Aim: One limitation for a wider use of the proximal isovelocity surface area method (PISA) for the evaluation of the mitral valve area (MVA) in patients with mitral stenosis (MS) is the requirement of an angle correction factor (angle alpha between the mitral leaflets) which cannot be obtained using the machine's built-in software and requires a manual measurement. The aim of the present study was to evaluate if the use of a fixed angle could provide an acceptable MVA estimation.
Methods and results: In 48 patients (53 +/- 14 years, 75% female and 32% atrial fibrillation), MVA was prospectively measured by planimetry (MVA(2D)) and PISA (PISA(mes)). The angle alpha was manually measured on paper prints using a protractor. MVA(2D) was 1.38 +/- 0.56 cm(2) [0.5-2.40]. PISA(mes) (alpha = 104 +/- 13 degrees inter-quartiles 90-115) was 1.34 +/- 0.64 cm(2) [0.31-2.95] and did not differ from and correlated well with MVA(2D) (P = 0.25; r = 0.93, P < 0.0001). MVA estimated using the PISA method and a fixed angle value from 90 to 110 (MVA(alpha)(=90) to MVA(alpha)(=110)) progressively increased from 1.20 +/- 0.66 to 1.48 +/- 0.81 cm(2). Only MVA(alpha)(=100) (1.34 +/- 0.74 cm(2)) did not differ from and correlated well with both MVA(2D) and PISA(mes) (both P > 0.35 and r > 0.90, P < 0.0001).
Conclusion: The angle formed by the mitral leaflet only slightly changes in between patients and use of a fixed angle value of 100 degrees provides an accurate estimation of the MVA by the PISA method in patients with MS. This simplification would facilitate and extend the use of the PISA as an additional method for the assessment of MS severity in routine practice.