Ventricular Septal Defect And The Presence Of Heart Murmurs

Heart murmurs are commonly detected during auscultation in patients with ventricular septal defect (VSD). There are two primary mechanisms behind the formation of these murmurs. In the case of a small VSD, high-pressure blood flow from the left ventricle passes through the narrow opening into the low-pressure right ventricle. This creates a jet effect that generates a distinctive murmur, one of the key reasons why small VSDs are often associated with audible heart sounds.

Size And Sound: An Interesting Relationship

Interestingly, the smaller the defect, the higher the pitch of the murmur tends to be. This inverse relationship between the size of the VSD and the intensity or pitch of the murmur can be quite surprising. On the other hand, in cases of large VSDs, the situation changes significantly. Clinically, these are often referred to as non-restrictive VSDs, where the diameter of the defect exceeds that of the aorta.

Large VSDs And The Absence Of Murmurs

With a large VSD, there is a substantial opening in the septum between the left and right ventricles. Blood flows freely from the left ventricle to the right, causing the right ventricle to function under high pressure. As a result, there may be sufficient mixing of blood between the two ventricles, and in many cases, no murmur is heard at the ventricular level.

Secondary Effects On The Pulmonary Valve

However, the increased volume of blood passing through the VSD into the right ventricle eventually leads to an overload in the pulmonary artery. Even though the pulmonary valve and vessels may be of normal size, the excessive flow can create turbulence, mimicking a condition known as relative pulmonary valve stenosis. This turbulence is what often leads to the detection of a secondary murmur in these cases.

Understanding The Differences In Murmur Mechanisms

Therefore, the mechanisms behind heart murmurs in small versus large VSDs are quite different. Some very small defects, measuring only 1-2mm or 2-3mm, may not produce any noticeable murmur at all. This variability is important to understand, especially in the context of natural healing.

Murmur Intensity Is Not Always Indicative Of Defect Size

In some cases, as a VSD begins to close on its own, the murmur may initially be moderate in intensity. As the defect reduces to around 4-5mm, the murmur may actually become louder. However, if the defect continues to shrink further, down to 2-3mm or less, the amount of blood shunting from left to right decreases significantly. As a result, the murmur may become barely audible or even disappear altogether.

For this reason, the loudness or softness of a heart murmur alone cannot reliably indicate the size of a ventricular septal defect. Accurate diagnosis should always be based on imaging techniques such as echocardiography rather than auscultation alone.