PATHOLOGY - Cardiac Pathology Flashcards
What is heart failure?
Heart failure is when the heart is unable to pump enough blood around the body to meet the body’s demand
What are the six underlying mechanisms of heart failure?
Pump failure
Obstruction
Regurgitated blood flow
Shunted blood flow due to congenital disease
Heart/major blood vessel rupture
Cardiac conduction disorders (arrhythmias)
What are the three clinical signs of acute heart failure?
Intermittent weakness
Syncope
Sudden death
What is syncope?
Syncope is the loss of consciousness for short periods of time caused by cerebral hypoperfusion
What causes sudden death in acute heart failure?
Cardiogenic shock (cells don’t receive enough oxygenated blood leading to cell death) and acute pulmonary oedema
What is congestive heart failure?
Congestive heart failure is chronic heart failure which leads to congestion and consequential oedema around the body
What are the two classifications of heart failure based on pumping ability?
Systolic heart failure
Diastolic heart failure
What is systolic heart failure?
Systolic heart failure is a failure in ventricular contraction during systole
What is diastolic heart failure?
Diastolic heart failure is a failure in ventricular relaxation/ventricular filling during diastole
What are the three anatomical classifications of heart failure?
Left-sided heart failure
Right-sided heart failure
Biventricular heart failure
What are the consequences of left sided heart failure?
Left sided heart failure is when the left ventricle is unable to pump enough blood into the aorta, causing tissue hypoperfusion. In addition, left-sided heart failure can cause a backup of blood into the pulmonary veins and pulmonary circulation, causing pulmonary congestion, increasing hydorstatsic pressure, resulting in pulmonary oedema
What are the four main clinical signs of left-sided heart failure?
Tissue hypoperfusion
Pulmonary congestion/oedema
Dyspnoea
Coughing
What is a key histological sign of chronic left-sided heart failure?
Haemosiderin-laden macrophages (heart failure cells)
What are Haemosiderin-laden macrophages (heart failure cells)?
The pulmonary congestion caused by left-sided heart failure can cause erythrocytes and proteins to leave the blood vessels into the alveoli where they will be engulfed by alveolar macrophages, leading to the formation of haemosiderin-laden macrophages (heart failure cells)
How does left-sided heart failure initially cause left ventricular hypertrophy?
When there is decreased cardiac output, this triggers vasoconstriction and hypertension to maintain core tissue perfusion (heart and brain). However, this hypertension causes increased arterial pressure and thus increased afterload and increased cardiac workload, which can lead to hypertrophy of the left ventricle. Initially, this hypertrophy serves as a compensatory mechanism to maintain cardiac output
What are the long-term effects of left ventricular hypertrophy?
Over time, left ventricular hypertrophy will reduce the ability of the ventricle to relax leading to impaired ventricular filling and thus a decrease in stroke volume and cardiac output
How does the renin-angiotensin aldosterone system respond in response to left-sided heart failure?
When there is decreased perfusion of this kidneys, this will activates the renin-angiotensin aldosterone system. This will lead to sodium and water reabsorption and increased fluid retention, thus increasing the blood volume that is entering the left ventricle, increasing contractility, stroke volume and cardiac output
What is the harmful effect of renin-angiotensin aldosterone system activation in response to left-sided heart failure?
The renin-angiotensin aldosterone system increases blood volume which will increase the back up of blood into the pulmonary veins and pulmonary circulation, worsening the pulmonary congestion and oedema. Increasing the blood volume will also increase the central venous pressure and the preload
How does the sympathetic nervous system respond to left-sided heart failure?
The sympathetic nervous system causes an increase in the heart rate to increase cardiac output, causes vasoconstriction to redirect blood to core tissues (heart and brain) and activates the renin-angiotensin aldosterone system
What are the consequences of right sided heart failure?
Right sided heart failure is when the right ventricle is unable to pump enough blood into the pulmonary trunk, causing pulmonary hypoperfusion. In addition, right-sided heart failure can cause a backup of blood into the cranial and caudal vena cavae and systemic circulation, causing systemic congestion resulting in systemic oedema
What are the five main clinical signs of right-sided heart failure?
Pulmonary hypoperfusion
Jugular venous distension
Ascites
Hepatomegaly
Splenomegaly
What is ‘nutmeg’ liver?
‘Nutmeg’ liver is the mottled appearance of the liver as a result of chronic hepatic venous congestion
What is the term used to describe right-sided heart failure caused by respiratory disease or dysfunction?
Cor pulmonale
How can high altitude disease (brisket disease) cause cor pulmonale?
Increased altitude causes hypoxaemia leading to pulmonary vasoconstriction and pulmonary hypertension, increasing the arterial pressure and afterload, so the right side of the the heart has to contract more to overcome this resistance to eject blood into the pulmonary trunk and into the lungs
What is cardiac tamponade?
Cardiac tamponade is compression of the heart due to pericardial effusion
What is haemopericardium?
Haemopericardium is the accumulation of blood in the pericardium
List three possible causes of haemopericardium
Atrial rupture
Aortic rupture
Neoplasia (haemangiosarcoma)
What is hydropericardium?
Hydropericardium is transudate oedema in the pericardium
List five possible causes of hydropericardium
Congestive heart failure
Pulmonary hypertension
Renal failure
Hypoproteinaemia
Systemic diseases
What is pericarditis?
Inflammation of the pericardium
What is Traumatic reticulopericarditis (hardware disease)?
Traumatic reticulopericarditis (hardware disease) is damage to the reticular wall caused by the ingestion of wire, nails etc, allowing bacteria to enter the peritoneum and cause peritonitis which can progress to pericarditis
How can pericarditis be diagnosed?
Sample pericardial fluid for bacterial culture and viral PCR
What is a pericardial hernia?
A pericardial hernia is protrusion of the abdominal viscera through the diaphragm into the pericardium
What are the two main physiological changes seen in the myocardium?
Hypertrophy
Atrophy
What is a common physiological cause of myocardial hypertrophy?
Increased workload
What is a common physiological cause of myocardial atrophy?
Decreased workload
What is concentric myocardial hypertrophy?
Concentric myocardial hypertrophy is an increase in the cardiomyocyte width
What causes concentric myocardial hypertrophy?
Pressure overload of the myocardium
What is eccentric myocardial hypertrophy?
Eccentric myocardial hypertrophy is an increase in the cardiomyocyte length
What causes eccentric myocardial hypertrophy?
Volume overload of the myocardium
What is the key feature that is only seen in pathological myocardial hypertrophy?
Fibrosis
List four examples of myocardial disease
Myocardial degeneration
Myocardial necrosis
Myocarditis
Cardiomyopathy
What are the four possible causes of myocardial degeneration?
Myocardial lipofuscinosis
Fatty degeneration
Vacuolar degeneration
Myocytolysis
What is myocardial lipofuscinosis?
Myocardial lipofuscinosis is the accumulation of lipofuscin in the cardiomyocyte cytoplasm
What is fatty degeneration of the myocardium?
Fatty degeneration of the myocardium is lipid accumulation in the cardiomyocyte cytoplasm
What is vacuolar degeneration of the myocardium?
Vacuolar degeneration of the myocardium is water accumulation in the cardiomyocyte cytoplasm
What is myocytolysis?
Myocytolysis is lysis of the cardiomyocytes
What is the histological appearance of myocardial necrosis?
Hypereosinophilic muscle fibres
Pyknotic nuclei
How does myocardial necrosis decrease the contractility of the myocardium?
Necrosis causes inflammation and fibrosis which is non-functional and thus decreases contractility
List three biomarkers which can be used to identify myocardial necrosis
Creatine kinase
Cardiac troponin 1
Natriuretic enzymes
Why is creatine kinase an unreliable biomarker for myocardial necrosis?
Creatine kinase can also be elevated due to skeletal muscle injury and is thus not specific to the heart
What is myocarditis?
Myocarditis is inflammation of the myocardium
Give two examples of viruses which can cause myocarditis in dogs
Canine parvovirus 2
Canine distemper virus
Which key histological feature is indicative of viral myocarditis?
Intranuclear inclusion bodies
What is the most common cause of bacterial myocarditis in cats and dogs?
Bartonella bacterial infection
Which disease can progress to myocarditis?
Traumatic reticulopericarditis
What is cardiomyopathy?
Cardiomyopathy is a general term used to describe diseased or dysfunction of the myocardium
What is primary cardiomyopathy?
Primary cardiomyopathy is cardiomyopathy without an underlying pathological cause
What are the three classifications of primary cardiomyopathy?
Hypertrophic primary cardiomyopathy
Dilated primary cardiomyopathy
Restrictive primary cardiomyopathy
What is the key characteristic of hypertrophic primary cardiomyopathy?
The presence of myocardial hypertrophy
What is the key characteristic of dilated primary cardiomyopathy?
The presence of ventricular dilation
What is the key characteristic of restrictive primary cardiomyopathy?
Stiffness of the ventricles
Which two breeds of cat are predisposed to feline hypertrophic primary cardiomyopathy?
Maine Coon
Rag Doll
Why are Maine Coon and Rag Doll cats predisposed to Feline hypertrophic primary cardiomyopathy?
Maine Coon and Rag Doll cats have a mutation in the gene encoding for the cardiac myosin-binding protein C (MYBPC)
Which species is most likely to suffer from dilated primary cardiomyopathy?
Dogs
What are the two forms of canine dilated primary cardiomyopathy?
Fatty infiltrative degenerative dilated cardiomyopathy
Attenuated wavy fibre dilated cardiomyopathy
Which two breeds of dog commonly suffer from fatty infiltrative degenerative dilated cardiomyopathy?
Boxers
Dobermans
What is secondary cardiomyopathy?
Secondary cardiomyopathy is cardiomyopathy with an underlying pathological cause
What are the two most common underlying causes of secondary cardiomyopathy in cats?
Hyperthyroidism
Taurine deficiency
What are the seven forms of heart valve disease?
Valve haemocysts
Valve lymphocysts
Valve calcification
Valve mineralisation
Endocardiosis (Myxomatous valvular degeneration)
Endocarditis
Chordae tendinae rupture
What are heart valve haemocysts?
Heart valve haemocysts are blood filled cysts on the valve cusps
What are heart valve lymphocysts?
Heart valve lymphocysts are lymph filled cysts on the valve cusps
What is endocardiosis (myxomatous valvular degeneration)?
Degenerative valve disease characterised by myxomatous degeneration where elastin and collagen are disrupted leading to proteoglycan deposition resulting in valve cusp and chordae tendinae thickening
Which valve is most likely to have endocardiosis?
Mitral valve
Which breed of dog is predisposed to mitral myxomatous valvular degeneration (endocardiosis)?
Cavalier King Charles Spaniels
What is endocarditis?
Inflammation of the endocardium and the heart valves