The value of multiple 2D ultrasound scanning views in the detection of congenital heart disease in the second trimester (18 to 24 weeks)

Abstract

Introduction: Congenital Heart Disease (CHD) represents the most common type of congenital malformation in the fetus, yet the rate of antenatal detection of CHD is very low. Any improvement in antenatal detection would lead to better prenatal and postnatal care, and may significantly reduce neonatal morbidity and mortality of this condition. Antenatal detection of CHD may be improved by the introduction of additional scanning views to the anomaly 2-Dimensional (2D) ultrasound scan carried out routinely in Malta. The aim of this study was to explore this hypothesis by including additional views in routine local scans. Methods: The population sample included 600 randomly selected women of all ages in their second trimester (from 18 to 24 weeks), who had an elective appointment at the local general hospital (Mater Dei Hospital) for routine antenatal anomaly ultrasound scanning, during the period of July 2014 to June 2015. These women were scanned using (1) the conventional 4 chamber view (4CV), plus additional views, including (2) the left outflow tract, (3) the right outflow tract, (4) the 5-chamber view and (5) the 3-vessel view. The composite scan including a115 views was named the Extended Cardiac Ultrasound Examination (ExCUSE). All views were timed so that an idea of the increased scanning time when implementing these extra views could be garnered. The outcome of the study sample group of mothers that gave birth to neonates with or without CHD was followed up prospectively. The results obtained by the Basic and ExCUSE scanning were then confirmed or refuted clinically after the delivery of the infants. Validity testing, that is, sensitivity and specificity of the 4CV and the ExCUSE views was carried out. This was also done for each and every view to obtain extra information. Lastly, hypothesis testing was performed to confirm whether there was a significant difference between the detection rate of CHD by using the 4CV alone and the detection rate of CHD by ExCUSE scanning or not. Results: During the 12 month study period, that is, between July 2014 and June 2015, there were 61 cases of children of up to 1 year of age who were diagnosed with CHD by Paediatric Echocardiography, of which 19 were part of the study cohort of 600. Of these 19 patients, a diagnosis of some form or other of CHD was made by antenatal scanning in 12 cases, 1 via the 4CV alone, 4 by both the 4CV plus at least 1 of the ExCUSE views and 7 by 1 or more of the ExCUSE views alone (that is, where the 4CV was normal). Furthermore, on average, anomaly scanning that included the ExCUSE views took approximately 6 minutes longer to perform. Hypothesis Testing using the Chi-square test (specifically, McNemar's Test) was carried out and, consequently, the Null Hypothesis was rejected. This meant that there was a significant difference between the detection rate of CHD by the 4CV compared with the ExCUSE views. The sensitivity of the 4CV was found to be 31.6% and its specificity was calculated to be 100%, whilst the sensitivity and specificity of the ExCUSE views were found to be 63.1% and 100%, respectively. Conclusions: Recommendations based on these findings included: a protocol to standardise the approach to the diagnosis of CHD antenatally using additional views to the 4CV; recommendations regarding training in fetal heart scanning; recommendations regarding other and/or new techniques such as the use of Doppler, transvaginal (TV) scanning and 3-Dimensional (3D) Echocardiography; and recommendations regarding workloads that accommodate the increase in scanning time when scanning the fetal heart using the new protocol.