Structural properties in ruptured mitral chordae tendineae measured by synchrotron-based X-ray phase computed tomography.

Abstract

The link between the structural properties and the rupturing of chordae tendineae in the mitral valve complex is still unclear. Synchrotron-radiation-based X-ray phase computed tomography (SR-XPCT) imaging is an innovative way to quantitatively analyze three-dimensional morphology. XPCT has been employed in this study to evaluate the chordae tendineae from patients with mitral regurgitation and to analyze structural changes in the ruptured chordae tendineae in patients with this condition. Six ruptured mitral chordae tendineae were obtained during surgical repairs for mitral regurgitation and were fixed with formalin. In addition, 12 healthy chordae tendineae were obtained from autopsies. Employing XPCT (effective pixel size, 3.5 µm; density resolution, 1 mg cm-3), the density of the chordae tendineae in each sample was measured. The specimens were subsequently analyzed pathologically. The mean age was 70.2 ± 3.0 in the rupture group and 67.2 ± 14.1 years old in the control group (p = 0.4927). All scans of chorda tendineae with SR-XPCT were performed successfully. The mean densities were 1.029 ± 0.004 in the rupture group and 1.085 ± 0.015 g cm-3 in the control group (p < 0.0001). Density based on SR-XPCT in the ruptured mitral chordae tendineae was significantly lower compared with the healthy chorda tendinea. Histological examination revealed a change in the components of the connective tissues in ruptured chorda tendinea, in accordance with the low density measured by SR-XPCT. SR-XPCT made it possible to measure tissue density in mitral chordae tendineae. Low density in mitral chordae tendineae is associated with a greater fragility in ruptured mitral chordae tendineae.