Mitral valve annular dilatation caused by left atrial myxoma.

We report a case of mitral valve annular dilatation caused by a large left atrial myxoma. A 69-year-old woman presented in pulmonary oedema. She was found to have a large left atrial myxoma prolapsing into the left ventricle in diastole causing severe functional mitral stenosis. At operation, the myxoma was completely excised from its attachment to the atrial septum. The mitral valve looked anatomically normal but the mitral annulus was dilated. The intraoperative Trans Oesophageal Echocardiogram (TOE) on weaning from cardiopulmonary bypass confirmed a dilated mitral annulus with moderate mitral regurgitation (MR). We elected not to place an annuloplasty ring in anticipation of improvement with postoperative remodelling. However, mitral regurgitation worsened after discharge becoming moderately severe and remains so after 1 year follow-up despite optimal medical treatment. This case suggests that annular dilatation can result from mechanical dilatation by a large left atrial myxoma. Intraoperative mitral valve annuloplasty should be considered in the presence of moderate MR as postoperative remodelling does not occur.