Right to Left shunt Flashcards
What are the 2 key conditions for right-to-left shunts?
1) Tetralogy of fallot
2) Transposition of the great arteries
Typical presentation of right to left shunts?
- Typical presentation is with cyanosis (O2 sats < 94%) usually in the first week of life.
How do you determine the cardiac cause of cyanosis?
- Hyperoxia (Nitrogen washout) test is used to determine if cyaosis is the result of cyanotic heart disease - if lung disease and persistent pulmonary hypertension of the newborn have been ruled out.
How do you treat cyanotic heart disease?
1) Stabilise airway - ABCDE
2) Start prostaglandin infusion e.g. Alprostadil
- Neonates presenting with cyanotic heart disease in the first few days of life are duct dependant (there is reduced mixing between oxygenated blood from lung and deoxygenated blood from body)
- Maintenance of duct potency is key to early survival of these children
- Observe for potential side effects: apnoea, jitteriness, seizures, flushing, vasodilation, hypotension
What are the 4 anatomical features of Tetralogy of the Fallot?
1) Large ventricular septal defect
2) Overriding aorta with respect to the ventricular septum
3) Pulmonary stenosis (RV outflow obstruction)
4) Right ventricular hypertrophy
Epidemiology of tetralogy of the fallot?
1) Presents around 1-2 months
2) Most common cause of cyanotic congenital heart disease
3) Transposition of great arteries is the most common lesion at BIRTH (TOF presents 1-2 months later)
Clinical presentation of tetralogy of the fallot??
1) Severe cyanosis
2) Hypercyanotic spells - rapid increase in cyanosis with irritable crying inconsolable, breathlessness and pallor (tissue acidosis), MI and CVS (even death)
3) Squatting on exercise
4) Signs - clubbing, loud harsh ejection systolic murmur at left sternal angle.
Diagnosis of Tetralogy of the fallot?
1) CXR - Small boot shaped heart due to right ventricular hypertrophy
2) ECG - normal at birth, RV hypertrophy when older
3) ECHO DIAGNOSTIC
Treatment of Tetralogy of the Fallot?
1) Surgery at 6 months to close VSD and relieve RV outflow - shunt between subclavian artery and pulmonary artery (for infants very cyanosed).
2) Hypercyanotic spells: Usually self-limiting but if prolonged beyond 15 mins prompt treatment:
- Pain relief: morphine
- beta-blocker: relieve pulmonary muscular obstruction
- IV fluids
- Bicarbonate to correct acidosis
- Muscle paralysis and artificial ventilation to reduce metabolic oxygen demand.
What is Transposition of the Great Arteries?
The aorta is attached to the RV, and pulmonary artery to the LV - oxygenated blood is pumped back to the lungs and deoxygenated blood returned to the body.
- Two parallel circulations so unless there is mixing of blood this condition is incompatible with life.
- Fortunately there are associated anomalies: ASD, VSD, PDA which can achieve mixing in the short term - duct-dependant circulation.
Clinical presentation of Transposition of the Great Arteries?
1) Cyanosis
2) Presentation on day 2 with severe spike in cyanosis due to duct closure (reduction in mixing)
3) Second heart sound loud and single
4) No murmur
Diagnosis of TofGA?
1) CXR - ‘egg on side’ cardiac shadow
2) ECG - normal
3) ECHO DIAGNOSTIC
Treatment of TofGA?
1) Key is to improve blood mixing
2) Ensure patency of doctors arteriosus via prostaglandin (IV Alprostadil)
3) Surgery:
- Baloon atrial septostomy (opens foramen ovale for mixing)
- Arterial switch procedure: performed in neonatal period, where PA and aorta are transected and switched, coronary arteries have to be transferred across to the new aorta.
