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. Author manuscript; available in PMC: 2016 Oct 18.
Published in final edited form as: Anesth Analg. 2016 Jul;123(1):14–20. doi: 10.1213/ANE.0000000000001276

Table 2.

Methods for Mitral Stenosis Orifice Area Assessment

Method Area calculation Advantages Limitations
Planimetry Direct measurement Independent of loading conditions and chamber compliance Calcification/dropout, particularly in degenerative MS
Imaging plane alignment
Pressure half-time MVA = 220/PHT Simple Abnormal loading conditions, impaired LV compliance
Aortic regurgitation, ASD, VSD
Atrial tachycardia
Continuity equation MVA = (LVOT CSA × LVOT VTI)/(MV VTI) Relatively independent of CO and abnormal loading conditions Valvular regurgitation
Intracardiac shunts
Irregular rhythms
PISA MVA = 2 π R2 × α/180 × Va/Vmax Independent of CO, loading conditions, regurgitant lesions Technically challenging
Irregular rhythms
Geometric assumptions

α = mitral valve leaflet angle; ASD = atrial septal defect; CO = cardiac output; CSA = cross-sectional area; LV = left ventricle; LVOT = left ventricular outflow tract; MS = mitral stenosis; MV = mitral valve; MVA = mitral valve area; PHT = pressure half-time; PISA = proximal isovelocity surface area; R = radius of the isovelocity hemispheric shell; Va = shell aliasing flow velocity; Vmax = maximum diastolic flow velocity; VSD = ventricular septal defect; VTI = velocity time integral.