Mitral Heart

MITRAL HEART, a special form of the heart silhouette determined during fluoroscopy with X-rays in the dorsoventral direction on X-ray photographs, on orthodiagrams, and upon 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 valvular defects and, in particular, in mitral stenosis. The typical silhouette of the mitral heart appears in this case as follows: the lower arc of the right cardiac contour (the contour of the right atrium) is rounded; the median-right dimension of the cardiac shadow is increased; on the left contour of the heart, the second and third arcs (the arc of the pulmonary artery and the auricle of the left atrium) clearly bulge; the apex of the heart is somewhat pointed, and the heart has a more vertical position. A similar shape of the heart arises under pathological conditions in the following manner. With an enlargement of the right ventricle, the right atrium is displaced to the right and upward, and the right lower arc of the cardiac shadow becomes more convex; this is promoted even more by the enlargement of the right atrium. On the other hand, the conus arteriosus pulmonalis and the arc of the pulmonary artery, as a consequence of the enlargement of the right ventricle, are displaced to the left and upward, and the left ventricle and left auricle are displaced posteriorly. With a very large enlargement of the right ventricle, it can form the lower part of the lower right arc, and also, over a small space, participate in the formation of the contour of the left lower arc between the left auricle and the apex; very rarely, the right ventricle entirely forms the lower left arc. Simultaneously, as a consequence of the enlargement of the right ventricle, the heart rotates along its longitudinal axis (in the direction of the clock hands, if viewed from the side of the apex); as a result of this, the left lower arc becomes less convex, and the apex becomes pointed. The dilation of the conus arteriosus pulmonalis and its trunk as a result of stagnation in the lesser circulation causes the bulging of the second arc on the left, which is characteristic of the mitral heart. According to the generally accepted view, in the mitral heart, the third left arc also projects more strongly as a consequence of the enlargement of the left atrium, respectively the left auricle; but many radiologists believe that with the enlargement of the left atrium, its left border does not shift to the left, and they attribute the characteristic change in the contour of the cardiac shadow on the left mainly to the enlargement and protrusion to the left of the pulmonary artery arc. With a moderate degree of cardiac dilation, in its mitral configuration, the left contour represents an almost straight line descending obliquely from the shadow of the aortic arc to the apex of the heart; with stronger degrees, the second and third arcs on the left sharply bulge. The dilation of the left atrium is determined during fluoroscopy in oblique directions. In the first oblique direction, it protrudes with a convex shadow into the retrocardiac space. A similar shape of the heart is typical, as already mentioned, for hearts with a defect of the mitral valve, in particular for uncomplicated stenosis of the left venous orifice [see separate plate (articles 79–80), Fig. 5]. In mitral regurgitation, the left lower contour of the heart has more rounded outlines, and the median-left dimension is increased due to the enlargement and hypertrophy of the left ventricle (see separate plate, Fig. 6). The mitral shape of the heart is observed to a greater or lesser degree also in all other pathological processes that lead to difficulty in the work of the right heart and to circulatory disturbance in the lesser circulation. These include: 1) certain types of congenital heart defects—patent ductus arteriosus, interatrial septal defect, and rarely pulmonary stenosis; 2) sclerosis of the pulmonary artery; the hypertrophy of the right heart in this case often reaches very large sizes; 3) emphysema; 4) extensive cicatricial processes in the lungs; 5) sometimes in lesions of the heart muscle, when all sections of the heart dilate to an almost equal degree and there is absolute arrhythmia, which is accompanied, as a rule, by an enlargement of the left atrium; 6) the heart sometimes has a mitral configuration in Graves' disease due to the dilation of the pulmonary artery. In addition, the mitral configuration of the heart can also occur in the absence of pathological changes on the part of the heart and circulatory difficulties in the lesser circulation, for example, in persons of asthenic build, when, as a consequence of the low standing of the diaphragm, the longitudinal axis of the heart becomes more vertical and the second and third arcs bend upward and to the left. In right-sided scoliotic chest, the heart is displaced to the left and also acquires a mitral shape. In cicatricial processes in the lung tissue and adhesive pleural processes in the region of the left hilus, the heart in its middle part is pulled over to the left, and the waist of the heart on the left is smoothed out. But in all these cases, the enlargement of the atrial shadow is not determined. In general, there are no exact boundaries between the pathologically altered mitral heart and the mitral configuration of the heart under the indicated physiological conditions. See also the figures (radiodiagnosis) to the articles Heart defects and Heart.

N. Potet.

MICHAELIS, Gustav Adolph (1798–1848), author of a classical work on the narrow pelvis, published after Michaelis's death by his successor to the chair, C. Litzmann ("Über das enge Becken nach eigenen Beobachtungen und Untersuchungen", Kiel, 1851, 2nd ed., Leipzig, 1865). In addition to this work, M. left several more scientific works, including a description of a case of quadruple Cesarean section on the same woman. Under the burden of severe experiences in connection with the unceasing epidemic of puerperal fever in his clinic, M. took his life by throwing himself under a train. The "Michaelis rhombus" is named in honor of M.

Article headword: MITRAL HEART