The Crescendo Murmur to the Mt in Mitral Stenosis The Presystolic Murmur

1. What is the appearance or shape of a murmur that is produced by atrial contraction forcing blood through a stenotic mitral valve?

ANS: It should follow the curve of atrial pressure rise and fall, i.e., it should be crescendo-decrescendo.

2. What is the actual shape of the diastolic murmur produced by atrial contraction at the end of diastole in MS?

ANS: It is crescendo to the first sound. This murmur is often called "presystolic."

3. Does the presystolic crescendo murmur of MS extend to the M1?

Mitral Stenosis Pathology

There should be no mitral murmurs between the A2 and the OS, because this is isovolumic relaxation time. Note the slow Y descent of the left atrium due to the difficulty in emptying the left atrium through the stenotic valve. This accounts for the pressure gradient and murmur, both of which are decrescendo except for the very beginning and end.

The "preystolic" murmur in this 45-year-old woman with moderately severe MS begins with the onset of ventricular contraction, as shown by the simultaneous apex cardiogram tracing taken at very fast paper speed. However, blood is still flowing from the left atrium to the LV until mitral valve closure (Mj). Therefore, cardiologists prefer to consider this period as part of diastole.

Mitral Stenosis Pressure Curves

Onset of LV contraction

These simultaneous phonocardiograms, left atrial und LV pressure tracings were taken with catheter-tip micromanonieter pressure transducers to eliminate any time delays due to tubing. Note that the "presystolic" crescendo of the MS murmur occurs during ventricular systole. This is from a 43-year-old man, mildly symptomatic, with severe MS, but only a small amount of calcium in his mitral valve. His left atrial A wave was 32 mmHg, but his cardiac index was 2.7, which is low-normal. He had a grade 3/6 diastolic rumble at the apex, of which only the presystolic component is seen well in these phonocarcdiograms.

Onset of LV contraction

These simultaneous phonocardiograms, left atrial und LV pressure tracings were taken with catheter-tip micromanonieter pressure transducers to eliminate any time delays due to tubing. Note that the "presystolic" crescendo of the MS murmur occurs during ventricular systole. This is from a 43-year-old man, mildly symptomatic, with severe MS, but only a small amount of calcium in his mitral valve. His left atrial A wave was 32 mmHg, but his cardiac index was 2.7, which is low-normal. He had a grade 3/6 diastolic rumble at the apex, of which only the presystolic component is seen well in these phonocarcdiograms.

4. What may we call the time between ventricular contraction and closure of the mitral valve or Mj?

ANS: The preisovolumic contraction period.

Note: This period is prolonged in MS because both the high left atrial pressure and the stiffness of the mitral valve have to be overcome before the mitral valve can be closed.

5. If the presystolic crescendo murmur actually occurs during LV contraction, i.e., during the preisovolumic LV contraction period, is it really presystolic?

ANS: If systole is defined as beginning with ventricular contraction (physiologists' systole), then only the first part of the murmur in sinus rhythm is presystolic because it begins at the time of peak atrial contraction before the ventricle contracts. Most of the murmur, however, is actually an early systolic murmur because it occurs during the preisovolumic contraction period of LV contraction. This is apparent from the observation that most of the crescendo murmur to the M, occurs after the onset of the QRS. However, because the auscultator's systole begins with the S,, it is not necessary to change the traditional terminology of presyscolic murmur. By a presystolic murmur, then, the auscultator means "immediately before the first heart sound."

6. What is the probable cause of the presystolic crescendo?

ANS: As the mitral valve orifice is being reduced by LV contraction the velocity of forward flow is increasing as long as the pressure is higher in the left atrium than in the LV [1].

7. Is atrial contraction required to produce the presystolic crescendo murmur?

ANS: No. In atrial fibrillation the late crescendo occurs but only during short diastoles, because only during short diastoles is the left atrial pressure high enough to maintain high-velocity flow during preisovolumic ventricular contraction. This also explains why sinus rhythm and atrial contraction helps to produce the pre-M1 crescendo. Atrial contraction can elevate left atrial pressure sufficiently to create the necessary increased velocity of forward flow as the mitral valve orifice is being reduced by ventricular contraction.

Presystolic murmur in a patient with mitral stenosis and atrial fibrillation. The best presystolic crescendo to the M,, occurring at the end of a short diastole begins with the start of mitral valve closure on the mitral valve "gated" echocardiogram (MVE) and with the start of LV contraction, point C of the apex cardiogram (ACG). The presystolic murmur occurs during preisovolumic LV contraction. (From P. Toutouzas et al. Mechanism of diastolic rumble and presystolic murmur in mitral stenosis. Br. Heart J. 36:1096, 1974.)

Presystolic murmur in a patient with mitral stenosis and atrial fibrillation. The best presystolic crescendo to the M,, occurring at the end of a short diastole begins with the start of mitral valve closure on the mitral valve "gated" echocardiogram (MVE) and with the start of LV contraction, point C of the apex cardiogram (ACG). The presystolic murmur occurs during preisovolumic LV contraction. (From P. Toutouzas et al. Mechanism of diastolic rumble and presystolic murmur in mitral stenosis. Br. Heart J. 36:1096, 1974.)

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