Part 49

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.

=Narrowing of the Mitral orifice.= In addition to the same general symptoms as the last named lesions, there is a sighing, blowing, purring or rasping sound, according to the degree of narrowing, heard before the first sound of the heart. It is the noise of the blood rushing through the narrowed orifice between auricle and ventricle. It is usually loudest behind the middle of the shoulder on the left side. Feeble pulse, frequent imminence of suffocation and filling of the limbs, etc., are nearly constant.

=Narrowing of the Tricuspid orifice.= Symptoms nearly identical with the last. Venous pulse more constant. Blowing murmur sometimes loudest on the right side of the chest.

=Induration or insufficiency of the aortic valves.= Blowing murmur with the second sound of the heart. Double rushing sound in the carotid with each heart’s beat. There is an appreciable interval between the beat of the heart and corresponding pulsation at the jaw.

=Induration or insufficiency of the pulmonary valves.= Blowing murmur with the second heart sound, but no corresponding double sound in the carotid, nor any marked retarding of the pulse.

=Loose coagula in the heart= or adherent ones (polypi) produce one or other of the above class of symptoms, according to the particular orifice they tend to block or the valves whose function they impair.

Anæmia and leukæmia may have blowing murmurs with the first or second heart sound.

=Embolism.= =Plugging of arteries.= Another class of symptoms sometimes supervenes because of loose clots being washed on into the arteries, and blocking them when they reach those that are too small to transmit them. These symptoms will be as varied as the organs whose arteries are plugged. If in the brain there may be dulness, stupor, vertigo, somnolence, delirium; if in the liver, biliary and digestive derangement; if in the lungs, cough with the other signs of pneumonia and abscess; and if in the limbs lameness and paralysis, (brought on or aggravated by exercise, and often removed by a few minutes’ rest), wasting of the muscles, etc. (See Embolism).

Causes. These are in the main the same as those of pericarditis. Weak health, exposure to extremes of weather, punctures with foreign bodies, but above all, the rheumatic constitution are common causes. Indeed rheumatism appears more prone to attack the serous membrane lining the heart cavities than that enveloping it externally. One reason for this is to be found in the great and incessantly recurring strain on the fibrous structure of the valves, and particularly in hard worked horses and hunting dogs in which the strain is often extreme. It has been argued that the increased blood pressure caused by digitalis is an appreciable cause. Its frequent connection with rheumatism is shown in the rheumatic lesions of joints and fibrous structures seen in carcasses dead of endocarditis.

Diseases in the muscular substance of the heart as cysts, abscess, etc., frequently extend to the endocardium.

Among other causes must be mentioned disease-changes in the blood. These may act on the valves directly as in the case of lactic acid injected by Dr. Richardson, into the peritoneum with the view of producing rheumatism and successfully as regards the lesions of the cardiac valves; or indirectly by determining coagulation and irritation of the lining membrane coming into contact with the clot. The very fibrinous and plastic state of the blood in extensive inflammations is a probable cause of the occurrence of clots in the heart, and the frequency of such clots in the dog has been ascribed to the plasticity of his blood (Leblanc). The injection of pus into the blood or the absorption of microbes from diseased surfaces will sometimes produce ulcerative disease of the valves. The same is true as regards the germs of omphalitis, pneumonia, arthritis and other infectious diseases.

Lafosse records certain cases of endocarditis due to extension of the disease from inflamed veins.

Prognosis. Endocarditis is always attended with great danger to life, but it is more likely to terminate in chronic valvular disease which quite unfits the animal for useful work. Mild cases may terminate in complete recovery.

Treatment. This is in the main the same as that adopted in the early stages of pericarditis. Absolute rest is of prime importance. Laxatives, sedatives and counterirritants are to be mainly relied upon. Belladonna and chloroform on the chest behind the left elbow may be used. As there is not the same danger from effusion, diuretics need not be pushed to the same extent. Digitalis must be avoided if possible until the high fever subsides. In infective cases, quinia, salicylate of soda, salol, or hyposulphite of soda may be given. Later give tincture of muriate of iron.

In rhemuatic cases, treat as for an acute attack of rheumatism. Frequent large doses of salicylate of soda or salol, large doses of acetate of potass and colchicum, warm clothing and counterirritants to the region of the heart are especially demanded. (See Rheumatism.)

When clots are suspected, and when endocarditis threatens to lapse into the chronic form, it is recommended to give iodide of potassium (horse and ox 1 drachm, dog 5 grains, twice daily) with carbonate of ammonia or of potass and bitter tonics. A lengthened rest after apparent recovery is essential to avoid permanent valve lesions.

CARDITIS. MYOCARDITIS.

Definition. Rare. Complicates pericarditis and endocarditis, wounds of the heart, and tubercular and other deposits. Symptoms. Treatment.

Definition. Inflammation of the muscular substance of the heart.

This is a rare affection and is necessarily limited to a small portion of the heart’s substance, otherwise, the cardiac contractions must cease in obedience to the general law that the normal function of an inflamed organ is for the time abolished. It is mainly seen as a concomitant of endocarditis or pericarditis, and extends only to the superficial muscular layers; or it results from a wound as in the penetration of the heart by a needle or other sharp pointed body and is then equally circumscribed. It has been seen as a complication in infectious diseases—aphthous fever, pyæmia, septicæmia, pneumonia and tuberculosis.

The evidences of the existence of carditis are chiefly the lesions met with after death. 1st, The existence of abscesses in the heart’s substance associated with polypus (Gowing, Leblanc, etc.,) or otherwise (Reynal). Also diffuse suppuration in the heart’s substance (Puze, etc.) 2nd, Softening of the muscular substance, a state occasionally met with when an animal has died of ruptured heart. 3d, Ulceration of the walls of the heart as reported by Mercier in a case of endocarditis. 4th, Transformation, and induration of the heart’s substance whether into fibrous tissue, cartilage or bone. This last condition of the walls of the right auricle and ventricle has been repeatedly seen in old horses, the change being in certain cases so extensive that one is left in wonder as to how circulation could have been carried on. Three specimens of this kind were preserved in the museum of the Alfort Veterinary College, Paris, and the Royal Veterinary College, London. Lafosse records two cases of gangrene of the internal layers of muscle in endocarditis.

The symptoms are those of acute heart disease generally modified somewhat by the precise location of the inflamed spot, and treatment need not differ materially from that applied for inflammation of the investing membranes, inner and outer, and for the infectious disease which it complicates.

CHRONIC VALVULAR DISEASE OF THE HEART.

This, as already noticed, is a common result of endocarditis, the valves being most obnoxious to disease in such cases. The symptoms are those mentioned under endocarditis as characterizing disease of the different valves, such as incapacity for exertion, difficult breathing, palpitation, irregularity or intermission of pulse, venous pulse, abnormal heart sounds, unsteadiness of the limbs when driven, and dropsical swellings in the limbs and elsewhere. The reader is referred to endocarditis for particulars, it being borne in mind that these symptoms are not in this case associated with fever.