135,503 research outputs found
Residual mitral regurgitation after repair for posterior leaflet prolapse- Importance of preoperative anterior leaflet tethering
Background
Carpentier's techniques for degenerative posterior mitral leaflet prolapse have been established with excellent long‐term results reported. However, residual mitral regurgitation (
MR
) occasionally occurs even after a straightforward repair, though the involved mechanisms are not fully understood. We sought to identify specific preoperative echocardiographic findings associated with residual
MR
after a posterior mitral leaflet repair.
Methods and Results
We retrospectively studied 117 consecutive patients who underwent a primary mitral valve repair for isolated posterior mitral leaflet prolapse including a preoperative 3‐dimensional transesophageal echocardiography examination. Twelve had residual
MR
after the initial repair, of whom 7 required a corrective second pump run, 4 underwent conversion to mitral valve replacement, and 1 developed moderate
MR
within 1 month. Their preoperative parameters were compared with those of 105 patients who had an uneventful mitral valve repair. There were no hospital deaths. Multivariate analysis identified preoperative anterior mitral leaflet tethering angle as a significant predictor for residual
MR
(odds ratio, 6.82; 95% confidence interval, 1.8–33.8;
P
=0.0049). Receiver operator characteristics curve analysis revealed a cut‐off value of 24.3° (area under the curve, 0.77), indicating that anterior mitral leaflet angle predicts residual
MR
. In multivariate regression analysis, smaller anteroposterior mitral annular diameter (
P
<0.001) and lower left ventricular ejection fraction (
P
=0.002) were significantly associated with higher anterior mitral leaflet angle, whereas left ventricular and left atrial dimension had no significant correlation.
Conclusions
Anterior mitral leaflet tethering in cases of posterior mitral leaflet prolapse has an adverse impact on early results following mitral valve repair. The findings of preoperative 3‐dimensional transesophageal echocardiography are important for consideration of a careful surgical strategy.
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Bilayer registry in a multicomponent asymmetric membrane : dependence on lipid composition and chain length
A question of considerable interest to cell membrane biology is whether phase
segregated domains across an asymmetric bilayer are strongly correlated with
each other and whether phase segregation in one leaflet can induce segregation
in the other. We answer both these questions in the affirmative, using an
atomistic molecular dynamics simulation to study the equilibrium statistical
properties of a 3-component {\em asymmetric} lipid bilayer comprising an
unsaturated POPC (palmitoyl-oleoyl-phosphatidyl-choline), a saturated SM
(sphingomyelin) and cholesterol with different composition ratios. Our
simulations are done by fixing the composition of the upper leaflet to be at
the coexistence of the liquid ordered () - liquid disordered ()
phases, while the composition of the lower leaflet is varied from the phase
coexistence regime to the mixed phase, across a first-order phase
boundary. In the regime of phase coexistence in each leaflet, we find strong
transbilayer correlations of the domains across the two leaflets,
resulting in {\it bilayer registry}. This transbilayer correlation depends
sensitively upon the chain length of the participating lipids and possibly
other features of lipid chemistry, such as degree of saturation. We find that
the domains in the upper leaflet can {\em induce} phase segregation in
the lower leaflet, when the latter is nominally in the mixed () phase.Comment: 6 figure
The Latin Leaflet
In the present work, we apply the asymptotic homogenization technique to the equations describing the dynamics of a heterogeneous material with evolving micro-structure, thereby obtaining a set of upscaled, effective equations. We consider the case in which the heterogeneous body comprises two hyperelastic materials and we assume that the evolution of their micro-structure occurs through the development of plastic-like distortions, the latter ones being accounted for by means of the Bilby–Kröner–Lee (BKL) decomposition. The asymptotic homogenization approach is applied simultaneously to the linear momentum balance law of the body and to the evolution law for the plastic-like distortions. Such evolution law models a stress-driven production of inelastic distortions, and stems from phenomenological observations done on cellular aggregates. The whole study is also framed within the limit of small elastic distortions, and provides a robust framework that can be readily generalized to growth and remodeling of nonlinear composites. Finally, we complete our theoretical model by performing numerical simulations
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