pulmonary venous obstruction
• Development of pulmonary hypertension
• Associated cardiac anomalies

Without surgical correction, TAPVR has poor natural prognosis, with survival to adulthood being extremely rare 5.

Important Considerations

• Early detection and surgical treatment are crucial for survival 3
• Pulmonary hypertension management is critical in the perioperative period, especially in developing countries with limited resources 7
• Intrinsic pulmonary venous obstruction (endocardial sclerosis) carries a worse prognosis than extrinsic obstruction 2