Australian Doctor 12th July Issue 2024 | Page 24

24 HOW TO TREAT : IDENTIFYING HEART DISEASE IN CHILDHOOD

24 HOW TO TREAT : IDENTIFYING HEART DISEASE IN CHILDHOOD

12 JULY 2024 ausdoc . com . au
PAGE 22
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