Paediatrics chapters
Acyanotic congenital heart disease: VSD, PDA and ASD
The three common left-to-right shunts in children: how a VSD, PDA and ASD change blood flow, the murmur and second heart sound of each, the X-ray and ECG findings, when they close by themselves and when they need indomethacin, a device or surgery.
- VSD, PDA and ASD are left-to-right shunts: no cyanosis, but extra lung blood flow, heart failure in large defects and, if untreated, pulmonary hypertension and Eisenmenger syndrome.
- Murmurs: VSD harsh pansystolic at the lower left sternal edge; PDA continuous machinery murmur under the left clavicle with bounding pulses; ASD soft ejection murmur with wide fixed split S2.
- Many small VSDs close by themselves; a preterm PDA may close with indomethacin or ibuprofen; ASDs and persisting shunts need device or surgical closure.
On this page
Overview
Acyanotic heart lesions are of two kinds:
- Volume load (left-to-right shunts): VSD, PDA, ASD.
- Pressure load (outflow obstruction): pulmonary stenosis, aortic stenosis, coarctation of the aorta.
In a left-to-right shunt, oxygenated blood goes back to the lungs. The child is pink, but the lungs are flooded and the heart works harder. Large shunts cause heart failure in infancy; long-standing ones damage the lung vessels and cause pulmonary hypertension. When lung pressure exceeds systemic pressure, the shunt reverses and the child becomes blue: Eisenmenger syndrome.
In left-to-right shunts, the shunt grows after the first few weeks as pulmonary vascular resistance falls. That is why heart failure from a large VSD appears after some weeks, not at birth, and why the murmur may be missed on the first day.
Ventricular septal defect (VSD)
Basics
- The commonest congenital heart lesion: 25-30% of all CHD.
- Site: membranous (perimembranous) septum most often; muscular defects are next.
- Size: small or restrictive defects are under about 0.5 cm; moderate ones measure 0.5 to 1.0 cm; large or non-restrictive ones exceed 1.0 cm.
- An inlet VSD is part of the AV canal (endocardial cushion) defect, typical of Down syndrome.
Haemodynamics
- Blood goes from the high-pressure left ventricle to the right ventricle and lungs.
- Shunt size depends on the defect size and the ratio of pulmonary to systemic resistance.
- Extra blood returns to the left atrium and left ventricle, which dilate; with large defects both ventricles hypertrophy.
- Over time the lung arterioles thicken. If pulmonary resistance rises above systemic resistance, the shunt reverses (right to left), heart failure signs fade and cyanosis appears: Eisenmenger physiology.
Clinical features by size
| Feature | Small VSD | Moderate VSD | Large VSD |
|---|---|---|---|
| Symptoms | None; murmur found at routine check | Fast breathing, feeding problems, chest infections, poor growth | Heart failure from early infancy, sweating on feeds, failure to thrive, recurrent chest infections |
| Precordium | Normal | Thrill | Bulging precordium, apical thrust, thrill |
| S2 | Normal | Split, loud P2 | Loud P2, narrowly split |
| Murmur | Loud, harsh pansystolic at lower left sternal edge, often with a thrill | Loud pansystolic at left sternal edge | Pansystolic (softer, more blowing) plus apical mid-diastolic rumble from heavy flow across the mitral valve |
A loud murmur does not mean a big hole. A small VSD (maladie de Roger) gives a loud harsh murmur because of the high pressure gradient across it. In a large VSD with rising lung pressure, the murmur becomes softer.
Investigations
| Test | Small VSD | Large VSD |
|---|---|---|
| Chest X-ray | Normal or slight cardiomegaly | Cardiomegaly, plethoric lungs, enlarged left atrium and ventricle; with pulmonary hypertension the central pulmonary arteries enlarge and the peripheral ones prune |
| ECG | Normal | Biventricular hypertrophy; RVH dominates when pulmonary resistance is high |
| Echocardiography | Shows site and size of the defect; Doppler estimates pressures | Same |
Extreme left (superior) axis deviation with a VSD suggests an endocardial cushion (AV canal) defect, as in Down syndrome.
Management
Small VSD: reassure; normal life and normal activity. Many close by themselves.
Large VSD (medical): aims are to control heart failure and prevent pulmonary vascular disease. Use diuretics, digoxin and afterload reduction, with extra calories. If the infant does not respond, or pulmonary pressure rises, surgery should not be delayed.
Surgical indications:
- Heart failure not controlled by full medical treatment (repair, or pulmonary artery banding if repair is not possible, in the first year).
- Failure to thrive despite treatment.
- Rising pulmonary hypertension (repair is needed before 2 years to prevent irreversible lung vessel disease; infants of 6-12 months with rising pressure should be repaired).
- Child over 2 years with pulmonary flow more than twice systemic flow (Qp:Qs over 2:1).
- Supracristal VSD, associated pulmonary stenosis, or development of aortic regurgitation.
Repair is by patch closure at open-heart surgery.
Prognosis and complications
- 30-50% of small defects close spontaneously, mostly in the first year, and most of those that will close do so by 4 years.
- Complications: heart failure, recurrent chest infections, growth failure, infective endocarditis, pulmonary hypertension, Eisenmenger syndrome, aortic regurgitation.
Patent ductus arteriosus (PDA)
Basics
- The ductus joins the pulmonary artery to the descending aorta in the fetus. It closes functionally soon after birth (rising oxygen tension, falling prostaglandin E) and later anatomically by fibrosis, becoming the ligamentum arteriosum.
- About 10% of CHD; girls more than boys (2:1).
- Common in preterm and very low birth weight babies (especially with lung disease) and in congenital rubella.
- In a term baby, a duct still open after the first few weeks rarely closes by itself; in preterms, spontaneous closure is usual.
Pathophysiology
- After birth aortic pressure exceeds pulmonary pressure through both systole and diastole, so blood flows aorta to pulmonary artery continuously.
- Up to one half to two thirds of left ventricular output may go round the lungs and back to the left atrium and left ventricle, which enlarge.
- Diastolic run-off from the aorta lowers diastolic pressure: wide pulse pressure and bounding pulses.
Clinical features
- Small PDA: no symptoms; murmur only.
- Large PDA: heart failure, breathlessness on feeding, poor weight gain, repeated chest infections. Preterm babies may need more oxygen or fail to wean from the ventilator.
- Bounding (collapsing) pulses with a wide pulse pressure; heaving apex.
- Continuous "machinery" murmur in the second left intercostal space (under the left clavicle), with a thrill; loud P2.
- If pulmonary hypertension develops, the diastolic part of the murmur disappears.
Investigations
| Test | Finding |
|---|---|
| Chest X-ray | Normal if small; large duct gives cardiomegaly, left atrial and left ventricular enlargement and plethoric lungs |
| ECG | Normal if small; LVH or biventricular hypertrophy if large; RVH with pulmonary hypertension |
| Echocardiography | Shows the duct and the direction of flow; enlarged left heart chambers |
Management
Preterm infants (medical closure):
- Indomethacin or ibuprofen (prostaglandin synthesis inhibitors).
- Indomethacin 0.2 mg/kg IV per dose, 3 doses 8-12 hours apart.
- Indomethacin contraindications: creatinine above 1.7 mg/dL, thrombocytopenia, active renal or gut bleeding, NEC, sepsis.
Term infants and children:
- A persisting PDA should be closed at any age: small ducts to prevent endocarditis, larger ones to prevent heart failure and pulmonary vascular disease.
- Options: surgical ligation and division, or transcatheter device (coil or occluder) closure where available.
Indomethacin closes the duct; prostaglandin E1 keeps it open. Prostaglandin is used in duct-dependent lesions (TGA, pulmonary atresia, critical coarctation, hypoplastic left heart).
Complications and prognosis
- Complications: heart failure, infective endocarditis (endarteritis), pulmonary hypertension and Eisenmenger syndrome.
- A small PDA allows a near-normal life; spontaneous closure after infancy is very rare.
Atrial septal defect (ASD)
Types
| Type | Site | Notes |
|---|---|---|
| Ostium secundum | Middle of the septum (fossa ovalis) | Commonest; AV valves normal |
| Ostium primum | Low in the septum | Often a cleft mitral valve with regurgitation; part of the AV septal defect spectrum (Down syndrome) |
| Sinus venosus | High, near the SVC entry | Least common type; may come with anomalous pulmonary venous return (Nelson) |
A patent foramen ovale on its own is not counted as an ASD. ASD makes up about 10% of CHD.
Haemodynamics
- The right ventricle is more compliant than the left, so blood crosses from the left atrium to the right atrium.
- Extra flow passes through the tricuspid and pulmonary valves; the right atrium, right ventricle and pulmonary artery enlarge.
- In large defects lung flow is 2-4 times systemic flow.
Clinical features
- Secundum ASD is usually asymptomatic and found on routine examination; heart failure in childhood is rare. Older children may tire on exertion.
- Wide, fixed split S2: the right ventricle ejects extra volume, so P2 is late; the atria share pressure, so breathing does not change the split.
- Soft ejection systolic murmur at the upper left sternal edge, from extra flow across the pulmonary valve (not from the defect itself).
- Ostium primum may add an apical pansystolic murmur of mitral regurgitation, with effort intolerance and recurrent chest infections.
"ASD: A Split that Doesn't move": wide, fixed splitting of S2.
Investigations
| Test | Secundum ASD | Primum ASD |
|---|---|---|
| Chest X-ray | Enlarged right heart and pulmonary artery, plethoric lungs | Similar |
| ECG | Right axis deviation, partial RBBB, RVH | Left (superior) axis, partial RBBB |
| Echocardiography | Defect seen; enlarged right ventricle with paradoxical septal motion | Defect and cleft mitral valve |
Partial RBBB with right axis = secundum ASD; partial RBBB with left (superior) axis = primum ASD.
Management and outcomes
- Closure is advised for all symptomatic children and for asymptomatic ones with a shunt ratio of 2:1 or more, usually before starting school.
- Akbar describes closure at open-heart surgery. Nelson adds that many secundum defects can now be shut with a device in the catheter laboratory, while primum and sinus venosus defects need surgery.
- Surgical mortality is under 1%; long-term outlook is excellent after closure in childhood.
- Endocarditis prophylaxis is not needed for isolated secundum ASD, but is for primum defects with mitral regurgitation.
Other acyanotic lesions to recognise
| Lesion | Key clue |
|---|---|
| Coarctation of the aorta | Weak or delayed femoral pulses (radiofemoral delay); arm systolic pressure 20 mmHg or more above the legs; murmur over the back; rib notching and "figure 3" sign in older children; neonatal form presents in shock as the duct closes (treat with PGE1); linked to Turner syndrome |
| Aortic stenosis | Ejection systolic murmur at the right upper sternal edge radiating to the neck, ejection click; balloon valvuloplasty first; supravalvular type in Williams syndrome |
| Pulmonary stenosis | Ejection systolic murmur at the upper left sternal edge, soft P2 |
Murmur and S2 comparison
| Lesion | Murmur | Site | S2 | Pulses |
|---|---|---|---|---|
| VSD | Harsh pansystolic | Lower left sternal edge | Normal (small); loud P2 (large) | Normal |
| PDA | Continuous machinery | Second left space, under clavicle | Loud P2 | Bounding |
| ASD | Soft ejection systolic | Upper left sternal edge | Wide fixed split | Normal |
Expect: VSD as the commonest CHD and membranous as the commonest site; the harsh pansystolic murmur at the lower left sternal edge and why it may be missed in the first days; spontaneous closure of small VSDs; surgical indications (uncontrolled failure, rising pulmonary pressure before 2 years, Qp:Qs over 2:1, aortic regurgitation); the machinery murmur and bounding pulses of PDA, its link with prematurity and rubella, and indomethacin with its contraindications; wide fixed split S2 and partial RBBB in ASD with right axis for secundum and superior axis for primum; Eisenmenger reversal with cyanosis; rib notching and radiofemoral delay in coarctation.
Quick revision
- Left-to-right shunts: VSD, PDA, ASD; shunt grows as lung resistance falls after birth.
- VSD: 25-30% of CHD; harsh pansystolic LLSE; large VSD gives failure in early infancy and apical diastolic rumble.
- Small VSDs: 30-50% close, mostly in year 1. Repair large ones before 2 years if pulmonary pressure rises.
- PDA: machinery murmur, bounding pulses; preterm and rubella; indomethacin 0.2 mg/kg x3.
- ASD: secundum commonest; wide fixed split S2; partial RBBB; closure if Qp:Qs 2:1 or more, before school.
- Primum ASD / AV canal: superior axis, cleft mitral valve, Down syndrome.
- Eisenmenger: shunt reverses, cyanosis appears, failure signs fade.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).
FAQ
Why might a large VSD have no murmur on the first day of life?
Pulmonary resistance is still high at birth, so little blood crosses the defect; the murmur appears as resistance falls over the following weeks.
What makes the PDA murmur continuous?
Aortic pressure is higher than pulmonary pressure in both systole and diastole, so blood flows through the duct throughout the cardiac cycle.
Why is the second heart sound fixed in an ASD?
The two atria are joined, so breathing changes pressure in both together and the delay in pulmonary valve closure stays the same through the respiratory cycle.
What is Eisenmenger syndrome?
Long-standing high lung blood flow scars the lung arterioles until pulmonary pressure exceeds systemic pressure, the shunt reverses and the child becomes cyanosed; timely repair of large shunts aims to prevent this.