Mitral valve area calculations immediately after percutaneous balloon mitral valvuloplasty: effect of the atrial septal defect

Department of Cardiology, Johannesburg Hospital, University of Witwatersrand, South Africa.

OBJECTIVES. The aim of this study was to assess the effect of the atrial septal defect on mitral valve area calculations after balloon mitral valvuloplasty. BACKGROUND. There is poor correlation between the hemodynamic-derived and Doppler mitral valve area immediately after mitral valvuloplasty. The reasons for this are unclear. METHODS. Twenty-five patients with severe mitral stenosis were studied. After balloon mitral valvuloplasty, serial mitral valve area calculations were performed with 1) the mitral dilating catheter across the atrial septum, 2) the 7F catheter across the atrial septum, and 3) with the atrial puncture site occluded with the balloon catheter. RESULTS. The mitral valve area determined by the Gorlin formula with balloon occlusion of the atrial septum was smaller than the mitral valve area determined without balloon occlusion (mean +/- SD 1.8 +/- 0.43 vs. 2.24 +/- 0.67 cm2, p < 0.005 for the mitral dilating catheter across the atrial septum and 1.8 +/- 0.43 vs. 2.19 +/- 0.52, p < 0.05 for the 7F catheter across the atrial septum). The mean of the differences between the mitral valve area derived by the Gorlin formula and by the Doppler pressure half-time method was smaller with the atrial septum occluded than when the dilating catheter or the 7F catheter was across the atrial septum (0.12 +/- 0.26 vs. 0.56 +/- 0.48 cm2 [p < 0.005] and 0.12 +/- 0.26 vs. 0.48 +/- 0.55 cm2 [p < 0.05]). Left to right shunting was detected less frequently by oximetry (60%), than by shunt ratios calculated by using the cardiac output measurements with and without balloon occlusion of the atrial septum (84%). CONCLUSIONS. The presence of left to right shunts after mitral valvuloplasty may account for some of the discrepancies between mitral valve area found at cardiac catheterization and that by the Doppler pressure half-time method; thus, the latter method may be reliably used to follow up patients in the long term.