Characteristics Of The Ejection Murmur

1. What valvular flow event is implied by the term ejection murmur?

ANS: The term implies a murmur that is produced by blood flowing forward through a semilunar valve (aortic or pulmonary valve) during systole.

2. What is characteristic of ejection murmurs on a phonocardiogram?

ANS: They start with the final component of the first heart sound (S1); are diamond, rhomboid, or kite-shaped; and finish before the second sound of the side of the heart from which the murmur originates. This means that a left-sided ejection murmur will finish before the A2, and a right-sided ejection murmur will finish before the P2.

3. Why must an ejection murmur be crescendo-decrescendo in loudness?

ANS: The configuration and loudness of a murmur across a valve is controlled mainly by the shape of the gradient. This gradient is proportional to the velocity and acceleration of flow.

In aortic stenosis (AS), as the pressure in the left ventricle (LV) rises to just above diastolic pressure in the aorta, it takes a short time to overcome the inertia of the aortic blood and walls. Therefore, the initial gradient across the aortic orifice is slight, and the murmur starts softly.

This murmur could be either pulmonary or aortic, since it ends before both components of the second sound.

This murmur may be a pulmonary ejection murmur, since, although it extends beyond the A2, it finishes before the P2.

This murmur could be either pulmonary or aortic, since it ends before both components of the second sound.

This murmur may be a pulmonary ejection murmur, since, although it extends beyond the A2, it finishes before the P2.

A simultaneous aortic and LV pressure tracing (taken with a catheter-tip micromanometer to eliminate time delays through tubes) in a subject with valvular AS. The shape of the murmur follows the shape of the gradient (shaded area).

The pressure gradient and velocity of flow then increases toward mid-systole, as does the murmur. As soon as the ventricle begins to reach the stage of reduced ejection, just past the middle of systole, the flow decreases, and the murmur decreases.

Just before the valve closes, the velocity of forward flow has decreased so much that even if the murmur does extend to the second sound by phonocardiogram, the ear cannot hear the very end of this faint decrescendo part of the murmur.

The decrescendo at the end of an ejection murmur is steep enough so that if the murmur is short, with the peak early in systole, a pause before the S2 is easily perceived. Such a murmur and obvious pause suggests a small gradient. (See figure on p. 198.) However, if the stenosis is more than mild, the peak may reach mid-systole with no obvious pause between the end of the murmur and the S2, and it may be difficult to know that it is not a pansystolic regurgitant murmur. However, if the ejection murmur is louder than the S2, the steep decrescendo allows you to hear even a very soft S2. A regurgitant murmur that is louder than the S2 will eliminate any S2 that is not louder than the murmur.

4. What happens to the loudness of an ejection murmur after a long diastole, as in the long pause after a premature ventricular contraction or after the long diastoles of atrial fibrillation? Why?

ANS: It becomes louder because a. The long period of diastole allows a larger volume to collect in the LV and stretch its walls. This increased volume is ejected during the next systole with increased energy by means of the Starling effect.

b. A long diastole allows more peripheral runoff and therefore a reduction in afterload. This causes an increase in the velocity of myocar-dial shortening and an increase in the volume of forward flow.

c. The postextrasystolic potentiation following an early ventricular depolarization (as with premature ectopic beats) produces a positive inotropic effect on the ventricle and contributes to the loudness of the ejection.

5. Why do the pitch or frequency characteristics of an ejection murmur not change when the murmur is soft?

ANS: Ejection murmurs are produced by the entire stroke volume passing through the aortic or pulmonary valves with each systole. Therefore there will always be enough flow to produce low and medium frequencies, even when the obstruction or gradient across the valve is trivial. This is not true for regurgitant murmurs.

A phonocardiogram and simultaneous aortic and LV pressure tracing from a 16-year-old boy with valvular AS. Not only did the murmur and gradient increase after the long diastole, but the ejection sound also increased. Note that the small gradient of the premature ventricular contraction (PVC) itself produced only a short early systolic murmur.

A phonocardiogram and simultaneous aortic and LV pressure tracing from a 16-year-old boy with valvular AS. Not only did the murmur and gradient increase after the long diastole, but the ejection sound also increased. Note that the small gradient of the premature ventricular contraction (PVC) itself produced only a short early systolic murmur.

6. How can you best define an ejection murmur?

ANS: It is best defined as an "ejection murmur complex," i.e., it is a murmur that begins at the end of the S1, is crescendo-decrescendo, ends before the second sound of its side, becomes louder after long diastoles, and retains low and medium frequencies even when soft.

7. How can you tell by auscultation that a murmur is markedly crescendo-decrescendo?

ANS: A rhythmic cadence is created by the sequence of the S1 followed by the peak of the crescendo followed by the S2:

huh-huh-duh

S1 Peak S2 of diamond

Note: If an S2 is missing, the rhythm of "huh-huh" tells you that the murmur is crescendo-decrescendo. If the S1 is missing, the rhythm of "huh-duh" also tells you that the murmur is crescendo-decrescendo.

Prolonged Murmur
The peak of the ejection murmur produces a recognizable cadence or rhythm even if only one of the heart sounds is present.

8. How can the loudness of an ejection murmur tell you whether or not there is a significant gradient across a valve?

ANS: A soft murmur, i.e., grade 2 or less, is likely to signify an unimportant gradient, provided that artifactual reasons for the softness, such as obesity or heart failure, are absent. If the murmur is very loud, i.e., grade 4/6 or more, the gradient is likely to be at least 20 mmHg. Unfortunately, a loud murmur does not tell you how much over 20 mmHg the gradient may be.

9. List some factors, besides a thin chest wall, that spuriously increase the loudness of systolic ejection murmurs, i.e., without reflecting the degree of the gradient.

ANS: Any cause of increased flow, such as exercise, thyrotoxicosis, arteriovenous fistula, anemia, shunt, or excessive diastolic filling, as in bradycardia or aortic regurgitation.

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