Key result
Transecting anterior mitral basal stay chords narrows the aortomitral angle by ~3 degrees.
Why the study?
The function of the anterior mitral basal stay chords is not yet known, despite their suggested role in maintaining the aortomitral angle and influencing systolic anterior movement risk.
Does transection of anterior mitral basal stay chords narrow the aortomitral angle in a sheep model?
Does transection of anterior mitral basal stay chords narrow the aortomitral angle in a sheep model?
Transection of anterior mitral basal stay chords narrows the aortomitral angle, suggesting these chords balance the elastic recoil of the ascending aorta and their loss may increase the risk of systolic anterior movement.
OBJECTIVES: The function of the anterior mitral basal "stay" chords (SC) is not yet known. Collagen fiber orientation of the anterior mitral leaflet (AML) suggests that local stress is directed from papillary muscles (PM) over SC and AML to fibrous trigones (FT), maintaining the aortomitral angle (AMA). It has been shown that narrowing of AMA increases risk of systolic anterior movement (SAM). METHODS: Sonomicrometry crystals were implanted in six sheep at the left ventricular (LV) apex, PM tips (M1, M2), FT (T1, T2), posterior mitral annulus (PMA), and base of aortic right coronary sinus (RCS). The retracting force of ascending aorta was measured. RESULTS: Transection of SC resulted in an increase of distance M1-T1 and M2-T2. Consequently, the AMA narrowed at end systole by -3.26+/-0.85 degrees (p<0.05) and at end diastole by -4.16+/-1.28 degrees (p<0.05). A force of 1.8+/-0.2 N was needed to pull the recoiling ascending aorta back to its original position. CONCLUSIONS: The elastic recoil of ascending aorta is balanced by SC, which connect PM to FT and constitute the center of the LV base. Transection of SC narrows AMA and increases the risk of SAM.
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Goetz et al. (2003) studied this question. Transection of stay chords (SC) vs. Baseline (pre-transection) was evaluated on Aortomitral angle (AMA) at end systole and end diastole (MD -3.26 degrees (end systole) and -4.16 degrees (end diastole), p=<0.05). Transection of the anterior mitral basal stay chords narrowed the aortomitral angle at end systole by -3.26+/-0.85 degrees (p<0.05) and at end diastole by -4.16+/-1.28 degrees (p<0.05).
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