Cardiovascular 1, 2 and 3 Flashcards
Describe CV embyrology?
- Heart develops from splanchnic mesenchyme in cardiogenic area
- Single heart tube- surrounding mesenchyme thickens to from myoepicardial mantle- dilations and constrictions forms 4 chambers
- Cardiac looping- heart converted from tube to C-shaped structure
- Cardiac septation- atrial septum primordia and ventricular septum primordia divide left and right
- Atria partitioned by septum primum and secundum (incomplete until afer birth)
What is the foramen ovale?
Incomplete septum secundum allows blood to pass from left to right
After birth forms the fossa ovalis
What do the left and right 4th aortic arches form?
Left- proximal part of arch or aorta
Right- proximal part of subclavian artery
Describe foetal circulation from the placenta to the placenta?
- Placenta to umbilical veins- liver/ductus venosus
- Liver to vena cava to the right atrium
- Right atrium through foramen ovale to left atrium
- Left atrium to aorta- systemic arteries
- Systemic arteries to umbilical arteries to placenta
What is the pericardium, epicardium, endocardium and myocardium?
Pericardium (sack)- one layer of the mesothelium with central layer of connective and adipose tissue
Epicardium- one layer of mesothelium on connective tissue and adipose tissue fused to the myocardium
Endocardium- endothelium identical to arterial with connective tissue and purkinje fibres in ventricle
Myocardium- muscle layer
Describe the histology of the myocardium
Centrally placed nuclei
Sarcomeric cross-striations
Ratio muscle fibre : capillaries 1:1
Purkinje fibres
Arranged in bundles
Connective tissue
What are the PM alterations of the the heart?
Blood clotting- red clots- atria, RV
Rigor mortis- occurs in left myocardium
Animals with prolonged heart disease may lack aquate glycogen for rigor mortis
Chicken fat clots- sedimentation of erythrocytes, closts of colourless fibrin
Haemoglobin imbibition- PM lysis of erythrocytes released Hb- red staining
Barbituate crystals- from phenobarbitone injection
What are the different pathological mechanisms of cardiovascular dysfunction?
Pump failure- weak contractility, myocardial disease
Obstruction of flow- valvular stenosis, vascular narrowing
Regurgitant flow- valvular dysfunction
Shunted flow- congenital defects
Ruptures- heart wall/ major vessels
Conduction disorders
What is cardiac syncope?
How is is characterised?
What can cause it?
Fainting/loss of conscious
Characterised clinically by collapse, loss of consciousness and extreme changes in HR and blood pressure
Myocardial necrosis, ventricular fibrillation, arrythmias, cardiac inhibition
What is congestive heart failure and the responses?
CHF- slow or gradual loss of puming efficiency, associated with pressure overload, volume overload, progressive myocardial damage
Reduced renal blood stimulated RAAS- sodium and water retention causing hypertension and increased workload on heart
Responses-
Cardiac dilation
Hypertrophy
Decompensation
Death
What does subacute and chronic Left/Right sided heart failure cause?
What are the causes of Right/Left sided heart failure?
Left-
Subacute- pulmonary congestion and oedema
Chronic- pulmonary congestion and oedema, fibrosis and hemosiderosis (iron deposits from erythropoesis)
Causes- left sided cardiomyopathies, dysfunction of aortic/mitral valve
Right-
Subacute- passive systemic congestion, hepatomegaly and splenomegaly
Chronic- systemic oedema (ascites), nutmeg liver
Causes- right sided cardiomyopathy, pulmonary hypertension, dysfunction of tricupsid and pulmonary valves
How can congenital defects of the heart present differently?
Extreme defects- animals do not survive in utero
Mildest defects- could have no clinical signs
Defects with immediate severity
Clinical signs- cardiac failure- cyanosis, excercise intolerance
What can cause congenital defects of the heart and pericardium?
Single or multiple gene defects
Toxins- thalidomide
Physical agents
Nutritional deficiencies
What does this image show?
What is acardia?
Amorphus globosus- acardiac monster attached to placenta
Acardia- agenesis of the heart
What is ectopia cordis?
Congenital development of the heart outside the thoracic cavity
What is patent ductus arteriosus?
Vascular channel between the pulmonary artery and aorta- allows blood to bypass the lung during foetal life- should convert to ligamentum ateriosum
Remains and therefore blood shunted from left to right causing:
Pulmonary hypertension therefore RV pressure overload, concentric hypertrophy, volume overload then eccentric hypertrophy
What are the two types of atrial septal defects?
Failure of foramen ovale to close
True septal defect- faulty development of interatrial septum
What does a ventricular septal defect cause?
Failure of inteventricular septum- bull dog, springer, Westie
Shunts blood left to right- equal pressures, pressure hypertrophy of right ventricle, volume hypertrophy of left
What are the three types of semilunar valve stenoses?
Supravalvular
Valvular
Subvalvular
Circumferential band of fibrous or musculat tissue of the valvular tissue- above or at level of tissue
What is a pulmonic stenosis?
What does it cause?
What species are affected?
Narrowing of pulmonart artery- usually valvular lesions
Causes pressure overload- right concentric hypertrophy- leads to roughening, deformatino and dilation of the surface of the pulmonary artery
Species- beagle, bulldog, Chihuahua
What causes subaortic stenosis?
What does it lead to?
Subvalvular lesions- thick zone of endocardial fibrous tissue that encircles the left ventricular outflow below the valve
Microscopically- endocardial mesenchymal necrosis and fibrosis
Pressure overload in LV- concentric hypertrophy
Pigs, dogs- boxer/GSH
What tetralogy of fallot?
Anomaly of four lesions
Ventricular septal defect
Pulmonic stenosis
Dextroposition of the Aorta
Secondarily- hypertrophy of the RV
Bulldogs and Keeshond
What are valvular haemotomas?
Haematocyst or lymphocysts frequently observes on the atrioventricular valves in ruminants
Generally regress spontaneously
Haematocyst- bulging, blood filled cysts
Lymphocyts- bulging, ywlloe serum-filled cyst
How does a persistent right aortic arch cause megaoesophagus?
Right 4th aortic arch- not left- develops and ascends in the right midline
Ligamentum arteriosum forms a vascular ring over the oesophagus and trachea
Oesophageal obstruction and dilation- megaoeosphagus
GSH, irish setter, great dane
What is valvular agenesis/hypoplasia?
Failure of valves to develop
What causes peritoneopericardial diaphragmatic hernia?
Dogs- with incomplete development of diaphragm
Abdominal viscera can be located in pericardial sac
What circulatory disturbances can there be of CV?
Haemorrhages
Frequent lesion in endocardium, myocardium, pericardium
Petechiae, ecchymoses- septicaemia
Mulberry heart disease
What is the normal appearance and ammount of pericardial fluid?
Clear, viscous fluid
Horse/cow- 100ml
Dog/cat- 10ml
What is hydropericardium?
What are the different causes of it and associated agents?
How do acute and chronic cases appear differently?
What are the consequences?
Hydropericardium- accumulation of clear to light yellow, watery serous fluid in the pericardial sac
Associated with vascular injury- generalised oedema:
- Increased vascular permeability- virus (influenza) , bacteria (clostridium), III hypersensitivity, toxins (paraquat)
- Increased IV hydrostatic pressure- pulmonary hypertension (LCHF, high altitude disease)
- Decreased IV osmosotic pressure- decreases albumin (malnutrition)
- Decreased lymphatic drainage- obstruction
Consequences- cardiac tamponade or compression, which impairs cardiac filling and venous return
What is haemorrhagic pericardial effusion?
What breed of dog does it affect?
Deposits of small amounts of blood, chronically
Great Dane, St Bernard, GSH
What is haemopericardium?
What can cause it?
Accumulation of large amount of blood in pericardium causing cardiac tamponade, leading to compression and interfereing with cardiac filling and empyting
Atrial rupture due to haemagiosarcoma of right atrium in dogs
Rupture of intrapericardial aorta in horses
Complications of intracardiac injection
What is a pneumopericardium and a cyclopericardium and what can cause them?
Pneumopericardium- air filled
Pulmonary ruptures, perforations of oesophagus/stomach
Cyclopericardium- specific gravity >1.015
Rupture of thoracic duct, often gelatinous and white