Congenital Heart Defects

Overview and early presentation

Congenital heart defects/diseases (CHD) are common, occurring in about one in 100 newborns. Many types of CHD require prompt diagnosis and care, both medical and surgical, to improve survival and health. In some of the milder cases, CHD might resolve on its own (e.g. small ventricular septal defects) or require only regular
follow-up. At the other extreme are the critical CHDs, a heterogeneous group of structural heart anomalies that have in common the fact that, if undiagnosed and untreated, they can lead to a baby becoming very sick and dying in the newborn period.

Critical CHDs (CCHDs) include conditions such as hypoplastic left heart syndrome, in which the abnormally small left ventricle cannot support systemic circulation, leading to shock; and conditions such as tetralogy of Fallot or pulmonary atresia, which tend to cause visible cyanosis (bluish tinge on skin, especially notable in the fingers, toes, lips and nose). At times, newborns with CCHD can present a combination of cyanosis and heart failure or shock.

Prompt diagnosis is crucial, but can be challenging. A diagnosis of CCHD can be suspected in a newborn but requires the clinician to have a high level of suspicion, as the findings – often a sick infant getting worse – mimic other common conditions of the newborn, such as infection (e.g. sepsis) or lung disease (e.g. pneumonia).

• Often the baby appears fairly normal at birth, but gets worse in the next 24–72 hours, as the ductus arteriosus (a fetal structure that helps blood move between aorta and pulmonary artery) closes. An open ductus can help compensate some of the abnormal physiology in CCHD, and when it closes, the baby might decompensate quickly. This timing unfortunately means that in some cases an undiagnosed baby with a CCHD is discharged home, and may get very sick at home, without ready access to hospital care.
• In many types of CCHD, the blood oxygen saturation is low. When it is low enough, cyanosis appears. A pulse oximeter, a simple non-invasive instrument available in many nurseries, can measure oxygen saturation quickly and identify low levels even before cyanosis appears. A low oxygen saturation is seen in other
  conditions such as lung disease, but typically in CCHD, giving oxygen to the baby does not significantly improve the saturation (whereas it will in many cases of lung disease). Pulse oximetry is used in many places to perform newborn screening for CCHD; a specific protocol has to be used for best results.
• Auscultation is helpful. Many types of CCHD produce murmurs, but a murmur can be absent in some very severe CHDs, so the absence of a murmur does not exclude that the child has a CCHD.
• Palpation of peripheral pulses – including in the groin and feet – can provide clues to a diagnosis of coarctation of the aorta, in which pulses in the arms are palpable but those in the groin or feet (pedal pulses) are not.
• In general, the first diagnostic tool is clinician suspicion. Consider the possibility of critical CHDs in every sick newborn. All four pulses may be weak or absent in conditions where cardiac output is low, as can occur, for example, with hypoplastic left heart syndrome.

Babies suspected of having a clinically significant CHD in the newborn period require urgent follow-up with a clinician familiar with CHDs, ideally a paediatric cardiologist aided by appropriate imaging, typically an echocardiogram. In expert hands, an echocardiogram can quickly exclude a major CHD or provide a firm specific diagnosis. Such a diagnosis is extremely helpful for planning the care of the baby.