Mitral Heart

Mitral Heart, a special form of cardiac silhouette, determined upon X-ray examination in dorso-ventral direction on X-ray photographs, on orthodiagrams, and through precise percussion of the borders of relative cardiac dullness; this form is called mitral because it is observed in its most typical form in mitral valve defects and particularly in mitral stenosis. The typical silhouette of the mitral heart appears as follows: the lower arch of the right contour of the heart (contour of the right atrium) is rounded; the mid-right dimension of the cardiac shadow is increased; on the left contour of the heart, the II and III arches (arch of the pulmonary artery and appendage of the left atrium) protrude distinctly; the apex of the heart is somewhat pointed, and the heart assumes a more vertical position. Such a form of heart arises under pathological conditions as follows. With enlargement of the right ventricle, the right atrium is displaced to the right and upward, and the lower right arch of the cardiac shadow becomes more convex; this is further promoted by enlargement of the right atrium. On the other hand, the conus arteriosus of the pulmonary artery and the arch of the pulmonary artery, due to enlargement of the right ventricle, are displaced to the left and upward, while the left ventricle and left appendage are displaced backward. With very great enlargement of the right ventricle, it may form the lower part of the lower right arch, and also on a small space participate in the formation of the contour of the lower left arch between the left appendage and the apex; very rarely does the right ventricle entirely form the lower left arch. Simultaneously, due to enlargement of the right ventricle, the heart rotates around its longitudinal axis (in the direction of the clock hands when viewed from the apex); as a result, the lower left arch becomes less convex, and the apex becomes pointed. The dilation of the conus arteriosus of the pulmonary artery and its trunk due to stagnation in the lesser circulation causes the characteristic protrusion of the II arch on the left in M. s. According to the generally accepted view, in M. s. the III left arch also protrudes more strongly due to enlargement of the left atrium, resp. the left appendage; but many radiologists believe that with enlargement of the left atrium, its left border does not shift to the left, and attribute the characteristic change in the contour of the cardiac shadow on the left mainly to the enlargement and leftward protrusion of the arch of the pulmonary artery. With moderate degrees of cardiac enlargement, with its mitral configuration, the left contour represents almost a straight line, descending obliquely from the shadow of the aortic arch to the apex of the heart; with stronger degrees, the II and III arches on the left protrude sharply. Enlargement of the left atrium is determined upon examination in oblique directions. In the first oblique direction, it bulges with a convex shadow into the retrocardiac space. Such a form of heart is typical, as already mentioned, for hearts with mitral valve defects, particularly for uncomplicated narrowing of the left venous opening [see separate table (pp. 79-80), Fig. 5]. With mitral valve insufficiency, the lower left contour of the heart has more rounded outlines, and the mid-left dimension is increased due to enlargement and hypertrophy of the left ventricle (see separate table, Fig. 6). The mitral form of heart is observed to a greater or lesser degree also with all other pathological processes that lead to difficulty in the functioning of the right heart and to disturbance of circulation in the lesser circulation. These include: 1) certain types of congenital heart defects-persistence of the ductus arteriosus, defect of the septum between the atria, and rarely-stenosis of the pulmonary artery; 2) sclerosis of the pulmonary artery; hypertrophy of the right heart in this case often reaches very large dimensions; 3) emphysema; 4) extensive scar processes in the lungs; 5) sometimes with lesions of the heart muscle, when all parts of the heart dilate to almost equal degree and there is atrial fibrillation, which is as a rule accompanied by enlargement of the left atrium; 6) sometimes in Basedow's disease, the heart assumes a mitral configuration due to dilation of the pulmonary artery. - Furthermore, the mitral configuration of the heart can also occur in the absence of pathological changes in the heart and difficulties in circulation in the lesser ^CIRC^LE, for example in individuals of asthenic build, when due to the low position of the diaphragm the longitudinal axis of the heart becomes more vertical and the II and III arches bulge upward and to the left. With right-sided scoliosis, the heart is displaced to the left and also assumes a mitral form. With scar processes in the pulmonary tissue and adhesive pleural processes in the area of the left hilus, the middle part of the heart is pulled to the left, the waist of the heart on the left is smoothed out. But in all these cases, enlargement of the shadow of the atrium is not determined. In general, there are no precise boundaries between pathologically altered M. s. and the mitral configuration of the heart under the physiological conditions mentioned. See also the illustrations (radiodiagnosis) for the articles Heart Defects and Heart.

n. Potte. MJ1XAEJlMCrycTaB (Gustav Adolph Michae-iis, 1798-1848), author of a classical work on the narrow pelvis, published after the death of Michaeils by his successor on the chair K. Licsman («iber das en-ge Becken nach ei-genen Beobachun-gen und Untersu-chungen», Kiel, 1851, 2.Aufl., Lpz., 1865). Besides this work, M. left several other scientific works, including a description of a case of four successive cesarean sections on the same woman. Under the pressure of severe experiences connected with the continuing epidemic of puerperal fever in his clinic, M. took his own life by throwing himself under a train. In honor of M., the 'Michaels rhombus' is named.