Congenital Heart Defects Flashcards
What are the two shunts present in the foetal circulation which allow mixing of the oxygenated and deoxygenated blood?
Ductus arteriosus
Foramen ovale
Describe the foetal circulation
The foetus receives oxygenated blood from the mother’s placenta. Because the lungs are not fully formed, the vascular resistance within the pulmonary arteries is high therefore the blood from the IVC takes the path fo elastic’s resistance and passes through the foramen ovale directly into the left atrium. A minority of blood will pass into the right ventricle and through the pulmonary vein but nearly all of this passes through the ductus arterioles into the aorta.
The chambers of the heart are identified by their characteristic and not by their position. T/F?
True
What is the difference in morphology between the appendages of the right and. left atria?
Right- broad appendage
Left - narrow, sausage-shaped appendage
What is the difference in morphology between the right and. left ventricles?
Right - heavy trabeculations, muscular band called the moderator band, chordae tendinae insert into the septum
Left - smooth endocardium, 2 papillary muscles, ellipsoid cavity
The atrioventricular valve always follows the atrium. T/F?
False - it follows the ventricle
The aortic and pulmonary valves always stay with their relevant artery and so can be connected to the wrong ventricle. T/F?
True
Give examples of acyanotic congenital heart defects
Ventricular septal defects Persistent ductus arteriosus Atrial septal defects Pulmonary stenosis Aortic stenosis Coarctation of the aorta
Give examples of cyanotic congenital heart defects
Tetralogy of fallot
Transposition of the great arteries
Atrioventricular septal defects
What is the most common type of atrial septal defect?
Secundum
Where in the atria does the hole occur in a secundum atrial septal defect?
Centre of the atria
Where in the atria does the hole occur in a primum atrial septal defect?
Close to the atrioventricular valve which can distort the valve leading to it becoming leaky or regurgitant
How can a secundum atrial septal defect lead to right ventricular failure?
Causes a left to right shunt as blood moves from a higher to lower pressure. The extra blood being received into the right ventricle causes right ventricle dilation which inhibits the ability of the ventricle to pump efficiently and will eventually cause right ventricular failure
It is not unusual for ASDs to be first diagnosed in adulthood. T/F?
True
What are the possible presentations of an atrial septal defect?
Murmur
Arrhythmia and palpitations due to stretching of right atrium
Shortness of breath
Embolic stroke
How are atrial septal defects treated?
Surgically with a sternotomy
Through the groin vessels with a transcatheter device
At what point in the aorta is a coarctation commonly seen?
Insertion point of the ductus arteriosus.
After the left subclavian artery
How can a coarctation of the aorta lead to left ventricular failure?
The narrowing of the aorta means that the left ventricle has to generate a higher pressure to push the blood through so the patient will develop left ventricular hypertrophy which can progress to left ventricular failure
What are the possible presentations of severe coarctation of the aorta?
Poor lower limb perfusion (cold feet, claudification of the legs, abdominal angina)
Headache and nosebleeds due to increased systemic pressure proximal to the coarctation
Hypertension may be the result of coarctation of the aorta. T/F?
True
What discrepancies in blood pressure may you find in a patient with coarctation of the aorta?
Upper limb pressure is greater than the lower. limb pressure
There may be radio-femoral defat in coarctation of the aorta. T/F?
True
What other congenital defects is aortic coarctation associated with?
Bicuspid aortic valve
Berry aneurysms
How can coarctation of the aorta be treated?
Surgery - narrowed aorta is cut out or reconstructed using the subclavian artery
Transcatheter - balloon passed through and inflated to stretch the narrowed artery
Describe the congenital defect which occurs in transposition of the great arteries?
The aorta and the pulmonary artery switch places so that the aorta is attached to the right ventricle and the pulmonary artery is connected to the left ventricle
Transposition of the great vessels affects males more than females. T/F?
True - in a 4:1 ratio
How can the embryonic shunts be kept open in a baby with transposition of the great arteries to keep the infant alive until surgery can be performed?
Prostaglandins
Describe the atrial switch procedure which used to be performed on patients with transposition of the great arteries?
A channel is created for venous blood to pass into the pulmonary artery via the left ventricle and the atrial septum is cut away to allow oxygenated blood to pass through the right atrium and into the aorta via the left ventricle. This is how venous blood is redirected to the appropriate side of the heart
What is the major issue with the atrial switch procedure used to treat patients with transposition of the great arteries?
The right ventricle is expected to pump blood through the systemic circulation which is not designed to do and so systemic ventricular failure will develop over time
In the arterial switch procedure to treat transposition of the great arteries, the aorta and pulmonary artery are disconnected and switched into their appropriate positions. What is the major difficulty in this procedure?
Care needs to be taken with the coronary arteries which have to be reconnected to the aorta
If not carefully stitched back on, these can occlude and cause an Mi or sudden-death post-operatively.
What are the four components to tetralogy of fallot?
Ventricular septal defect
Right ventricular outflow obstruction
Overriding aorta
Right ventricular hypertrophy
What is an overriding aorta?
Aortic valve is enlarged and appears to arise from both the left and right ventricles
What is involved in the corrective surgery for tetralogy of fallot?
Closing VSD with a patch
Resection of the right ventricular outflow obstruction
Enlargement of the pulmonary artery with a patch.
What are some of the long term issues with repaired tetralogy of fallot?
Progressive regurgitation of the pulmonary valve leading to right ventricle overload, dilatation and eventually failure
Increase in right ventricular pressure can cause a rise in right atrial pressure which then dilates and can trigger arrythmia
Patients with BT shunts may develop pulmonary artery stenosis
What is a univentricular heart?
A congenital heart condition which results in only one effective pumping ventricle.
What are some of the anomalies which can be described as single ventricle defects?
Tricuspid atresia
Hypoplastic left heart syndrome
Doublet inlet of left ventricle
Surgery in patients with univentricular hearts aims to create two functioning ventricles but this is not possible in all patients. In this case, what type of circulation will be created for the patient?
Fontan circulation
Describe fontan circulation
A single ventricle supports the systemic circulation by disconnected it form the pulmonary valve and artery
The IVC and SVC are redirected and plumbed straight into the pulmonary arteries ultimately bypassing the heart altogether. Deoxygenated blood flows directly from the IVC/SVC to the pulmonary arteries, is oxygenated in the lungs and returns to the left atrium, passes through the mitral valve into the single ventricle and is then passed through the aortic valve into the aorta and systemic circulation
Describe the timeline of surgeries required to create a Fontan circulation
BT shunt - first few days after birth
Norwood procedure - first week of life
Bi-driectional glen - 3-6 months
Fontan completion - 2-3 years
Describe the Norwood operation
The right ventricle becomes the systemic ventricle
A new aorta is made from part of the pulmonary artery and the original artery is reconstructed to provide blood flow to the body
A small tube graft is placed either from an artery to the lung vessels or from the right ventricle to the lung vessels
Describe the BT shunt procedure
The carotid or subclavian artery is connected directly to the pulmonary artery
Describe the bi-drectional glen procedure
The SVC is taken off the heart and sewn directly onto the pulmonary artery
Why are patients with a Fontan circulation so haemodynamically vulnerable?
Without a right ventricle to actively pump blood into the pulmonary circulation, a sufficiently high systemic venous pressure is require to drive the deoxygenated blood directly into the pulmonary arteries
Pulmonary vascular resistance needs to be low for optimal flow into the lungs
