Circulation

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9 Circulation

Rahul Roy, Richard Beach, Graham Derrick

Introduction

Heart disease causes dread in parents and carers. This is usually because their experience of heart disease is in adults whose ischaemic heart disease causes chest pain, peripheral oedema or sudden death. In developed countries cardiac problems in children are usually congenital and present with heart murmur, breathlessness or cyanosis. Recent advances have made congenital heart disease an eminently treatable condition, and many children with murmurs have normal hearts and need no treatment at all. Do not forget when talking to families how frightening talk of heart problems will be.

History

Serious heart disease in children presents with poor growth, breathlessness, pallor or cyanosis. In babies this causes feeding problems – breaking off in mid-feed, with panting or ‘grunting’ respiration and sometimes sweating. Murmurs (e.g. ventricular septal defect, VSD) may not be evident at birth, but may be apparent by the time of the 8-week check. Older children with heart disease may lack energy and tire easily.

Ask about any episodes of cyanosis, pallor or distress. Check for a family history of cardiac problems in children. Reassure the family that the grandfather’s recent heart attack is unlikely to be relevant. Ask about any previous treatments or heart operations.

Examination

Make a non-threatening start by feeling the radial and then the brachial pulse. Remember that the pulse is faster in infants than in older children and adults. Some irregularity of the pulse (sinus arrhythmia) is normal in healthy children. The character of the pulse may be abnormal in aortic stenosis (low volume) or patent ductus arteriosus (PDA; collapsing or ‘bounding’ pulse). Palpating the femoral pulses feels intrusive to the child – leave it until the end, but do not forget to do it. Radiofemoral delay is not of use in paediatrics as most children are too small for the delay to be perceptible.

Ideally the examination can now proceed through inspection of the praecordium, palpation, auscultation and percussion, but in an active toddler you may need to grab opportunities to examine as they present. Remember that children who have had cardiac catheterization may have impalpable pulses and small scars in the groin or antecubital fossa over the femoral or brachial artery. Listen to the heart sounds at each of the four sites shown in Figure 9.1. At each site listen carefully for first and second heart sounds. In the pulmonary area it should be possible to hear the pulmonary and aortic components separately. An extra sound at the apex following the second sound is the third sound. This is usually physiological in children. In children with a cardiac failure there may be a gallop rhythm produced by third and fourth sounds. Finally, listen for heart murmurs. Try to decide where the murmur is best heard, how loud it is and whether it is a pansystolic (i.e. beginning with, and not separate from, the first heart sound) or an ejection systolic murmur. Diastolic murmurs are rare in childhood, but listen carefully all the same.

Figure 9.1 Auscultation points.

Blood pressure measurement is important in children, but is best left until last as it may be distressing. In infants, blood pressure can be measured using an automated blood pressure machine – palpation techniques are unreliable. In older children the blood pressure can be measured using a stethoscope in the normal way, but the correct size cuff must be used. The cuff should cover two-thirds of the length of the upper arm, and the bladder should encircle at least 80% of the arm. Centile charts for blood pressure are available in the UK. Blood pressure should be measured in the right arm in almost all circumstances, and both arms if there are thoracotomy scars.

The following scheme is recommended.

Inspection

• Central cyanosis – look at the tongue; measure oxygen saturation if in doubt

• Jugular venous pressure – the short neck and skin folds in infants only allow this examination in older children

• Look at the chest wall for operative scars – a left or right thoracotomy scar may be easily overlooked because the incision is posterior and can be hidden by the arms – lift the arms and look round to the scapula

• Before examination, plot growth on the chart as children with heart disease may fail to thrive, and measure the respiratory rate.

Palpation

• Examine the hands and look for:

• Finger clubbing – finger clubbing suggests chronic disease

• Splinter haemorrhages if there have been concerns about endocarditis – though in children these are as likely to be traumatic.

• The pulse – establish the rate, rhythm and nature of the pulse; in young children the brachial pulse is easier to identify than the radial pulse

• Feel for the apex beat

• Feel for thrills over the chest wall and over the right carotid. Thrills palpable in the sternal notch can be present in both aortic or pulmonary stenosis.

Investigations

A chest X-ray will allow assessment of cardiac size and pulmonary vasculature. An ECG may give information on the relative size of the cardiac chambers and on cardiac strain. Characteristic abnormalities are seen with some congenital heart defects, e.g. superior QRS axis and ostium primum atrial septal defect (ASD) or tricuspid atresia. Transcutaneous oxygen saturation, ideally in the right arm, will more reliably detect cyanosis. If saturation is less than 95%, in the absence of a sufficient alternative explanation, echocardiography is indicated. An echocardiogram allows accurate diagnosis of cardiac anatomy and a useful assessment of cardiac function. Cardiac catheterization accesses the heart through a catheter usually inserted into the femoral artery. This technique enables therapy, e.g. balloon atrial septostomy, to create an artificial ASD in transposition of the great vessels, as well as aiding diagnosis.

It is likely that motion-tolerant pulse oximetry of newborn infants will be introduced during the currency of this textbook, following the publication of a major trial in over 20 000 newborn infants, in November 2011, which demonstrated effectiveness in early detection of severe congenital heart disease. The UK National Screening Committee is currently considering its nationwide introduction.

Heart disease in infants

The neonate with a heart murmur

The circulation alters dramatically at the time of birth as the umbilical cord is cut and the lungs, rather than the placenta, become the source of oxygenated blood. Turbulent flow during these changes leads to transient murmurs in the neonate. A neonatal murmur may also be the first sign of significant congenital heart disease leading on to cyanosis or cardiac failure if undiagnosed. Check carefully for possible cardiac symptoms – see below. If the baby remains asymptomatic, and careful assessment discovers no abnormality, then a transient pulmonary flow murmur is likely. This will normally resolve within 48–72 hours of birth. An echocardiogram is essential if there is clinical uncertainty.

Changes in the circulation at birth (Figure 9.2)

1. The umbilical cord is clamped and cut, cutting off flow to and from the placenta.

2. The lungs become aerated and pressure in the pulmonary circulation drops.

3. Extra blood pours into the lungs as a result of this drop in pressure and returns via the pulmonary veins to the left atrium.

4. This changes the relative pressures in the left and right atria, and encloses the foramen ovale by a flap valve effect.

5. Normal lung function produces a marked rise in the oxygenation of the neonatal blood.

6. Muscles in the wall of the ductus arteriosus contract and lead to a physical, and later anatomical, closure of the duct.

7. The pulmonary pressure continues to drop over the first 1–2 months of life.

Figure 9.2 Changes in the circulation at birth. (a) The fetal circulation; (b) the newborn circulation.

Case 9.1

A baby with collapse (left ventricular outflow tract obstruction)

Edward, a 4-day-old baby, was discharged from the maternity unit after a normal routine examination, only to collapse within a few hours. He was rushed to the A&E department. He was pale and shocked with weak, thready brachial pulses, but no palpable femoral pulses. He was grunting with tachypnoea and marked respiratory distress.

The baby in Case 9.1 was urgently intubated and ventilated, and resuscitated with fluids – including saline and bicarbonate because of a severe metabolic acidosis. The differential diagnosis was thought to be overwhelming sepsis, congenital heart disease with cardiac failure or a metabolic disorder. In view of the impalpable femoral pulses, a prostaglandin E₂ infusion was commenced. Coarctation of the aorta was confirmed by echocardiography and Edward was transferred urgently to a children’s cardiac unit.

Left ventricular outflow tract obstruction may arise from hypoplastic left heart syndrome, critical aortic stenosis or, as in Case 9.1, coarctation of the aorta. The left ventricle fails to eject blood into the obstructed aorta, and the circulation is maintained by blood flow through the ductus arteriosus, bypassing the obstruction. When the ductus arteriosus closes, catastrophic collapse occurs, with pulmonary oedema, pallor, shock and acidosis. In hypoplastic left heart syndrome, children are born without an effective left ventricle and rely on the right ventricle to perfuse both lungs and systemic systems. Using prostaglandin E₂ to keep the ductus arteriosus open may sustain life until palliative surgery may be performed. There is practical and ethical debate as to the advisability of surgery for these children, as the prognosis remains guarded.

Case 9.2

A blue baby (congenital cyanotic heart disease)

Emma, a healthy term neonate, was noted to be cyanosed by her midwife at 6 hours of age. There was no breathlessness and the baby had taken a feed. On examination, there was a soft systolic murmur. Pulse oximetry showed an oxygen saturation of 66%. Oxygen administration did not improve this significantly. A diagnosis of probable cyanotic congenital heart disease was made, and a precautionary prostaglandin E₂ infusion commenced, pending echocardiography.

Children with neonatal cyanosis need an urgent diagnostic work-up (as in Case 9.2). If lung perfusion depends on a PDA, these children may deteriorate rapidly when the duct closes.

Transposition of the great vessels and tetralogy of Fallot account for over 90% of cases of cyanotic congenital heart disease. Transposition of the great vessels is the commonest cause of cyanotic congenital heart disease at birth.

In transposition of the great vessels, the left ventricle is connected to the pulmonary artery, feeding oxygenated blood back through the pulmonary artery to the lungs. The right ventricle returns deoxygenated blood to the aorta; thus there are two independent circulations. Common mixing through the ductus arteriosus or an associated VSD allows ingress of oxygenated blood into the systemic circulation. An arterial switch operation in the neonatal period is the treatment of choice.

In Fallot’s tetralogy the combination of a VSD and right ventricular outflow tract obstruction restricts blood flow to the lungs and leads to right ventricular hypertrophy, with a right to left shunt through the VSD producing cyanosis. The more severe the pulmonary stenosis, the earlier the presentation with cyanosis. Typically, cyanosis becomes evident at 3–6 months of age. Treatment requires surgery to close the VSD and relieve the right ventricular outflow tract obstruction by muscle resection, valvotomy and patch enlargement of the valve itself. This is normally undertaken in the first year of life.

Case 9.3

A breathless baby with failure to thrive (congenital acyanotic heart disease)

Adam, an 8-week-old infant, was failing to grow as expected. Feeding was becoming more difficult and he seemed pale, breathless and sweaty after feeds. Examination revealed tachycardia and tachypnoea even at rest. There was no cyanosis, but he had a loud pansystolic murmur, audible at the apex, with an overlying thrill. The liver was enlarged 3 cm below the costal margin, confirming cardiac failure. Echocardiography showed a large VSD.

Other more complex congenital heart lesions, such as tricuspid atresia, Ebstein’s anomaly, or pulmonary atresia, cause cyanosis by a combination of limiting pulmonary blood flow and common mixing of oxygenated and de-oxygenated blood. Surgical treatment may include creating a shunt between the arterial and pulmonary circuits to maintain lung perfusion. These shunts, if successful, will produce an audible, continuous murmur best heard over the surgical scar – a useful tip in an examination.

VSDs (such as in Case 9.3) are the commonest congenital heart defect. The communication between the ventricles leads to blood flow from the high-pressure left ventricle to the low-pressure right ventricle. Infants do not usually present in the neonatal period when the left and right pressures are similar, but, as the pulmonary artery pressure drops, pulmonary blood flow increases with resultant pulmonary hypertension and pulmonary oedema.

Cardiac failure is treated initially with diuretics. Some VSDs can get smaller or even close spontaneously with time and even large lesions may be treated medically in the first instance. Surgery is indicated if medical treatment fails, or if it is predicted that the VSD will not close because of its morphology. PDA is the other principal cause of left-to-right shunt, and may present in the same way.

PDA is especially common in premature infants, as the mechanism for duct closure is immature. In these babies increased pulmonary blood flow as a result of left-to-right shunting through the duct may complicate pre-existing lung disease and lead to ventilator dependence. Symptomatic preterm infants may be treated medically with indomethacin or ibuprofen, which inhibits prostaglandin synthesis leading to duct closure.

Heart disease in children

The older child with a heart murmur

Murmurs are often heard at routine checks before children go to school or while they are being examined during intercurrent illnesses.

The innocent murmur

Innocent ejection systolic murmurs are caused by turbulent blood flow within any part of the circulation. See Box 9.1 for the characteristics of innocent murmurs.

Box 9.1

Characteristics of innocent murmurs

• Asymptomatic

• Localized to the left sternal edge

• Postural – volume varies with sitting/standing (not invariably true)

• Short duration

• Soft in quality

• No radiation

• Otherwise normal examination with normal cardiac impulse and no palpable thrill

It may also be possible to hear turbulent flow in the venous return from the head and neck. This produces a continuous murmur usually heard under the clavicle, variable with respiration and position of the neck. These murmurs disappear when the child lies down.

With experience and a careful clinical examination it is possible to define an innocent murmur without the need for further investigation, but any murmur that does not obey these rules must be investigated.

Left-to-right shunts

Ventricular septal defects (VSDs) are due to defects in the septum separating the high-pressure left ventricle from the low-pressure right ventricle producing high flow if large or very turbulent flow if small. Large VSDs present in the neonatal period with heart failure as described above. Smaller lesions, which are not haemodynamically significant, may produce an impressive pansystolic murmur in an asymptomatic toddler or older child (‘Maladie de Roger’). The murmur is harsh, high pitched and often associated with a thrill. These may close spontaneously through childhood and no treatment is usually necessary.

Patent ductus arteriosus (PDA) is usually asymptomatic if it presents with a heart murmur in mid-childhood. The physical signs of PDA are only collapsing or ‘bounding’ pulses if the left-to-right shunt through the duct is large, because the blood ejected into the aorta rapidly runs through the PDA into the low-pressure pulmonary circulation. There is usually a continuous ‘machinery’ murmur under the left clavicle. This does not sound like a venous hum, being much louder, and does not go away when the child lies down. Treatment can be usually accomplished safely and effectively via cardiac catheterization.

Atrial septal defects (ASDs) are also asymptomatic in childhood but troublesome to adults if they are allowed to persist until the third or fourth decade, when atrial enlargement can precipitate atrial arrhythmias. There is a left-to-right shunt at atrial level but with relatively low flow due to the low-pressure gradient. The physical findings are subtle – the key sign is a palpaple right ventricular parasternal impulse and the wide and fixed splitting of the cardiac second heart sound heard over the pulmonary area. Otherwise the ejection systolic murmur could easily be confused with an innocent murmur – emphasizing the importance of listening to the heart sounds in children. An ostium primum ASD is a much more significant defect that requires surgery in early childhood, and may be associated with an apical pansystolic murmur in addition, from left atrioventricular valve incompetence.

Outflow tract obstruction

Coarctation of the aorta arises where the thoracic aorta is constricted at some point. It presents in the neonatal period if severe, or may present with a heart murmur alone, often heard over the back in the older child. Hypertension proximal to the coarctation may be observed. Poor femoral pulses, or a marked difference between the blood pressure in the upper and lower limbs, help to make the diagnosis. Coarctation may become more severe as time passes and may result in left ventricular failure. Treatment is surgical. Coarctation is very rare in girls, and may indicate Turner syndrome.

Aortic or pulmonary stenosis arises due to congenital narrowing of the atrioventricular valves, and produces ejection systolic murmurs. Aortic or pulmonary valve stenosis may also produce an ejection click – an additional sound after the first heart sound heard distant from the maximal intensity of the murmur, often at the apex of left lower sternal edge and before the onset of the murmur. Aortic stenosis murmurs are best heard in the aortic area, and may transmit to the neck. There is often a thrill over the murmur, and in the right carotid. Listen carefully for an early diastolic murmur indicating accompanying regurgitation. (It is best heard at the left sternal edge with the child sitting forward in full expiration.) The murmur of pulmonary stenosis is heard in the pulmonary area and radiates to the back. These conditions may present with symptoms in the neonatal period but more frequently turn up in mid-childhood. Monitoring is needed. Valves can be dilated with a balloon attached to a catheter. Open surgery and valve replacement are rarely needed in childhood.

Arrhythmias

Case 9.4

An infant with a rapid heart beat

Robin, an 8-month-old infant, presented with a sudden onset of pallor, altered consciousness and grunting respirations. On assessment, his pulse could not be easily palpated. Capillary refill was 6 seconds. On auscultation, the heart rate was extremely fast and on ECG was in excess of 250 beats per minute with narrow QRS complexes.

If the complexes on the ECG are narrow, as in Case 9.4, the arrhythmia is most likely to be a supraventricular tachycardia – the commonest pathological childhood arrhythmia. Broad complex tachycardia may be supraventricular or ventricular in origin. If the heart beats fast enough there is no time for refilling and the circulation fails, as in this case. It can occur at any age, including in utero, when treating the mother may control it. There is rarely a structural defect. Management is to restore sinus rhythm with vagal manoeuvres, medication or if necessary DC cardioversion (see Appendix I, p. 287).

Ninety per cent of children will have no further attacks after infancy, and preventative treatments may often be stopped after then. The main differential diagnosis is a symptomatic sinus tachycardia where the heart beats rapidly in response to shock, fever and severe systemic illness. Sinus tachycardia rarely exceeds 200 beats per minute, whereas supraventricular tachycardia usually exceeds 220 beats per minute.