Cor triatriatum is a rare congenital cardiac anomaly in which a fibromuscular membrane divides the atrium in two. In its most common form, cor triatriatum sinister, the left atrium is divided into an upper chamber that receives the pulmonary veins and a lower chamber that is related to the left atrial appendage and the mitral valve orifice. However, variable types of subtotal cor triatriatum are also noted, with only the right or left pulmonary veins draining into the upper chamber.
An embryologically unrelated membrane may rarely divide the right atrium; this finding, so-called cor triatriatum dexter, is usually asymptomatic and is mostly reported as an incidental finding.
The location of the atrial appendage is a key landmark in this congenital malformation. It differentiates cor triatriatum from a physiologically similar condition, supravalvular mitral stenosis. In cor triatriatum the left atrial appendage is invariably associated with the lower chamber, which is below the membrane.
This is a very rare malformation. Incidence is approximately 0.1-0.4% of all infants with congenital cardiac disease. Approximately 75% of patients die in infancy (generally from pulmonary hypertension) if the defect is unrepaired. If the communication between the proximal and distal chambers is not restrictive or if an atrial septal defect allows decompression of the hypertensive left atrium, the prognosis is significantly improved.
The natural history of this defect depends on the size of the communicating orifice between the upper and lower atrial chambers. If the communicating orifice is small, the patient is critically ill and may succumb at a young age (usually during infancy) to congestive heart failure and pulmonary edema. If the connection is larger, patients may present in childhood or young adulthood with a clinical picture similar to that of mitral stenosis. Cor triatriatum may also be an incidental finding when it is nonobstructive.
Cor triatriatum may be associated with other cardiac defects in as many as 50% of cases. Examples of associated cardiac defects include:
- atrial septal defect
- persistent left superior vena cava with an unroofed coronary sinus
- partial anomalous pulmonary venous connection
- ventricular septal defect
- tetralogy of Fallot
- atrioventricular canal
- double outlet right ventricle.
Associated bicuspid pulmonary valve, aortic valve atresia, and heterotaxy have also been described. Congenital pulmonary vein stenosis is a very rare association with cor triatriatum.
The presentation of cor triatriatum is one of decreased cardiac output and pulmonary venous hypertension. If a connection between the common pulmonary venous chamber and the right atrium is present, pulmonary overcirculation may result in significant right ventricular enlargement.
The only treatment is surgical correction. Most postoperative deaths occur in the first 30 days. The early mortality rate in each large series was consistently 15-20%. Early deaths had a higher rate of associated severe cardiac anomalies.
Long-term results are excellent, with long term survival of 80-90% in patients surviving surgery. Survivors have excellent functional results without residual sequelae and a life expectancy that approaches that of the general population. This is particularly true when repair is performed in infancy.
Source: Medscape, 06-30-2009
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