Clinical application in routine practice of the proximal flow convergence method to calculate the mitral surface area in mitral valve stenosis

Background: Two-dimensional (2D) echocardiography planimetry, the Doppler pression half-time (PHT), and the continuity equation methods were used to estimate mitral valve area (MVA) in patients with mitral stenosis (MS). Recently, the proximal isovelocity surface area (PISA) method has been shown to be accurate for calculating MVA. The purpose of this study is (1) to compare in a large non-selected population the accuracy of the PISA and planimetry methods for echocardiographic estimation of MVA; (2) to determine the effect of atrial fibrillation (AF), Wilkins score, associated mitral regurgitation (MR), aortic regurgitation (AR), and of commissural calcifications on the accuracy of the PISA method. Methods: One hundred and eight consecutive patients with rheumatic MS were studied (76 females and 32 males; mean age: 36 ± 12 years); 64 were in sinus rhythm; 51 had associated MR and 46 had AR. By the PISA method, MVA was calculated assuming a uniform radius flow convergence region along a hemispherical surface. Results: The mean value of 2D MVA was 1.32 ± 0.59 cm² (0.4–3.1 cm²) and that of PISA MVA 1.33 ± 0.62 cm² (0.38–3 cm²). MVA calculated using the PISA method correlated well with 2D MVA (r = 0.93, y = 0.97x + 0.04, p < 0.0001, SEE = 0.21 cm²). The correlation was also good in patients with AF (r = 0.93, y = 0.99x + 0.03, p < 0.0001, SEE = 0.21 cm²), with MR (r = 0.94, y = 1.014x + 0.003, p < 0.0001, SEE = 0.19 cm²), with AR (r = 0.93, y = 0.90x + 0.11, p < 0.0001, SEE = 0.2 cm²), when Wilkins score was >8 (r = 0.92, y = 0.96x + 0.06, p < 0.0001, SEE = 0.19 cm²), and in patients with commissural calcifications (r = 0.90, y = 0.88x + 0.009, p < 0.0001, SEE = 0.20 cm²). Conclusion:Our study shows that in routine practice, MVA calculated by the PISA method correlated well with the area obtained by planimetry even in the presence of commissural calcifications, associated MR, AR, AF and of high Wilkins score. Therefore, the PISA method provides a reliable measurement of the MVA in MS under different anatomic and clinical conditions and may be a useful alternative method for calculating MVA.