Australian Doctor 12th July Issue 2024 | Page 24

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the scapulae is very soft or

absent , particularly with the onset of cardiac failure . 25 , 27 The right-to-left shunt at duct level will manifest with a reduction in the oxygen saturation in the foot ( post-ductal , see figure 6 ) compared with the right hand ( preductal . A difference of less than 3 % is accepted as normal ; a difference of more than 3 % warrants further investigation . 5 , 6 Occasionally , unrecognised mild desaturation in both the pre-ductal and post-ductal readings may prompt a search for respiratory and / or other causes .

While false positives are reported as 14 out of 10,000 screenings , it is estimated that five out of six children with critical congenital heart disease may be detected . 6 Screening is especially important as it may prevent newborn infants being readmitted to hospital in a shocked state from a rapid closure of the ductus once they are home — as most infants are discharged within 48-72 hours of deliv-

Figure 3 . Hypoplastic left heart syndrome .

Centers for Disease Control and Prevention , National Center on Birth Defects and Developmental Disabilities

Centers for Disease Control and Prevention , National Center on Birth Defects and Developmental Disabilities

is unclear to the attending clinician . The murmur may be innocent and the rest of the cardiovascular examination normal . Parents do need to know that their child has a normal heart , so if the GP is unable to provide a clear answer , then a referral is warranted .

There is still debate about whether an echocardiogram is required once the attending cardiologist is confident of the diagnosis . A 2020 study suggested that , if the echocardiogram — a non-invasive and relatively inexpensive investigation — is shown to be normal , this further reassures the parent that the murmur is innocent and their child has a normal heart . 30 Occasionally , the echocardiogram may detect an abnormality not suspected by the clinical examination . 31 Echocardiograms done by standalone services need careful interpretation as an incidental finding of a patent foramen ovale , trivial or mild tricuspid or pulmonary incompetence may be normal findings in an infant or young

ery . A more gradual duct closure may

child and not the cause of the inno-

lead to the baby becoming unwell ,

cent murmur .

feeding poorly , developing tachyp-

A further confounding factor is

noea and being brought in for review .

that trivial or mild pulmonary or aortic

Pulse oximetry screening is a simple

valve stenosis or a small VSD may not

investigation that is already compul-

be readily detected on an echocardio-

sory in many states in the US and is

gram despite the presence of an ejec-

increasingly performed in Australia . 28

tion click and / or murmur . Note that a

Supraventricular tachycardia in the newborn

SVT diagnosed in utero allows for

congenital abnormality of the aortic valve even if minor , such as a bicuspid valve without a gradient , may be associated with an aortopathy , resulting

treatment to be instituted via medicating the mother . 22 However , SVT presenting in the newborn period or shortly after may be missed . SVT can lead to heart rates of 220-240bpm compared with a sinus tachycardia that may jump to 200bpm or more in a crying baby . If the SVT is self-terminating , the infant may appear

Madfolk67 / CC BY-SA : bit . ly / 3wQrgdp

in dilatation of the ascending aorta . 32 These patients require long-term surveillance .

Occasionally , murmurs that sound innocent may arise from an underlying cardiac abnormality . For example , the innocent vibratory or musical murmur of childhood may arise from trivial / mild subaortic stenosis or a soft

well . If the episode is prolonged ,

ejection systolic murmur in the pul-

that is lasting more than 12-24 hours ,

monary area commonly designated as

signs of congestive cardiac failure

an innocent physiological pulmonary

may develop . These include tachyp-

flow murmur may be due to increased

noea , the development of a large

flow across the pulmonary valve aris-

liver , slight pitting oedema over the

ing from a large ASD or unobstructed

dorsum of the foot or anterior to the

total anomalous pulmonary veins . 2

tibia , poor feeding and irritability . 29

The same may apply to a venous

If an ECG is done during an epi-

hum , where a continuous murmur is

sode , a regular narrow complex

heard at the upper-right sternal edge .

tachycardia is noted , typical of the

If heard elsewhere , consider the pos-

common re-entry SVT . However , if

sibility of a coronary artery fistula .

the arrhythmia reverts spontane-

Note that the presence of a scar may

ously , the diagnosis may not be con-

be related to the surgical insertion of

sidered . An interval ECG that shows

a modified aortopulmonary shunt as

pre-excitation suggests the possi-

required in an infant with pulmonary

bility of SVT . Most infants with SVT

atresia or a severe tetralogy of Fallot .

seemingly outgrow the problem , with only a third re-presenting in later childhood / adulthood .

Figure 4 . Twin-to-twin transfusion .

Any murmur presenting with additional cardiovascular signs ( see box 2 ) warrants referral .

DIAGNOSIS OF HEART DISEASE IN INFANCY AND CHILDHOOD

ROUTINE examination of an infant

at one month of age may detect murmurs related to communications between the systemic and pulmonary

Table 1 . Changes in pO2 in respiratory and cardiac conditions

Condition Room air 100 % oxygen

Respiratory cause

Transposition of the great vessels 28-30mmHg 30-32mmHg

Substantial rise of the pO2 to 150mmHg or more , reaching levels of 250mmHg

systolic murmur may be heard in the pulmonary area from increased flow across the pulmonary valve . 7 Suspect this diagnosis if there is wide splitting of the second heart sounds . A soft diastolic murmur from increased flow across the tricuspid valve might be difficult to hear .

Confounding features

PULMONARY HYPERTENSION A serious cardiac abnormality may occasionally be present with little or no murmur . This is especially so if the pulmonary vascular resistance fails to drop following the birth of the infant . As an example , some infants with Tri-

circulations , such as a VSD , PDA or an atrioventricular septal defect ( AVSD ).

It takes about a month for the PVR to fall to about half of the suprasystemic level before delivery and about six months to fall to less than a third of systemic vascular resistance . 3

The fall in pulmonary resistance allows for an increasing left-to-right

Right-to-left shunts arising , for example , from a severe tetralogy of Fallot

Obligatory mixing as occurs with an unobstructed total anomalous pulmonary venous drainage or a truncus arteriosus

35-40mmHg

75-80mmHg

45-50mmHg

120-130mmHg

As a general rule , stenotic lesions ( even if trivial or mild ) usually result in a murmur — for example , mild aortic or pulmonary stenosis . A murmur arising from incompetence of the mitral , tricuspid , aortic and , occasionally , pulmonary valve only becomes audible if there is at least mild , but probably moderate , regurgitation . 27

somy 21 remain relatively well with minimal tachypnoea and no murmurs but signs suggestive of pulmonary hypertension , which may be difficult to recognise in infants and young children . The infant ’ s heart rate is fast , with the second heart sounds summated into a single sound . Here , a louder summated second heart

shunt , depending on the size of the

Murmurs are also detected in

sound in the pulmonary area com-

communication .

the newborn . A murmur from an ASD

decreased compliance of the hypertro-

older infants and children when they

pared with the aortic area suggests

Turbulence related to the shunt

will take longer to manifest as the

phied RV in the newborn , which takes

present with an intercurrent illness ,

pulmonary hypertension . Occasion-

results in a murmur , although occa-

left-to-right shunt is at atrial level and

many months to atrophy following a

usually an URTI . The presence of a

ally , the summated second heart

sionally turbulence from a small mus-

occurs mainly during diastole . This

drop in the pulmonary arterial pres-

murmur that persists after the child is

sound or the second component of

cular VSD may result in a murmur in

shunt is limited to some extent by the

sures . Even then , only a soft ejection

well warrants referral if the diagnosis

the second heart sounds may be so