Tricuspid atresia is a severe cyanotic congenital heart disease characterized by the failure of formation or complete closure of the tricuspid valve, resulting in the absence of a direct connection between the right atrium and right ventricle. This anomaly prevents the normal passage of venous blood into the right ventricle, leading to significant alterations in intracardiac and systemic circulation. Survival is only possible due to the concomitant presence of additional cardiac defects, such as an atrial septal defect, ventricular septal defect, or a patent ductus arteriosus, which allow mixing of oxygenated and deoxygenated blood and ensure a minimum pulmonary blood flow. Given the severity of the clinical picture, tricuspid atresia requires early and complex palliative surgical strategies to ensure long-term survival.
The etiology of tricuspid atresia lies in an early anomaly of cardiac morphogenesis that occurs during the fourth and fifth week of embryonic development. The embryological defect consists of the absence or incomplete formation of the right atrioventricular junction, due to failure of fusion and differentiation of the endocardial cushions and atrioventricular valvular tissue. This leads to the complete absence of a functional tricuspid valve and the formation of a fibrous or muscular membrane that entirely separates the right atrium from the underlying right ventricle.
The main risk factors associated with the development of tricuspid atresia are predominantly genetic and chromosomal, including:
No direct relationship with specific environmental factors has been demonstrated, although some early maternal exposures, such as alcohol, teratogenic drugs, or viral infections (rubella), have occasionally been associated with increased risk.
From the standpoint of the pathogenetic mechanism, the absence of the tricuspid valve results in a complete block of communication between the right atrium and right ventricle. This causes chronic blood accumulation in the right atrium, forcing the blood to flow through an atrial septal defect (usually a patent foramen ovale or atrial septal defect) into the left atrium, resulting in mixing of venous and arterial blood. The mixed blood then reaches the left ventricle, which assumes the task of maintaining both systemic and pulmonary circulation through communicating structures (ventricular septal defect, patent ductus arteriosus, or collateral circuits).
The resulting pathophysiology is dominated by early and marked cyanosis, secondary to the obligatory mixing of venous and arterial blood. Depending on the associated anomalies, pulmonary circulation may be significantly compromised, leading to clinical variability in the degree of blood oxygenation. The right ventricle, generally hypoplastic and nonfunctional, does not contribute to the circulation. The left ventricle, subjected to double workload, may initially compensate by maintaining an adequate output but is at risk over time of progressing to pathological dilation and secondary systolic dysfunction.
The severity of the disease depends heavily on the size of the associated defects (atrial and ventricular), the integrity and duration of patency of the ductus arteriosus, and the presence or absence of associated pulmonary stenosis or atresia. These elements directly influence prognosis and determine the type and timing of palliative interventions necessary to ensure sustainable circulation and an acceptable quality of life.
The clinical manifestations of tricuspid atresia are early, pronounced, and typically dominate the clinical picture from the very first days or weeks of life. Symptomatology is closely related to the severe oxygenation deficit of the blood and the altered intracardiac hemodynamics, characterized by the obligatory mixing of oxygenated and desaturated blood.
The most common clinical presentation is marked central cyanosis, evident immediately after birth or within the first weeks of life. This cyanosis is resistant to oxygen therapy and worsens following physiological closure of the ductus arteriosus if there is inadequate pulmonary blood flow.
Other early signs and symptoms include:
Cyanosis may worsen further if the atrial septal defect is restrictive, impeding the outflow of venous blood from the right atrium. In this scenario, severe systemic venous congestion develops, with hepatomegaly, jugular venous distension, and possible peripheral edema. Concomitant pulmonary stenosis or atresia further worsens the situation by compromising already precarious pulmonary circulation and oxygen saturation.
On physical examination, the most consistent finding is persistent central and peripheral cyanosis, with cold, hypoxic extremities. On cardiac auscultation, there is generally no characteristic murmur of tricuspid valve insufficiency or stenosis, due to the complete absence of the valve. However, a systolic ejection murmur is often present, related to abnormal flow through an associated ventricular septal defect or possible pulmonary valve stenosis. The second heart sound may be single and accentuated, reflecting reduced pulmonary circulation and the absence of normal valve tone separation.
Newborns with severe forms often present in critical condition at birth or within the first hours of life, requiring immediate stabilization and urgent pharmacological treatment (such as administration of prostaglandins to maintain ductus arteriosus patency). In patients with less severe associated anomalies and relatively preserved pulmonary circulation, clinical presentation may be more subtle, though still evident within the first months of life, with symptoms such as dyspnea, reduced tolerance to minimal exertion, and poor weight gain.
Timely clinical diagnosis of tricuspid atresia, through careful evaluation of clinical and auscultatory signs in the first days of life, is fundamental for the prompt initiation of instrumental diagnostic investigations and the planning of an effective and early therapeutic strategy.
The diagnosis of tricuspid atresia is usually established early after birth, guided by the obvious clinical presentation, dominated by persistent cyanosis and respiratory distress. The diagnostic suspicion is primarily based on clinical criteria, such as cyanosis resistant to oxygen therapy, early respiratory failure, and signs of systemic venous congestion.
The first instrumental investigations, which are rapidly accessible and useful for the initial assessment, include:
Definitive and detailed diagnosis relies on transthoracic echocardiography (TTE), which is the diagnostic gold standard. Echocardiography confirms the absence of the tricuspid valve and the complete separation between the right atrium and right ventricle. Direct visualization usually shows a small or rudimentary right ventricle, not communicating with the overlying atrium. The examination also demonstrates the associated cardiac defects essential for maintaining circulation: an atrial septal defect (generally large), a ventricular septal defect, and assessment of ductus arteriosus patency. Color Doppler completes the investigation by evaluating intracardiac blood flow, documenting the obligatory mixing of oxygenated and desaturated blood, and assessing the degree of pulmonary circulation compromise.
Transesophageal echocardiography (TEE), although rarely necessary in neonates, may be useful in cases with particularly complex anatomy or for defining essential anatomical details for surgical planning.
In selected cases, cardiac magnetic resonance imaging (CMR) can provide additional essential information to evaluate the volume and function of the left ventricle, detailed morphology of the associated defects, and the presence of possible extracardiac vascular anomalies.
Similarly, cardiac computed tomography (CT) has limited indications, mainly reserved for cases requiring precise extracardiac anatomical definition, such as assessment of the pulmonary arteries or systemic vascular structures prior to palliative surgical correction.
The differential diagnosis of tricuspid atresia is limited but important. It must be distinguished from other cyanotic congenital heart diseases, such as hypoplastic left heart syndrome, pulmonary atresia with intact ventricular septum, and transposition of the great arteries. Echocardiography, in expert hands, enables easy differential diagnosis based on the precise anatomical definition of the cardiac chambers and valves involved.
Diagnostic speed and accuracy are essential to promptly initiate initial medical therapy (maintenance of ductus arteriosus patency with prostaglandins) and to plan, with precision, the palliative surgical strategy, which is the only realistic possibility for ensuring long-term survival and acceptable quality of life.
The treatment of tricuspid atresia is complex, multidisciplinary, and based on a sequential surgical strategy with palliative intent, aiming to ensure a physiologically sustainable univentricular circulation. The therapeutic goal is not to reconstruct normal cardiac anatomy, but rather to create a stable hemodynamic circuit in which systemic and pulmonary blood are separated as much as possible, despite the absence of a functioning right ventricle.
Initial neonatal management is medical, aimed at stabilizing the newborn and maintaining ductus arteriosus patency through continuous infusion of prostaglandins (PGE1). This approach ensures adequate pulmonary perfusion until the first surgical intervention is performed. In neonates with restrictive atrial septal defect or non-patent foramen ovale, urgent atrial septoplasty (Rashkind procedure) may be required to allow mixing of venous and arterial blood and prevent acute systemic congestion.
The surgical strategy consists of three main stages:
Short-term prognosis has improved significantly due to optimized neonatal intensive care, surgical techniques, and careful patient selection. Survival into adulthood is now possible in a significant proportion of patients (70–80% at 10 years), particularly in those managed in high-volume, experienced centers.
However, even after completion of the Fontan procedure, patients require close and continuous follow-up: univentricular circulation, while stable, exposes patients in the long term to complications such as progressive ventricular dysfunction, atrial arrhythmias, chronic systemic venous hypertension, protein-losing enteropathy, and thromboembolic risk.
Positive prognostic factors include the absence of extracardiac anomalies, favorable cardiac morphology (adequate pulmonary vessel size, left ventricular compliance), satisfactory hemodynamic balance in intermediate stages, and good response to the staged strategy. Conversely, poorly tolerated Fontan physiology or failure of cavopulmonary separation are high-impact events on survival and quality of life.
The complications of tricuspid atresia arise both from the intrinsic pathophysiology of the malformation and from the long-term effects of the palliative univentricular circulation established by the Fontan procedure. The complexity of management and the chronicity of the hemodynamic condition require vigilant, long-term monitoring to effectively prevent and treat adverse events.
In the natural untreated course, tricuspid atresia quickly leads to death due to severe hypoxia, congestive heart failure, and metabolic acidosis, often within the first weeks or months of life. Closure of the ductus arteriosus in an unstable neonate can cause a dramatic reduction in pulmonary blood flow and circulatory collapse. In cases with restrictive atrial septal defect, episodes of syncope, hypoxic seizures, and sudden death may occur.
After palliative surgical treatment, the main medium- and long-term complications are:
Furthermore, surgically treated patients may develop complications specific to the Fontan strategy, including:
In the long term, some patients may require heart transplantation, indicated in cases of failed univentricular physiology, severe systemic ventricular dysfunction, or uncontrollable complications (e.g., refractory PLE or advanced cirrhosis).
A constant, multidisciplinary follow-up—encompassing pediatric and adult cardiologists, hepatologists, hemodynamics specialists, and nutritionists—is essential to monitor the complications of the Fontan circulation and to ensure improved survival and quality of life.