A Method for Automating 3-Dimensional Proximal Isovelocity Surface Area Measurement

Abstract

The proximal isovelocity surface area (PISA) is used for the echocardiographic quantification of effective orifice areas in valvular stenosis and regurgitation. Typically measured in 2 dimensions, the PISA relies on the geometric assumption that the shape of flow convergence is a hemisphere and that the orifice is a single circular point. Neither assumption is true. The objective was to develop a method for automating the measurement of the PISA in 3 dimensions and to illuminate the actual shape of the flow convergence pattern and how it changes over time. Retrospective, single-case study. Major urban hospital. This study was based on a single patient undergoing mitral valve replacement. No additional interventions were performed in the patient. The effective orifice areas calculated from the serial hemispheric, hemi-elliptic, and 3-dimensional (3D) PISAs during diastole were compared with the corresponding planimetric anatomic mitral orifice area. The effective orifice areas based on the manual and automated measurements of 3D PISAs more closely approximated the anatomic orifice than the effective orifice areas calculated using hemispheric or hemi-elliptic PISAs. An automated analysis of 3D color Doppler data is feasible and allows a direct and accurate measurement of a 3D PISA, thus avoiding reliance on simplistic geometric assumptions. The dynamic aspect of cardiac orifices also must be considered in orifice analysis.