The Normal Impulse Gradient Murmur and the Increased Flow Murmur

1. How can a systolic murmur be produced across a normal semilunar valve? ANS: There is always a forward pressure gradient across a semilunar valve, as there must be in any pipe with a forward flow.

Flow direction

Flow direction

The gradient between the upstream and downstream manometers may not be measurable by the usual cardiac catheter techniques. If, however, the gradient is increased enough by obstruction to flow, a semilunar valve, or even a local protuberance from one wall, enough turbulence may occur to produce a murmur.

2. What is the relationship between the gradient across the semilunar valve and the shape of the murmur?

ANS: The greater the gradient across a semilunar valve, the louder and longer the murmur and the later the peak of the crescendo-decrescendo.

Aortic and LV pressure tracings together with a phonocardiogram from a 40-year-old man with an innocent aortic ejection murmur. Note the early systolic gradient between the LV and aorta, which is the normal impulse gradient found not only in normal left-sided chambers but also normally seen between the right ventricle and pulmonary artery. This tracing is taken by a single catheter with two end holes, in order to obtain absolutely accurate timing and pressure differences across the aortic valve.

Aortic and LV pressure tracings together with a phonocardiogram from a 40-year-old man with an innocent aortic ejection murmur. Note the early systolic gradient between the LV and aorta, which is the normal impulse gradient found not only in normal left-sided chambers but also normally seen between the right ventricle and pulmonary artery. This tracing is taken by a single catheter with two end holes, in order to obtain absolutely accurate timing and pressure differences across the aortic valve.

3. In what percentage of normal subjects is the normal impulse gradient ejection murmur heard?

ANS: In 100%, depending on a. The soundproofing of the room. All normal subjects have an ejection murmur in a soundproof room, usually along the left sternal border [1].

b. The age of the subject. About 90% of healthy children up to age 14 have ejection murmurs on ordinary clinical examination in a quiet but not soundproof room [2]. 'These murmurs are usually maximal at the left sternal border. About 15% of adults under age 40 have an innocent ejection murmur.

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