Papillary Muscle Dysfunction Murmurs

1. How can different kinds of papillary muscle dysfunction produce MR murmurs of different shapes?

ANS: a. If, when the ventricle contracts, one papillary muscle is unable to contract or is attached to infarcted muscle at its base, the papillary muscle and its chordae will be longer than the opposite normally contracting papillary muscle and its chordae. As the systolic pressure rises and the LV cavity decreases in size, the portion of the mitral leaflets with the relatively long papillary muscle and its chordae will project more and more into the left atrium, producing a crescendo murmur to the S2. (See figures on p. 220.)

Diastole Systole

A noncontracting papillary muscle may make its chordae-plus-papillary muscle relatively longer as the ventricle becomes smaller. This is most likely to produce a murmur that becomes progressively louder as systole proceeds (crescendo murmur to the S2).

A noncontracting papillary muscle may make its chordae-plus-papillary muscle relatively longer as the ventricle becomes smaller. This is most likely to produce a murmur that becomes progressively louder as systole proceeds (crescendo murmur to the S2).

b. Fixed shortening of a papillary muscle by marked fibrosis or by attachment to an aneurysmal or dilated akinetic area will cause pansystolic regurgitation.

c. The murmur may be decrescendo if dilatation is the major cause of the regurgitation.

2. How does the presence of an S4 help tell you the etiology of an MR murmur?

ANS: If an S4 is present, it strongly suggests papillary muscle dysfunction secondary to a cardiomyopathy. Rheumatic MR is rarely associated with an S4.

Note: The degree of MR after infarction is greater for posterior than for anterior infarction.

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