In the lower animals ruptures of the heart have been observed as the
result of (a) extraordinary exertion, (b) violent concussion, and (c)
ulceration and degeneration. The rupture of the fatty heart in the lower
animals is not common.
=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.