Ejection Sound in Pulmonary Stenosis PS

1. What proof can be offered that the ejection sound heard in valvular PS it an opening sound of the pulmonary valve?

ANS: a. It is not present in pure infundibular stenosis.

b. It occurs at the peak of opening of the pulmonary valve on echocardiography.

2. Why does the pulmonary ejection sound tend to disappear with inspiration in valvular PS?

ANS: The sudden upward movement of a dome-shaped pulmonary valve produces the sound. If the valve is already in the domed or near-domed position when the RV contracts, there will be no sound or only a soft sound. On inspiration, the increased blood drawn into the right atrium causes it to contract more strongly at the end of diastole. This raises the end-diastolic pressure in the RV just before the ventricle contracts to a level that may be higher than the pulmonary artery pressure. This is easy to understand if you realize that pulmonary artery diastolic pressure in PS may not be much more than 7 mmHg, and RV end-diastolic pressure in PS can easily exceed 7 mmHg. Thus the pulmonary valve will be raised into the domed position at the end of diastole if the end-diastolic pressure in the RV rises to 8 mmHg with a strong right atrial contraction.

On expiration, the end-diastolic pressure in the RV falls, and the pulmonary valve is now in the down position at the beginning of RV systole. Ventricular contraction can now balloon the pulmonary valve upward into a dome, causing a click.

These RV and pulmonary artery pressure tracings show how inspiration can raise the end-diastolic RV pressure above pulmonary artery (PA) pressure because of a strong right atrial contraction plus a thick RV.

3. Why does the aortic ejection sound not change significantly with respiration?

ANS: The end-diastolic pressure in the LV in AS, even when very high (the normal end-diastolic pressure is not much higher than 10 mmHg), can never exceed the usual diastolic pressure in the aorta (which is rarely ever lower than 50 mmHg). Therefore, expiration alone can never force the aortic valve into an upward domed position at the end of diastole.

On the left is shown how right atrial contraction is assisted by inspiration in raising RV pressure higher than pulmonary artery pressure. This causes the pulmonary valve to dome upward before the RV contracts. On the right is depicted the effect of a reduction in RV diastolic pressure caused by expiration resulting in a downward position of the pulmonary valve when the RV begins to contract.

A high-frequency phonocardiogram from the third left interspace of a patient with PS and an RV pressure of 100 mmHg. The ejection sound tells you that the obstruction is valvular. Note that it disappears on inspiration.

Note: A pulmonic ejection sound tends to occur more often in mild to moderate stenosis, i.e., with RV pressures of not over 70 mmHg. (Normal RV systolic pressure is about 25 mmHg.)

4. Where is the pulmonary ejection sound best heard?

ANS: Wherever pulmonary sounds and murmurs are best heard, i.e., anywhere along the left sternal border.

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