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
How does myocardial necrosis appear histologically when it is recent necrosis?
- Fibres appear swollen and hypereosinophilic because they have lost their nuclear material
- Striations on the cardiac myocytes are indistinct, and nuclei are pyknotic
- Scattered basophilic granules represent calcified mitochondria
- Shredded appearance because of hypercontraction and the formation of multiple transversely oriented bars of disrupted contractile material (contraction band necrosis)
What does pyknotic mean?
Pyknotic is the irreversible condensation of chromatin in the nucleus of a cell undergoing necrosis or apoptosis
How does myocardial necrosis appear histologically when it is 24-48 hours old?
Necrotic areas are infiltrated by inflammatory cells (macrophages, neutrophils) to phagocytose and lyse the necrotic cellular debris
How does myocardial necrosis appear histologically when it is weeks old?
Persistent stromal tissue - fibroblasts, collagen and capillaries
Myocardial necrosis is seen in which disease of pigs?
Mulberry heart disease
What are the causes of myocardial necrosis in mulberry heart disease?
- Vitamin E deficiency
Nutritional, due to diet with high content of unsaturated fatty acids leading to peroxidation of the cell membranes.
What are the 3 main pathological components of mulberry heart disease?
- Necrosis
- Hydropericardium
- Haemorrhages
What is the cause of equine myocardial degeneration?
Monensin intoxication
What are the pathogenic signs of equine myocardial degeneration caused by Monensin intoxication?
- Arrhythmic heart beat and ventricular fibrillation
- Petechial pericoronal haemorrhages
- Necrosis of myocytes
Which species is the least susceptible to monensin?
Poultry
can use it to treat parasites in chickens
What is the effect of chemotherapeutic agents (e.g. Doxorubicin) on the heart?
Cause necrosis of cardiac myocytes
How does the appearance of necrosis due to chemotherapeutic agents (e.g. Doxorubicin) appear?
Dose-related chronic cardiotoxicity characterized pale myocardium, hyaline necrosis, hydropic degeneration of the myocytes
Inflammation of the myocardium is termed?
Myocarditis
What are the portals of entry for inflammation of the myocardium
- Haematogenous dissemination
- Embolic dissemination from vegetative endocarditis into the coronary arterial tree
What are the 6 different types of myocarditis?
- Purulent – neutrophil dominated
- Necrotising
- Haemorrhagic
- Lymphocytic
- Eosinophilic
- Granulomatous
What is a vegetation?
Abnormal growths that contain collections of bacteria may form in your heart at the site of the infection and damage the heart valves, which can cause them to leak
Myocarditis is seen which with canine viral infection?
Canine parvovirus
- Usually affects pups <10 weeks of age
- Cells that are rapidly dividing are the target cells for parvovirus
- Viral agents may produce acute necrosis with little or moderate lymphocytic inflammatory response
Give some other examples of viruses causing myocarditis
- West Nile virus
- Foot and mouth disease virus
- Canine distemper
- Bluetongue in sheep
What is the cause of purulent myocarditis?
Bacteria
- Direct extension of pericarditis and/or endocarditis
Give examples of bacterial causes of purulent myocarditis
- Burrelia burgdorferi: lyme disease
- Histophilus somni
- Black leg
- Listeria monocytogenes
- Streptococcus equi
- Staphylococcus aureus
Equine disseminated granulomatous myocarditis is caused by which bacteria?
Mycosis
Aspergillosis
Give 3 examples of protozoan parasites that infect the heart
- Sarcocystis spp
- Toxoplasma spp
- Neospora spp
Give 2 examples of cestodes that infect the heart
cysticercus spp
hydatid cyst
Give 2 examples of nematodes which infect the heart
- Dirofilaria immitis
- Angiostrongylus vasorum
Describe the cycle of Sarcocystis spp
Normally develop in 2-host cycles consisting of an intermediate host (prey) and the final host (predator)
e. g. Cattle-dog, Cattle-cat, cattle-human, sheep-dog, sheep-cat, etc
- Incidental finding
Canine myocarditis is caused by which infectious agents?
Toxoplasmosis - Toxoplasma gondii
Neosporosis - Neospora caninum
Describe the pathology of Toxoplasma gondii
- Affects immunosuppressed and young animals
- Tachyzoites spread systemically and caused interstitial pneumonia, myocarditis, hepatic necrosis, meningoencephalomyelitis. chorioretinitis, lymphadenopathy and myositis
- T gondii is also an important cause of abortion and stillbirth in sheep and goats and pigs
- Heart => necrosis and chronic pyogranulomatous myocarditis
Describe the pathogenesis of Neospora caninum
Puppies: CNS /neuronal symptom dermatitis, hepatitis, pneumonia, and myocarditis can occur Adult dogs: sporadically develop neosporosis
The name of the dog heart worm is?
Dirofilaria immitis
Which other canine worm damages the heart?
Lungworm
Angiostrongylus vasorum
Describe the pathology of Angiostrongylus vasorum
- Adults live in pulmonary artery and RV; larvae are found in lung parenchyma
- Enlarged RV, cardiac silhouette rounded
- Right sided heart failure
- Eosinophilic vasculitis
- Multifocal granulomatous and eosinophilic pneumonia
- Bleeding disorder
Give an example of a benign endothelial cell neoplasia
Haemangioma - tumour arising from endothelial cells in vessels
Describe the gross and histological appearance of a haemangioma
Gross - Red-black blood containing masses that protrude into the lumen or epicardial surface
Histo - well differentiated vascular spaces lined by endothelial cells
Give an example of a malignant endothelial cell neoplasia
Haemangiosarcoma
Describe the gross and histological appearance of a haemangiosarcoma
Gross – similar to haemangioma (Red-black blood containing masses that protrude into the lumen or epicardial surface)
Histologically - scattered, elongated plumb neoplastic endothelial cells.
- Often highly metastatic
A tumour of striated muscle (myocardium) is termed?
Rhabdomyoma
Rhabdomyosarcoma
A tumour of the epi- / pericardium is termed?
Mesothelioma
Give 3 examples of heart base tumours
- Aortic body tumours
- Ectopic thyroid adenoma / carcinoma
- Metastases: sarcoma / carcinoma
What are the consequences of aortic body tumours?
- Surround and compress great vessels
- Arise at the base of the heart and can cause vascular obstruction and cardiac failure
Describe the appearance of aortic body tumours
Large white, firm masses that surround and compress the great vessels and atria
Describe the histological appearance of aortic body tumours
Microscopically the neoplastic cells are polyhedral with vacuolated cytoplasm and abundant fibrous connective tissue.
What is a chemodectoma?
Chemodectoma is a rare tumour of the neuroendocrine tissue of the carotid body
