What are the ventricles ?
What is the Ventricular septum ?
The heart has 2 pumps; pumping blood is the main function of the heart; the 2 pumps are separated by a wall called the ventricular septum. The right pump receives the blue blood which has to go to the lungs for picking up oxygen. This pump has to push blood into its vicinity (heart and lungs being close by within the chest); so the normal pressure in this pump is 30-35 mmHg.
The Left Pump pushes the red blood into the lungs; it has to ensure blood reaches all the parts of the body so the pressure here is equivalent to the blood pressure (upper number of BP i.e. Systolic).
What is a Ventricular septal defect (VSD)
A defect in the wall which separates the ventricles is called a VSD. The high pressure in the Left pump as compared to the Right ensures that the blood flows from the left to the right pump (therefore is called a L to R shunt). This implies red (left sided) blood gets into the blue (right sided) blood; this implies that in this condition the patient is not going to be blue.
How common is it?
It is one of the most common defects of the heart. Infact it is the most common defect.
Can it be detected before birth ?
Yes, it can be detected before and at birth. Often, it will detected on an ultrasound. But on fetal echocardiogram there is a better chance of it being picked up. The way this hole is noticed, is by seeing abnormal flow across the septum. But, during fetal life the pressure between the 2 pumps is the same. So, there is not much flow across the hole and that makes it difficult to pick up.
What is the age at which it is most often diagnosed?
Most often it will get diagnosed around the first month of life. The child has maximum symptoms from the hole around 6 weeks of age.
Why is it not diagnosed earlier?
Since the pressure between the 2 chambers is same, no flow across the hole happens at birth and therefore, no extra sound is produced. As the lung pressure drops between 7th and 28th day of life, significant flow starts across the hole; so, the sound gets heard of the flow across the hole.
How does a small hole differ from a large hole?
A small hole allows little amount of blood to go across the hole. A large hole gets a lot more of blood across the hole. This extra amount of blood coming to the right side of the heart immediately gets transmitted to the lungs from where it goes to the left side of the heart. So, it is really the left side if the heart, the left upper and lower chambers which get to see this extra amount of blood!
If this blood amount is large, the left side of the heart gets dilated and volume overloaded. This can be seen on an X-ray as enlarged heart. This reverses once the extra blood flow stops.
If the amount of blood is large, there will also be an increase in pressure in the right side of heart and in the lungs. While with the Small VSD the volume will be so small the left heart won’t enlarge. And neither will the pressure in the right heart go up.
At what age is VSD closed?
VSD when large has to be closed by the 3rd to 6th month of life. The decision to close the
VSD has to be made well in time to give family enough time to accommodate to the fact that
heart surgery has to be done on their child and that apart from the emotions of the decision
(how so ever safe it might be, parents will take time to decide and accept), there are
financial (or insurance clearance issues also).