VSD (Ventricular septal defect)

Ventricular septal defect or VSD refers to a defect (hole) in the interventricular septum (the structure in the heart that separates the two ventricles and prevents the blood in the right ventricle from mixing with that in the left ventricle). It is the most common congenital heart disease.

Whenever there is a defect in the septum between the two ventricles some blood from the left ventricle is pumped into the right ventricle with every contraction because the pressure in the left ventricle is greater than that in the right ventricle. This causes a left to right shunt of blood. The amount of shunt depends on the size of the defect.

Small VSDs (less than 3 mm in diameter): These children do not suffer from any major problem. About 80% of VSDs come under this category. They will close spontaneously. Those in the muscular portion of the interventricular septum close earlier than those in the membranous portion.

About 90% will close by 6 years and the remaining 10% during school years. The shunting of blood across the defect causes turbulence in blood flow which is heard as a murmur using a stethoscope.

The murmur is usually heard soon after birth but sometimes may be detected later.

Moderate VSDs (3-5mm is diameter): About 3-5% of children suffering from V S D have moderate sized defect. Most of them do not suffer from complications like heart failure or pulmonary hypertension. They should be followed up regularly to see whether the defect is becoming smaller.

Large VSD with normal pulmonary pressure (6-10mm): These children are at increased risk of developing heart failure and require surgery. Surgery before the age of 2 years can prevent irreversible pulmonary hypertension. It is usually done between 3 to 6 months of age.

Large V S D with pulmonary hypertension: If not operated early those with large V S D ultimately develop pulmonary hypertension. With severe pulmonary hypertension blood may flow from the right ventricle to the left ventricle causing right to left shunt.

Such children develop cyanosis (bluish discoloration of skin and mucous membrane due to presence of deoxygenated hemoglobin). The prognosis for such patients is very poor. This condition is called Eisennenger syndrome.

Symptoms and signs: Those children with small to moderate defects may not display any symptoms and are diagnosed on routine clinical examination which reveals a murmur due to turbulent blood flow across the defect.

Those with large defects become symptomatic early. They develop frequent attacks of cough, may not be able to feed properly and not gain weight. A prominence may be noted over the left side of the chest. When the murmur is loud the vibrations can sometimes be felt by keeping a hard on the left side of the chest. This is called thrill.

Xray of the chest may be normal in those with small or moderate defects. In a child with large defect there will be enlargement of the heart. Pulmonary vascular marking may be prominent due to increased blood flow.

Echocardiography with color Doppler studies will confirm the diagnosis.

Treatment: Those with small defects usually do not need any medication. They should be followed up till the defect closes.

Those with moderate to large defect who develop cardiac failure should be admitted and treated with diuretics (drugs which increase urine output) and drugs to improve cardiac function.

Children with ventricular septal defects are at increased risk of developing infection of the heart a condition called infective endocarditis especially following therapeutic procedures on the teeth and gums. Hence they need to be put on antibiotics just before such procedures.

Early surgery is indicated in those with large VSDs. A patch is used to cover the defect. Surgery is usually performed between 3 to 6 months. The prognosis after surgical correction is generally good.

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