MR Due to Ruptured Chordae

1. How does spontaneous rupture differ from that due to infective endocarditis?

ANS: Spontaneous ruptures usually occur in one of the 25 major chordae closer to the papillary muscles than to the leaflets, thus involving at least four or five small terminal branches. Infective endocarditis usually involves only a few terminal branches.

2. What is the shape and frequency of the usual MR murmur of spontaneously ruptured chordae? Why?

ANS: It is a decrescendo, mixed-frequency murmur. It is decrescendo because the left atrium does not enlarge much with acute severe MR, due to the nondistensible pericardium around the atria. This poor left atrial compliance may raise the V-wave pressure to a very high peak as high as 70 mmHg toward the end of systole). The rise in left atrial pressure plus a precipitous fall in LV pressure toward the end of systole decreases the end-systolic gradient and murmur. (See figure on p. 222.)

3. Why may ruptured chordae imitate aortic stenosis (AS)?

ANS: If posterior chordae rupture, producing a flail posterior cusp, the stream of regurgitation may strike the atrial septum in such a way that it can generate murmurs with the shape and radiation into the carotids that are typical of those seen with AS murmurs.

Note: Despite good radiation into the second right interspace and neck, the murmur of a posterior chordae rupture is still usually loudest at the apex.

Left atrial V wave pressure of 56 mmHg

mmHg

This is a left atrial (wedge) and LV pressure tracing from a 23-year-old woman with ruptured mitral chordae. The shaded area is under the left atrial (wedge) pressure curve. The slight delay in the peak wedge pressure is due to the fact that wedge pressures (taken by a catheter wedged into the distal pulmonary arterial branches) always show a delay in comparison with direct left atrial pressure tracings. The rapid increase in V-wave pressure during systole rapidly decreases the gradient across the mitral valve and will tend to cause both a decrescendo gradient and murmur. The decompressing effect on the LV of the massive loss of blood into the left atrium causes a late systolic fall in LV pressure. This end-systolic decrease in LV pressure further decreases the gradient across the mitral valve toward the end of systole.

4. What is the characteristic radiation of an MR murmur caused by rupture of the anterior chordae?

ANS: It may radiate along the spine and if loud, even to the top of the head. See illustration on p. 223.

5. Which diastolic sound tells you that a loud MR murmur is due to ruptured chordae rather than to rheumatic heart disease?

ANS: The healthy atrial wall resists acute dilatation in patients with ruptured chordae. It responds to the stretch produced by the massive regurgitant stream with a Starling effect, and by contracting strongly it often produces an S4, which is rare in rheumatic MR.

Left atrial V wave pressure of 56 mmHg

mmHg

These views of the valve rings from above show how posterior ruptured chordae (on left) can direct the regurgitant stream against the aorta and cause the murmur to be transmitted like an aortic ejection murmur. The diagram at right shows how ruptured anterior chordae can direct the regurgitant stream posteriorly against the spine.

These views of the valve rings from above show how posterior ruptured chordae (on left) can direct the regurgitant stream against the aorta and cause the murmur to be transmitted like an aortic ejection murmur. The diagram at right shows how ruptured anterior chordae can direct the regurgitant stream posteriorly against the spine.

6. What are the usual causes of ruptured chordae?

ANS: Infective endocarditis on either a rheumatic or a prolapsed myxomatous mitral valve. Often a prolapse has been present for years before the rupture but has not been recognized as such.

7. What most closely imitates the auscultatory findings of ruptured chordae?

ANS: A severe form of prolapsed mitral valve with marked mysomatous degeneration. This is known as the floppy valve syndrome.

Note: Most mitral valves are removed or repaired because of mitral regurgitation due to severe prolapse.

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