Atrial septal defect

Isaac Yeboah Health Oct - 20 - 2013 , 12:57

Atrial septal defect (ASD) is one of the most commonly recognised heart defects seen. It is also a type of hole in heart commonly seen in adulthood, even though the child is born with this condition.

As you may recall, the heart has four chambers; two upper chambers called atria and two lower chambers called ventricles. Like the lower chambers, the upper two chambers, the atria, are separated by a partition or curtain called septum.

The atrial septal defect is characterised by a defect or hole in this septum or partition. As a result of this hole, oxygen-rich-blood returning from the lungs pass directly to the right atrium to mix with oxygen-poor blood going to the lungs.

Depending on the size of the defect, magnitude of the blood shunting from one chamber to the other, and associated anomalies, can result in a spectrum of diseases from no significant heart problems to severe debilitating heart failure.

This type of hole in heart can go undetected for decades. This is because of the subtle nature of physical examination findings and, often, minimal symptoms during the first two to three decades.

The three major types of atrial septal defect, determined by the position of the hole, account for 10 per cent of all congenital heart diseases and as much as half of congenital heart diseases present in adulthood.

The ASD is more commonly seen in females. Patients with ASD can be asymptomatic through infancy and childhood, though the timing of clinical presentation depends on the degree of blood leaving the left side of the heart to the right.

This shunt is called left-to-right shunt. Symptoms become more common with advancing age. By the age of 40, 90 per cent of untreated patients have symptoms. Atrial septal defect is a congenital cardiac disorder caused by the spontaneous malformation of the septum.

The magnitude of the left-to-right shunt across the ASD depends on the defect size, the relative compliance of the ventricles resistance against which the heart has to pump.

With small ASD, left atrial pressure may exceed right atrial pressure, whereas with large ASD, mean atrial pressures are nearly identical. The chronic left-to-right shunts results in increased blood flow to the lungs, causing congestion in the lungs.

Resistance against too much blood flow in the lungs is commonly normal in children with ASD, accounting for why children with this condition often go undetected.

Even isolated defects of moderate-to-large size may not cause symptoms in childhood. However, some may have symptoms of getting tired easily, recurrent respiratory infections, or difficulty in breathing after minimal exercise.

Blood flow across the ASD does not usually cause a noise in the heart called murmur, however. In the absence of heart failure, this is the sign picked by most doctors to cause them to investigate for an abnormality of the heart. However, the ASD with moderate-to-large left-to-right shunts result in a murmur.

Due to so much blood going to the lungs, children with this condition tend to have a lot of recurrent chest infections and this may bring them to the hospital instead of the basic heart problem.

The decision to repair any kind of atrial septal defect is based on clinical laboratory information, including the size and location of the ASD, the magnitude and hemodynamic impact of the left-to-right shunt, and the presence and degree of arterial pressures in the lungs.

In general, elective closure is advised for all ASDs with evidence of right ventricular overload or with a clinically significant shunt. Lack of symptoms is not a contraindication for repair.

In childhood, spontaneous closure of a type of this hole in heart called the ostium secundum may occur. However, in adulthood, spontaneous closure is unlikely.

Patients may be monitored relatively conservatively for a period before intervention is advised. Considerations and even contraindications to consider no intervention include the small size of the defect and shunt.

Long-term prevention of death and complications is best achieved when the ASD is closed before age 25 years. Fortunately, this operation is easily carried out at the National Cardiothoracic Centre in Korle Bu.