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1. Which left ventricular (LV) hemodynamic events occur in diastole after the S2 but before the S3?

ANS: Isovolumic relaxation, and after opening of the mitral valve, early rapid filling of the LV.

2. When does isovolumic relaxation begin and end in the LV?

ANS: It begins with aortic valve closure and ends with mitral valve opening. As soon as isovolumic relaxation ends and the mitral valve opens, the LV fills rapidly from the left atrium.

-Aortic pressura curve

LV pressure curve

L atrial pressure curve

LV pressure curve

L atrial pressure curve

Between point A (aortic valve closure) and point B (mitral valve opening), the volume in the LV is unchanged. This is therefore the isovolumic relaxation period.

3. Does the ventricle fill most rapidly in early, middle, or late diastole?

ANS: In early diastole. The ventricle has two rates of expansion: an early rapid one and a later slow one. Once the aortic valve opens, the LV expands very rapidly during isovolumic relaxation; even after the mitral valve opens, it continues to expand rapidly during the phase of rapid ventricular filling. From the time the aortic valve closes to make the S 2 to the end of the rapid filling phase when the S3 occurs is a fairly short period of time of about 120 ms. This can be imitated by saying "two-three" as quickly as possible. At the end of the rapid filling phase, rapid expansion of the ventricle is checked by unknown forces, and the slow expansion phase takes over.

4. What percentage of ventricular filling occurs in the early rapid filling phase of diastole in comparison with the later slow filling phase of diastole?

ANS: About 80%. After the initial rapid filling, the volume of the ventricle changes very little until atrial contraction squeezes the last 20% of blood into the ventricle.

5. At what point during the rapid filling phase of the LV pressure curve does the S3 occur?

ANS: Near the end of the rapid pressure drop in the LV, i.e., near the point at which rapid expansion changes to the slow expansion phase.

Note: Some rapid filling continues to occur after the S3.

At slow rates (top line) the S3 is much closer to the S2 than to the following St; i.e., it falls in the first quarter of diastole. At fast rates (bottom line) it may occur in mid-diastole.

At slow rates (top line) the S3 is much closer to the S2 than to the following St; i.e., it falls in the first quarter of diastole. At fast rates (bottom line) it may occur in mid-diastole.

6. In what part of diastole does the S3 usually fall?

ANS: In the first third in patients with normal heart rates, and in the middle third in those with tachycardias.

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