Causes of congenital heart disease
Most are secondary to fault embryogenesis in weeks 3-8. Known causes include:
- Sporadic genetic abnormalities and most encode for transcription factors required for normal development.
- Trisomy 13, 15, 18 and 21 (Down's Syndrome).
- Congenital rubella
- Gestational diabetes
- Tetragenic drugs
Occurs when pressure in the right side of the heart increases to above the systemic circulation pressures, the blood is then shunted from the right (now high pressure) to the left (low pressure).
Left to right shunt
Oxygenated blood from left side of the heart mixes with deoxygenated blood from the right side of the heart.
Increased pulmonary blood flow/pressure (medial arterial hypertrophy and vascular consriction in the pulmonary vessels) that can lead to pulmonary HTN and HF.
Can result in Eisenmenger syndrome.
Right to left shunt
Also termed 'cyanotic congenital heart disease'.
Blood from the right side enters the left side, causing cyanosis due to diminished pulmonary blood flow and poorly oxygenated blood entering the system circulation.
Right to left shunt causes
Can occur in:
Tetralogy of the falllot
Transposition of the great arteries
Persistent ductus arteriosus (risk of paradoxical embolism, from the right circulation to the left).
Clinical symptoms of right to left shunt
- Finger clubbing
left to right shunt causes
Coarctation of the aorta
Narrowing of the aorta. M:F, 2:1, except more common in Turner's syndrome (XO). Accompanied by a biscupid aortic valve in 50% of cases. May be associated with a PDA.
Clinical manifestations of coarctation of the aorta
Depends on whether there is a PDA present.
Narrowing occurs after arch of aorta branches, asymptomatic until adult life, upper limb HTN, weak lower limb pulses. lower limb arterial insufficiency.
With a PDA
Narrowing occurs after the arch of aorta branches, then there is a PDA, present in early life with lower limb cyanosis.
Can occur at three levels:
- Valvular: valves may be hypoplastic/dysplasic/abnormal number of valves.
- Subaortic: subvalvular thickened ring or collar of dense endocardial tissue below the level of the cusps.
- Supravalvular: aortic wall is thickened causing luminal constriction
Obstructive congenital abnormalities
- Corctation of the aorta
- Pulmonary stenosis and atresia
- Aortic stenosis
Ventricular septal defect
30% isolated anomaly - rest in conjunction with another abnormality - small, may close spontaneusly (up to 50%). Large defects can have pulmonary HTN and right ventricular hypertrophy from birth.
Atrial septal defect
Differs to a patent foramen ovale which can cause a left to right shunt, usually isolated anomaly, may be asymptomatic until 30s then a risk of pulmonary HTN.
Patent ductus arteriosus
90% isolated anomaly. Murmur. Close early if possible. Remember the ductus arteriosus connects the pulmonary trunk to the aorta after the aortic arch branches.
Tetralogy of the fallot
- Aorta that overrides the VSD
- Subpulmonary stenosis
- Right ventricular hypertrophy
Malalignment of teh aorta and pulmonary artery with the ventricles. Severity depends on the subpulmonary stenosis.
Transposition of the great arteries
Separation of the systemic and pulmonary circulations as the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. Incompatible with postnatal life unless a shunt (ie ASD of VSD) exists. Needs fixing ASAP.
Persistent truncus arteriosus
Single great artery receives blood from both ventriles and gives rise to systemic, pulmonary and coronary circulations.