As The Cause Of A Split S

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J. How long after the Mj does the aortic ejection sound (Al) occur in normal subjects?

ANS: The usual AJ occurs at the end of isovolumic contraction (i.e., about 40-60 ms [0.04 -0.06 s] after the Ml). To help you judge this normal split of the first sound interval, a 40-ms split takes as long as it does to say "pa-da" moderately quickly. The 60-ms split can be imitated by saying "pa-ta" as quickly as possible. (A 40- to 60-ms split is a moderately wide split.)

2. Which valvular abnormalities are the usual causes of an aortic ejection sound (or click)?

ANS: a. A bicuspid aortic valve without stenosis. (Bicuspid valves may or may not become stenotic.) b. A stiff aortic valve, such as that occurring in AS or hypertension.

Note: Hypertension may stretch the aortic root, causing the cusps to become taut and therefore to open with a sharp sound.

Apex (high frequency)

This phonocardiogram is from a 40-year-old woman with mild hypertension. The third component is probably an aortic ejection sound. This sounded simply like a widely split S1, probably because the T1 was too close to the Ml to be audible.

Bicuspid Aortic Valve Murmur Sounds
Aortic root tracing from a 23-year-old man with congenital AS taken with a catheter-tip electromanometer so that there are no tubing delays. The aortic ejection sound (AES) is coincident with the moment of peak opening of the valve. SM = systolic murmur.

3. What features suggest that the aortic ejection sound or click, as in aortic stenosis, is due to an opening snap of the aortic valve and not merely to forceful ejection into the aorta?

ANS: a. It disappears with severe calcification of the aortic valve; conversely, the louder the sound the more mobile the valve can be shown to be. b. It is not a feature of supravalvular AS or of obstruction below the valve, i.e., hypertrophic obstructive cardiomyopathy (HOCM) or discrete subvalvular stenosis.

4. Where is the aortic ejection sound best heard?

ANS: The ejection sound is well heard wherever aortic events are best heard, i.e., anywhere in a straight line or "sash area" from the second right interspace to the apex. The ejection click of AS, however, is most often heard best at the apex because the AS murmur may be loud enough elsewhere to obscure the click.

5. What additional information does an aortic ejection sound give you in the presence of AS?

ANS: a. It helps to locate the site of the AS because only valvular AS characteristically has an audible ejection sound. b. The absence of an ejection sound in valvular AS implies a calcified aortic valve. A calcified valve of that degree is highly correlated with a gradient of more than 50 mmHg.

6. What features may suggest that an aortic ejection sound is due to a bicuspid aortic valve (nonstenotic)?

ANS: a. If it is loud, especially if it is louder than the M1, and is associated with a louder A2 than normal. b. If it is associated with aortic regurgitation (AR), usually of only mild to moderate degree. (AR is commonly associated with a bicuspid aortic valve.)

Note: A bicuspid aortic valve may calcify in patients over 50 years old and lead to AS of any degree, or it may remain nonstenotic permanently.

This patient with a bicuspid aortic valve showed (on the left) a triple S1 of M1 Tj A1 in 1953, at age 28. Twenty-five years later the late aortic ejection pound (labeled X) is louder than the Mj, and no stenosis has developed.

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