Characteristics of Regurgitant Systolic Murmurs

1. The high-pressure gradient that is usually present in most regurgitant lesions mentioned above will imply that regurgitant systolic murmurs will have predominantly high frequency, and this will make the murmurs sound more blowing in quality (42). They can be imitated by long whispering "hoo," "haaa," or saying a long "shoo."

2. The regurgitant murmur could acquire lower and medium frequencies and sound harsher if the degree of regurgitation is severe, resulting in a large amount of backward flow.

3. Since the pressure gradient often persists between the chambers well into the isovolumic relaxation phase and beyond, the murmur often will not end before the S2 and will often spill over into the very early part of diastole. Thus, there is generally no pause between the end of the murmur and the S2. The audibility of S2 with a regurgitant murmur, however, is mainly related to the relative loudness of the murmur and the S2. The S2 may be audible if the grade of the murmur is softer than the grade of the S2. If the murmur is louder than the S2, then the murmur lasting all the way to the S2 will engulf the S2. This will result in S2 not being heard separately.

4. Regurgitant murmurs, unlike ejection murmurs, usually do not change in intensity significantly following sudden long diastole, as may happen following the compensatory pause after a premature or ectopic beat or during varying cycle lengths in atrial fibrillation (43). The mechanisms involved in postextrasystolic potentiation were discussed under ejection murmurs. Regurgitant lesions imply that there are two outlets for the blood to flow during systole. For instance, in the case of mitral regurgitation, one outlet is the aorta and the other is through the regurgitant or incompetent mitral valve into the left atrium. The extra volume of blood received by the ventricle during the long diastolic interval by the Starling mechanism will increase the contractility of the ventricle. This will be further aided by the extrasystolic potentiation from the premature depolarization. During the long diastolic pause the aortic pressure will continue to fall, and this will result in decrease in afterload when the ventricle will begin to eject. The more complete emptying of the ventricle will result in a larger amount of forward flow into the aorta because of the fall in afterload accompanying the falling aortic pressure during the pause. This usually means that the volume of blood going in the reverse direction would remain relatively the same, keeping the regurgitant flow and the resulting murmur the same.

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