Three-dimensional anatomic features of the mitral valve that predict systolic anterior motion occurring during dobutamine stress echocardiography.

Abstract

Left ventricular outflow tract obstruction related to systolic anterior motion (SAM) of the mitral valve is a common complication of dobutamine stress echocardiography (DSE). However, the mechanisms underlying SAM have not been fully characterized. The objective of the present study was to use three-dimensional echocardiography to identify anatomic features of the mitral valve that predispose to SAM during DSE. We retrospectively evaluated consecutive patients included prospectively in our database and who had undergone 3D echocardiography (including an assessment of the mitral valve) before DSE. Patients who had developed SAM during DSE (the SAM+ group) were matched 2:3 with patients who did not (the SAM- group). One hundred patients were included (mean age: 67±10). Compared with SAM- patients (n=60), SAM+ patients (n=40) had a lower mitral annular area, a smaller perimeter, and a smaller diameter (p<.01 for all, except the anteroposterior diameter). The SAM+ group had also a narrower mitral-aortic angle (126±12° vs. 139±11° in the SAM- group; p<.01) and a higher posterior mitral leaflet length (1.4±.27cm vs. 1.25±.29, respectively; p<.01). Furthermore, the mitral annulus was more spherical, more flexible, and more dynamic in SAM+ patients than in SAM- patients (p<.05 for all). In a multivariate analysis of anatomic variables, the mitral-aortic angle, the mitral annular area, and posterior leaflet length were independent predictors of SAM (p ≤ .01 for all). In a multivariate analysis of standard echo and hemodynamic variables, the presence of wall motion abnormalities at rest (p<.01) was an independent predictor of SAM. SAM during DSE is multifactorial. In addition to the pharmacologic effects of dobutamine on the myocardium, 3D echocardiographic features of the mitral valve (a smaller mitral annulus, a narrower mitral-aortic angle, and a longer posterior leaflet) appear to predispose to SAM.