Nine girls are presented with variable late systolic murmurs (usually best heard sitting up); five of the nine had mid systolic clicks, minimal to mild mitral regurgitation, and striking variable primary electrocardiographic T wave abnormalities. Data from a tenth girl, who has not yet had cardiac catheterization, with similar clinical features are included. The functional anatomy of the mitral valve and some of the factors that give rise to such a picture are discussed. A detailed cineangiographic analysis of the mitral regurgitation is made with stress on the role of the posterior leaflet and posterior papillary muscle. A quantitative angular analysis of the T waves is made. The vectorcardiogram's superiority to the standard electrogram is made clear in this regard.
We believe that this syndrome is caused by posterior papillary muscle dysfunction, though the etiology, including the reason why only girls should be affected, is not known. The prognosis is believed to be good.