On the human left ventricular shape

The geometry of the heart plays a major role in cardiac function. The purpo se of this study was to characterize analytically the geometric properties of the left ventricular (LV) three-dimensional (3D) shape, while excluding the effects of aspect ratio and size. Two groups of human hearts were studi ed by Cine-CT. The first group was composed of 10 healthy volunteers and th e second of 9 pathological hearts. The hearts were scanned from apex to bas e. The endocardial borders of each LV scan were traced and used to reconstr uct the 3D LV at end-diastole (ED) and end-systole (ES). Using a special no rmalized helical shape descriptor, denoted "geometrical cardiogram" (GCG), the typical 3D normal ED and ES shapes were determined. These typical shape s were then analytically approximated via a discrete cosine transform (DCT) . The shape of each LV was then investigated for its correspondence to five analytically defined shapes: (i) a cone, (ii) a sphere, including all elli psoidal shapes, (iii) a cylinder. (iv) a truncated ellipsoid, and (v) the D CT approximation of the normal LV shape. The results indicate that the norm al LV shape can be well approximated by using only seven coefficients of th e DCT. Conicity was the only geometrical feature which did not change from ED to ES in the normal group of hearts. The most prominent shape difference between normal and abnormal hearts was the significantly reduced conicity of the latter. Conicity is an important feature of LV geometry. The possibl e contribution of the conical shape to LV ejection efficiency is also discu ssed. (C) 1999 Academic Press.