Assessment of Mitral Valve Area

With a 3-D homogeneous data set using anyplane echocardiography it is possible to pinpoint the cut plane to the the tips of the mitral valve so the true anatomic valve area can be measured (see Figure 5). The advantage of this method is that, contrary to 2-D echocardiography, proper alignment of the cut plane is controlled in a 3-D data set. It is important because errors due to malpositioning can be obviated. It has been shown that malpositioning errors can achieve up to 88% (1.5cm2) in the measurement of the mitral valve area that is not acceptable in the management of patients with mitral stenosis.(9) In addition, assessment of the anatomic mitral valve area is advantageous because it is haemodynamically independent, contrary to effective mitral valve area (measured by pressure half-time and proximal isovelocity surface area (PISA) methods), which is haemodynamically influenced by associated abnormalities (aortic insufficiency and increased left ventricular stiffness).

Figure 5: Mitral Valve Area Measurement Using Anyplane Echocardiography

Two long-axis cut planes perpendicular to each other (A and B). By guidance of line of intersection, optimal short-axis cut plane was selected (C). 3-D data set and spatial alignment of 3-D cut planes (D).

In the first studies carried out by Kupferwasser et al. and Chen et al. the mitral valve area was assessed by anyplane 3-D trans-oesophageal echocardiography (TOE).(10,11) The mitral valve area assessed by 3-D echocardiography was compared with the mitral valve area measured by 2-D methods (2-D planimetry and pressure half-time) and invasively assessed mitral valve area according to the Gorlin formula. Only Kasliwal et al. compared the mitral valve areas by 3-D echocardiography with the true mitral orifice measured directly at operation.(12) The comparison achieved a high degree of agreement (r=0.95); thus, 3-D echocardiography can currently be considered as a new clinical standard in the assessment of the anatomic mitral valve area. 3-D echocardiography has also been shown as accurate in the assessment of mitral valve area using a transthoracic approach. Sugeng et al. confirmed that freehand 3-D transthoracic echocardiography, compared with 2-D planimetry, pressure half-time and PISA methods, was the most accurate when compared with invasively determined