Congenital Heart Disease: cyanotic Flashcards
Outline the causes of right to left shunt
R to L shunt: Early cyanosis - blue baby
- D-transposition of great vessels
- Tetralogy of Fallot
Outline the hyperoxia (nitrogen washout test)
Used to determine the presence of heart disease in a cyanosed neonate
- The infant is placed on 100% oxygen (headbox or ventilator) for 10 minutes
- If the right radial arterial pressure of oxygen (PaO2) remains LOW, (< 15kPa) after this, a diagnosis of cyanotic congenital heart disease can be made
Lung disease and persistent pulmonary hypertension must be excluded
Blood gas analysis is necessary in this scenario because oxygen saturations are NOT reliable enough
Management if the cyanosed neonate
Stabilise the airway, breathing and circulation (ABC), with artificial ventilation if necessary
- Start prostaglandin infusion (5ng/kg per minute)
- Most infants with cyanotic heart disease presenting in the first week of life are duct-dependent i.e. there is reduced mixing between the oxygenated blood returning from the lungs and deoxygenated blood from the body.
- Maintaining duct patency is KEY to early survival
Prostaglandins help to maintain duct patency
- Side-effects of prostaglandins: apnoea, jitteriness and seizures, flushing, vasodilation, hypotension
- The infant might need intubation due to apnoea
Outline tetralogy of Fallot
The MOST COMMON cause of cyanotic congenital heart disease
Can occur in conjunction with Trisomy 21 or 22q11 deletion (Di George syndrome)
Comprises of FOUR defects:
- A large VSD
- Overriding of the aorta with respect to the ventricular septum (meaning deoxygenated blood from the RV flows directly into the aorta entrance)
- Sub-pulmonary stenosis causing RV outflow tract obstruction
- RV hypertrophy as a result
Caused by anterosuperior displacement of the infundibular septum
Most cases are diagnosed:
* Antenatally
* Following the identification of a murmur in the first 2 months of life
* Cyanosis may NOT be obvious at this stage
* However, some may present with severe cyanosis
Clinical features of tetralogy of Fallot
Symptoms
- Severe cyanosis
- Hypercyanotic (‘Tet’) spells: Important to recognise because they can lead to MI, cerebrovascular accidents and death
These are characterised by a rapid increase in cyanosis, usually with irritability and inconsolable crying because of severe hypoxia
- Breathlessness and pallor because of tissue acidosis may also be present
- On auscultation, there is a short murmur during a spell
- Squatting on exercise (in older children): increases total peripehral resistance, increases afterload, decreases right to left shunting
- Poor feeding, agitation
IMPORTANT: these features develop in late infancy and is rare in developed countries
Signs
* Clubbing will develop in older children
* Loud harsh ejection systolic murmur at the left sternal edge from day 1 of life
NOTE: as RV outflow tract obstruction increases, the murmur will shorten, and cyanosis will increase
Investigations of tetralogy of Fallot
CXR: Image result for cxr boot shaped heart
- Relatively small heart
- May have an up-tilted apex due to right ventricular hypertrophy
- May be a right-sided aortic arch
- It looks like a ‘boot shaped heart’
Pulmonary artery bay- a concavity on the left heart border where a normal pulmonary artery and right ventricular outflow tract should be
Decreased pulmonary vascular markings (due to reduced flow)
ECG
* Normal at birth
* RV hypertrophy in older children
Echocardiography
* Cardiac catheterisation may be required to show the detailed anatomy of the coronary arteries
Management of tetralogy of Fallot
Initial management
- IV Alprostadil (Prostaglandin E1) infusion to maintain PDA whilst awaiting surgery
- Oxygen
- Keep baby warm
Surgery (at around 3-6 months)
* Modified Blalock-Taussig shunt
* Insert an artificial tube between the subclavian artery and pulmonary artery
Other shunts that can be used:
* Waterson: ascending aorta to right pulmonary artery
* Potts: descending aorta to left pulmonary artery
Right ventricular outflow obstruction stenting/ balloon dilation
* Balloon is inserted into the narrow part of the pulmonary artery and then inflated
Open heart surgery
* Patch is placed over the VSD and the pulmonary stenosis is enlarged
Hypercyanotic spells are usually self-limiting followed by a period of sleep
If this is prolonged (> 15 minutes), they need prompt treatment:
1. Manoeuvres to increase systemic venous return e.g. positioned with knees to chest
2. Sedation and pain relief(morphine)
3. IV propranolol- works as a peripheral vasoconstrictor and by relieving sub-pulmonary muscle obstruction
NOTE: can also give another a-adrenoceptor agonist which has similar effects
4. IV volume administration
5. Bicarbonate to correct acidosis
6. Muscle paralysis and artificial ventilation to reduce metabolic oxygen demand
Complications of Tetralogy of fallot
Complications
- Residual pulmonary incompetence
- Aortic root dilation
- Sustained ventricular tachycardia
- Delayed neurodevelopment
- Sudden death
Prognosis
* Mortality in the first year of life (1/3), 50% mortality in the second year of life
* Untreated TOF causes delayed growth and development, including puberty
Outline the transposition of great arteries
A condition in which the main arteries are connected the wrong way:
- Right Ventricle -> Aorta
- Left Ventricle à Pulmonary artery
This means that deoxygenated blood is returned to the body and oxygenated blood is returned to the lungs
This means that there are two parallel circulations (which is NOT compatible with life unless there is mixing of blood between them)
However, this condition tends to be associated with some naturally occurring associated anomalies e.g. VSD, ASD, PDA
This condition is the result of the failure of the aorticopulmonary septum to spiral
Clinical features of Transposition
Symptoms
1. Cyanosis (may be profound and life-threatening)
2. Present on Day 2 of life when ductal closure leads to a reduction in mixing of saturated and desaturated blood
NOTE: cyanosis is less severe and presentation is delayed if there is more mixing of blood from associated anomalies
3. May have symptoms of congestive heart failure at 4-8 weeks of life
Signs
1. Cyanosis- ALWAYS present
2. Second heart sound is often LOUD and single
3. NO murmur, but may be a systolic murmur from increased flow or stenosis within the LV (pulmonary) outflow tract
4. Low oxygen saturations on day 1 of life
Investigations of transposition
Investigations
CXR
* Image result for tga egg on side
Narrow mediastinum with an ‘egg on side’ appearance of the cardiac shadow
* This is caused by the anteroposterior relationship of the great vessels, narrow vascular pedicle and hypertrophied RV
* Increased pulmonary vascular markings (due to increased pulmonary blood flow)
ECG – usually normal, possible RVH
Echocardiography
* Essential to demonstrate abnormal arterial connections and associated abnormalities
Management of transposition
Initial management
- Prostaglandin E1 infusion- Maintain PDA (MANDATORY)
- Balloon atrial septostomy- life-saving procedure
- A catheter with an inflatable balloon is passed through the umbilical or femoral vein and then on through the right atrium and foramen ovale
- The balloon is inflated within the left atrium and then pulled back through the atrial septum.
- This tears the atrial septum, breaking the flat valve of the foramen ovale and encourages mixing of blood in the atrium
Definitive Corrective Surgery (ASO)
* This is usually the Arterial Switch Operation in the neonatal period
* The pulmonary artery and aorta are transected above the arterial valves and switched over
* The coronary arteries also need to be transferred to the new aorta
Complications/ Prognosis of transposition
Complications
* Cardiopulmonary issues:
* Neopulmonary stenosis
* Neopulmonary regurgitation
* Neoarotic root dilation
* Coronary artery disease
* Neurodevelopmental problems
Prognosis
Survival into adulthood is common after ASO (90% 20-year survival rate)
Outline tricuspid atresia
Absence of tricuspid valve and hypoplastic RV; requires both ASD and VSD for viability
Clinical features of tricuspid atresia
Cyanosis and SoB
* Presents very early (10mins)
* Similar to ToF presentation but ToF presents at 1-6m of age
o Ejection Systolic Murmur at left sternal edge
o Hypoplastic left heart
Summary of cyanotic congenital heart defects
Ebstein’s anomaly
