Prenatal diagnosis of congenital heart disease (CHD) during routine obstetric sonography has been aptly named the sonographer’s Achilles heel. Although CHD occurs more commonly than any other major congenital abnormality, the detection rate remains low. The goal of this study was to improve the prenatal diagnosis of CHD during routine obstetric sonography through the development and implementation of a simple and effective screening protocol.

Introduction Congenital heart disease (CHD) comprises a wide variety of abnormalities, from relatively benign ventricular septal defects to life-threatening complex malformations of the outflow tracts or the heart chambers. Cardiac abnormalities are the most common of all congenital malformations, with an incidence of 75 cases per 1000 live births.1 Despite improvements in treatment and surgical advances that have resulted in decreased mortality, CHD is still a major cause of death in infancy.2 Heart defects comprise one quarter to one third of all birth defects and are a large contributor to infant mortality.3 Not all forms of major CHD will be evident at birth or in the neonatal period.4,5 Even complex CHDs commonly go undetected until after the infant is discharged home, leading to avoidable morbidity and mortality.6,7 Kuehl et al.8 reported that during the first week of life, one quarter of deaths due to CHD occurs before the diagnosis of CHD is made, and occasionally the cardiac lesion is never recognized. Prenatal detection of CHD is beneficial as it may make it possible to improve preoperative conditions, postoperative survival, and neurological outcomes. It also allows for perinatal preparation for both families and care providers. Most major CHD cases can be detected prenatally in experienced hands.9,10 However, despite the wide use of prenatal ultrasound and the fact that screening for CHD has been well established for the past 25 years, the proportion of CHD cases diagnosed prenatally remains low.1,11–12 Many attempts have been made to address this shortcoming. In 1977, Lee et al.14 described the use of sonography to identify fetal cardiac structure. The literature since that time is replete with articles on the failure of prenatal sonographic screening for detection of CHD, with a reported detection rate that varies widely from 4.5% to 63%.15,16 Continuing education for the frontline screener has been suggested by many to be an effective means of improving detection rates; however, each article cites the expense of such a program as a limiting factor.17,18 The approach described in this study differed from others in that it focused the sonographer’s attention on the fundamentals of scanning to determine if a fetal heart was normal or abnormal. This study describes the process of creating a new fetal heart screening protocol that has been successfully implemented at the population level. Sonographers along with team members from three disciplines developed an educational intervention that was delivered to all sonographers in the province. The focus of the study was the development of a protocol that allows sonographers of every skill level to identify normal cardiac anatomy consistently and confidently. This approach of seeking 100% specificity in identifying a short target list of complex congenital cardiac abnormalities is not described in the literature to date.

Materials and Methods A-four part plan was devised to achieve the goals of the study: Development of a simple but highly focused fetal heart screen protocol to identify the critical anatomical markers that would enable the sonographer to decide if the heart was normal or abnormal. Creation of a checklist that sonographers were asked to use on every examination. A continuing education program that provided several educational events to teach sonographers how to follow the new protocol, which included education on how to perform outflow tract views. Initiation of a feedback loop to the original sonographer of both positive and negative findings. In 2004 a survey was sent to all obstetric sonographers in the province (16 sonography departments, including urban and rural hospitals, plus two fetal assessment units). Current practice relating to prenatal cardiac sonography was evaluated, including the views of the fetal heart obtained, the sonographer level of confidence in performing a cardiac screen, and the perceived success rate in obtaining these views. The survey asked sonographers about the proportion of cases in which they routinely evaluated the fetal heart by looking at the four-chamber view and if they included assessment of the outflow tracts. Information gathered in the survey indicated that less than half of the sonographers in Manitoba were routinely evaluating outflow tracts during their fetal heart screen. This information was used to create and deliver an educational intervention that focused on teaching sonographers how to evaluate outflow tracts and how to improve their evaluation of the four chambers. The education was geared toward the sonographers but also included all radiologists and obstetric perinatologists, with the anticipated outcome being a change in the practice of fetal heart screening across our province. The survey was readministered in 2007 following the educational intervention, which was delivered to all practicing sonographers in the province. Chi-square analysis (Fisher’s exact test) was used to test the difference in the distribution of cases receiving a complete evaluation (i.e., four-chamber view with outflow tracts) before and after the educational intervention. The intervention included instruction on the critical aspects of a fetal heart screen, the four-chamber view, and outflow tract evaluation. Sonographers were asked to use the developed guidelines when attempting the four-chamber view and to evaluate outflow tracts in all cases. The protocol included that each screen should include video clips of both views. The Bannatyne Campus Research Ethics Board of the University of Manitoba (the equivalent to the Institutional Review Board, or IRB, in the United States) granted ethical approval for this study prior to its initiation.

Results The pre-intervention survey indicated first that all participants (n = 52) wanted additional training in fetal heart screening. Second, all sonographers were performing an evaluation of the heart in a four-chamber view. However, only 61% (32/52) were routinely attempting to evaluate the outflow tracts, and these had limited success. If the outflow tracts were not seen, a follow-up examination was not automatically performed, and reports would state “fetal heart not well seen.” Considering that only 61% were attempting to evaluate the outflow tracts, coupled with the reported limited success in obtaining them, only approximately 25% of the fetal heart screenings performed included adequate four-chamber and outflow tract views. When asked why they did not perform outflow tract evaluation, 30% (16/52) stated that it was not required by the interpreting radiologist. Twenty-one percent responded that they did not know how to perform the outflow tract views. In 2007, 69 sonographers were working in the obstetrical field (an increase from the 52 in 2004) and all 69 returned the postintervention survey. All 69 of the sonographers were routinely performing an evaluation of the four-chamber view. It is worth noting that at this point, outflow tract views were attempted by all sonographers (69/69), and their success rate in obtaining them increased as well. At a majority of the sites, the obstetric examination was not considered complete until the outflow tracts were well seen. If necessary, the patient was asked to wait until the fetus changed position to be able to see the heart well, and at times, the patient was brought back another day. This was not done immediately at every hospital, but this change in practice slowly became the new standard of practice in Manitoba. All sonographers reported that their interpreting radiologist now requested outflow tract evaluation. No sonographer stated that they did not know how to perform the outflow tract evaluation. The results in Table 2 show that the distribution of cases on which sonographers reported performing outflow tract views improved significantly (P < .0001). Before the intervention, only 61% of sonographers attempted an outflow tract view, versus 100% after the intervention. (For the complete survey, see Appendix.) Table 2. Sonographer survey synopsis. View larger version

Discussion A sonographer in a small rural hospital and a clinical instructor in an urban tertiary care center started this project. Every education session was aimed at the average sonographer. With the guidance of a sonologist, the fetal heart screen was pared down to one that is highly focused to find the most critical heart abnormalities yet was obtainable by any sonographer in any setting. The learning curve for each sonographer took many months; however, once the technique was mastered, this added only minutes to each examination. Bricker et al.19 reported the time required to examine the fetal heart decreased as sonographers gained more experience and confidence. Focusing the fetal heart screen to key anatomical markers made the method attainable to all sonographers. By minimizing the diagnostic options to “normal or other,” sonographers were relieved from the burden of knowing a long list of pathologies. With time, sonographers became more comfortable with the screen, and the detection rate on all heart abnormalities increased. Our unpublished findings indicate that there was an increase in the detection of cardiac lesions outside the target group, such as Tetralogy of Fallot. This was a consequence of the increased level of competence with the screening method and the increased attention to the fetal heart. In some cases, it made the obstetric scan more efficient as sonographers realized the efficacy of looking at the fetal position first, to see if the heart could be seen well. Previously, many sonographers would leave the heart scan until the end of the exam when the fetal position might have been suboptimal for cardiac imaging. Examination of previous missed diagnoses with the pediatric cardiologist revealed that many of the abnormalities not diagnosed were CHDs that could have been identified on a four-chamber view. The same abnormality was picked up in some cases and missed in others. Comparison of these cases showed that in a remarkable number of “misses,” the fetal heart was examined when the fetus was in a position that made that evaluation less effective. Therefore, the decision was made to ask sonographers to wait until the fetus turned to a more optimal position before evaluating the heart. It was made clear to the sonographers the expectation was a screening protocol only, not a fetal echocardiogram. Sonographers were not taught the dozens of CHDs, focusing instead on the technical factors that contribute to a “good” fetal heart evaluation. Even with major improvements in case detection rates, this new process did not increase scan times or wait times. Furthermore, caseloads for both the Fetal Assessment Units (FAU) and the pediatric cardiologist were not increased. On the contrary, the lead cardiologist for the study confirmed that knowing about a fetal diagnosis in advance saved time and expedited the entire process from diagnosis to counseling and to any eventual referral to cardiac surgery.

Conclusion The sonographer’s role is vital in ensuring that no potentially fatal congenital heart lesion is missed. The four-step fetal heart screening protocol described in this study has been successfully implemented and well accepted among all sonographers in Manitoba, significantly improving prenatal cardiac screening of the population. This was accomplished at minimal expense, using resources already in place. Well over 95% of pregnant women undergo obstetric sonographic examination in the province, providing an opportunity for a fetal heart screen during the routine examination. Fetal echocardiography is performed on less than 1% of these pregnancies. Though a detailed fetal echo performed by a pediatric cardiologist would be the gold standard in prenatal diagnosis of CHD, our study indicates that a simplified, focused fetal heart screen can be effective and attainable by any sonographer, regardless of experience level, available equipment, and whether in a tertiary or community care center.

Appendix Sonographer Survey Section 1 1. Do you take a 4 chamber view of the heart? yes no

2. Do you take the views of the outflow tracts? yes no

Section 2 3. If you take the outflow tract views, in which percentage of second and third trimester obstetric cases do you successfully obtain them? < 25% 25–50% 50v75% 100%

4. Compared to your confidence in obtaining and assessing the 4 chamber view, how confident are you in your ability to obtain the outflow tracts? more confident same confidence slightly less confident less confident much less confident

5. Do you feel you would benefit from extra training to obtain the outflow tract views? yes no

Section 3 6. If you take no other views of the fetal heart other than the 4 chamber, what is the reason? not required by supervising physician equipment limitation time limitation do not know how to obtain the outflow tract views other _______________________________

7. Do you feel you need extra training to obtain the outflow tract views with confidence? yes no



Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Funding

The authors received no financial support for the research, authorship, and/or publication of this article.