Dynamic balance of the aortomitral junction.
ABSTRACT The aortic and mitral valves have been studied in isolation, as if their functions were independent. We hypothesized that both valves work in synchrony on the basis of the shared myocardial pump and orifice.
Six sonometric crystals (7 sheep) were placed in both trigones, the midpoint of the anterior and posterior anulus, and the lateral extremities of the posterior anulus. In a separate series of animals, 3 crystals (8 sheep) were implanted in the aortic annular base of the right, left, and noncoronary sinuses of Valsalva. In an acute, open-chest model, under stable hemodynamic conditions, geometric changes were time related to simultaneous left ventricular and aortic pressures.
From mid-diastole to end-systole, the mitral anulus area contracted by -16.1% +/- 1.9% (mean +/- SEM), whereas the aortic base area expanded by +29.8% +/- 3.3% during systole. The mitral anulus deformation was heterogeneous. In systole, the anterior mitral anulus expanded (intertrigonal distance, +11.5% +/- 2.3%) and the posterior mitral anulus contracted (distance between lateral extremities of the posterior anulus, -12.1% +/- 1.5%). The intertrigonal distance corresponded to the base of the left and noncoronary sinus of Valsalva, which expanded similarly during systole (+12.9% +/- 2.0%). The anteroposterior diameter of the mitral anulus was reduced twice that of the transverse diameter. This disparity of reduction can be explained by the posterior displacement of the intertrigonal area corresponding to the systolic aortic root expansion.
Mitral anulus deformation is closely related to aortic root dynamics. During systole, the posterior movement of the aortic curtain allows for aortic root expansion, probably to maximize ejection, whereas during diastole, aortic root reduction participates in mitral anulus dilatation. These findings should affect mitral and aortic surgical approaches.
- SourceAvailable from: Masaaki Takeuchi[show abstract] [hide abstract]
ABSTRACT: Background: The aortic and mitral valves are anatomically linked through a fibrous continuity. The investiga-tors hypothesized that severe aortic stenosis (AS) would alter this fibrous continuity, affecting both the mitral valve and left ventricular function, and that mitral valve function would be altered after aortic valve replacement (AVR). The aim of this study was to evaluate the impact of AS and its treatment with surgical AVR on the mitral valve. Methods: Three-dimensional transesophageal echocardiography (using a Philips iE33 system) was performed on 49 patients: 20 controls with normal valves and left ventricular function, 20 with AS and normal left ventric-ular function studied before and after AVR, and nine with systolic heart failure and normal valves. Custom soft-ware tracked the aortic and mitral valves in three-dimensional space, allowing automated measurements of aortic and mitral annular (MA) morphology throughout the cardiac cycle. Results: Patients with AS before AVR had reduced MA velocities. After AVR, aortic and MA areas were signif-icantly smaller throughout the cardiac cycle compared with controls and pre-AVR values. MA displacement was reduced after AVR and in patients with systolic heart failure compared with those with AS and controls.
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ABSTRACT: Mitral valve annuloplasty is a common surgical technique used in the repair of a leaking valve by implanting an annuloplasty device. To enhance repair durability, these devices are designed to increase leaflet coaptation, while preserving the native annular shape and motion; however, the precise impact of device implantation on annular deformation, strain, and curvature is unknown. In this article, we quantify how three frequently used devices significantly impair native annular dynamics. In controlled in vivo experiments, we surgically implanted 11 flexible-incomplete, 11 semi-rigid-complete, and 12 rigid-complete devices around the mitral annuli of 34 sheep, each tagged with 16 equally spaced tantalum markers. We recorded four-dimensional marker coordinates using biplane videofluoroscopy, first with device and then without, which were used to create mathematical models using piecewise cubic splines. Clinical metrics (characteristic anatomical distances) revealed significant global reduction in annular dynamics upon device implantation. Mechanical metrics (strain and curvature fields) explained this reduction via a local loss of anterior dilation and posterior contraction. Overall, all three devices unfavorably caused reduction in annular dynamics. The flexible-incomplete device, however, preserved native annular dynamics to a larger extent than the complete devices. Heterogeneous strain and curvature profiles suggest the need for heterogeneous support, which may spawn more rational design of annuloplasty devices using design concepts of functionally graded materials.Annals of biomedical engineering 03/2012; 40(3):750-61. · 2.41 Impact Factor
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ABSTRACT: The purpose of this study was to assess deformation dynamics and in vivo mechanical properties of the aortic annulus throughout the cardiac cycle. Understanding dynamic aspects of functional aortic valve anatomy is important for beating-heart transcatheter aortic valve implantation. Thirty-five patients with aortic stenosis and 11 normal subjects underwent 256-slice computed tomography. The aortic annulus plane was reconstructed in 10% increments over the cardiac cycle. For each phase, minimum diameter, ellipticity index, cross-sectional area (CSA), and perimeter (Perim) were measured. In a subset of 10 patients, Young's elastic module was calculated from the stress-strain relationship of the annulus. In both subjects with normal and with calcified aortic valves, minimum diameter increased in systole (12.3 ± 7.3% and 9.8 ± 3.4%, respectively; p < 0.001), and ellipticity index decreased (12.7 ± 8.8% and 10.3 ± 2.7%, respectively; p < 0.001). The CSA increased by 11.2 ± 5.4% and 6.2 ± 4.8%, respectively (p < 0.001). Perim increase was negligible in patients with calcified valves (0.56 ± 0.85%; p < 0.001) and small even in normal subjects (2.2 ± 2.2%; p = 0.01). Accordingly, relative percentage differences between maximum and minimum values were significantly smallest for Perim compared with all other parameters. Young's modulus was calculated as 22.6 ± 9.2 MPa in patients and 13.8 ± 6.4 MPa in normal subjects. The aortic annulus, generally elliptic, assumes a more round shape in systole, thus increasing CSA without substantial change in perimeter. Perimeter changes are negligible in patients with calcified valves, because tissue properties allow very little expansion. Aortic annulus perimeter appears therefore ideally suited for accurate sizing in transcatheter aortic valve implantation.Journal of the American College of Cardiology 01/2012; 59(2):119-27. · 14.09 Impact Factor