After suffering a streptococcal throat infection, a 12-year-old immigrant boy develops cardiac symptoms that are attributed to rheumatic fever. Years later, at the age of 34 he is admitted to the hospital with pulmonary edema. Further examination reveals a diastolic murmur at the apex and mitral stenosis is diagnosed. Before surgical evaluation, which of the following findings can be attributed to mitral stenosis?

Dilation of the left atrium is the obvious complication following long-standing mitral stenosis. Echocardiography is the simplest and most precise method of showing enlargement of the left atrium. Frequently, there is a latency period of 15-20 years before symptoms become evident. Important complications of mitral stenosis include exertional dyspnea caused by an increase in left atrial pressure and backup of blood with possible pulmonary edema, decreased cardiac output, atrial fibrillation, emboli (15%), and pressure in the intermediate third of the esophagus as seen on an esophogram after barium swallow. The pulse in mitral or aortic stenosis is reduced.