Objectives: The first objective was to develop a quantitative method for tracking the three-dimensional geometry of the mitral valve. The second was to determine the complex interrelationships of various components of the mitral valve in vivo.
Methods and results: Sixteen sonomicrometry transducers were placed around the mitral vale anulus, at the tips and bases of both papillary muscles, at the ventricular apex, across the ventricular epicardial short axis, and on the anterior chest wall before and during cardiopulmonary bypass in eight anesthetized sheep. Animals were studied later on 17 occasions. Reproducibility of derived chord lengths and three-dimensional coordinates from sonomicrometry array localization, longevity of transducer signals, and the dynamics of the mitral valve and left ventricle were studied. Reproducibility of distance measurements averages 1.6%; Procrustes analysis of three-dimensional arrays of coordinate locations predicts an average error of 2.2 mm. Duration of serial sonomicrometry array localization signals ranges between 60 and 151 days (mean 114 days). Sonomicrometry array localization demonstrates the saddle-shaped mitral anulus, its minimal orifice area immediately before end-diastole, and uneven, apical descent during systole. Papillary muscles shorten only 3.0 to 3.5 mm. Sonomicrometry array localization demonstrates nonuniform torsion of papillary muscle transducers around a longitudinal axis and shows rotation of papillary muscular bases toward each other during systole.
Conclusion: Tagging of ventricular structures in experimental animals by sonomicrometry array localization images is highly reproducible and suitable for serial observations. In sheep the method provides unique, quantitative information regarding the interrelationship of mitral valvular and left ventricular structures throughout the cardiac cycle.