Rupture during severe exertion occurs in the perfectly healthy heart. The ruptures take place in the weakest point, and most commonly in the fibrous ring which encircles the base of the heart and attaches the great aorta. This is occasionally seen to happen in very spirited horses during a severely contested race or when a heavy load is being dragged up hill. Percivall mentions the case of a horse at a Woolich racing meeting, which had just lost a heat by half a head and which died just after passing the winning post, with ruptured right auricle.
Cases occur during coitus (Hering), tympany (Anacker, Mayer, Perdan) and operations (Stockfleth).
Rupture from Concussion more frequently implicates the muscular walls which have not the same power of resistance when they receive the blow in a relaxed condition. Parker met with a case of rupture of the right auricle at its base or at the line of its union with the ventricle. The subject was a pony which ran away down hill and struck his right shoulder violently against a cart wheel. In other instances the rupture takes place in the posterior vena cava, and particularly if its walls have been the seat of disease. Gamgee found rupture of the commencement of the azygos vein in oxen killed by pithing in the slaughter houses of Ferrara, and Professor Maffei subsequently found that out of 3095 oxen killed in these abattoirs 57 had this vein ruptured. Gamgee’s explanation of the occurrence is that “the instant the animals are pithed the walls and contents of the chest become paralyzed, the heart becomes an inert bag filled with fluid, the jerk of which as the animal falls, causes rupture of the containing vessel at its weakest part and this is in truth the vena azygos whose walls are thin and only protected externally by the pleura.” Hertwig gives other cases resulting from falls.
Perforation of the heart from ulceration is sometimes seen in cows when sharp pointed metallic bodies from the stomach make their way into its substance. An alleged case of rupture following ulceration of the walls of the right ventricle is recorded by Gaullet.
Inflammation, softening, fatty and calcareous degeneration, dilatation, atheroma, and the presence of parasitis in its substance render the heart more friable and predispose to rupture.
Lesion. The rupture is often at the fibrous ring encircling the aorta or pulmonary artery; in other cases in the muscular wall of ventricle or auricle.
Symptoms. Death may be practically instantaneous. If delayed there is hurried breathing, anxiety, weakness, pallor of the mucous membranes, staggering, trembling, vertigo, stupor, and convulsions.
DISEASES OF ARTERIES.
The chief morbid conditions seen in arteries are: Wounds, inflammation, thrombosis, embolism, degeneration, and aneurisms. Wounds belong essentially to surgery.