Accurate assessment of the true mitral valve area in rheumatic mitral stenosis
- King's College Hospital, London, UK
- Correspondence to Professor Mark J Monaghan, Kings College Hospital, Department of Non-Invasive Cardiology, 2nd Floor, Hambleden Wing, Denmark Hill, London SE5 9RS, UK; monaghan{at}compuserve.com
Rheumatic mitral valve stenosis (MVS) is still a common condition, especially in developing countries. Echocardiography has a primary role in its diagnosis, assessment of its severity and its functional implications. The indications for the quantification of MVS have recently changed. The European Association of Echocardiography/ American Society of Echocardiography guidelines in 20091 recommend using either the pressure gradient across the mitral valve (MV) by continuous wave Doppler, the pressure half time or MV planimetry. The recent European guidelines on the management of valve disease2 advise, as the method of choice, measurement of the MV area (MVA) by planimetry whenever feasible. Continuity equation for the estimation of valve area, proximal isovelocity surface area and the calculation of the mean transvalvular gradient, using Doppler velocities are suggested when additional assessment is needed.
It is worth questioning the reasons for this recent change in recommendations. The indirect methods of measuring the MVA have been tested in the past and have shown moderate reliability compared with cardiac catheterisation.3 ,4 However they are influenced by many variables such as heart rate, cardiac output, left ventricular systolic and diastolic functions, left ventricular and atrial compliance, left ventricular hypertrophy and concomitant valve disease.5–9 In these common clinical scenarios, Doppler-derived measurements of the MV area don't allow an accurate assessment of MVS severity.
Instead, MV planimetry is a direct and relatively hemodynamic-independent measurement of MVA. However in the presence of significant leaflet calcification, severe left atrial dilatation or distortion of the valve anatomy, it can be very challenging to obtain a perfect geometric alignment at the MV leaflet tips in a parasternal short-axis view using two-dimensional (2D) echocardiography. This clearly leads to an inaccurate measurement of the MVA. …
