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...
Either annuloplasty ring prevented the perturbations of mitral leaflet and annular--but not papillary muscle tip--3-D geometry during acute LV ischemia. By fixing the septal-lateral annular dimension and preventing lateral displacement of the lateral annulus, annuloplasty rings prevented systolic septal-lateral leaflet separation and posterior leaflet restriction, and no acute IMR occurred. The flexible ring allowed posterior displacement of the posterior leaflet edge and the lateral annulus, which was not observed with a semi-rigid ring.
Background-Asymmetrical mitral annular (MA) dilatation and papillary muscle dislocation are implicated in the pathogenesis of functional mitral regurgitation (MR). Methods and Results-To determine the mechanism by which annular and papillary muscle geometric alterations result in MR, we implanted radiopaque markers in the left ventricle, mitral annulus, anterior and posterior mitral leaflets, and papillary muscle tips and bases in 2 groups of sheep. One group served as controls (CTL, nϭ7); an experimental group (EXP, nϭ9) underwent topical phenol application to obliterate anterior annular and leaflet muscle (confirmed histologically ex vivo). After 1 week of recovery, markers were imaged with biplane videofluoroscopy, and hemodynamic data were recorded. MA area (computed from 3-dimensional marker coordinates) was 11% to 13% larger in the EXP group than in the CTL group (PϽ0.05 by ANOVA). This area increase resulted exclusively from intercommissural axis increase except in 1 heart with large (Ͼ1 cm) increases in both the intercommissural and septolateral annular axes. The anterior papillary muscle tip in EXP was displaced from CTL by 2.9Ϯ0.23 mm toward the anterolateral left ventricle and 2.5Ϯ0.12 mm toward the mitral annulus at end systole; the posterior papillary muscle geometry was unchanged. Transthoracic echocardiography revealed MR only in the heart exhibiting biaxial annular enlargement.
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