Transcript Description

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
1. Infection: parvoviral myocarditis
2. Idiopathic degeneration (unknown etiology-most cases)
3. Toxicosis:
1.
2.
3.
4.
Doxorubicin is antineoplastic agent with cardiotoxicity in dogs.
IV ethyl alcohol injection
Cobalt toxicity.
Anesthetic drugs.
4. Neoplasia
5. Multisystemic or metabolic disorders: hypothyroidism,
pheochromocytoma, and diabetes mellitus.
6. 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:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
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
P
T
S
Normal
P
R
Q
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
1. Microfilaria called Dirofilaria immitis that is transmitted by
mosquitoes.
2. heartworms normally reside in the pulmonary arteries and
right ventricles without significantly interfering with blood
supply.
3. The infection starts when the mosquitoes ingest the
microfilariae (first stage larvae L1) that molt twice in the
mosquito to infective L3.
4. 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
1.
2.
3.
4.
5.
Cough
Dyspnea
Hemoptysis
Fatigue, weight loss
Signs of right heart failure: ascites,
tachypnoea, jugular vein pulsation and
distension
6. Pulmonary edema.
7. 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
1. Mitral valve regurgitation. The mitral
valve is the valve that separates the
left atrium from the left ventricle.
1. 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.
2. 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
The heart rate begins to increase
help raise the blood pressure
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
1. History and clinical signs.
2. 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) •
Questions