A simple different method to use proximal isovelocity surface area (PISA) for measuring mitral valve area.

BACKGROUND: Angle-correction is an important limiting factor for using proximal isovelocity surface area (PISA) method in measuring mitral valve area (MVA). In this study, we derived a novel formula, which simplifies the angle-correction, and tested its use in patients with mitral stenosis (MS).
METHODS: The study included 30 MS patients without concomitant aortic or mitral regurgitation. We used mathematical equations and established a relation between the angle and its corresponding border, 'a', by using linear regression analysis. It was found that MVA is equal to [(1.11*a2 + 0.95)* r2 (Val/Vmax)]. We compared this formula with plain angle-corrected and solid angle-corrected PISA methods, planimetry (reference method) and pressure-half time method by linear regression analysis.
RESULTS: All methods were in significant relation with the reference method, two-dimensional planimetry. We found that there is a good relation between our method and planimetry (r = 0.79, p < 0.001), pressure half-time method (r = 0.85, p < 0.001), angle-corrected PISA method (r = 0.99, p < 0.001), and solid angle-corrected PISA method (r = 0.88, p < 0.001). The time duration of the new method was shorter (p < 0.001).
CONCLUSION: Our method is an easy way for applying angle-corrected PISA method to mitral valve area measurement in patients with mitral stenosis. Absence of the need for estimating the angle is the major advantage.