Aorto-Mitral Annular Dynamics

Background. The aortic and mitral valves are coupled through fibrous aorto-mitral continuity, but their synchronous dynamic physiology has not been completely characterized. Methods. Seven sheep underwent implantation of five radiopaque markers on the left ventricle, 10 on the mitral annulus, and 3 on the aortic annulus. One of the mitral annulus markers was placed at the center of aorto-mitral continuity (mitral annulus "saddle horn"). Animals were studied with bi-plane videofluoroscopy 7 to 10 days postoperatively. Total circumference and lengths of mitral fibrous annulus, mitral muscular annulus, aortic fibrous annulus, and aortic muscular annulus were calculated throughout the cardiac cycle from three dimensional marker coordinates as was mitral annular area and aortic annular area. Aorto-mitral angle was determined as the angle between the centroid of the aortic annulus markers, the saddle horn, and the centroid of the mitral annulus markers. Aortic annulus and mitral annulus flexion was expressed as the difference between maximum and minimum values of the aortic and mitral annulus angles during the cardiac cycle. Results. Mitral and aortic annular areas changed in roughly a reciprocal fashion during late diastole and early systole with an overall 32 ± 8% change in aortic annular area and a 13 ± 13% change in mitral annular area. Aortic fibrous annulus changed much less than aortic muscular annulus (6 ± 2% vs 18 ± 4%; p = 0.0003) as did mitral fibrous annulus relative to mitral muscular annulus (4 ± 1% vs 8 ± 2%; p = 0.004). Aortic annulus and mitral annulus flexion was 8 ± 2° and increased to 11 ± 2° (p = 0.009) with inotropic stimulation. Conclusions. Dynamic aortic and mitral annular area changes were not mediated through the anatomic fibrous continuity. Aorto-mitral flexion, which increased with enhanced contractility, may facilitate left ventricle ejection. The effect of valvular surgical interventions on aorto-mitral flexion needs further investigation.