Detection of congenital heart defects
A recent study on epidemiological data of the potential impact of technology on the diagnosis of congenital malformations demonstrated that mainly the diagnosis of cardiac malformations that were not preferentially present with overt symptoms increased in a 14-year period. The authors suggested that these findings might at least partially be explained by increased screening uptake (and intensity), resulting in improved diagnosis of milder cases of selected common malformations7. Although the detection rates of CHD have reportedly increased in national or community-wide regional programs in the last decade8-11, the sensitivity still ranges somewhat between 22.5 % and 52.8 %12. Local policies, parental sociodemographics, screening access, operator expertise and the type of CHD most likely account for the wide variability in the antenatal diagnosis of CHD13. However, the most striking issue is that the vast majority of CHDs actually occur in the population deemed to be at low risk, and only 10 % of fetal CHD cases occur in pregnancies with known risk factors, such as increased nuchal translucency, family history, or fetal extracardiac malformations14. The diagnosis of CHD in this collective clearly shows operator dependency and is directly correlated with the capability of recognizing that the appearance of the heart deviates from normal15. This may be related to what Sklansky & De Vore wrote in their 2016 commentary; i.e., future prenatal cardiac examination and ameliorated detection of altered cardiac anatomy should not only be based on the recommended views and imaging modalities but also on the quality of the clips and the angles at which they are acquired16.
A controversial debate exists on which set of cardiac scanning planes should be obtained to screen for CHD. As very recently published, the implementation of extended cardiac views beyond the four-chamber view (4CV) (as shown in figure 1) recommended by the 2014 Consensus Report guidelines for detailed anatomic ultrasound survey led to an increase in examination time and the frequency of both incomplete scans and the rate of repeat examinations17. Moreover, the authors stated that detection of CHDs did not improve in their cohort. Similar findings were reported by Sun et al., who could not register any significant change in both referrals and prenatal diagnoses of critical outflow tract anomalies despite revised obstetrical imaging guidelines18.
According to a Dutch study addressing the reasons why congenital heart defects are being missed during fetal life, the lack of adaptational skills appears to play an important role in undetected CHDs19. It may also require a logical approach to understanding congenital heart disease rather than an approach in which the various lesions are memorized20. A prerequisite for this is a standardized display of all cardiac diagnostic planes to capture crucial information on anatomical (spatial) arrangements that will dictate later functional characteristics of the heart.