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Figure 1 Centerline method for analyzing wall motion through the cardiac cycle. (A) Envelopes are constructed demarcating the inner and outer bounds of the LV contours from every angiographic frame in the cardiac cycle. (B) A centerline is drawn midway between the inner and outer envelopes. Motion is measured along 100 chords constructed perpendicular to and evenly spaced along the centerline. To simplify the display and analysis, the LV contour is divided into 20 segments by averaging the motion at consecutive sets of five chords. Motion is normalized by the length of the end diastolic perimeter and expressed as a percent. LV = left ventricle.