[Determination of left ventricular center of contractile motion by two-dimensional echocardiography]

To quantify left ventricular (LV) regional wall motion using two-dimensional echocardiography, reference points such as the center of left ventricular gravity or an intersecting point of radial grids were conventionally used, assuming that they were near or at the center of LV contractile motion. However, since the LV does not contract homogeneously, their positions might be quite different. Endocardial high density spots in two-dimensional echocardiograms were used as markers for LV regional wall motion, and we determined the center of LV contractile motion (C) at papillary muscle level in the parasternal short-axis view for 10 normal subjects (control group) and eight patients with aortic regurgitation (left ventricular volume overload; LVVO group). In one subject, each of six endocardial high density spots extracted from different LV regions, and were traced frame by frame throughout one cardiac cycle using a video motion analyzer, and their systolic movements were shown by six vectors. Using the method of least squares, the point of convergence of vectors (C) was determined from the point toward which the six vectors were directed. The LV centers of gravity at end-diastole (Ged) and at end-systole (Ges) were also determined by tracing the endocardial surface on video frames. The distributions of C, Ges, and Ged were compared. In the control group, point C was at the point 35% distant from Ged toward the middle of the interventricular septum (IVS). Ges deviated from Ged in the same direction as point C, but the distance was one third of C(11%). In the LVVO group, the distribution of Ges referred to Ged was similar to that of the control group, however, point C was closer to Ged, since its deviation was 16% of the radius. These results suggest that point C, which is determined by the directions of regional wall motion, reflects the contractile pattern of the whole LV. This might be termed the center of LV contraction. Using it as a reference, we were able to obtain more accurate quantitative data about LV regional wall motion.