Acquired Lutembacher syndrome or mitral stenosis and acquired atrial septal defect after transseptal mitral valvuloplasty. Critical mitral stenosis in selected patients may be treated successfully with percutaneous mitral valvuloplasty. Complications of this procedure, particularly an atrial septal defect following transseptal approach, are generally of minor clinical significance. We describe a woman who initially underwent a successful percutaneous double-balloon mitral valvuloplasty via the transseptal approach. Three months later she presented with right-sided heart failure. Color Doppler echocardiography and cardiac catheterization demonstrated an atrial septal defect (ASD) as well as restenosis of the mitral valve. We conclude that significant ASDs may occur following transseptal mitral valvuloplasty with appearance of right ventricular failure and that color Doppler imaging aids in the diagnosis of this new variant of the classical Lutembacher syndrome. 