What makes s2 heart sound

This differs from a fixed split S2, which exhibits the same amount of splitting throughout the entire respiratory cycle and is explained below. Any condition that causes a nonfixed delay in the closure of the pulmonic valve, or early closure of the aortic valve, will result in a wide split S2. In mitral regurgitation, this is due to a large proportion of the left ventricular stroke volume entering the left atrium, causing the left ventricular pressure to decrease faster.

A fixed split S2 is a rare finding on cardiac exam; however, when found, it almost always indicates the presence of an atrial septal defect. A fixed split S2 occurs when there is always a delay in the closure of the pulmonic valve, and there is no further delay with inspiration; compare this to a widened split S2, as described above. To explore why an atrial septal defect results in a fixed split S2, we must consider the altered cardiac hemodynamics present, which result in a fixed delay in PV closure.

During inspiration, as usual, there is an increase in venous return to the right side of the heart, and thus increased flow through the PV — delaying its closure. The alteration in a patient with an ASD occurs during expiration. As the person expires, the pressure in the right atrium decreases because there is less venous return.

The decreased pressure allows more blood to flow abnormally through the ASD, from the high pressured left atrium to the right atrium, ultimately resulting again in increased flow through the pulmonic valve — again, delaying its closure. Given the lower vascular resistance of the pulmonary artery, during inspiration, the pulmonary artery is able to tolerate more volume of blood before the pressure above the valve increases.

Additionally, during inspiration, more blood fills the right ventricle leading to a slightly longer ejection time, adding to the delayed pulmonic valve closure. This video was created by Dr. Click this link to see his collection of medicine educational videos. The 25 The 25 Visit the Abraham Verghese Interviews Dr.

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