Tetralogy of Fallot Flashcards
What are the four anatomical abnormalities seen in the tetralogy of fallot?
Ventricular septal defect
Right ventricular hypertrophy
Pulmonary stenosis
Overriding aorta
What is the genetic aetiology of tetralogy of fallout?
Multifactorial - genetic and environmental
Chromosomal -> T21, DiGeorge syndrome
Singe gene -> JAG1 mutations (Alagille syndrome - autosomal dominant), NKX2-5, FOG2/ZFPM2
What is the environmental aetiology of tetralogy of fallot?
Maternal diabetes mellitus
Gestational alcohol exposure
Maternal use of retinoic acid
Maternal phenylketonuria
What is the key pathology per defect in tetralogy of fallot?
VSD - shunting of blood
PS -> at or below pulmonary valve, resistance of blood flow out of the pulmonary artery = resistance to right ventricular ejection
RVH -> in response to higher pressure and workload on RV it hypertrophies
Overriding aorta ->straddles both ventricles above the VSD -> receives both oxygen rich and depleted blood
What is the clinical manifestation of the abnormalities seen in tetralogy of fallot?
Right to left shunting of blood -> bypass the lungs -> deoxyganted blood enters systemic circulation causing cyanosis
Lead to hypoxemia and polycythemia -> inc blood velocity and risk of VTE
Tets spells -> sudden exacerbation of cyanosis triggered by crying, laughter etc
What determines the severity of disease in complete/classic Tetralogy of fallot?
Degree of pulmonary stenosis
What are the features of pink or atypical tetralogy of fallot?
TOF with minimal pulmonary stenosis
Less severe obstruction to pulmonary blood flow presents with mild cyanosis
What are the features of tetralogy of fallot with pulmonary atresia?
Severe -> may have complete lack of formation of pulmonary vale for no blood from heart to lungs
Relies on collateral arteries to compensate for impaired blood flow
What are the features of tetralogy of Fallot with absent pulmonary valve syndrome?
Absent or dysplastic pulmonary valve causing significant dilation and distortion of pulmonary arties and branches
What is the summarised classical presentation of teralogy of fallot?
Cyanotic infant with dyspnea and failure to thrive
Harsh sounding murmur heard best at left sternal border due to right ventricular outflow tract
What are the common signs/symptoms of tetrology of fallor at diagnosis?
Abnormal foetal ultrasound scans
Hypoxia at birth
Heart murmur on newborn exam
What are the additional signs/symptoms of tetrology of fallot?
Cyanosis - mild or severe
Heart murmur in first with month
Acute deepened cyanosis - tet spells when reversal of shunt across the VSD leading to right to left shunt
Poor feeding and growth
What is heard on auscultation of a transposition of the greater arteries?
Loud single second heart sound and absence of murmurs
What are the key investigations for suspected teralogy of fallot in the neonate?
Oxygen sats at birth
Echo - first line
CXR - boot shaped heart
What second line tests may be used to diagnose tetrology of fallot in a newborn?
Hyper-oxygenation: deliver 100% FiO2 is inc >25mmHg to greater than >100mmHg increased resp not cardio
Cardiac catheterisation - for coronary artery anatomy and degree of pulmonary vascular disease
What is the initial treatment for tetrology of fallot?
Neonatal resus -> additional IV prostaglandin E1 to keep ductus arteriosus open or metal stent
Synthetic shunt between aorta and pulmonary artery
Transcatheter stent to dilate stenosed pulmonary artery
What is the definitive treatment for tetralolgy of fallor?
Corrective surgery 3-6months
Correction RV outflow tract obstruction, widening pulmonary valve, closure of VSD
What is the management of tet spells in tetralogy of fallot?
Position infant on back and flex knees
Oxygen administration in hospital
Prophylactic propranolol
What are the potential complications of ToF?
Delayed neurodevelopment
Reduced exercise tolerance
Sustained ventricular tachycardia
Aortic root dilation
Pulmonary valve regurgitation
What is the prognosis of tetralogy of fallot?
Without intervention very poor
With surgical correction up to 90% survival 30yrs.
