Percutaneous mitral valve dilatation was performed in a 61-year-old female patient with severe mitral valve stenosis. The valve could be dilated, but a moderate left to right atrial shunt was present after the procedure. Although the mitral valve area had increased from 1 cm2 to 1.7 cm2, the patient presented 1 week later with right heart failure, explained by right heart volume overload resulting from the persistent shunt. Clinical status quickly improved with diuretics. Although this evolution has not been previously reported, it may be expected in older patients with decreased compliance of pulmonary arteries and right heart chambers.