Circularity index of left ventricular shape in the assessment of heart disease

: Left ventricular volume and ejection fraction obtained by cineangiography are useful to evaluate global left ventricular function in humans. Left ventriculography provides evidence of the effect of coronary artery stenosis on regional wall motion in patients with coronary artery disease. Changes in left ventricular shape are also found in various heart diseases. The left ventricular cavity is normally ellipsoid in shape, but becomes flat in hypertrophic cardiomyopathy, globular in dilated cardiomyopathy, and aneurysmal in some patients with myocardial infarction. This study developed a new method to quantify regional and global left ventricular shape. Regional circularity index (RCI) was defined as GD divided by r (GD = distance from each 5-degree endocardial margin to the center of gravity, r = radius of the circle equal to left ventricular area). The global circularity index (GCI) was derived from the sum of magnitude of RCI-1. The end-systolic GCI was related to end-systolic left ventricular wall stress (r = 0.71, p < 0.001). The change in GCI during systole was related to left ventricular ejection fraction (r = 0.79, p < 0.001). In severe cases of dilated cardiomyopathy, the left ventricle became more spherical during ejection. End-systolic left ventricular moment around the minor axis had a good correlation with left ventricular ejection fraction (r = 0.81, p < 0.001). Quantification of regional and global left ventricular shape can be used to estimate left ventricular wall stress from left ventricular shape. Left ventricular shape change during systole and the moment around the left ventricular short axis contributes to left ventricular ejection.