Mitral annulus strain by 3D echo reveals regional annular dysfunction in Barlow's disease

Abstract

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