In the gradual absorption of a pleuritic effusion, serous or purulent, the heart may not only regain its normal position, but is in many instances drawn toward the affected side by the contracting false membranes.
Of conditions of the mediastinum producing displacement, two only need be mentioned—aneurism and tumor. Very large aneurisms of the arch usually press the heart downward, and its axis may be transverse; but much depends on the direction of growth, and a slight lateral and downward dislocation is most frequently met with. Tumors do not necessarily cause displacement, but when large there may be some dislocation in the direction of the growth of the mass. Most extensive masses of mediastinal cancer may occur without any disturbance of the position of the heart.
Diseases of the abdominal viscera not uncommonly produce dislocation of the heart, generally upward. Extensive peritoneal effusion, gaseous or fluid, forces up the diaphragm, and with it the heart, which may assume the transverse position, and the apex beat as high as the third interspace. Gas much more readily than fluid rapidly lifts the diaphragm and produces upward dislocation of the heart. Diaphragmatic hernia of intestines or stomach may push the heart up or to one side.
Conditions of the liver not infrequently affect the position of the heart. Abscess or hydatid cysts of the left lobe may push the organ up and to the left. More rarely large hepatic tumors drag the diaphragm down, and with it the heart. Very great splenic enlargement, as in leukæmia, may push up the diaphragm and lift the heart.
Other abdominal growths, as large retro-peritoneal and ovarian tumors or aneurism of the abdominal aorta, may occasionally produce the same effect. Knowsley Thornton has given in Fothergill's work on the Heart an excellent account of the upward displacement of the heart in ovarian disease.
As a very rare circumstance, the heart is displaced by accidental injury to the chest-walls. The case which Stokes relates of this kind was probably, as he subsequently suggested, due rather to the effects of the pleuritic effusion which followed the accident.
The dislocations of the heart when gradually induced rarely disturb to any serious extent the functions of the organ.
Myocarditis.
Inflammation of the heart-muscle is rarely primary; usually it is associated with endo- or pericarditis, strain,7 embolic processes, disease of the arteries, or the presence of certain poisons—diphtheritic, rheumatic, etc.—in the blood.
7 Some French writers refer specially to the occurrence of myocarditis from strain or prolonged muscular exercise—myocardite des surmenes. Peter (Maladies du Coeur, Paris, 1883) gives two cases (without autopsy), and quotes a case from Revilliod, whose work (La Fatigue, Lausanne, 1880) I have not been able to consult.