On Leftsided Regurgitant Murmurs

1. What will happen to the loudness of a left-sided regurgitant murmur, such as that heard in mitral regurgitation (MR) or VSD, after a sudden long diastole?

ANS: The loudness usually remains about the same. (Listening for the effect of a sudden long diastole is one of best ways to differentiate an ejection from a regurgitant murmur.)

A high- and medium-frequency phonocardiogram taken at the apex together with an external carotid tracing from a 45-year-old woman with moderately severe chronic rheumatic MR, with few symptoms on digitalis alone. Because of atrial fibrillation, short and long diastoles are present, demonstrating that the murmur does not grow louder after long diastoles than after short or average diastoles.

A high- and medium-frequency phonocardiogram taken at the apex together with an external carotid tracing from a 45-year-old woman with moderately severe chronic rheumatic MR, with few symptoms on digitalis alone. Because of atrial fibrillation, short and long diastoles are present, demonstrating that the murmur does not grow louder after long diastoles than after short or average diastoles.

Note: If the pause is caused by a premature ventricular contraction (PVC), compare the postextrasystolic beat not with the PVC but with the normal cycle following the postextrasystolic beat. A PVC may be so premature that there is no time for any significant ventricular filling. Therefore, the loudness of a murmur produced by the PVC itself is of no significance.

2. Why does the left-sided regurgitant murmur not usually become louder despite a larger volume in the ventricle after a sudden long diastole, as after a PVC?

ANS: In MR, VSD, and PDA, the LV has two outlets during systole. The amount ejected through each outlet depends on the relative resistance beyond each outlet. During the PVC, the aortic pressure is less than normal because of the small stroke volume. During the long diastole after the PVC, the pressure beyond the aortic outlet falls still more, owing to continued long runoff into the periphery. Thus, by the time of the next systole the resistance at the aortic valve has dropped so low that blood is preferentially ejected into the aorta, and relatively less is regurgitated through the other orifice. One would think at first that this would make the murmur softer. However, because there is more volume in the LV at the end of a long diastole, the absolute quantity of blood regurgitated remains about the same as that after short diastoles.

3. When may the MR murmur become softer after a long diastole?

ANS: a. In the prolapsed mitral valve syndrome. (See the section on prolapsed mitral valve syndrome for explanation, p. 225). b. In some papillary muscle dysfunction murmurs, when myocardial ischemia rather than fibrosis causes the MR [1]. The long diastole may decrease myocardial ischemia by allowing more time for coronary filling and by decreasing the afterload due to the increased time allowed for aortic pressure to fall.

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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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