Cardiovascular pathology 1 Flashcards
Where does the heart develop from?
Splanchnic mesenchyme in the cardiogenic area
The embryological heart develops dilatations and constrictions which result in which 4 chambers?
- Sinus venosus
- Primordial atrium
- Primordial ventricle
- Bulbus cordis
How does the heart develop during cardiac looping?
The heart is converted from an elongated muscular tube into a C-shaped structure by a process termed looping
What are the precursors of the valve cusps called?
Endocardial cushions
Which two septum position the atria successively?
Septum primum
Septum secundum
The septum secundum is an incomplete partition and leaves …?
A foramen ovale
What is the role of the foramen ovale before birth?
Allows blood to pass from the right to the left atrium with reflux being prevented by a valve
What happens to the foramen ovale after birth?
Closes by fusion of the septum primum and septum secundum
The interventricular septum consists of which 3 parts?
- Muscular portion
- Membranous portion
- Conotruncal ridged
What do the 4th left and right aortic arches form?
Left - forms the proximal part of the arch of the aorta
Right - forms the proximal part of the right subclavian artery
Describe the flow of blood through fetal circulation starting at the umbilical veins
Umbilical veins => liver/ductus venosus => vena cava => right atrium => either through the foramen ovale to the left atrium and then aorta or to the right ventricle to the pulmonary artery, ductus arteriosus and then aorta => systemic arteries => umbilical arteries => placenta
Which 2 parts of foetal circulation are oxygen and nutrient rich?
Placenta
Umbilical veins
Which part of foetal circulation is oxygen and nutrient poor?
Umbilical arteries
Name and describe the sac surrounding the heart
Pericardium
- one layer of mesothelium with a central layer of connective tissue and adipose tissue
Name and describe the outer surface of the heart
Epicardium
- one layer of mesothelium and one connective tissue and adipose tissue
Name the muscle layer of the heart
Myocardium
What is the endothelium?
Identical to arterial endothelium with connective tissue and Purkinje fibres - lines the inner part of the heart
Describe the histological features of myocardium (cardiac muscle)
- Centrally placed nuclei
- Sarcomeric cross striations
- Ratio of muscle fibres to capillaries is 1:1
- Purkinje fibres arranged in bundles
- Connective tissue
Where are post-mortem clots seen in the heart and why do they occur?
Red clots in the atria, right ventricle, and large vessels at the base of the heart
- occur because the blood is static when circulation stops
How does rigor mortis affect the heart?
- Occurs in the left myocardium and produces contracted rigid ventricular walls
- Less pronounced in right side of heart
How will rigor mortis be different in the heart of animals with prolonged heart disease? Why is this?
- The ventricular chambers may fail to contract during rigor mortis: grossly soft muscles
- Occurs because there are inadequate glycogen reserves in cardiac myocytes
What are chicken fat clots?
- Sedimentation of erythrocytes
- Clots consist of colourless fibrin with no erythrocytes
What is haemoglobin imbibition?
Postmortem lysis of erythrocytes which produces a diffuse red staining of the endocardium
An intracardiac injection of barbiturate can lead to the presence of what PM?
Crystalline deposits
Name 5 post mortem changes that may be seen in the heart?
- blood clotting
- rigor mortis
- chicken fat clots
- haemoglobin imbibition
- barbiturate crystals
Give examples of pathophysiological mechanisms of cardiac dysfunction that can lead to heart failure?
- Pump failure: weak contractility, myocardial disease
- Obstruction of flow: valvular stenosis, vascular narrowing
- Regurgitant flow
- Shunted slow
- Ruptures of the heart wall or major vessels
What is cardiac syncope?
Fainting/loss of consciousness
- syndrome of cardiac failure decompensation
Describe cardiac syncope, its characteristics and causes
- a peracute/acute expression of cardiac disease
- Characterised by collapse, loss of consciousness, extreme changes in heart rate and blood pressure
- Massive myocardial necrosis, ventricular fibrillation, arrythmias and reflex cardiac inhibition
What is congestive heart failure?
Slow, gradual loss of cardiac pumping efficiency
What 3 factors is congestive heart failure associated with?
- Pressure overload (hypertension or stenosis)
- Volume overload (shunts, valvular regurgitation)
- Progressive myocardial damage
Reduced renal blood flow stimulates? What effect does this have on the heart?
RAAS - sodium and water retention
- Increased plasma volume and increase the workload on the already failing heart
What are the 4 responses to congestive heart failure?
- Cardiac dilation: activation of the RAAS causes a compensatory response in the form of cardiac dilation to try and increase CO
- Hypertrophy: increased in the size of an organ due to an increase in cell size
- Decompensation: compensatory mechanisms no longer sufficient
- Death
What are the causes of left sided heart failure?
- Left sided cardiomyopathies
- Dysfunction of aortic and mitral valves
Describe the subacute and chronic forms of left sided heart failure
Subacute - pulmonary congestion and oedema
Chronic - pulmonary congestion, oedema, fibrosis and haemosiderosis (excessive accumulation of iron deposits)
What are the causes of right sided heart failure?
- Right sided cardiomyopathies
- Pulmonary hypertension
- Dysfunction of tricuspid and pulmonary valves
Describe the subacute and chronic forms of right sided heart failure
Subacute - passive system congestion, hepatomegaly and splenomegaly
Chronic - systemic oedema, nutmeg liver
Congenital defects of the heart and pericardium may present what clinical signs?
- poor exercise intolerance
- cyanosis
- coughing
- stunted body growth
What are the causes of congenital defects of the heart and pericardium?
- Single or multiple gene defects.
- Toxins (thalidomide, ethanol),
- Physical agents (irradiation)
- Nutritional deficiencies (vit A, Zinc).
What is agenesis of the heart?
Absence of the heart - not viable
Describe amorphous globosus and its appearance
Spherical, covered in hair, acardiac monster attached to the placenta by a cord in cows.
Severely anomalous second fetus.
Congenital development of the heart at an abnormal site outside of the thoracic cavity is termed?
Ectopia cordis
Name some examples of congenital defects of the heart and pericardium
- Patent ductus arteriosus
- Atrial septal defects
- Ventricular septal defects
- Pulmonic stenosis
- Tetralogy of Fallot
- Persistent right aortic arch
Where is the ductus arteriosus found in vivo?
- Vascular channel between the pulmonary artery and aorta
- Allows blood to bypass the lungs during foetal life
A patent ductus arteriosus cases blood to be shunted where?
From the left side of the heart to the right
What are the consequence of a patent ductus arteriosus?
- Pulmonary hypertension => right ventricle pressure overload (concentric hypertrophy) => Left atria and ventricle volume overload (eccentric hypertrophy)
Give 2 examples of atrial septal defects
- Failure of closure of the foramen ovale (septal shunt that allows blood to bypass the lungs of the foetus)
- Faulty development of the interatrial septum
Which 3 breeds to predisposed to atrial septal defects?
Doberman
Pincher
Samoyed
Describe a ventricular septal defect and name which breeds are predisposed to it
Failure of closure of interventricular septum
- Bulldog, Springer spaniel and West Highland white terrier.
What are the consequence of failure of closure of the interventricular septum?
- Shunt left-to-right => equal ventricular pressures
- Pressure hypertrophy of the right ventricle
- Volume hypertrophy of the left ventricle due to additional blood
What are the 3 types of semi-lunar valve stenosis?
- Name is dependant on the level of narrowing
- Supra valvular
- Valvular
- Subvalvular
What causes semi-lunar valve stenosis?
Circumferential band of fibrous or muscular tissue of the valvular tissue – above, below or at the level of the valve
Describe pulmonic stenosis, its causes and consequence
- Valvular lesions: whitish bands of connective tissue visible at the base of the semi-lunar valve
- Pressure overload → concentric hypertrophy (right)
Describe subaortic stenosis, its causes and consequence
- Subvalvular lesions
- Thick zone of endocardial fibrous tissue that encircles the left ventricular outflow tract below the valve
- Causes a pressure overload => concentric hypertrophy of the left side
How does subaortic stenosis appear microscopically?
Endocardial mesenchymal proliferation, mucin and metaplastic cartilage.
- Gap between the valve and the lesion
Which 4 lesions make up the Tetralogy of Fallot?
- Ventricular septal defect
- Pulmonic stenosis
- Dextroposition of the aorta
- Hypertrophy of the right ventricular myocardium
Which is the main clinical signs of Tetralogy of Fallot?
Cyanosis
What are valvular haematomas?
Haematocyst or lymphocysts frequently observed on the atrioventricular valves in ruminants. Generally, they regress spontaneously and do not produce any functional abnormalities.
What are the consequence of a persistent right aortic arch?
Oesophageal obstruction and proximal dilation => regurgitation
What is a peritoneopericardial diaphragmatic hernia?
Dogs with incomplete development of the diaphragm. Abdominal viscera can be located in the pericardial sac.
