Wide split fixed 2nd hea sound is heard in : March 2005
**Core Concept**
A wide split fixed second heart sound is a clinical finding indicative of increased flow across the pulmonary valve, typically seen in conditions with high pulmonary blood flow or volume overload states. This phenomenon is related to the altered dynamics of the pulmonary valve and the left ventricle.
**Why the Correct Answer is Right**
The fixed splitting of the second heart sound is a characteristic finding in conditions that lead to increased flow across the pulmonary valve, such as atrial septal defects (ASDs). In ASDs, there is a left-to-right shunt at the atrial level, resulting in increased blood flow through the pulmonary valve and a fixed split of the second heart sound. This fixed split is due to the increased volume of blood flowing through the pulmonary valve, which does not change with respiration like it would in conditions with dynamic splitting. The increased flow causes the pulmonary valve to open earlier and close later, resulting in a split that does not change with inspiration or expiration.
**Why Each Wrong Option is Incorrect**
**Option A:** Mitral regurgitation is a condition that typically leads to a dynamic split of the second heart sound, not a fixed split. This is because the increased flow through the pulmonary valve in mitral regurgitation changes with respiration.
**Option B:** Pulmonary stenosis is a condition that typically leads to a decreased flow across the pulmonary valve, resulting in a single or narrowed second heart sound, not a wide split.
**Option C:** Ventricular septal defects (VSDs) can lead to a wide split second heart sound due to increased flow across the pulmonary valve, but it is not as characteristic as in ASDs and can be dynamic.
**Clinical Pearl / High-Yield Fact**
A fixed split second heart sound is a classic finding in atrial septal defects, and it is often used as a key clinical clue in the diagnosis of these conditions.
**Correct Answer:** C.