Chest radiographs are unreliable in predicting thrombi in the left atrium or its appendage in rheumatic mitral stenosis.

We have assessed the diagnostic accuracy of a flat or concave left mid-cardiac border (the region of the left atrial appendage) on conventional postero-anterior chest radiographs as a predictor of the presence of thrombi in the left atrium or its appendage in 80 patients with rheumatic mitral stenosis who subsequently underwent open-heart surgery. Forty-six patients (Group I) were found to have left atrial thrombus at surgery whereas 34 patients (Group II) showed no evidence of thrombosis. Only 22 of 46 patients in Group I showed a flat or concave left mid-cardiac border (sensitivity, 48%; specificity, 53%; positive predictive value, 58%). Furthermore in Group 1, the thrombus involved the left atrial appendage in 33 patients. In this subgroup only 14 patients showed a flat or concave left mid-cardiac border (sensitivity, 42%; specificity, 49%; positive predictive value, 37%). The presence of flatness or concavity in the left mid-cardiac border on conventional posterior-anterior chest radiographs in patients with rheumatic mitral stenosis is an unreliable indicator of the presence of thrombi in the left atrium or its appendage.