Effect of atrial septal defect created during balloon mitral valvuloplasty on calculation of cardiac output and mitral valve area.

We studied the effect of atrial septal defect (ASD), produced during transseptal puncture, on estimation of cardiac output (CO) and mitral valve area (MVA), after successful balloon mitral valvuloplasty (BMV) using the Inoue balloon in 20 patients. Oximetry run, pressure gradients, thermodilution CO and MVA were measured initially while temporarily occluding the ASD by partially inflating the Inoue balloon catheter. Measurements were repeated after withdrawing the balloon catheter into the right atrium. Post-BMV cardiac output and MVA were similar in both the situations (4.52 +/- 1.37 L/min vs 4.50 +/- 1.19 L/min; 1.89 +/- 0.4 cm2 vs 1.93 +/- 0.38 cm2 respectively, p = ns). Only 2 patients showed a step up at atrial level on oximetry (9% and 16% respectively) but did not have significantly different CO or MVA, both with ASD occluded or otherwise. We conclude that the magnitude of ASD created during BMV by Inoue balloon technique is small and does not significantly affect the estimation of CO or MVA if the septal puncture is done in the fossa ovalis area.