This term is now restricted to local or partial dilatations of the wall of one of the cardiac cavities. Formerly, dilatation of the heart or of one of its chambers was spoken of as aneurism. This rare condition70 is most frequently associated with fibroid degeneration, but other causes of local weakness of the walls, as ulcer, acute myocarditis, and fatty degeneration, have been present in a few cases. An instance is on record where the aneurism followed a stabbing wound of the chest.71 The left ventricle is usually involved; very few cases occur in the other chambers. The condition may be acute or chronic.
70 In the index catalogue there are references to only 18 cases by American authors. In the museums of Philadelphia there are only 5 specimens—3 in the museum of the College of Physicians; 1 each in the University and Pennsylvania Hospital cabinets.
71 Quoted by Legg, Bradshawe Lecture on Cardiac Aneurisms, London, 1883.
Acute aneurism is met with occasionally in ulcerative endocarditis, more rarely as the result of local softening due to myocarditis or plugging of a branch of a coronary artery. In severe endocarditis perforation is, I think, more common than the production of aneurism. In one case I saw a deep excavation at the upper part of the septum produce a bulging the size of a marble in the wall of the left auricle, and in another ulceration in one sinus of Valsalva had extended into the septum, the upper part of which presented an aneurismal dilatation which had ruptured into the left ventricle. Legg considers the production of acute aneurism by the rupture of abscesses or cysts as doubtful.
Chronic aneurism is almost confined to the left ventricle, and, as Cruveilhier pointed out,72 is the result of fibroid degeneration of the muscle. In a few instances fatty degeneration appears to have been the cause. The monographs of Thurnam,73 Pelvet,74 and Legg75 give the most complete account of the disease. They are more common in men than in women, and the majority of the cases occur after middle life.
72 Anatomie pathologique, Paris, 1835–42.
73 Medico-Chirurgical Transactions, vol. xxi., 1838.
74 Des Aneurysmes du Coeur, Paris, 1867.
75 Loc. cit.
The situation of the aneurism is most frequently at the apex—59 of 90 cases collected by Legg. They are usually rounded in shape, and may vary in size from a marble to a cocoanut. The sac may be double, as in a case described by Janeway,76 or, as in a specimen in Guy's Hospital Museum, the whole wall of the ventricle may be covered with aneurismal bulgings. In the simplest form there is a rounded dilatation at the apex, and the lower part of the septum is lined with thrombi. Often the tumor is distinctly sacculated, and communicates with the ventricle by a very small orifice. The pericardium is usually thickened, and calcification may occur in the walls. Rupture seems rarely to occur—in only 7 of the 90 cases collected by Legg. Of other parts of the ventricle, the septum and the undefended space at the highest part of the septum just below the aortic ring are most often involved. This latter situation is sometimes the seat of a congenital dilatation, usually a small, thin, smooth sac without thrombi, which has no pathological significance.