Acute reduction of mitral valve area after percutaneous balloon mitral valvuloplasty: assessment with Doppler continuity equation method. Mitral valve areas before and after balloon mitral valvuloplasty were serially determined by the Doppler continuity equation method in 16 patients. Ultrasound examinations were performed before and immediately after balloon inflation and 24 hours, 1 week, and 1 month after valvuloplasty. Mitral valve area determined by the Doppler continuity equation method correlated well with that determined at catheterization by the Gorlin formula, not only before but also immediately after balloon inflation (y = 0.87 x + 0.05, standard error of estimate = 0.22 cm2, r = 0.90). Serial calculation of mitral valve area by the Doppler continuity equation method showed a slight but significant decrease in the valve area at 24 hours after balloon mitral valvuloplasty but no change after that. We conclude that the Doppler continuity equation method provides an accurate estimation of mitral valve area before and even after balloon valvuloplasty. Mitral valve area dilated by balloon inflation is decreased slightly within 24 hours after the procedure, which corroborates valve stretch as one mechanism for increasing mitral valve area with balloon valvuloplasty. Estimation of mitral valve area immediately after balloon mitral valvuloplasty may overestimate the long-term efficacy of the procedure. 