Efficacy of Chordal Cutting to Relieve Chronic Persistent Ischemic Mitral Regurgitation

Abstract

Background-Mitral regurgitation (MR) conveys adverse prognosis in ischemic heart disease. Leaflet closure is restricted by tethering to displaced papillary muscles, and is, therefore, incompletely treated by annular reduction. In an acute ischemic model, we reduced such MR by cutting a limited number of critically positioned chordae to the leaflet base that most restrict closure but are not required to prevent prolapse. Whether this is effective without prolapse, recurrent MR, or left ventricular (LV) failure in chronic persistent ischemic MR, despite greater LV remodeling, remains to be established. Therefore, we studied 7 sheep with chronic inferobasal infarcts known to produce progressive MR over 2 months. In all of those sheep, after a mean of 4.1 months, the 2 central basal (intermediate) chordae were cut at the chronic ischemic MR stage. 3-Dimensional echo quantified MR, LV function, and valve geometry. Five other sheep were followed for a mean of 7.8Ϯ1.2 months after inferobasal infarction with chordal cutting. Results-All

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

“…12,13 A decrease in load-dependent LV ϩdP/dt max was also observed but failed to reach statistical significance (Pϭ0.16). Although this lack of difference in a load-dependent measure of LV function after chordal cutting is consistent with the findings from Messas et al, 10,11 subtle alterations in loading conditions may have influenced LV dP/dt despite the paired sequential nature of our experimental design.…”

“…31 Conversely, Messas et al did not observe a decline in LV ejection fraction after cutting the second-order chordae. 10,11 This may be because ejection fraction is a load-dependent index of LV systolic function and LV volume status was purposefully adjusted in their experiment after intraoperative chordal cutting to restore pre-CPB (and prechordal cutting) cardiac output and LV pressures. 10,11 In the present experiment, we used PRSW and E es (load-independent indexes of global LV systolic function) and the experimental design allowed for paired, sequential comparisons between precut and postcut conditions in the same animals without confounding factors such as a procedure on CPB or preload alterations between study conditions.…”

“…Kunzelman et al reported differences in first-order and second-order chordae material properties, which may reflect these specific roles: First-order chordae are stiffer (ie, less extensible), consistent with preventing leaflet prolapse, whereas the larger, more elastic second-order chordae may mediate valvular-ventricular interaction. 9 Nonetheless, cutting second-order chordae has recently been proposed as a therapeutic intervention for patients with ischemic MR to reduce leaflet apical tethering and improve leaflet coaptation, 10,11 which calls for a more complete understanding of the role of the second-order chordae in ventricular mechanics. If these chordae are important for LV systolic function, then they may be even more so in the setting of ischemic MR in hearts that are already impaired.…”

“…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.…”

Noninvasive Measurements of the Mitral Annulus Geometry by Newly-developed Quantitation Software With Real-time Three-dimensional Echocardiography: A Validation Study

“…Annuloplasty is a common surgical strategy for ischemic/functional MR, however MR often persists after annuloplasty [12][13][14][15]. Recently, new surgical strategies have been expected to reduce chronic persistent ischemic MR after annuloplasty [16][17][18][19]. Understanding the precise mechanism of functional MR is a prerequisite in the complicated surgery, and 3D measurements provide important geometric information of the mitral valve apparatus.…”