PATHOLOGY - Congenital Cardiac Disease Flashcards
What are the two classifications of heart murmurs in puppies and kittens?
Nonpathological murmurs
Pathological murmurs
What are the six characteristics of non-pathological murmurs?
- Murmurs are softer or absent at rest, with changes of position or phase of respiration
- Short duration
- Systolic murmur
- No other associated abnormal heart sounds or physical exam findings
- Murmur localised on the left side
- Grade I or II
What are the two classifications of non-pathological murmurs in puppies and kittens?
Functional mumur
Innocent murmur
What is a functional murmur?
A functional murmur is where there is no heart disease detected and there is a plausable physiological explanation for the murmur
What can cause a functional murmur?
Changes in blood viscosity
Increased cardiac output
Give an example of a condition that can cause a functional murmur and explain why
Anaemia decreases blood viscosity causing increased blood flow velocity and turbulent blood flow, resulting in a functional murmur
What is an innocent murmur?
An innocent murmur is when there is no heart disease detected however there is no obvious physiological explanation for the murmur
What is the likely cause of innocent murmurs?
The likely cause of innocent murmurs is the larger stroke volume in puppies and kittens relative to great vessel size
What are the three most common congenital heart diseases seen in dogs?
Pulmonic stenosis
Patent ductus arteriosus (PDA)
Subaortic stenosis
Which congenital heart diseases are Boxers predisposed to?
Pulmonic stenosis
Subaortic stenosis
Which congenital heart diseases are German Shepherds predisposed to?
Patent ductus arteriosus (PDA)
Persistent right aortic arch
Which congenital heart disease are Bulldogs predisposed to?
Pulmonic stenosis
Which congenital heart disease are Labradors predisposed to?
Tricuspid valve dysplasia
Which congenital heart disease are Bull Terriers predisposed to?
Mitral valve dysplasia
What is the most common congenital heart disease in cats?
Ventricular septal defects
What is pulmonic stenosis?
Pulmonic stenosis is the structural malformation that causes an obstruction of blood flow from the right ventricular outflow tract into the pulmonary artery
Describe the pathophysiology of pulmonic stenosis
Pulmonic stenosis causes an obstruction of blood flow from the right ventricular outflow tract, resulting in pressure overload and compensatory right ventricular concentric hypertrophy. As the right ventricle hypertrophies, ventricular compliance diminishes, leading to impaired ventricular filling. This will further reduce blood flow into the pulmonary artery and consequently the blood flow to the left side of the heart, resulting in decreased stroke volume and cardiac output. Concentric hypertrophy increases the surface area of the myocardium resulting in the oxygen demand exceeding the oxygen supply from the coronary circulation, resulting in oxygen deficiency, resulting in systolic dysfunction and right-sided heart failure. This will eventually result in a backup of blood from the right side of the heart resulting in right-sided congestive heart failure
How does pulmonic stenosis result in a heart murmur?
Since the blood has to flow through a narrow opening, this results in turbulent blood flow and a heart murmur
How can you determine the severity of pulmonic stenosis on clinical exam?
The severity of the pulmonic stenosis corresponds with the intensity of the heart murmur heard on auscultation
What are the six clinical signs of pulmonic stenosis?
Asymptomatic
Left sided basal crescendo-decrescendo systolic murmur on auscultation
Exercise intolerance
Syncope
Weak pulse
Signs of right-sided congestive heart failure
How can pulmonic stenosis present on an ECG?
Right bundle branch block (RBBB)
What are the four key signs of pulmonic stenosis on radiography?
Cardiomegaly
Increased sternal contact
Prominant pulmonary artery
Heart looks like an inverted ‘D’ on ventrodorsal radiograph
What are the two key signs of pulmonic stenosis on echocardiography?
Right ventricular concentric hypertrophy
Turbulent blood flow at the pulmonary valve (doppler)
What is the most common form of pulmonic stenosis?
Valvular pulmonic stenosis
What are the two classifications of valvular pulmonic stenosis?
Type A: Narrowed or fused heart valves
Type B: Narrowed annular ring
What can be done to treat type A valvular pulmonic stenosis?
Balloon valvuloplasty
What is a balloon valvuloplasty?
A balloon valvuloplasty is a procedure used to widen a narrow heart valve. A catheter is inserted into the jugular vein and guided into the right side of the heart to the pulmonary valve. When the pulmonary valve is reached and the balloon is in position, it is inflated to widen the valve
When would a balloon valvuloplasty not be an appropriate treatment method for pulmonic stenosis?
Type B valvular pulmonic stenosis
Supravalvular pulmonic stenosis
Subvalvular pumonic stenosis
Due to the muscular and annular ring involvement, the balloon will not be strong enough to widen the stenosis
What is a transvalvular pulmonic stent angioplasty?
A transvalvular pulmonic stent angioplasty is where a catheter is inserted into the jugular vein and guided into the right side of the heart to the pulmonary valve. When the pulmonary valve is reached and the balloon is in position, it is inflated to widen the pulmonic valve enough to place a stent
When would a transvalvular pulmonic stent angioplasty be an appropriate treatment method?
Type B valvular pulmonic stenosis
Supravalvular pulmonic stenosis (however may not be successful)
Subvalvular pulmonic stenosis
What is the prognosis for pulmonic stenosis?
Good prognosis
What is the ductus arteriosus?
The ductus arteriosus is a foetal connection between the pulmonary artery and the aorta
Describe the pathophysiology of a patent ductus arteriosus (PDA)
A patent ductus arteriosus is the persistance of the foetal connection between the aorta and the pulmonary artery after birth. Since the pressure is greater in the left side of the heart, this causes a left-to-right shunt where oxygenated blood shunts from the aorta into the pulmonary artery via the patent ductus arteriosus, resulting in increased blood flow into the pulmonary artery and pulmonary circulation and consequently a volume overload of the left side of the heart, resulting in compensatory left ventricular eccentric hypertrophy. Furthermore, this increased blood flow to the pulmonary circulation causes pulmonary hypertension which causes pressure overload on the right side of the heart, resulting in compensatory right ventricular concentric hypertrophy
How can a patent ductus arteriosus cause differential cyanosis?
The right ventricular concentric hypertrophy can cause the pressure on the right side of the heart to exceed the pressure on the left side of the heart, causing a right to left shunt where deoxygenated blood shunts from the pulmonary artery into the aorta via the patent ductus arteriosus. Since the branches of the aorta that supply the upper body are located above the patent ductus arteriosus, the upper body tends to receive oxygenated blood, and the deoxygenated blood that has been shunted through the patent ductus arteriosus (PDA) will flow downwards affecting the lower body more significantly, causing differential cyanosis
What are the six possible clinical signs of a patent ductus arteriosus (PDA) where there is a left-to-right shunt?
Asymptomatic
Continuous/machinery murmur
Exercise intolerance
Syncope
Signs of left sided congestive heart failure
Bounding pulse
What causes the bounding pulse palpated in patients with a patent ductus arteriosus?
Due to the increased blood volume in the left ventricle, there will be an increased stroke volume which elevates systolic pressure. However, diastolic pressure will be lower than normal because, between cardiac ejections, blood will run out of the aorta via two pathways - into systemic circulation and through the open ductus arteriosus which will decrease the volume of blood that would normally be flowing within the systemic circulation and the arteries become less distended so the pressure decreases more than usual before the next cardiac ejection begins. This increases the difference between systolic and diastolic pressure, increasing pulse pressure resulting in a bounding pulse
What are the possible clinical signs of a patent ductus arteriosus (PDA) where there is a right-to-left shunt?
No continuous/machinery murmur
Differential cyanosis
Hindlimb weakness
Why might a patient’s haematocrit increase if they have a right-to-left PDA shunt?
The differential cyanosis results in kindey hypoperfusion which will stimulate erythropoiesis and increased red blood cell production, resulting in an increased haematocrit
What are the three key signs of a patent ductus arteriosus (PDA) on a radiograph?
Cardiomegaly
Prominent aorta
Signs of left-sided congestive heart failure (such as alveolar lungs signs and increased size of the pulmonary veins)
What are the three key signs of a patent ductus arteriosus (PDA) on echocardiography?
Left ventricular eccentric hypertrophy
Potentially right ventricular concentric hypertrophy
Abnormal blood flow between aorta and pulmonary artery (doppler)
Which two methods can be used to treat a patent ductus arteriosus?
Surgical ligation
Catheter based occlusion
However cannot be done for a right to left shunt
When is surgical ligation of a patent ductus arteriosus an appropriate treatment method?
Surgical ligation of a patent ductus arteriosus is appropriate in smaller animals where catheter based occulsion is not feasible
How do you carry out catheter based occlusion of a patent ductus arteriosus?
A catheter is inserted into the femoral artery and guided into the aorta and into the patent ductus arteriosus which can be occluded. Or, the catheter can be inserted into the jugular vein and guided into the pulmonary artery into the right-side of the heart and pulmonary artery until it reaches the patent ductus arteriosus
Which two imaging techniques should you use to guide catheter based occlusion?
Fluoroscopy
Transoesophageal echocardiography
Which three occlusion tools can you use for catheter based occlusion?
Embolisation coil
Duct occluder (ACDO)
Vascular plug
What is the main disadvantage of the embolisation coil?
The embolisation coil can become unstable and be displaced into the body
What is the main disadvantage of the duct occluder (ACDO)?
The duct occluder (ACDO) has to be orientated is a specific way to properly occlude the patent ductus arteriosus
Which occusion tool can be inserted via the arterial and venous catheterisation method?
Vascular plug
The other two can only be inserted via the femoral artery
What is the prognosis for a patent ductus arteriosus?
The prognosis is good if there are no severe secondary changes
What is subaortic stenosis?
Subaortic stenosis is the structural malformation that causes an obstruction of blood flow from the left ventricular outflow tract into the aorta
Describe the pathophysiology of subaortic stenosis
Subaortic stenosis causes an obstruction of blood flow from the left ventricular outflow tract resulting in pressure overload and compensatory left ventricular concentric hypertrophy. As the left ventricle hypertrophies, ventricular compliance diminishes, leading to impaired ventricular filling and reduced stroke volume and cardiac output. Concentric hypertrophy increases the surface area of the myocardium resulting in the oxygen demand exceeding the oxygen supply from the coronary circulation, resulting in oxygen deficiency, resulting in systolic dysfunction and left-sided heart failure. This will eventually result in a backup of blood from the left side of the heart into the pulmonary circulation, resulting in left-sided congestive heart failure
How does sub-aortic stenosis result in a heart murmur?
Since the blood has to flow through a narrow opening, this results in turbulent blood flow and a heart murmur
What are the six clinical signs of subaortic stenosis?
Asymptomatic
Left sided basal crescendo-decrescendo systolic murmur
Exercise intolerance
Syncope
Anacrotic, weak pulse
Signs of left sided congestive heart failure
What are the three key signs of subaortic stenosis on a radiograph?
Cardiomegaly
Increased sternal contact
Signs of left-sided congestive heart failure (such as perihilar alveolar lungs signs and increased size of the pulmonary veins)
What are the key signs of subaortic stenosis on echocardiography?
Left ventricular concentric hypertrophy
Narrowing below the aortic valve
Turbulent blood flow at the aortic valve (doppler)
What are atrioventricular septal defects?
Septal defects are a congenital defect in which there is an opening in the cardiac septa which divide the heart chambers
What is the most common form of an atrioventricular septal defect?
Perimembranous atrioseptal defect (located in the membranous septum, a portion of the septum located near the heart valves)
Describe the pathophysiology of a ventricular septal defect
A ventricular septal defect allows for abnormal blood flow between the ventricles. Since the pressure is greater in the left side of the heart, this causes a left-to-right shunt where oxygenated blood shunts from the left ventricle into the right venticle via the septal defect, resulting in increased blood flow into the pulmonary circulation and consequently a volume overload of the left side of the heart, resulting in compensatory left ventricular eccentric hypertrophy. Furthermore, this increased blood flow to the pulmonary circulation causes pulmonary hypertension which causes pressure overload on the right side of the heart, resulting in compensatory right ventricular concentric hypertrophy
How can a ventricular septal defect cause central cyanosis?
The right ventricular concentric hypertrophy can cause the pressure in the right side of the heart to exceed the pressure on the left side of the heart, causing a right to left shunt where deoxygenated blood shunts from the right ventricle into the left ventricle via the defect. Deoxygenated blood will be shunted into the systemic circulation resulting in central cyanosis
What are the six clinical signs of a ventricular septal defect?
Asymptomatic
Right sided systolic murmur
Excercise intolerance
Syncope
Signs of left sided congestive heart failure
Central cyanosis (with a right-to-left shunt)
(T/F) The severity of the ventricular septal defect corresponds with the intensity of the heart murmur
FALSE. A smaller and less severe ventricular septal defect will produce a more intense murmur compared to a larger, more severe ventricular septal defect
What is the key sign of a ventricular defect on echocardiography?
Blood flow between the left and right ventricles (doppler)
What is the Tetralogy of Fallot?
The Tetralogy of Fallot is a congenital heart defect resulting is a right to left shunt due to four collective defects
What are the four collective heart defects that cause the Tetralogy of Fallot?
Pulmonic stenosis
Over-riding aorta
Ventricular septal defect
Right ventricular concentic hypertrophy
What is tricuspid valve dysplasia?
Tricuspid valve dysplasia is a malformation of the tricuspid valve
Describe the pathophysiology of tricuspid valve dysplasia?
Malformation of the tricuspid valve results in valvular insufficiency, resulting in volume overload on the right side of the heart resulting in compensatory right atrial enlargement and right ventricular eccentric hypertrophy and potentially right-sided congestive heart failure
What is a double-chambered right ventricle?
A double chambered right ventricle is when the right ventricle is divided into two chambers - a high pressure and low pressure chamber
What is a persistent right aortic arch?
A persistent right aortic arch is where the aortic arch develops from the right rather than the left fourth aortic arch, resulting in abnormal positioning of the ligamentum arteriosum, forming a ring like structure around the oesophagus, causing constriction
What are the key clinical signs of a persistent right aortic arch?
Regurgitation
Weight loss
Failure to thrive
When do the clinical signs of a persistent right aortic arch typically arise?
The clinical signs of a persistent right aortic arch typically arise at weaning when the patient is converted from liquid to solid food. Liquid food can typically pass through the oesophageal narrowing however solid food cannot
Which dogs breeds are predisposed to a persistent right aortic arch?
German Shepherds
Irish Setters
