2.3.2 3D semi-automated TEE aortic annulus measurement
Semi-automated aortic annulus measurements were made using the MVN program, normally designed for detecting the mitral valve annulus. This was achieved by scrolling the image in a multi-planar reconstruction mode to maximal aortic valve opening, aligning the aorta in an upright direction in the 2 orthogonal planes (figure 3, frame A and B) and defining the 4 annular points of aortic valve insertion. The software then automatically placed the remaining annular points with the operator able to manually override this placement if there was disagreement in 8 long axis frames of the aorta (giving 16 points of annular placement) Manual override of the automated placement of the annulus points did occur in at least 2 or more places for the majority of patients and tended to occur most often in the setting of acoustic shadowing by valvular calcium. However any adjustment made was minor in nature and did not add significantly to analysis time. The software then gave the circumference and area of the aortic annulus and the area was converted to a diameter by the equation
D= \(\sqrt{}\left(\frac{A}{\pi}\right)\times 2\) where D=diameter and A=area.