Answer

A. The LV S3

Expiration can make the S3 louder by the following:

Increasing blood flow out of the lungs into the left atrium (LA) and LV.

The stethoscope coming closer to the chest wall.

The apex beat coming out of the ribs in expiration and thus even S3 can be palpated by this phase.

The S3 is very sensitive to the proximity of the stethoscope to the apex beat, since it is a low-pitched sound.

When the bell of the stethoscope is applied very lightly to the apical region and the patient is turned to the left lateral decubitus position, the LV S3 is heard particularly during expiration.

B. The pericardial knock

The ventricle is restricted to the extent in which it can expand.

This is compensated by very early diastolic filling.

There is also an excessive catecholamine surge in the LV.

Further increase in venous return to the right atrium (RA) on inspiration can only cause the filling pressure to increase, as the right ventricle (RV) is unable to accommodate this increase.

This increase of the RA pressure and the inability of the RV to accommodate this rise results in rise of jugular venous pressure (JVP) or failure of the JVP to fall on inspiration, producing the Kussmaul's sign.

During expiration, the filling pressure of the RA is still high; hence, the filling occurs in the same way to the RV, causing no change in the pericardial knock.

However, the pericardial knock is sensitive to changes in blood volume. Diuretics which decrease the RA filling pressure can eliminate the pericardial knock.

Publication Date:
31 October 2021 (online)

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