A diagnostic imaging apparatus generates a three-dimensional diagnostic image representation. The image representation is converted into an image representation of the patient's heart. A left lower posterior point of the heart image representation is selected as a first approximation of a left ventricle apex and a line of preselected orientation is drawn through the first approximation apex as a first approximation ventricle axis. The ventricle axis is redefined by generating short axis slices across the approximated ventricle axis, isolating a selected one of the ventricles, determining a centroid of each short axis slice of the selected ventricle, and fitting the axis to the apex approximation and the centroids. The apex location is redefined by looking for the lowermost short axis slice orthogonal to the redefined axis which intersects the ventricle volume and selecting the intersection point as the next approximation of the apex. The axis and apex redefining are iteratively repeated to determine the ventricle axis and apex automatically.