[Mass and geometry of the left ventricle. Methods of angiographic determination]

Hypertrophy is a myocardial adaptation to pathological conditions of overload and leads to a reduction of cardiac afterload. Angiocardiography (the so-called reference method) allows calculation of mass and volume after opacification of the left ventricle in two orthogonal planes, based on different mathematical models: the area-length method: the left ventricle is assumed to be ellipsoid. The short axis diameter and the volume are calculated from measurements of the area of the left ventricle in the long axis; Simpson's method: the ventricle is divided into sections along its long axis. The diameters of the sections are measured in each incidence. Left ventricular volume is calculated from the area of each section and the distance between two sections; myocardial mass: calculation of the myocardial mass requires measurement of the volumes of the left ventricle with the diameters increased by twice the wall thickness. The accuracy of these measurements depends on several factors: geometrical: true parallelism between the long axis of the ventricle and the planes of projection; influence of the contrast medium in the volume and contraction; this is negligible in the first three systoles; detection of the ventricular contours: this may be manual or automatic and requiring techniques of image digitalization. Therefore, the calculation of ventricular mass is directly related to volume determination, and hypertrophy can only really be quantified by mass/volume or wall thickness/diameter ratios.