CV pathology 3

What is the meaning of cardiomegaly and what are the different types?

• Enlargement of the heart

• Hypertrophy

• Dilation

• Cardiomyopathy

What is ventricular hypertrophy?

“Compensatory mechanisms” – physiological response, maintains adequate cardiac output e.g. response to exercise

Represents a reversible increase in muscle mass (increase in size of muscle cells, NOT hyperplasia).

What is the difference between primary and secondary ventricular hypertrophy?

• Secondary - compensatory response to increased workload

  • Physiological response (athletic animal) - maintain adequate cardiac output

  • Pathological - volume overload

• Primary - irreversible idiopathic hypertrophic cardiomyopathy

What are the features of eccentric ventricular hypertrophy?

• Heart with normal / enlarged ventricular chambers

• Walls of normal / decreased thickness

• Produced by volume overload (valve insufficiencies, septal defects)

What are the features of concentric ventricular hypertrophy?

• Heart with small ventricular chambers that have thick walls which compress the chamber lumens

• Produced by pressure overload (e.g. valvular stenosis, systemic hypertension, pulmonary disease (hypertension))

What could cause a pressure overload?

• valvular stenosis

• systemic hypertension

• pulmonary disease (hypertension)

What is the meaning of cor pulmonale?

An alteration in the structure and function of the right ventricle (RV) of the heart caused by a primary disorder of the respiratory system

Which is concentric/eccentric ventricular hypertrophy?

• Concentric - left (thicker walls)

• Eccentric - right (dilated chamber lumen and normal walls)

What causes right ventricular hypertrophy?

Cor pulmonale due to increase flow resistance in pulmonary circulation.

• Dirofilariosis (heart worm) and congenital pulmonic stenosis in dogs

• High altitude disease (pulmonary hypertension) in cattle

• Chronic alveolar enphysema in horses (heaves)

  

What can cause left sided hypertrophy?

• Systemic hypertension (chronic renal failure)

• Congenital subaortic stenosis

  

When does ventricular dilation occur?

• Myocardium cannot undergo hypertrophy because of insufficient time, inadequate nutrition or diseases

• Same reasons as hypertrophy - compensatory response to inc CO

• Dilation allows stretching of cardiac muscle cells to increase contractile force and increases stroke volume is the result

• (terminal lesion in many cardiac diseases)

What are examples of primary cardiomyopathies

• Dilated cardiomyopathy

• Hypertrophic cardiomyopathy

  • Different to hypertrophies because they are secondary to other disease (these happen spontaneously)

• Restrictive cardiomyopathy

What cardiomyopathies can you have with a known pathogenesis?

• Toxic

• Nutritional

• Genetic causes

What species is hypertrophic cardiomyopathy common in and what occurs secondary to this?

• Young adult to middle aged cats

• Cats die from left atrial thrombosis due to pooling of blood and caudal aorta thromboembolism (from the atrial thrombi -one of top differentials for cat with sudden death)

• (Uncommon in dogs, may occur in large breeds)

  

How does Hypertrophic cardiomyopathy present grossly?

• Hearts are enlarged (increased cardiac silhouette)

• Prominent concentric hypertrophy of the left ventricle, interventricular septum

• Dilation of the left atrium

  

How does Hypertrophic cardiomyopathy present histologically?

• Disarrays of hypertrophic degenerated myocytes (unusual angles)

• Interweaving arrangement of fibres and interstitial fibrosis

  (normal below for reference)

  

What species is dilated cardiomyopathy common in and what causes it?

• Middle aged dogs – idiopathic or autosomal recessive or X-linked mode of inheritance.

• Cats with low tissue concentrations of taurine. Taurine supplementation in commercial diets has resulted in dramatic reduction of cases

How does dilated cardiomyopathy present grossly?

• Biventricular dilation

• White thickened endocardium

• Walls are normal, may be thinner

• Increased heart weight (more than 1% of BW)

  

How does dilated cardiomyopathy present histologically?

• Interstitial fibrosis

• Fatty infiltration and myocyte degeneration

• Attenuated wavy fibres

• Variable

  

Describe the features of bovine dilalated cardiomyopathy?

• well–grown 2-3 year-old Holstein cattle.

• peripheral oedema, jugular distension,

• fluid accumulations in the body cavities.

• enlargement of the heart with a rounded “globose” shape

What is restrictive cardiomyopathy and when would this occur?

• Walls are rigid and the heart is restricted from stretching and filling with blood properly

• Rhythmicity and contractility of the heart may be normal

• Stiff walls of the heart chambers keep them from adequately filling.

• Cats with endocardial lesions (inflammation, fibrosis, fibroelastosis) that impair the ventricular flow

What will be seen with restrictive cardiomyopathy?

How does myocardial necrosis lead to death?

When cardiac conduction is disrupted

or

Cardiac decompensation, cardiac dilation and congestive heart failure

What causes myocardial necrosis?

• Nutritional deficiencies: Vitamin E / Selenium deficiency [calves, lambs, foal] mulberry heart disease [pigs]

• Plant intoxication

• Ionophore toxicity

• Doxirubicin - chemo drug

• Secondary to myocarditis

Describe how myocardial necoriss presents grossly

• Affected areas are pale, yellow to white and dry

• They can become gritty due to dystrophic calcification

• Common in the papillary muscles

Describe how myocardial necoriss presents histologically

• Fibres appear swollen and hypereosinophilic (hyalin necrosis)

• Striations are indistinct, and nuclei are pyknotic

• Infiltration of inflammatory cells (macrophages and neutrophils)

What are the features of mulberry heart disease in pigs?

• Peroxidation of the cell membranes due to Vit E/ selinium deficiency

• Necrosis

• Hydropericardium

• Haemorrhages

What can Equinemyocardial degeneration cause?

• arrhythmic heart beat

• ventricular fibrillation

• petechial pericoronal haemorrhages

• necrosis / hyalinosis of myocytes

How does the use of doxorubicin make the heart appear grossly?

• Pale myocardium

• Hyaline necrosis

• Hydropic degeneration of the myocytes

  (chemo drug)

What is the portal of entry for myocarditis?

• Haematogenous dissemination

• Embolic dissemination from vegetative endocarditis into the coronary arterial tree

What are the types of myocarditis?

• purulent (from vegetative endocarditis)

• necrotising (toxoplasmosis in dogs and cats)

• haemorrhagic (black leg)

• lymphocytic ( parvoviral myocarditis)

• eosinophilic (sarcocystosis)

• granulomatous (fungi)

When can canine parvovirus cause myocarditis?

• Puppies less than 10 weeks of age - cardiomyocytes are not post mitotic

• Acute necrosis with little or moderate lymphocytic inflammatory response

Describe this histological image of purulent myocarditis?

• Increase in neutrophils

• Degeneration of surrounding cells

What can cause purulent myocaditis?

• Direct extension of pericarditis (eg. "hardware disease" wire in cattle)

• Direct extension of endocarditis (eg. erysipelas in pigs)

What myocarditis is being shown here?

• Equine disseminated granulomatous myocarditis - Mycosis / aspergillosis

• Macrophages and fungal hyphae present

What protozoan parasites are found in the heart?

• Sarcocystis sp.

• Toxoplasma sp.

• Neospora sp.

What metazoan parasites are found in the heart?

• Cestodes

  • Cysticercus sp.

  • Hydatid cyst.

• Nematodes

  • Dirofilaria immitis (dogs and cats)

  • Angiostrongylus vasorum (dogs)

What does toxoplasma gondii cause in the heart?

Necrosis and chronic pyogranulomatous myocarditis

What does neospora cause?

• CNS /neuronal symptom

• dermatitis

• hepatitis

• pneumonia

• myocarditis can occur - adult dogs sporadically develop neosporosis

What causes lungworm in dogs and where are the worms found?

• Angiostrongylus vasorum

• Adults live in pulmonary artery and RV

• Larvae in the lung parenchyma

What does Angiostrongylus vasorum cause?

• Enlarged RV, cardiac silhouette rounded

• Right sided heart failure

• Eosinophilic vasculitis

• Multifocal granulomatous and eosinophilic pneumonia

• Bleeding disorder

What is the most prevalent tumour of the heart and pericardium?

• Endothelial cell neoplasia

• Haemangio-

Where do haemangiomas originate?

Tumour arising from endothelial cells in vessels (e.g. of the skin)

How does a haemangioma present grossly and histologically?

Gross - Red-black blood containing masses that protrude into the lumen or epicardial surface.

Histologically – well differentiated vascular spaces lined by endothelial cells

Where will you often find a haemangiosarcoma?

Right atrium in dogs, spleen in dogs

How does a haemangiosarcoma present grossly and histologically?

Gross – similar to haemangioma

Histologically - scattered, elongated plump neoplastic endothelial cells

What are examples of heart base tumours?

• Aortic body tumours - chemodectoma (could occlude great vessels - pressure overload)

  

• Ectopic thyroid

• Metastatic (bovine lymphoma)