Quality and Loudness

1. What is the dominant frequency or pitch of the usual AR murmur? Why?

ANS: The dominant frequency is high. If the AR is mild, then the murmur will be due more to a large gradient than to flow, and the murmur will therefore be purely high-pitched and blowing. If the AR is moderate, the murmur will be due to a greater flow as well as to a high-velocity jet, and it will have mixed frequencies but still be dominantly high. If the AR is severe, the murmur may be very rough due to an excess of low and medium frequencies.

Note: Although the more low frequencies there are the more severe the AR, the reverse is not necessarily true, i.e., a pure high-frequency murmur may be present with moderately severe AR. Presumably the low-frequency components are transmitted to areas not accessible to the stethoscope.

2. How can you best imitate by voice the sound of a typical mild AR murmur, i.e., a purely high-pitched murmur?

ANS: In Mexico this has been called an "aspirative" AR murmur and is imitated by breathing in noisily through the mouth. If you breathe out quickly with the mouth open or whisper "ah," you can easily imitate the classic AR murmur.

Note: Because it sounds so much like a breath sound, the patient should hold his or her breath in expiration to allow you to perceive this murmur better.

3. How can you increase the loudness of the very soft AR murmur?

ANS: a. The standard method is to get the stethoscope closer to the heart by having the patient sit up and lean forward. Then press hard with the stethoscope diaphragm over the sternum or left sternal border during held expiration. Another method, not widely known, is to do the same but with the patient in the left lateral decubitus position. b. You can increase peripheral resistance. To do this:

(1) Ask the patient to squat and auscultate the patient's chest immediately. The increase in venous return for a few beats will also help increase the murmur; and/or

(2) Have the patient do isometric exercise by means of a handgrip. The elevation of systolic blood pressure after 3 min of 33% maximum handgrip pressure is greater in patients with AR than in normal subjects.

(3) Administer a vasopressor drug.

Note: A soft AR murmur (or MR murmur) may disappear in pregnancy, owing to the fall in resistance.

4. What is the significance of a musical AR vibratory or "dove-coo" AR murmur?

ANS: Musical aortic diastolic murmurs often occur in patients with a perforated leaflet, as in infective endocarditis, everted leaflets (often luetic), or rupture of an aortic sinus of Valsalva. Ruptures of leaflets are usually secondary to myxomatous transformation or infective endocarditis.

L. lower sternal border High frequency

L. lower sternal border High frequency

Luetic AR was suspected as the cause of this aortic diastolic murmur. Note the regular vibrations seen in all phonocardiograms of musical murmurs.

Luetic AR was suspected as the cause of this aortic diastolic murmur. Note the regular vibrations seen in all phonocardiograms of musical murmurs.

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