Transesophageal Echocardiographic Analysis of the Systolic Pattern of the Anterior Mitral Leaflet in Patients with Flat Chest

Transesophageal echocardiography was conducted to determine the systolic pattern of the anterior mitral leaflet in patients with flat chest, and to differentiate it from that associated with mitral valve prolapse. The fronto-sagittal index (an index of chest flattening) was determined in 50 subjects using chest radiographs, and was used to classify them into a flat chest group (index < 0.38, n= 28) and a normal chest group (index ≥ 0.38, n= 22). We then used transesophageal echocardiography to examine the anterior leaflet in these subjects. A significant positive correlation was observed between the fronto-sagittal index and the short-to long-axis diameter ratio of the left ventricle in all patients. These parameters, and the left atrial dimension were lower in the flat than the normal chest group. The clear zone area of the anterior leaflet during mid-to late-systole was significantly larger in the flat chest group. However, no intergroup differences existed in the rough zone area of the anterior leaflet or in the middle scallop area of the posterior leaflet. Mitral regurgitation was observed in 20 and 12 subjects in the flat and normal chest groups, respectively. The maximum mitral regurgitant area did not differ between the two groups. The clear zone area of the anterior leaflet increased significantly following inhalation of amyl nitrite in 22 subjects of both groups, but the other areas did not increase. The mitral regurgitant area decreased or disappeared after amyl nitrite at a similar rate in each group. Thus, the decrease in the antero-posterior dimension of the thorax in subjects with flat chest affects the systolic pattern of the clear zone of the anterior leaflet more than that of the rough zone of the anterior leaflet or the posterior leaflet. This systolic pattern in such patients differs from that associated with mitral valve prolapse.