4- Paediatric Cardiology (Cyanotic defects) (2/2) Flashcards
Cyanotic defects
A group of heart defects that present with central cyanosis- blood in the systemic circulation is not saturated with oxygen so pO2 is low.
- Tetralogy of Fallot
- Transposition of the great arteries
- Tricuspid atresia
Tetralogy of fallot
Characterised by 4 defects that present together: right to left cardiac shunt (bypassing the childs lungs)
1. Pulmonary stenosis - the pulmonary artery or valve is narrowed, so less blood can enter
2. Overriding aorta - aorta is large and situated right next to the VSD so most of the blood in the heart flows through it
3. Ventricular septal defect- allows blood from the right ventricle which cannot be pumped through the stenosed pulmonary artery/valve to move into the left ventricle and be pumped around the body via the aorta
4. Hypertrophy of the right ventricle- in an attempt to generate more force to pump blood through the stenosis in the pulmonary artery
Risk factors for ToF
- Rubella infection
- Increased age of mother
- Alcohol consumption during pregnancy
- Diabetic mother
presentation of ToF
Murmur
- Arises due to pulmonary stenosis
- Ejection systolic murmurs loudest over pulmonary area (second intercostal space, left sternal border)
General symptoms
* Cyanosis (blue discolouration of the skin due to low oxygen saturations)
* Clubbing
* Poor feeding
* Poor weight gain
* Ejection systolic murmur heard loudest in the pulmonary area (second intercostal space, left sternal border)
* Tet spells
Tet spells
“Tet Spells” are intermittent symptomatic periods where the right to left shunt becomes temporarily worsened, precipitating a cyanotic episode. This happens when the pulmonary vascular resistance increases or the systemic resistance decreases. For example, if the child is physically exerting themselves they are generating a lot of carbon dioxide. Carbon dioxide is a vasodilator that causes systemic vasodilation and therefore reduces the systemic vascular resistance. Blood flow will choose the path of least resistance, so blood will be pumped from the right ventricle to the aorta rather than the pulmonary vessels, bypassing the lungs.
These episodes may be precipitated by waking, physical exertion or crying. The child will become irritable, cyanotic and short of breath. Severe spells can lead to reduced consciousness, seizures and potentially death
management of Tet spells
Older children may squat when a tet spell occurs. Younger children can be positioned with their knees to their chest. Squatting increases the systemic vascular resistance. This encourages blood to enter the pulmonary vessels.
Any medical management of a tet spell should involve an experienced paediatrician, as they can be potentially life threatening.
- Supplementary oxygen is essential in hypoxic children as hypoxia can be fatal.
- Beta blockers can relax the right ventricle and improve flow to the pulmonary vessels.
- IV fluids can increase pre-load, increasing the volume of blood flowing to the pulmonary vessels.
- Morphine can decrease respiratory drive, resulting in more effective breathing.
- Sodium bicarbonate can buffer any metabolic acidosis that occurs.
- Phenylephrine infusion can increase systemic vascular resistance.
investigations of ToF
- Echocardiogram best for establishing diagnosis
o With doppler flow study - X-ray- ‘boot shaped heart’
management of ToF
Management
- Neonates- prostaglandin infusion – maintain ductus arteriosus
- Definitive treatment: open heart surgery (5%)
- Poor prognosis without treatment
why does ductus arteriosus need to be maintained in ToF
will provide additional pulmonary blood flow and increase the child’s oxygen level.
Transposition of the great arteries background
- Basically the aorta leads from the right ventricle, instead of left and the pulmonary artery leads from the left ventricle
- Associated with
o Ventricular septal defect
o Coarctation of the aorta
o Pulmonary stenosis
Pathophysiology of transposition of the great arteries
- The aorticopulmonary septum forms, but does not spiral, therefore when the baby is born the aorta arises from the right ventricle, and the pulmonary trunk arises from the left ventricle
- The pulmonary and systemic circulation are almost separates, with only an ASD and PDA allowing some oxygenated blood to enter the systemic circulation
o Immediate survival depends on a shunt between systemic circulation and pulmonary circulation which allows blood flowing through the body an opportunity to get oxygenated in the lungs e.g. PDA or ASD or VSD
Presentation of Transposition of the great arteries
- Detected during pregnancy with antenatal USS
- Typical presentation
- Cyanosis at or within a few days or birth
- Initially a patent ductus arteriosus or ventricular septal defect can initially compensate by allowing blood to mix- however will develop resp distress, tachycardia, poor feeding, poor weight gain and sweating
Management of transposition of the great arteries
- This is a neonatal emergency and prostaglandins must be given to the baby quickly in order to maintain the PDA and allow some oxygenated blood into the systemic circulation until surgery can be performed
- Balloon septostomy
o Involves inserting a catheter into the foramen ovale via umbilicus and inflating a balloon creating a large atrial septable defect -> allows blood returning from the lungs (on the left side) to flow to the right side of the ehart and out through the aorta to the body - Definitive management: open heart surgery
o Cardiopulmonary bypass machine is used to perform an “arterial switch” procedure within a few days of birth
o If required VSD or ASD can be corrected at the same time
Management of transposition of the great arteries
- This is a neonatal emergency and prostaglandins must be given to the baby quickly in order to maintain the PDA and allow some oxygenated blood into the systemic circulation until surgery can be performed
- Balloon septostomy
o Involves inserting a catheter into the foramen ovale via umbilicus and inflating a balloon creating a large atrial septable defect -> allows blood returning from the lungs (on the left side) to flow to the right side of the ehart and out through the aorta to the body - Definitive management: open heart surgery
o Cardiopulmonary bypass machine is used to perform an “arterial switch” procedure within a few days of birth
o If required VSD or ASD can be corrected at the same time
Tricuspid atresia background
- The tricuspid valve fails to form
Pulmonary atresia background
- The pulmonary valve fails to form
univentricular heart
- The ventricular septum doesn’t form, so oxygenated and deoxygenated blood mixes in the ventricle, and gets pumped into both the aorta and pulmonary trunk
Hypoplastic left heart
- Mitral or aortic valve are stenosed in utero which means that less blood flows into the left ventricle- results in left ventricle being underdeveloped
- ASD allows blood to flow into the right side of the heart and be pumped to the pulmonary artery and a PDA allows this blood to enter the aorta from the left pulmonary artery
