The "proximal isovelocity surface area" method in assessing mitral valve area in patients with mitral stenosis and associated aortic regurgitation.

BACKGROUND. This study compares the mitral valve area determined by Doppler color mapping of the proximal isovelocity surface area (PISA) and by Doppler pressure half-time with that obtained by two-dimensional planimetry in patients affected by mitral stenosis, with and without associated aortic regurgitation. Pressure half-time frequently overestimates the mitral valve area in patients with mitral stenosis and associated aortic regurgitation. PISA is an alternative method for determining mitral valve area in mitral stenosis and is not influenced by regurgitant lesions. METHODS. We studied 76 patients with mitral stenosis; aortic regurgitation ≥ 2 was present in 24 patients. The PISA was recorded from the apex and the transmitral maximal flow rate, Q (ml/s), was calculated using the hemispheric equation Q = 2πR2 × AV × α/180, where R (cm) is the maximal radius of the PISA, AV (cm/s) is the aliasing velocity and α/180 is a correction factor accounting for the α inflow angle formed by the mitral leaflets. Mitral valve area, A (cm2), was calculated by continuity equation A = Q/V, where V (cm/s) is the peak transmitral flow velocity measured by continuous wave Doppler. RESULTS. The mitral valve area by two-dimensional planimetry (range 0.5-2.4 cm2; mean 1.33 + 0.41 cm2) was consistent with both PISA (r = 0.83; SEE 0.23 cm2) and pressure half-time (r = 0.79; SEE 0.25 cm2) methods. Similar agreement was found for the 36 patients with mitral regurgitation and for the 30 patients in atrial fibrillation. However, in patients with aortic regurgitation ≥ 2, pressure half-time overestimated two-dimensional and PISA determined mitral valve areas by 0.24 ± 0.25 cm2 (p < 0.01). CONCLUSIONS. In patients with mitral stenosis and significant aortic regurgitation, the PISA method is more accurate than pressure half-time in assessing mitral valve area. This method may be a reliable alternative when pressure half-time is affected by aortic regurgitation and two-dimensional planimetry images are unsuitable for anatomic evaluation.