Total Anomalous Pulmonary Venous Connection (TAPVC)

Total Anomalous Pulmonary Venous Connection (TAPVC) is a rare congenital heart defect (1-2% of congenital heart anomalies) with an estimated incidence of 1 in 15,000 live births.
In TAPVC, pulmonary veins do not drain directly into the left atrium but instead connect to anomalous venous pathways that eventually reach the systemic circulation. This differs from Total Anomalous Pulmonary Venous Return (TAPVR), where pulmonary veins drain directly into systemic veins.
This abnormal pathway prevents the normal return of oxygenated blood to the left heart, leading to hypoxemia and right heart volume overload. Neonatal survival depends on the presence of compensatory shunts, primarily:

Patent Ductus Arteriosus (PDA): crucial to maintaining systemic perfusion during the first hours of life.
Atrial Septal Defect (ASD): essential for allowing oxygenated blood to pass into the left atrium.

TAPVC shares several features with Total Anomalous Pulmonary Venous Return (TAPVR), but differs in certain key aspects, which are summarized in the Table at the end of the page.

Anatomy and Pathophysiology

Under normal conditions, pulmonary veins drain into the left atrium, allowing oxygenated blood to enter systemic circulation. In TAPVC, however, pulmonary veins do not connect directly to the left atrium but rather pass through anomalous venous pathways before reaching systemic circulation. The main anatomical subtypes of TAPVC include:

Suprasystemic TAPVC: Drainage occurs into the innominate vein or the superior vena cava.
Infrasystemic TAPVC: Pulmonary veins drain into the inferior vena cava or the ductus venosus.
Cardiac TAPVC: Pulmonary venous blood returns to the heart via the coronary sinus or directly into the right atrium.
Mixed TAPVC: A combination of multiple anomalous drainage pathways.

The obstructed form of TAPVC is a neonatal emergency, leading to severe pulmonary hypertension, metabolic acidosis, and cardiac failure.

Signs and Symptoms

The clinical presentation depends on whether venous return obstruction is present.

Neonatal cyanosis, due to the failure of oxygenated blood to reach the left atrium.
Tachypnea and respiratory distress, indicating severe hypoxemia.
Feeding difficulties and fatigue, especially in neonates.
Cardiomegaly and pulmonary congestion, seen in obstructive forms.
Cardiac murmur, often associated with a large ASD.

Diagnosis

The diagnosis is based on advanced imaging techniques:

Fetal echocardiography: useful for prenatal diagnosis.
Neonatal echocardiography: the primary diagnostic tool to confirm the anatomical defect.
Cardiac MRI: indicated in complex cases to define venous pathways.
Cardiac catheterization: reserved for selected cases.

Treatment

Surgical repair is the only definitive treatment and should be performed as soon as possible.

Anastomosis of pulmonary veins to the left atrium: restores normal drainage.
Closure of the atrial septal defect (ASD): stabilizes systemic circulation.
Preoperative management: ventilatory and pharmacological support in critically ill neonates.

Prognosis

With timely intervention, long-term survival is favorable, but long-term follow-up is essential to monitor post-surgical complications, such as:

Postoperative pulmonary venous stenosis, which may require reintervention.
Persistent pulmonary hypertension, especially in late-diagnosed cases.
Post-surgical arrhythmias, due to cardiac remodeling.

Without treatment, the mortality rate exceeds 90% in the first months of life, particularly in cases with venous obstruction.

Comparison Table

Characteristic	TAPVR (Total Anomalous Pulmonary Venous Return)	TAPVC (Total Anomalous Pulmonary Venous Connection)	Common Features
Definition	Anomalous connection of all pulmonary veins to a systemic venous system instead of the left atrium.	Anomalous connection of pulmonary veins to systemic venous structures with potential obstruction.	Absence of direct connection between pulmonary veins and the left atrium.
Abnormal drainage pathways	Superior vena cava, innominate vein, coronary sinus, inferior vena cava, ductus venosus.	Superior vena cava, inferior vena cava, coronary sinus, or mixed connections.	Pulmonary venous return occurs in abnormal locations.
Main compensatory shunt	ASD (Atrial Septal Defect): Allows oxygenated blood to pass into the left atrium and ensures systemic oxygenation.	Patent Ductus Arteriosus (PDA): Necessary to bypass the pulmonary venous return obstruction and maintain systemic perfusion.	Requirement for a shunt to sustain systemic circulation.
Presence of ASD	Always present and crucial for survival.	Present but less critical compared to the PDA.	ASD allows blood mixing.
Role of PDA	Not essential for survival but may contribute to circulation.	Critical to maintaining systemic perfusion until the anomaly is corrected.	PDA can help temporarily stabilize the patient.
Pulmonary venous obstruction	Possible but not always present.	More frequent, especially in cases of infrasystemic venous return.	Obstruction worsens prognosis in both conditions.
Clinical manifestations	Neonatal cyanosis, tachypnea, progressive heart failure.	More severe cyanosis, critical respiratory distress if the PDA closes.	Early signs of hypoxemia.
Treatment	Early surgery to connect pulmonary veins directly to the left atrium.	Emergency surgery to restore pulmonary venous drainage and close the PDA.	Both require surgical correction.

References

Tweddell J.S. et al. Total Anomalous Pulmonary Venous Return: Surgical and Long-Term Outcomes. Ann Thorac Surg. 2021;111(6):1345-1358.
Jacobs M.L. et al. Management of Total Anomalous Pulmonary Venous Connection. Circulation. 2020;141(5):210-225.
Freedom R.M. et al. Clinical Spectrum of Total Anomalous Pulmonary Venous Return. J Am Coll Cardiol. 2019;136(3):950-962.
Bove E.L. et al. Surgical Considerations in Total Anomalous Pulmonary Venous Return. Pediatr Cardiol. 2018;39(4):680-695.
Van Praagh R. et al. Pathophysiology of Total Anomalous Pulmonary Venous Return. J Thorac Cardiovasc Surg. 2017;154(2):421-432.