Cor triatriatum is a rare congenital heart defect characterized by the presence of an intra-atrial membrane that partially or completely divides one atrium into two distinct chambers. This abnormal partition can obstruct normal atrial blood flow and lead to significant hemodynamic consequences, particularly if not diagnosed and treated early. The malformation can affect either the right or left atrium, with the most common form involving the left atrium, where a membrane separates pulmonary venous return from the rest of the heart.
Cor triatriatum accounts for a small percentage of congenital heart diseases, with a prevalence of approximately 1 case per 15,000–25,000 live births. Most cases are diagnosed during childhood, although some individuals may remain asymptomatic until adulthood, especially when the malformation is small.
The formation of cor triatriatum is related to an error during the embryological development of the atrium. Around the sixth week of gestation, the fetal heart undergoes a remodeling process that defines the final separation between the right and left atria. A disruption during this critical phase leads to the persistence of an intra-atrial membrane, creating a division within the atrium.
The main forms of cor triatriatum are:
Cor triatriatum sinister is often associated with other congenital cardiac anomalies, such as atrial septal defect (ASD) or mitral valve stenosis.
Cor triatriatum creates a physical obstruction to blood flow between the two atrial chambers. Depending on the size of the membrane and the position of the communication orifice, the degree of flow limitation can vary widely. Generally, reduced atrial flow can cause volume or pressure overload in the upstream cardiac chambers, impacting ventricular function.
In cor triatriatum sinister, the membrane can obstruct pulmonary venous return, leading to pulmonary congestion and pulmonary hypertension. Restricted flow through the communication orifice increases left atrial pressure, favoring the development of congestive heart failure and arrhythmias, such as atrial fibrillation.
Without treatment, the hemodynamic overload may lead to:
In some instances, the condition may progress to complications such as irreversible pulmonary vascular damage and Eisenmenger syndrome.
Cor triatriatum is a congenital anomaly that develops during fetal life. Although most cases are sporadic, certain genetic and environmental factors may increase the risk of occurrence.
The main predisposing factors include:
Preventing cor triatriatum is challenging. However, minimizing teratogen exposure, optimal pregnancy management, and maternal vaccination against rubella are fundamental preventive strategies. Nevertheless, no specific measures can fully prevent the anomaly.
The clinical presentation of cor triatriatum primarily depends on the size of the membrane, the presence of a communication orifice, and the severity of the hemodynamic overload. Severe forms usually present early with signs of congestive heart failure. Less severe forms may remain asymptomatic for years and be discovered incidentally in adulthood.
Patients with significant cor triatriatum typically present symptoms related to left atrial overload or pulmonary congestion. Major symptoms include:
In young children, the malformation can cause failure to thrive and growth retardation due to pulmonary congestion and increased cardiac workload.
On physical examination, the hallmark of cor triatriatum is a systolic murmur of variable intensity, often heard best at the upper chest. In cases of left atrial overload, an accentuated pulmonary component of the second heart sound may be noted, indicating pulmonary hypertension. An irregular heart rhythm due to atrial arrhythmias can also be detected.
Signs of pulmonary congestion, such as pulmonary crackles and jugular venous distension, may be present. In untreated pediatric cases, delayed physical development can also be observed.
Cor triatriatum should be suspected in patients presenting with symptoms suggestive of left heart failure, combined with a characteristic systolic murmur. The presence of a continuous or variable-intensity murmur guides clinicians toward the correct diagnosis.
Transthoracic echocardiography is the first-line examination for diagnosing cor triatriatum. Color Doppler imaging visualizes the intra-atrial membrane and the disturbed blood flow. Echocardiography also documents the communication between the two atrial chambers and evaluates the degree of hemodynamic overload.
If the transthoracic window is suboptimal or complications are suspected, transesophageal echocardiography provides a more detailed visualization and is useful for surgical planning.
Cardiac magnetic resonance imaging (MRI) is useful in complex cases, allowing precise evaluation of membrane dimensions and hemodynamic impact. It also offers detailed anatomical imaging without radiation exposure.
Cardiac catheterization is rarely necessary for diagnosis but may be employed in selected cases to directly measure pressures and plan treatment in advanced cases with significant hemodynamic compromise.
The treatment of cor triatriatum depends on the severity of the malformation, the extent of hemodynamic overload, and the presence of complications. In asymptomatic or mildly symptomatic cases, conservative management with periodic echocardiographic monitoring is appropriate to detect any progression of obstruction or ventricular dysfunction.
In patients with significant symptoms, such as congestive heart failure or atrial arrhythmias, therapeutic intervention becomes necessary.
Open-heart surgery remains the treatment of choice for hemodynamically significant cor triatriatum. The procedure involves the complete or partial resection of the intra-atrial membrane, restoring normal atrial blood flow. Surgery is performed under cardiopulmonary bypass, with very low morbidity and mortality rates in specialized centers.
In cor triatriatum sinister, membrane resection is usually carried out through a left thoracotomy. Surgical correction yields excellent long-term results, with normalization of cardiac hemodynamics and resolution of symptoms.
Percutaneous intervention for cor triatriatum is an emerging therapeutic option, although not yet widely adopted. It is suitable for selected patients with small, well-defined membranes. Using a closure device, the procedure is performed under general anesthesia via femoral venous access, offering a minimally invasive alternative to open surgery.
The prognosis for patients undergoing timely surgical correction of cor triatriatum is excellent. Following membrane resection, patients typically experience complete resolution of symptoms, normalization of cardiac function, and regression of chamber dilatation. Long-term survival is comparable to that of the general population, without a significant risk of late complications.
In untreated or late-treated cases, the risk of complications such as chronic heart failure, arrhythmias, and pulmonary hypertension is significantly increased. In severe cases, Eisenmenger syndrome may develop, complicating management and worsening prognosis substantially.
The main complications associated with untreated cor triatriatum include:
Early surgical correction significantly reduces the risk of these complications, allowing patients to achieve normal or near-normal quality of life and long-term survival.