Influence of Anterior Mitral Leaflet Second-Order Chordae Tendineae on Left Ventricular Systolic Function

Abstract

Background-The contribution of anterior mitral leaflet second-order ("strut") chordae tendineae to left ventricular (LV) systolic mechanics is debated; we measured the in vivo contribution of anterior chordae tendineae (ACT) and posterior chordae tendineae (PCT) to regional and global LV contractile function. Methods and Results-Eight sheep had radiopaque markers implanted in the LV epicardium, partitioning the ventricle into 12 regions. Microminiature force transducers and snares were sutured to anterior leaflet "strut" chordae originating from ACT and PCT papillary muscles. Chordal tension, marker images, and hemodynamic data were acquired before and after (CUT) severing ACT and PCT. Fractional area shrinkage and slope of the regional end-diastolic area-regional stroke work relation (r-PRSW) were computed for each LV region. CUT did not affect global LV systolic function but reduced FAS in LV segments near the PCT insertion site: equatorial posterior lateral (19Ϯ2% versus 16Ϯ2%, PϽ0.05 4 studies demonstrated that preserving the chordae tendineae during mitral valve surgery improves postoperative LV systolic function and clinical outcome. The chordae tendineae are commonly classified according to their insertion sites on the mitral leaflets. 5 The first-order (primary or "marginal") chordae insert on the leaflet free edges, the second-order (or "strut") chordae insert on the ventricular surface of the leaflets, usually near the junction between the rough and smooth zones, and the third-order chordae arise directly from the LV wall. The anterior mitral valve leaflet (AMVL) second-order chordae also have different origins within the ventricle. The anterolateral second-order chordae and papillary muscle originate in the midportion of the anterior LV wall, whereas the posteromedial second-order chordae and papillary muscle originate in the apical-posterior LV region. Second-order chordal transposition can be used to correct anterior mitral valve leaflet prolapse 6,7 ; cutting second-order chordae recently has been recommended as a surgical treatment for ischemic mitral regurgitation (IMR) to alleviate leaflet apical tethering during systole. 8 The in vivo effects of sacrificing second-order chordae on regional LV systolic function, however, have not been investigated. Since the mitral subvalvular apparatus has the dual role of preventing mitral leaflet prolapse as well as optimizing LV systolic pump function, knowing the functional role of the chordae tendineae should provide a more rational basis for mitral repair procedures that alter normal chordal anatomy. One study indicated that the second-order chordae are involved Hypothesizing that severing second-order chordae tendineae would adversely perturb regional LV systolic function, we implanted radiopaque myocardial markers and force transducers in sheep to measure regional and global LV systolic function and AMVL strut chordae tension before and after cutting both AMVL strut chordae. Methods Surgical PreparationEight adult male sheep were used. Details about...

Importance of Mitral Valve Second-Order Chordae for Left Ventricular Geometry, Wall Thickening Mechanics, and Global Systolic Function

“…Although we believe that the second-order chordae are important for valvular-ventricular interaction, debate exists because reports from a previous experiment in this laboratory failed to demonstrate changes in either load-dependent or load-independent indices of global LV function after transection of second-order chordae, 12,13 and Messas et al observed no change in LV ejection fraction after chordal cutting. 10,11 Alterations in regional LV systolic dysfunction (decreased fractional area shortening and decreased regional preload recruitable stroke work) adjacent to the PM insertion sites, however, have been observed.…”

“…In local cardiac coordinates [X 1 , X 2 , X 3 ], the 3 normal strain components measure myocardial stretch or shortening along the circumferential (E 11 ), longitudinal (E 22 ), and radial (E 33 ) cardiac axes. The 3 shear strains (E 12 , E 13 , and E 23 ) represent angle changes between pairs of originally orthogonal coordinate axes. Strains were interpolated along the centroid of the bead columns at 1% increments of wall depth from the epicardium at ED.…”

“…From a functional viewpoint, these observations suggest that second-order chordae provide important connections between the cardiac endoskeleton (along the fibrous annulus) and the LV free wall. 13 Collagen bundles have been identified in the anterior mitral leaflet radiating away from the strut chordae insertion points to the fibrous portion of the MA between the fibrous trigones. 9 In the present experiment, cutting the second-order chordae perturbed global LV geometry.…”

“…10,11 Alterations in regional LV systolic dysfunction (decreased fractional area shortening and decreased regional preload recruitable stroke work) adjacent to the PM insertion sites, however, have been observed. 13 We sought to clarify these issues and address the limitations inherent in our earlier experiment 12,13 by measuring global LV function and transmural systolic LV wall mechanics before and after transection of the second-order chordae.…”

Determination of the mechanical properties of normal and calcified human mitral chordae tendineae

“…The MCT link the free edges and the ventricular surface of both leaflets of the MV to the papillary muscles, thus preventing the backflow of the blood into the left atrium during ventricular contraction. Several equivalent classifications for the MCT are proposed in the literature [13,29,12,26,27,3,20,31,24]. In general, the MCTs are classified according to their insertion sites on the mitral leaflets.…”