Barlow’s disease affects the entire mitral valve apparatus, by altering several of the fundamental mechanisms in the mitral valve which ensures unidirectional blood flow between the left atrium and the left ventricle. In this paper, a finite element model of a patient diagnosed with Barlow’s disease with patient-specific geometry and boundary conditions is presented. The geometry and boundary conditions are extracted from the echocardiographic assessment of the patient prior to surgery. Material properties representing myxomatous, healthy human and animal mitral valves are implemented and computed response are compared with each other and the echocardiographic images of the patient. This study shows that the annular dilation observed in Barlow’s patients controls several aspects of the mitral valve behavior during ventricular systole. The coaptation of the leaflets is observed to be highly dependent on annular dilation, and the coaptation area reduces rapidly at the onset of mitral regurgitation. Furthermore, the leaflet material implementation is important to predict lack of closure in the FE model correctly. It was observed that using healthy human material parameters in the Barlow’s diseased FE geometry gave severe lack of closure from the onset of mitral regurgitation, while myxomatous material properties showed a more physiological leakage.

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Background Barlow's disease (BD) provides both diagnostic and therapeutic challenges. Annular dilation is typically seen in BD, however, data on regional deformation is lacking. Purpose We hypothesized that mitral annulus dilates non-homogenously during ventricular systole in BD. A method to calculate annular regional strain was developed and applied in a subset of BD patients and healthy controls. Methods Ten patients with BD and late systolic mitral regurgitation and nine healthy controls were studied. For each subject, the mitral annulus was segmented throughout the cardiac cycle using 3D echocardiography. Twelve evenly distributed geometrical points were annotated along the annular perimeter, enabling the creation of periodic degree-3 spline curves parameterized by arc length at each discrete time-frame. The motion of the mitral annulus was then acquired by assuming that heterogeneity in annular strain is small and finding the point-wise map that minimized the total displacement between the consecutive curves. Then, the end-diastolic annular curve was divided into 200 evenly distributed points around the annular perimeter, and the point-wise mapping was implemented to create a continuous movement of the discretized annulus throughout the cycle. Annular strain was then calculated for each individual line segment. The method presented herein is validated by comparing the strain between sonomicrometric crystals in pigs and the method described above. The timescale was normalized from ED (end-diastole) to mitral valve opening for each individual. The regional strains of the annulus were calculated with the ED configuration as reference. Results Hemodynamic data are presented in Table 1. In BD annulus area increased from 16.6±3.2 to 21.7±4.2 cm2 at end-diastole and peak systole, respectively (p<0.001). In controls, annulus area at end-diastole and end-systole was 9.6±2.2 cm2 and 9.2±1.8 cm2, respectively (NS). Figure 1 demonstrates non-homogenous regional strain at peak systole, with the most severe deformation in the posteromedial region. In healthy controls, peak systolic strain was similar in all segments. Conclusions In the present study, we have applied a novel non-invasive method to demonstrate non-homogenous deformation of the mitral annulus in Barlow patients. On average, the most severe deformation was seen in the posteromedial region. This finding may reveal further insight into the mechanisms of late systolic mitral regurgitation in BD as well as the design of annuloplasty in the future. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Trond Mohn Foundation

Background We know that the ventricular function has a profound effect on the mitral valve in chronic disease with ventricular remodeling. However, acute effects of ventricular function on the mitral valve apparatus are not well understood. Purpose To investigate the effect of left ventricular (LV) contractility on all aspects of mitral annular motion. Methods Eight piezoelectric transducers were implanted equidistantly around the mitral annulus in ten pigs. Sonomicrometer array localization recorded transducer position after weaning from bypass. LV contractility was evaluated by the slope of the end-systolic pressure-volume relationship. Mitral annular area was calculated from cubic spline interpolation through the annular points. Circularity and non-planarity angle were calculated from principal component analysis. Mitral annular excursion was calculated as the projected distance from the annular geometric mean point to the least square plane of the mitral annulus in end diastolic configuration. Results LV contractility was strongly associated to change in mitral annular area and mitral annular excursion (r=0.88, p<0.001 and r=0.90, p<0.001, respectively). Change in non-planarity angle was only moderately associated with LV contractility (r=0.68, p<0.03), whereas circularity was not (r=0.05, p<0.089). Conclusions LV contractility was closely related to mitral annular size reduction and apicobasal annular excursion, and only moderately associated to folding of the mitral annular saddle shape. No associations were found with change in mitral annular circularity. This is to our knowledge the first detailed description of the acute relationship between LV contractility and mitral annular dynamics. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Western Norway Regional Health Authority Research Grant