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Define heart failure
Heart failure is when the heart is unable to generate sufficient output to meet the demands of the body
List the 5 mechanisms of heart failure
- Inability of the heart to expand
- Damage to the myocardium
- Increased resistance to outflow
- Valvular defects
- Irregular rhythms
Where would you see oedema in a) left b) right sided heart failure?
- a) pulmonary oedema
- b) venous congestion and peripheral oedema
List some of the clinical signs of right sided heart failure
Jugular distention, hepatic and splenic enlargement, ascites and peripheral oedema
What appearance does chronic venous congestion cause a liver to have PM?
A 'nutmeg' liver
List some clinical signs of left sided heart failure
Cough and dyspnoea
What are the three intrinsic cardiac responses to heart failure?
Cardiac dilation, cardiac hypertrophy and increased cardiac rate
How does the RAAS system try to compensate for heart failure? Why does this not work long term?
- A decrease in renal perfusion triggers renin production. Angiotensinogen is produced in the liver which produces angiontensin I, then II in the lungs. This increases water and salt retention which increases the circulating volume, therefore increasing preload, CO and BO.
- In the long term there are degenerative changes to the kidney causing proteinuria and cardiac remodelling and myofibre dysfunction.
What is Cor Pulmonale?
Right sided heart failure secondary to pulmonary disease e.g. COPD.
List the layers of the heart wall from outside to inside
Pericardium, (pericardial space), myocardium, endocardium
Fluid (transudate or modified tranudate) gathering between the visceral and parietal layers of the pericardium
Blood in the pericardium
What is a common cause of haemopericardium in a) dogs b) horses?
- a) ruptured atria
- b) ruptured aorta
Inflammation of the pericardium
What is a common cause of pericarditis in cattle?
Hardware disease - bovine traumatic reticulopericarditis
Define cardiac tamponade
Acute cardiac compression due to accumulation of fluid
What is a conduction disorder?
Abnormalities in the conduction pathway of the heart
What do conduction disorders often result in?
What is an arrhythmia?
A variation from the normal rhythm of the heart
Which species commonly have primary conduction disorders that disappear with increased activity?
Give an example of an inherited arrhythmia in dogs
- Arrhythmogenic right ventricular cardiomyopathy - boxers
- Dilated cardiomyopathy - doberman
- Inherited ventricular arrhythmia - GSD
What is 'sick-sinus syndrome'?
A group of disorders involving the sino-atrial node that cause periods of ventricular standstill and paroxysms of supra ventricular tachycardia, which leads to syncope (loss of consciousness due to cerebral hypoperfusion)
What breed of dog is prone to getting 'sick-sinus syndrome'?
Define the following types of heart block a) first degree b) second degree c) third degree
- a) delay of impulse through AV node
- b) intermittent failure to conduct through AV node with dropped beats
- c) complete block
Describe normal cardiac muscle
Striated, intercalated discs, central nuclei
Give examples of when the heart may undergo atrophy/hypertrophy
- atrophy - bed rest, wasting diseases
- hypertrophy - exercise, hypertension, valvular stenosis
What is the difference between concentric hypertrophy and eccentric hypertrophy?
Concentric hypertrophy is when there is an increase in myoctye width due to addition of sarcomeres in parallel, whereas eccentric hypertrophy is when there is addition of sarcomeres in series.
Which is caused by a volume/pressure overload: concentric/eccentric hypertrophy?
- Volume overload - eccentric
- Pressure overload - concentric
Describe the differences in the following between physiological and pathological hypertrophy: heart function, gene expression, fibrosis/apoptosis and heart size
- Heart function - physiological = increase in HR, pathological = initially the heart can counterbalance any stress but long term the heart develops depressed cardiac function and goes into heart failure
- Gene expression - physiological - normal gene expression, pathological = fetal gene reactivation
- Fibrosis/apoptosis - physiological = none, pathological = intracellular fibrosis formation and increased number of apoptotic cardiomyocytes
- Heart size - both hypertrophies result in bigger heart size
List the 4 types of myocardial diseases
Degneration, necrosis, myocarditis, and cardiomyopathies
List four types of myocardial degeneration that are sublethal
Lipofuscinosis, fatty degeneration, myocytolysis and vacuolar degeneration
Describe what a lipofuscinosis heart would look like
A chocolate brown colour instead of pink/red
Describe the stages in myocardial necrosis
A normal cardiac myocyte undergoes injury which results in hyaline necrosis. There is then macrophagic invasion, as necrosis triggers inflammation, and eventually healing with fibrosis.
Give a cause of myocardial necrosis
White muscle disease in calves (selenium/vit E deficiency)
Give a cause of myocarditis in dogs
Histologically, what can provide a definitive diagnosis of canine parvovirus?
Brick-like inclusions in the nuclei of heart muscle cells
What parasite can cause parasitic myocarditis in sheep?
What biochemical markers can be detectable from 1-3hr to 10-14 days after damage to the myocardium?
Creatinine kinase, troponins
Which is more specific to heart damage: creatinine kinase or troponins?
What are the four types of primary cardiomyopathies?
Hypertrophic, dilated, restrictive and arrhythmogenic right ventricular
What can cause secondary cardiomyopathies in cats?
Hyperthyroidism and taurine deficiency
What can cause secondary cardiomyopathies in various species?
Drugs, toxins, nutritional disorders
In what breeds of cat is primary hypertrophic cardiomyopathy familial?
Maine Coon and American Shorthair
What type of primary cardiomyopathy is the least common?
What happens in restrictive cardiomyopathy?
There is increased ventricular stiffness (usually abnormal fibrosis) which causes loss of left ventricular diastolic function
What type of primary cardiomyopathy is most common in dogs?
Define valvular endocarditis
Inflammation of the heart valves
Define valvular endocardiosis
Degeneration of the heart valves
What breed of dog is prone to valvular endocardiosis?
Cavalier king charles spaniels
What does valvular endocardiosis look like on gross inspection?
Smooth, pearl-white thickenings on valve leaflets, +/- thickening of chordae tendinae
What valve is there most frequently endocardiosis on?
Which valve is most commonly affected by endocarditis in the following species: a) cattle b) pigs, sheep and dogs c) horses?
- a) tricuspid valve
- b) mitral valve
- c) aortic valve
What does endocarditis appear like on gross inspection?
Friable, yellow and grey masses or vegetations on heart valves
Present at birth, as a congenital abnormality or defect
Transmitted from parent to offspring - inherited
Present in some families and not others or occurs in more family members than would be expected by chance
Originating after birth, NOT caused by hereditary or developmental factors but by a reaction to environmental influences outside of the organism
What is the foramen ovale?
The foetal opening between the right and left atria
What is the ductus arteriosus?
The foetal shunt between the pulmonary artery and aorta
What is the ductus venosus?
The shunt that connects the portal and umbilical veins to the vena cava
What are the 3 main categories of congenital defects?
- Failure of closure of foetal structures
- Septal defects
- Great vessel defects
What condition results from a persistent ductus venous?
Hepatic encephalopathy - build up of ammonia in the blood due to incomplete detoxification in the liver which effects the brain
Where does blood flow from and to in an atrial septal defect?
From the LA to the RA
Which chamber distends in an atrial septal defect?
The right atrium
What chamber hypertrophies in a ventricular septal defect?
What can happen to blood flow in a chronic ventricular septal defect?
Pressure becomes higher on the right side so blood flows from the RV to LV
What does valvular insufficiency result in?
Regurgitation of blood
What is valvular stenosis?
Narrowing of the valves
Which valves typically suffer from a) insufficiency b) stenosis?
- a) mitral and tricuspid
- b) aortic and pulmonary
What is the term for a right to left shunt?
Tetralogy of Fallot
Does a right to left shunt result in too much or too little blood flowing to the lungs?
Why is there cyanosis as a result of tetralogy of fallot?
As deoxygenated blood enters systemic circulation
What congenital defects are the following species most susceptible to: a) dog b) cat c) cattle d) pigs e) horses
- a) patent ductus arteriosus, pulmonic stenosis, subaortic stenosis
- b) mitral dysplasia
- c) atrial septal defect, ventricular septal defect
- d) uncommon
Describe what happens in an animal with a patent right aortic arch
Food gets stuck in the oesophagus cranial to the ligamentum arteriosum. This causes megaoesophagus and regurgitation of food.
With regards to blood vessels, define a) hyperaemia b) congestion
- a) increased inflow
- b) decreased outflow
Redness in skin
What are the following composed of: a) transudate b) modified transudate c) exudate?
- a) water
- b) water, protein, a few cells
- c) water, protein, more cells
What direction does oncotic pressure move water in?
It moves water into blood vessels
What protein is responsible for most of the oncotic pressure?
What direction does hydrostatic pressure move water in?
It moves water out of blood vessels
Fluid/oedema in the abdominal cavity
What are the four mechanisms of oedema formation?
Vascular permeability is increased, intravascular hydrostatic pressure is increased, intravascular oncotic pressure is decreased, lymphatic drainage is decreased
Where do the following species tend to get oedema formation: a) dog b) cat c) horse d) cattle?
- a) ascites
- b) pleural effusion
- c) forelimbs (and scrotum)
- d) brisket
What can cause a decrease in oncotic pressure?
Hypoalbuminaemia due to liver failure, intestinal malabsorption, renal failure, parasitic infection
What are the three components of Virchow's triad?
Endothelial injury, abnormal blood flow and hypercoagulability
List 5 things that can disrupt normal circulation
Torsion, rupture, vascular thickening, vasculitis and thrombosis
Which blood vessel can rupture in horses?
Define the following: a) petechiae b) purpura c) ecchymoses d) haematoma e) haemothorax f) haemoperitoneum
- a) pinpoint haemorrhages
- b) medium sized haemorrhages
- c) large haemorrhages
- d) localised, extravascular collection of blood
- e) free blood in the abdomen
What is an aneurysm?
A dilation/thickening of a blood vessel wall
What is a dissecting aneurysm?
A split/tear in the wall which causes weakness. If blood moves into here it can form a clot.
What blood vessel can be damaged by a guttural pouch infection?
The internal carotid
What can rupture of the internal carotid result in?
Epistaxis or sudden death
What is the term for vascular thickening i.e. narrowing of the lumen with loss of elasticity?
What is the difference between dystrophic calcification and metastatic calcification?
- Dystrophic - mineral deposits secondary to tissue damage
- Metastatic - due to hypercalcaemia
What condition in dogs can lead to atherosclerosis?
How does hypothyroidism cause atherosclerosis?
Hypothyroidism causes depressed metabolic rate, decreased fat metabolism, accumulation of lipid in plasma which sticks to the side of vessels. Fibro-fatty plaques stick to the lipids and then you get calcium deposition on top of this.
What is vasculitis?
Inflammatory cells within the blood vessel wall
Give an example cause of vasculitis in cats
Feline infectious peritonitis
Give an example cause of vasculitis in ruminants
Give an example of parasitic cause of vasculitis
A solid mass forming in blood vessels from blood constituents is called a ...?
What is a 'saddle thrombi'? What species is this most common in?
- A saddle thrombi is a thrombus that moves from the heart to sit across the bifurcation of the aorta
How do cats with a saddle thrombus present?
Cold back legs, posterior paraparesis, no femoral pulse
What are the three causes of venous thrombosis
- Iatrogenic eg catheterisation
- Portal vein thrombosis
- Venal caval syndrome
Define vena caval syndrome
Occlusion of the vena cava by infiltration, thrombosis or compression
What is vena caval syndrome secondary to in a) dogs b) cattle
- a) heart worm infection, neoplasia
- b) hepatic abscesses
What is it called when lymphatic fluid escapes into the a) thorax b) abdomen?
- a) chylothorax
- b) chylous ascites
Give an example of an infectious cause of lymphangitis
Johne's disease, Actinobacillosis
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