Tetralogy of Fallot Flashcards
What is Tetralogy of Fallot?
It is defined as a congenital condition in which there is anterior malalignment of the aorticopulmonary septum
This results in the development of four co-existing pathologies; ventricular septal defect, overriding aorta, pulmonary stenosis and right ventricular hypertrophy
What class of congential heart disease is Tetralogy of Fallot?
Cyanotic
Describe the pathophysiology of Tetralogy of Fallot
The ventricular septal defect allows blood to flow through the ventricles
The ‘overriding aorta’ refers to the aortic valve being placed further to the right than normal – above the ventricular septal defect
This means that when the right ventricle contracts, the aorta is in the direction of travel of that blood, therefore a greater proportion of deoxygenated blood enters the aorta from the right side of the heart
The pulmonary stenosis results in greater resistance against the flow of blood from the right ventricle
This encourages blood to flow through the ventricular septal defect and into the aorta, rather than the normal route into the pulmonary vessels
Therefore, blood is shunted from the right heart to the left, leading to cyanosis
Ultimately, there is increased strain of the muscular wall of the right ventricle, as it attempts to pump blood against the resistance of the ventricle and pulmonary stenosis, resulting in right ventricle hypertrophy
What determines the degree of cyanosis and the clincial severity of Tetralogy of Fallot?
The degree of pulmonary stenosis, therefore the right ventricular outflow tract obstruction
What four risk factors are associated with Tetralogy of Fallot?
Older Mother Age > 40 Years Old
Pregnancy Alcohol Consumption
Diabetic Mother
Rubella Infection
What are the six clincial features of Tetralogy of Fallot?
Failure To Thrive
Feeding Difficulties
Cyanosis
Tet Spells
Syncope
Ejection Systolic Murmur
Describe the murmur associated with Tetralogy of Fallot
There is a crescendo-decrescendo murmur with a harsh ejection systolic quality
It is loudest in the pulmonary area, which is the second intercostal space, left sternal border
What is the pathophysiological cause of the murmur associated with Tetralogy of Fallot?
It due to right ventricular outflow obstruction caused by pulmonary stenosis - not the ventricular septal defect
What are hypercyanotic ‘tet’ spells?
They are defined as intermittent symptomatic periods, in which the right-to-left shunt becomes temporarily worsened, precipitating a cyanotic episode
What is the pathophysiology of hypercyanotic ‘tet’ spells?
These episodes occur when the pulmonary vascular resistance increases or the systemic resistance decreases
This increases the right-to-left shunt
What are the three causes of hypercyanotic ‘tet’ spells?
Crying
Physical Exertion
Pain
What are the five clincial features of hypercyanotic ‘tet’ spells?
Irritability
Cyanosis
Tachypnoea
Reduced Consciousness
Seizures
What are the five clincial features of hypercyanotic ‘tet’ spells?
Irritability
Cyanosis
Tachypnoea
Reduced Consciousness
Seizures
What three investigations are used to diagnose Tetralogy of Fallot?
ECG Scans
Chest X-Ray (CXR)
ECHO Scans
What are the four features of Tetralogy of Fallot on ECG scans?
Right Bundle Branch Block
Right Axis Deviation
Anterior Prominent R Waves
Posterior S Waves
This indicates right atrial enlargement and right ventricular hyerptrophy
What are the three features of Tetralogy of Fallot on CXR?
Boot Shaped Heart
Right Aortic Arch
Right Ventricular Hypertrophy
What is the gold standard investigation used to diagnose Tetralogy of Fallot?
ECHO Scans
What is the feature of Tetralogy of Fallot on ECHO scans?
Right-to-left shunt
What is the conservative management option of hypercyanotic ‘tet’ spells?
We advise younger children to bring their knees to their chest and older children to squat
What are the six pharmacological management options of hypercyanotic ‘tet’ spells?
Oxygen Therapy
IV Fluids
Morphine
Phenylephrine Infusion
Beta-Blockers
Sodium Bicarbonate
What are the two pharmacological management options of Tetralogy of Fallot?
Prostaglandin Infusions
Loop Diuretics
When are prostaglandin infusions used to diagnose Tetralogy of Fallot?
They are used to manage neonates with severe stenosis, who are awaiting surgical management
How are prostaglandin infusions used to diagnose Tetralogy of Fallot?
They maintain the patency of the ductus arteriosus - enabling blood to flow through the aorta back to the pulmonary arteries
When are loop diuretics used to manage Tetralogy of Fallot?
They are used when there is development of heart failure complications
Name a loop diuretic used to manage Tetralogy of Fallot
Furosemide
What is the surgical management option of Tetralogy of Fallot?
Open Heart Surgery
What is the definitive management option of Tetralogy of Fallot?
Open Heart Surgery
What is the open heart surgery used to manage Tetralogy of Fallot?
It involves closure of the ventricular septal defect, shunt placement between the aorta and the pulmonary aorta and widening of the pulmonary valve
In most cases, a second surgical procedure is required in older children, involving pulmonary valve replacement
