Tricuspid atresia is a rare and severe congenital heart defect, present at birth. It is characterized by the complete absence of the tricuspid valve, which normally separates the heart’s upper and lower chambers on the right side. This structural malformation prevents blood from flowing directly from the right atrium to the right ventricle. Classified as a cyanotic heart defect, tricuspid atresia is life-threatening and requires immediate medical intervention. The condition fundamentally alters the circulatory system, necessitating complex, staged surgical interventions.
The Core Problem: Abnormal Heart Structure
The normal heart has four chambers and four valves that direct blood flow efficiently. The tricuspid valve is situated between the right atrium, which receives deoxygenated blood, and the right ventricle, which pumps blood to the lungs. In tricuspid atresia, a solid sheet of tissue blocks the connection between the right atrium and right ventricle.
Because blood cannot enter the right ventricle, the chamber does not develop correctly, resulting in an underdeveloped (hypoplastic) right ventricle. This structural compromise renders the heart incapable of supporting a normal, two-ventricle circulation. Consequently, the left side of the heart must manage the entire volume of blood for both the body and the lungs.
Disruption of Normal Blood Flow
The anatomical defect forces a rerouting of blood flow necessary for survival. Deoxygenated blood returning to the right atrium must find an alternate path to the lungs via an obligatory right-to-left shunt. This shunting occurs through an opening between the heart’s upper chambers, such as a patent foramen ovale (PFO) or an atrial septal defect (ASD).
The oxygen-poor venous blood crosses this opening into the left atrium, mixing with oxygen-rich blood returning from the lungs. This mixed blood flows into the single functional pumping chamber, the left ventricle, which must supply both the systemic and pulmonary circulations. Systemic oxygen saturation depends on how much mixed blood reaches the lungs.
To supply the lungs, the mixed blood must exit the left ventricle and enter the pulmonary artery. This often relies on a ventricular septal defect (VSD), a hole between the lower chambers, allowing blood to flow from the left ventricle to the lungs. If no VSD is present, or if the pulmonary artery is blocked (pulmonary atresia), blood must reach the lungs through a patent ductus arteriosus (PDA). The PDA is a temporary fetal blood vessel that must be kept open with medication immediately after birth.
Symptoms and Diagnostic Confirmation
The presentation of tricuspid atresia varies based on the degree of blood flow to the lungs. If pulmonary blood flow is severely reduced, the newborn exhibits cyanosis within the first hours or days of life. Insufficient oxygenation also causes rapid breathing (tachypnea), difficulty feeding, and fatigue.
Conversely, if pulmonary blood flow is unrestricted or excessive, the baby may not be severely cyanotic but develops symptoms of heart failure by four to six weeks of age. These symptoms include poor weight gain, sweating while feeding, and labored breathing due to volume overload on the single left ventricle. A heart murmur is a common finding during physical examination.
Diagnosis is confirmed using an echocardiogram, a specialized ultrasound of the heart. This imaging test demonstrates the absence of the tricuspid valve, the small right ventricle, the enlargement of the left chambers, and the presence of shunts. An electrocardiogram (EKG) often shows a characteristic left axis deviation and evidence of left ventricular hypertrophy, reflecting the heart’s altered electrical activity. Fetal echocardiography can sometimes identify the defect during pregnancy, allowing for specialized delivery planning.
Staged Surgical Repair and Lifelong Care
Tricuspid atresia requires a multi-stage surgical strategy known as single-ventricle palliation to reconfigure circulation.
Stage 1: Initial Palliation
The first stage, performed in the neonatal period, establishes a stable source of pulmonary blood flow. For infants with reduced flow and severe cyanosis, a systemic-to-pulmonary shunt (e.g., Modified Blalock-Taussig-Thomas shunt) is placed to connect a systemic artery to the pulmonary artery. If the child has excessive pulmonary flow, a pulmonary artery band is placed instead to restrict blood flow and protect the lungs.
Stage 2: Bi-directional Glenn Procedure
This procedure, typically performed between four and six months of age, involves connecting the superior vena cava (returning deoxygenated blood from the upper body) directly to the pulmonary artery. This removes the upper body’s venous return from the single ventricle, allowing blood to flow passively to the lungs and reducing the volume workload on the left ventricle.
Stage 3: Fontan Operation
The final and most complex procedure is the Fontan operation, performed between 18 months and three years of age. This surgery completes the staged repair by diverting blood from the inferior vena cava (returning blood from the lower body) directly to the pulmonary artery. The Fontan procedure creates a total cavopulmonary connection, ensuring all deoxygenated blood flows passively to the lungs without using the heart’s pumping chambers.
While the Fontan circulation separates the oxygen-poor and oxygen-rich bloodstreams, it creates a non-pulsatile flow system that necessitates lifelong, specialized cardiac follow-up. Long-term complications are common due to chronic elevation of central venous pressure.
Common long-term complications include:
- Arrhythmias.
- Progressive hepatic congestion, which can lead to liver damage.
- Protein-losing enteropathy (PLE), a serious condition where chronic venous hypertension causes a loss of serum proteins into the gut, leading to persistent diarrhea and fluid accumulation.