Interatrial Communication
A congenital cardiac malformation characterized by a communication between the atrial chambers of the heart.
Epidemiology
Overall, openings between the atrial chambers account for about 6 to 8% of all congenitally malformed hearts. As a group, the prevalence at birth is between 6 to 9/10000; however, this is likely an underestimated due to the asymptomatic nature of the disease. The female-to-male ratio is 2-4:1.
Clinical description
There are four types of defects, named according to their position relative to the atrial septum. The ostium secundum defect is the most common type, accounting for three-quarters of all cases, located to the region of the oval fossa, most commonly due to a deficiency of the primary atrial septum (septum primum) but deficiency of the septum secundum (superior interatrial fold) may also contribute. The ostium primum defect, which accounts for one-sixth of defects, is in reality an atrioventricular septal defect, with shunting exclusively at atrial level. Only these two defects are true atrial septal defects. The sinus venosus defect (one-tenth of cases) is a hole outside the confines of the oval fossa, through which a caval vein and/or pulmonary vein(s) override the atrial septum or the septum secundum (superior interatrial fold) producing an interatrial or anomalous veno-atrial communication.The rarest defect, the coronary sinus defect, is a communication between the left atrium and the coronary sinus allowing interatrial communication through the orifice of the coronary sinus, and is due to absence or partial unroofing of the coronary sinus. Interatrial communications are most often asymptomatic in childhood but clinical manifestations can include: rapid breathing, shortness of breath, fatigue, sweating, palpitations, frequent respiratory infections, and poor growth. Symptoms often manifest by the age of 30 to 40 years. Adults with interatrial communications are at increased risk of developing pulmonary arterial hypertension, heart failure, arrhythmias, and stroke. About one third of affected children have an associated hereditary syndrome, such as Down's syndrome, Alagille syndrome, Holt-Oram syndrome, Ellis-van Creveld syndrome, or Noonan syndrome.
Etiology
Several susceptibility genes have been identified.
Diagnostic methods
The defect is most often suspected during a physical examination. Cardiac auscultation reveals a systolic outflow murmur. Echocardiography, chest X-ray and electrocardiogram, and cardiac catheterization may help the diagnosis, although the latter technique is now rarely required for diagnostic purposes.
Differential diagnosis
Differential diagnosis includes other congenital cardiac anomalies that result in left-to-right shunt at the atrial level, including partial atrioventricular septal defect and anomalous pulmonary venous return.
Antenatal diagnosis
A significant defect may be diagnosed during fetal life, although prenatal diagnosis is difficult as interatrial communication is an integral part of fetal circulation.
Genetic counseling
Most defects occur sporadically as a result of spontaneous genetic mutations, but hereditary forms have been reported. Familial secundum defects can be associated with mutations in transcription factors NKX2.5 (5q34), GATA4 (8p23.1), TBX6 (16p11.2), along with conduction disorders such as atrioventricular block.
Management and treatment
Closure of the defect is recommended if left-to-right shunt is important with right ventricular overload and dilatation. Transcatheter device closure is nowadays the treatment of choice for secundum defects beyond the infant period. For other types of interatrial communications, and in large secundum defects with deficient rims, open-heart surgery is indicated, and is complication-free in the majority of cases. Whatever the technique used, closure of the defect is rarely indicated before the age of 3 years. Large defects should be closed before the second decade of life.
Prognosis
Small-to-moderate defects may be asymptomatic and life expectancy is not reduced. In some children, small openings may close spontaneously (occurring in up to four-fifths of cases with small openings in the first 18 months of life). In some patients with large defects, Eisenmenger reaction can occur after the first decade of life.