In Vitro Quantification of Mitral Regurgitation of Complex Geometry by the Modified Proximal Isovelocity Surface Area Method

Background: Doppler echocardiographic methods, such as the proximal isovelocity surface area (PISA) method, are used to quantify mitral regurgitations (MRs). However, their accuracy and reproducibility are still being discussed, especially in the case of MR of complex geometry. The aim of this study was to evaluate the accuracy of the PISA method depending on the shape and number of regurgitant flows.

Methods: First, various MR shapes and severities (central, oblong, and multiple-jet MR) were mimicked in a left heart simulator. The effective regurgitant orifice area (EROA) was calculated using the standard and modified PISA methods and was compared to a reference value obtained from an electromagnetic flowmeter. Second, in order to clinically validate the in vitro findings, 16 patients were examined with two-dimensional (2D) echocardiography. The results were analyzed by comparing the PISA method and the echocardiographic 2D quantitative volumetric method.

Results: Both hemicylindrical and hemiellipsoidal PISA assumptions improved the quantification of the EROA for oblong MR compared with the traditional PISA method (hemispherical PISA assumption: 11 ± 4.6 mm², P < .01; hemicylindrical PISA assumption: 2 ± 0.8 mm², P = .83; hemiellipsoidal PISA assumption: 6 ± 3.7 mm², P = .05). In the case of multiple jets of different sizes, an improved EROA calculation was measured when both jets were considered (single hemispherical PISA assumption: 4.5 ± 0.7 mm², P < .01; double hemispherical PISA assumption: 2 ± 1.1 mm², P = .64).

Conclusion: For a correct diagnosis of MR, the PISA geometry must be considered. A measurement of both PISA radius and PISA width is necessary for an accurate quantification of an oblong MR. In the case of a double-jet MR, a measurement of the two radii is recommended.