1020-7 Afterload Dependence of Mitral Regurgitant Volume and Regurgitant Orifice Area by Quantitative Doppler

Abstract

Quantitation of the severity of mitral regurgitation (MR) is complicated by changes in loading conditions that occur either spontaneously or as a result of therapy. Effective regurgitant orifice area has been proposed as a more fundamental measure of the severity of MR than regurgitant volume. To test the hypothesis that regurgitant orifice area is less dependent on loading conditions than regurgitant volume, we studied the effects of afterload reduction with nitroprusside infusion on regurgitant orifice area and regurgitant volume by quantitative Doppler in 12 patients (age 34 to 77 years) with moderate or severe MR. Etiology of MR was dilated cardiomyopathy in 2, mitral valve prolapse in 7, infective endocarditis in 1, and rheumatic mitral valve disease (without stenosis) in 2. Regurgitant volume was calculated from the stroke volumes (area times velocity-time integral) in the left ventricular outflow tract and mitral annulus. Regurgitant orifice area was calculated as regurgitant volume divided by the velocity-time integral of the MR continuous wave Doppler envelope. MR could not be quantitated in 2 patients with prolapse and markedly eccentric jets due to inadequate alignment of the continuous wave Doppler beam. In the remaining 10 patients, nitroprusside decreased mean regurgitant volume significantly from 138 ± 82 to 116 ± 71 ml (p = 0.0017), while mean regurgitant orifice area remained unchanged (1.1 ± 0.7 vs 1.1 ± 0.7 cm 2 , p = 0.64). Thus in patients with mitral regurgitation, effective regurgitant orifice area is less afterload dependent than regurgitant volume, supporting the use of regurgitant orifice area as a more fundamental gauge of the severity of MR.