DISEASES OF CARDIOVASCULAR SYSTEM Myocardial diseases of dogs Dilated cardiomyopathy Heart worm diseases (Dirofilaria Immitis) Congestive heart failure

DILATED CARDIOMYOPATHY Definition It is a term describing the myocardial dysfunction characterized by reduced contractility, cardiac dilatation with or without cardiac arrhythmia. Clinically, the disease is char. By Weakness Exercise intolerance Pleural effusion JV distention

Etiology Infection: parvoviral myocarditis Idiopathic degeneration (unknown etiology-most cases) Toxicosis: Doxorubicin is antineoplastic agent with cardiotoxicity in dogs. IV ethyl alcohol injection Cobalt toxicity. Anesthetic drugs. Neoplasia Multisystemic or metabolic disorders: hypothyroidism, pheochromocytoma, and diabetes mellitus. Brain injury with excessive sympathetic stimulation that results in myocardial degeneration and necrosis

Pathogenesis: 1- Etiological factors decreased ventricular contractility reduction in systolic pump function declining cardiac output and dilatation of the heart. 2- Reduction in cardiac output sympathetic, hormonal and renal compensatory mechanisms become activated increasing heart rate, peripheral vascular hypertension. 3- Right and left congestive heart failure is a common complication

Clinical signs: Weakness and lethargy. Cough and dyspnea. Anorexia and weight loss. Exercise intolerance. Abdominal distension and syncope. Pale MM and prolonged capillary refill time (?). Weak and rapid pulse. Cardiac arrhythmia. Jugular venous distention and pulsation Pleural effusion and muffling of heart sounds. The QRS complex is widen and short (ventricular enlargement and weakness). The P wave is also widen and notched indicating atrial enlargement.

ECG changes in cardiomyopathy Q Normal R Q P S T Affected R

Treatment The primary goal of treatment is to provide adequate cardiac output Ionotropic drugs that increase the contractility of myocardium e.g. digoxin or dopamine. Diuretics to reduce blood volume and congestion e.g. furosemide (lasix). Vasodilators to enhance the forward cardiac output and reduce venous congestion e.g. nitroglycerine Bronchodilators such as aminophylline or thiophylline. Antiarrhythmic drugs: such as lidocaine or propranolol. Exercise restriction to minimize cardiac overload. Dietary sodium restriction to minimize water retention

HEARTWORM DISEASE Definition It is a parasitic infestation of the peripheral pulmonary arteries that results in pulmonary hypertension

Etiology Microfilaria called Dirofilaria immitis that is transmitted by mosquitoes. heartworms normally reside in the pulmonary arteries and right ventricles without significantly interfering with blood supply. The infection starts when the mosquitoes ingest the microfilariae (first stage larvae L1) that molt twice in the mosquito to infective L3. When the mosquitoes carrying L3 feed on dog, some of these larvae enter subcutis and molt to give L4 and then L5 young worm (100 days following infection) migrating to peripheral pulmonary arteries of the caudal lung lobes give mature females after 5 month release microfilaria

Pathogenesis the presence of adult worm in pulmonary arteries increases the reactive vascular lesions that results in pulmonary hypertension, endothelial cell swelling, increase the endothelial permeability periarterial swelling Excessive number of larvae migrate to heart then to vena cavae. Death of the adult heartworm leads to vascular occlusion and increases the pulmonary arterial resistance and lung consolidation alveolar hypoxia, cough, dyspnea, hemoptysis and right-side heart failure

Heart worm (Dirofilaria immitis)

Microfilaria in canine blood smear

Clinical signs Cough Dyspnea Hemoptysis Fatigue, weight loss Signs of right heart failure: ascites, tachypnoea, jugular vein pulsation and distension Pulmonary edema. Increased and abnormal lung sounds

Ascites

Diagnosis History Clinical signs Peripheral blood smear to see the microfilaria. N.B. Microfilaria may not present in the peripheral blood and this case is called occult infection. X ray: Right ventricular hypertrophy. Enlargement of pulmonary arteries

Treatment Adulticide drug: thiacetarsamide 2.2 mg/kg twice a day for 2 days. Larvicide: Ivermectin is given orally as a single dose 0.05 mg/kg 4 weeks after the adulticide therapy. Aspirin 5-10 mg/kg/day in dogs is indicated to block the pulmonary arterial disease and enhance the pulmonary outflow

CONGESTIVE HEART FAILURE Definition: Heart failure occurs when the output from the heart is no longer able to meet the body's metabolic demands for oxygen. Heart failure is an important cause of illness and death in dogs and cats.

Etiology Mitral valve regurgitation. The mitral valve is the valve that separates the left atrium from the left ventricle. Regurgitation means that blood moves backwards from the ventricle to the atrium when the ventricle is contracting, instead of flowing out into the aorta and then the body. Mitral valve disease usually occurs from chronic scarring of the valve (often due to bacterial infection),

2. Dilated cardiomyopathy, where the heart muscle becomes distended and incapable of properly transmitting the electrical current of the heart beat (more often seen in older, small breed dogs). 3. Cats, it usually associated with hypertrophic cardiomyopathy, where the heart muscle becomes too thick to work properly, and the chambers are too small to move an adequate amount of blood with each beat

Pathophysiology When the ventricle's performance and output decline the body activates several types of compensatory mechanisms in order to try to preserve blood pressure and cardiac output Many of the smaller blood vessels will constrict, or narrow, to help raise the blood pressure The heart rate begins to increase to get out as much blood to the body as possible The body starts to retain sodium and water, also to increase the blood pressure.

When excessive pressure is found in the ventricle during filling, edema begins to occur as fluid begins to seep (ooze) out of the blood vessels, into certain areas of the body, such as the lung tissue, around the outside of the lungs, and into the liver and abdomen leading to the so called congestive heart failure.

Clinical signs - Congestive heart failure is divided into left and right sided diseases. - The clinical symptoms of each one are different. A) Left sided congestive heart failure (CHF) (lung edema): 1- Respiratory distress- shortness of breath, and coughing 2- At first these symptoms may just be seen with exertion, but eventually they are seen even at rest. B) Right sided CHF is seen as: 1- Ascites, or fluid accumulation in the abdomen, causing a pot-bellied appearance. 2- Sometimes, fluid accumulates in the chest, around the lung tissue, causing compression of the lung tissue and heavy breathing. In both cases, weight loss can be seen, as well as decreased appetite,

Diagnosis History and clinical signs. X ray and ultrasonography: for the mitral insufficiency and the hypertrophic cardiomyopathy.

Treatment 1. Diuretic medication to reduce fluid in the lungs and to make the heart work. 2. Vasodilators are also often helpful to reduce the workload on the heart. 3. Diet changes may be necessary to reduce salt (sodium) intake, which in turn reduce retained fluids - especially in the lungs. This decreases the workload for the heart. 4. Reduce exercise regimen to help control signs of CHF. 5. Continued monitoring to maintain a stable condition of CHF.

Prognosis The prognosis for heart failure is generally poor unless the underlying heart disease is amenable to medical or surgical therapy. Most of the causes are slowly progressive, and patients seldom survive more than 6-12 months with therapy.

Heart sound in pet animals (dog and cat)

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