This study on the detection of severe congenital heart defects in Norway in 2016 showed that 58 % of heart defects were discovered before birth. In 48 % of the children who received a postnatal diagnosis, the heart defect was detected during a routine examination. In 12 % of live births with no known heart defect, the condition was discovered only after discharge from hospital. Coarctation of the aorta was the most common diagnosis in cases of late-detected heart defects.
Routine ultrasound examination in pregnancy identifies many fetuses with heart defects. This enables the birth of children with severe heart defects to take place at centres with paediatric cardiology and cardiac surgery expertise, but it has also led to the termination of many pregnancies after the discovery of heart defects (3). New international guidelines for ultrasound examinations in 2013 included several different views as standard (18). This was shown in an American study to increase the detection rate from 44 % to 69 % (19). This national study confirms that the prenatal detection rate is comparable to previous findings from Norwegian regional centres and from other countries including Denmark (5, 6, 20), but the study is too small to be able to examine the impact of the new guidelines.
Since severe heart defects cannot always be diagnosed prenatally, some children will still be born with these conditions. For these children, rapid diagnosis and appropriate treatment are critical for a successful outcome. Many of the heart defects discovered postnatally were identified during a medical examination prior to discharge from the hospital maternity unit. This confirms the importance of routine paediatrician-led examination of all neonates, and argues against early discharge from maternity units. It is also important to emphasise the need for prompt clarification with an echocardiogram should the clinical examination raise suspicion of a heart defect.
Auscultation of a heart murmur was the most common clinical finding that indicated a heart defect. However, it is important to be aware that murmurs are often present in children without heart defects, and about half of all children with heart defects do not have murmurs (21).
Screening with pulse oximetry is a simple and inexpensive test that was introduced in Norway in 2013 (22), and which has been shown in several studies to be cost-effective (23). In the current study, 15 % of heart defects with postnatal diagnosis were identified as a result of pulse oximetry. Given that some of these heart defects would probably also have been detected by routine medical examinations, we do not know exactly to what extent this technique has reduced the number of children with missed diagnoses.
Pulse oximetry has low sensitivity for left-sided obstructions, particularly coarctation of the aorta where oxygen saturation is usually normal or near normal (14). In this study, coarctation was the most common unrecognised heart defect upon discharge from maternity units. In children with a narrow coarctation, the systemic circulation is dependent on a persistent arterial duct, with symptoms first arising when the duct closes. This usually happens during the first few days of life, but may occur after several weeks. In the event of a critical stenosis, the condition can be life-threatening with rapid development of severe metabolic acidosis, cardiogenic shock and cardiac arrest. Immediate diagnosis and treatment to maintain blood flow through the arterial duct is life-saving. Similar symptoms may emerge in other duct-dependent heart defects including critical aortic stenosis, hypoplastic left heart syndrome, transposition of the great arteries, and tricuspid or pulmonary atresia.
Some studies have shown that routine echocardiography of all neonates reduces the number of unrecognised severe heart defects, but the procedure is technically demanding and resource intensive, and has an approximately 5 % false positive rate (24, 25). Standard Norwegian practice is to reserve echocardiography for children with a prenatal diagnosis or findings in a routine examination, or where there is clinical suspicion of a heart defect. The current study did not examine the usefulness of echocardiography.
Our study encompasses a nationwide cohort of children with severe congenital heart defects, and includes both committee-handled abortions and live-born children, but the study also has several weaknesses. The study included only patients born in 2016, and the number of individuals was relatively small. Non-severe heart defects, which are probably more likely to be detected later in life, were not included. We did not have the opportunity to quality assure the data on the number of abortions of fetuses with heart defects. We also have no information on the type of heart defect or on any comorbidities in this group. Unfortunately, Norway does not have a national registry of patients with congenital heart defects. Although Oslo University Hospital has national responsibility for the treatment of severe congenital heart defects in children and adolescents, some patients may have been examined and treated by local hospitals without the involvement of Oslo University Hospital. These individuals will therefore not be included in this study.
In summary, this study shows that most children with severe congenital heart defects are diagnosed during prenatal ultrasound examination or routine examinations prior to discharge from the maternity unit. However, almost half of children with severe heart defects that were detected postnatally were diagnosed outside of routine examinations, either as a result of symptoms or as an incidental finding. In some children, especially those with coarctation of the aorta, the diagnosis was not made until after discharge from the hospital maternity unit. It is important to emphasise the need for immediate hospitalisation and rapid assessment by a paediatric cardiologist of young children with suspected severe heart defects. This study also shows that there is a need for continuous quality assurance of the methods for detecting heart defects. Establishing a national quality registry of congenital heart defects will be a vital part of this work.