Cardiovascular pathology 3 Flashcards
What are the two types of myocardial rupture?
Traumatic e.g. bullet wound
Spontaneous e.g. insufficiency of mitral valve causing chronic left atrial dilation
Enlargement of the heart is termed?
Cardiomegaly
Describe the 3 forms of cardiomegaly?
- Hypertrophy: increase in the size and weight of the organ due to an increase in the size of each cells
- Dilation: expansion of the volume of the ventricle lumen
- Cardiomyopathy: disease of the myocardium
Ventricular hypertrophy acts as what kind of mechnism?
Compensatory - physiological response, maintains adequate cardiac output e.g. response to exercise
- A reversible increase in muscle mass
Describe primary and secondary ventricular hypertrophy
Primary = irreversible idiopathic hypertrophic cardiomyopathy, no known cause, disease of the myocardium itself Secondary = compensatory response to increased workload
Describe eccentric hypertrophy and how the heart changes
- Heart with normal / enlarged ventricular chambers: heart grows outwards and gets bigger
- Walls of normal / decreased thickness
- Myocardium is hypertrophic and has an increased mass
What is the cause of eccentric hypertrophy?
Volume overload e.g. valvular insufficiencies, septal defects
Describe concentric hypertrophy and how the heart changes
Heart with small ventricular chambers that have thick walls
What is the cause of concentric hypertrophy?
Produced by pressure overload e.g. valvular stenosis, systemic hypertension, pulmonary disease (hypertension)
What is Cor pulmonale?
A secondary alteration in the structure and function of the right ventricle caused by a primary disorder of the respiratory system
What are some species specific causes of right ventricular hypertrophy with Cor pulmonale
Due to increase flow resistance in pulmonary circulation
- Dirofilariosis (roundworms) and congenital pulmonic stenosis in dogs
- High altitude disease in cattle
- Chronic alveolar emphysema in horses
What are the two causes of left ventricular hypertrophy?
- Systemic hypertension
- Congenital subaortic stenosis
When does ventricular dilation occur?
Compensatory response to achieve increased cardiac output
Allows stretching of cardiac muscle cells to increase contractile force and increases stroke volume is the result
What are the 3 primary cardiomyopathies with unknown pathogenesis
- Dilated cardiomyopathy
- Hypertrophic cardiomyopathy
- Restrictive cardiomyopathy
What are the 2 clinical signs of a cardiomyopathy?
Dyspnoea
Anorexia
Which heart failure lesions occur as a result of cardiomyopathies?
Hydropericardium
Hydrothorax
Ascites
Subcutaneous oedema
Which animals are prone to hypertrophic cardiomyopathies, what are the consequences of them in this species?
- Common in young adult to middle aged cats
- Cats die from left atrial thrombosis and caudal aorta thromboembolism “saddle thrombosis”
- Uncommon in dogs, may occur in large breeds
How does a hypertrophic cardiomyopathy present grossly?
- Enlarged heart
- Prominent concentric hypertrophy of the left ventricle and interventricular septum
- Dilation of the left atrium: as the blood is returned to the heart through the pulmonary vein, it passes into the atrium but the volume of the ventricle is reduced
How does a hypertrophic cardiomyopathy present histologically?
- Prominent disarray of hypertrophic degenerate myocytes
- Interweaving array of fibres and interstitial fibrosis
- Fibrous CT between cardiac myocytes
- Cardiac myocytes have a chaotic structure
Which animals are most prone to dilated cardiomyopathies?
- Middle aged dogs: idiopathic or autosomal recessiveor X-linked mode of inheritance.
- Cats with low tissue concentrations of taurine
How does a dilated cardiomyopathy present grossly?
- Biventricular dilation
- White thickened endocardium (subendocardial fibrosis)
- Increased heart weight
How does a dilated cardiomyopathy present histologically?
- May see no histological lesion
- If there is: interstitial fibrosis, fatty infiltration, myocyte degeneration, attenuated wavy fibres
Describe the pathogenesis of bovine dilated cardiomyopathy
- Well–grown 2-3 year-old Holstein cattle (genetic component)
- Peripheral oedema and jugular distention
- Fluid accumulation in body cavities
- Enlargement of the heart with a rounded shape
Describe the gross appearance and function of restrictive cardiomyopathy
- Walls are rigid and the heart is restricted from stretching and filling properly with blood
- Rhythmicity and contractility may be normal
- Stiff chamber walls prevent them from adequately filling
- Short/irregular chordae tendinae
What is myocardial necrosis?
Death from acute cardiac failure, necrosis related arrhythmia when cardiac conduction is disrupted or cardiac decompensation, cardiac dilation and congestive heart failure
How does myocardial necrosis appear grossly?
Affected areas are pale, yellow to white and dry.
They can become gritty due to dystrophic calcification
Which areas of the heart are most effected by myocardial necrosis?
Papillary muscles and subendocardial myocardium
Give examples of causes of myocardial necrosis
- Nutritional deficiencies e.g. vitamin E
- Ischaemia: hypoxia
- Ionophore toxicity: Monensin intoxication
- Plants containing heart glycosides intoxication