Three-dimensional in-vivo dimensions of 'He's triangle' during acute left ventricular ischemia

Background and aim of the study: Changes in the dimensions of 'He's triangl e' (formed by mitral leaflet segments subtending two associated chordae ten dineae) derived from data obtained in in-vitro mitral valve models have bee n proposed to provide a mechanistic explanation for mitral leaflet malcoapt ation. The in-vivo dynamics of He's triangle, however, have not been hither to determined. Methods: Radio-opaque markers were placed in 13 sheep to delineate the mitr al annulus and four (of an infinite number of possible) He's triangles form ed by: (i) the anterior mitral leaflet (AML), first- (CT1) and second-order (CT2) chordae tendineae emanating from the anterior papillary tip (APT1) a s well as from the posterior papillary tip (PPT1), respectively; and (ii) t he posterior mitral leaflet (PML), CT1 and CT2 emanating from other loci on the anterior as well as the posterior papillary tips (APT2 and PPT2), resp ectively. Immediately postoperatively (anesthetized, open-chest), three-dim ensional end-systolic marker positions were measured before and during circ umflex coronary artery occlusion sufficient to produce mitral regurgitation , as verified by echocardiography. Results: During ischemia, three leaflet segments constituting one side of t hree He's triangles elongated: The AML attached to APT1 and to PPT1 by 1.5 +/- 1.2 mm (p <0.001) and 1.3 +/- 0.8 mm (p <0.001), respectively, and the posterior leaflet attached to APT2 by 1.4 +/- 1.9 mm (p = 0.02). Apart from a 0.9 +/- 1.1 mm (p = 0.02) increase in the length of CT2 attached to APT2 , the length of the seven other CT1 and CT2 remained relatively unchanged d uring acute left ventricular ischemia. Conclusion: With acute posterolateral ischemia, the lengths of CT1 and CT2 remained relatively constant, but the AML, and PML lengths were not constan t as the AML and PML 'unfurled' during acute left ventricular ischemia. The se geometric changes may provide further insight into the mechanisms of acu te ischemic mitral regurgitation, though it is not clear how they will be c linically helpful.