Major and minor axes of the normal mitral annulus

Background and aim of the study: A dilated or abnormally shaped mitral annu lus is a common cause of mitral valve regurgitation, and may be cured by an nuloplastic surgery. Multiplane transesophageal echocardiography (TEE) is t he diagnostic technique of choice. Our aim was to evaluate and suggest two- dimensional TEE reference values from a standardized procedure of measuring the mitral annular major and minor axes, and their cyclic changes. Methods: The annulus was approximated elliptic in the horizontal plane. The intercommissural (IC, major axis) and anteroposterior (AP, minor axis) dis tances were measured at end-systole (ES), at maximal valve opening (MO), an d at end-diastole (ED) from a mid-esophageal view, in 13 men and eight wome n with normal echocardiographic findings. Indexed values and reproducibilit y were calculated. Results: The success rate was 100% at ES, 90% at MO, and 29% at ED. ES dist ances were largest (p <0.001) and most reproducible (5-5.9%). Body weight, but not height or age, had a significant impact. ES 95% prediction interval s for IC were 27 to 46 mm (16-23 mm/m(2)) and 22 to 36 mm (13-18 mm/m(2)) f or AP (p <0.001). Corresponding body weight-corrected intervals were 0.39 t o 0.59 (IC) and 0.32 to 0.48 (AP) mm/kg. No subject had IC:AP <1.1 together with an AP >0.45 mm/kg. Conclusion: Among measurements made at ES, MO and ED, those at ES provided the most reproducible results, and high-quality images were obtained in nor mal, non-obese subjects. The distances should be judged in relation to body weight or surface area and each other. The largest IC distance and the mos t elliptic shape were at ES, while the annulus was minimal at ED. The proce dure and normal ranges presented may contribute to the evaluation of patien ts with mitral regurgitation.