In the early stage there may be a mere swelling of the valves, with as yet a smooth, unbroken surface, but with enlargement and increase of the connective tissue cells, later fungous vegetations start out from the surface, and on these the fibrine of the blood is deposited in layers.
Besides the formation of clots on their surfaces other changes occur on the cardiac valves as the result of inflammation. The organization of the exuded lymph within and upon them leads to rigidity, loss of elasticity, unevenness of their surface, contraction and puckering so that they can no longer approximate to each other, but leave the orifice imperfectly closed. They may, moreover, have gristle or bone deposited in their substance. The osseous degeneration of such new products appears to be the most common cause of those ossifications of the heart, of which specimens are to be found in nearly all veterinary museums.
Chronic valve disease is thus found to be a common result of endocarditis, and from the obstacle presented to the flow of blood through the different cardiac orifices by the rigid, inelastic and distorted valves, hypertrophy of the heart frequently supervenes.
In our domestic quadrupeds ante-mortem clots and fibrinous polypi have been chiefly formed in the right side of the heart, and diseased valves in the left.
Symptoms. The general symptoms agree in many respects with those of pericarditis. There are the same general symptoms of fever (temperature 102° to 106°), the same pinched, anxious countenance, the same shortness of breath and oppression when moved, the same violent heart’s action, and the same rapid, excitable pulse tending to be irregular and intermittent. Among the more specific symptoms are a very violent impulse of the heart against the left side, varying in force, however, in successive beats; a metallic tinkling accompanying the impulse and sometimes heard at some little distance from the body, a blowing murmur as soon as the changes in the valves render them insufficient to close the orifices, and, if the obstruction exists on the right side, venous pulse, general venous congestion, and dropsical swellings.
The pulse may at first have considerable force but, as insufficiency of the valves ensues, it becomes small and weak, its weakness forming a most marked contrast to the violence of the heart’s impulse against the side. The irregularity and intermission of the pulse is to be ascribed at first to the impaired nervous energy of the heart though later it is often due to the obstacle presented by clots to the flow of blood from the heart, so that a beat sometimes takes place without a corresponding pulsation. It may reach 80 or 160 per minute in horse or ox.
The blowing murmur when heard is one of the most characteristic symptoms but must be carefully distinguished from other allied heart sounds. If very loud it may be confounded with the friction sound of pericarditis, but may be differentiated by its invariable coincidence with some particular portion of the heart’s beat. The absence of local tenderness is another distinctive symptom. Again in pericarditis effusion takes place early annulling friction sound, and diminishing alike the impulse and the sounds of the heart.
It is of less practical value to be able to distinguish the precise seat of the murmur, yet the following data will guide to such a conclusion.
Simple induration or insufficiency of the Left Auriculoventricular (Mitral) valve. Paroxysms of palpitation, oppression, and difficulty of breathing; vertigo with loss of control over the limbs and vacillating gait; stupor, coma; slight tremor and blowing noise with the first sound of the heart; heart’s impulse, violent, but irregular in force, sometimes double; pulse feeble, irregular, unequal, or intermittent; sometimes though not at all constantly a venous pulse in the lower end of the jugulars. In chronic induration of this valve, or in osseous, or cartilaginous degeneration the same symptoms are shown. The more general symptoms may, however, require exercise to develop them.
Induration, etc., of the Right Auriculo-Ventricular (tricuspid) valve. The symptoms are almost identical with the last. Venous pulse is constant, and, particularly after exertion, the veins generally are distended. Dropsies are more common.