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Antenatal cardiac screening

The 5 Transverse Views is a method for screening a baby's heart before birth.

To be effective, screening should be part of an integrated, managed screening programme that ensures health professionals are properly trained and experienced, equipment is correctly set-up and all referrals are audited (with feedback from referrals used to verify that audit and highlight any training issues).

Antenatal cardiac screening should aim to detect virtually all major cardiac anomalies (i.e. approx. 4 per 1,000).

The 5 Transverse Views - Basics

The routine 20-week ultrasound anomaly scan is ideal for picking up heart problems, yet detection rates are still relatively low on average across the UK (approx. 23% in 1999 and are now estimated to be around 30%).

One problem has been the lack of a consistent and practical standard for fetal cardiac screening.

1. What is the 5-view protocol?

The 5 Transverse Views is a systematic examination of the normal fetal heart using a series of 5 views, roughly transverse to the fetal chest

The "5-view" protocol is designed to detect (but not diagnose) almost all forms of fetal heart disease in a practical and timely way, at around 20 weeks gestation

If a heart is normal, then 5 normal views in a transverse plane should be seen.  Sometimes a view cannot be seen clearly due to limb artefact (shadowing), old equipment, probes or set-up, fetal lie or maternal factors

If a normal view is NOT seen, you should suspect an abnormality
(see 2. Cardiac anomalies - when to refer?)

More information:  the 5 View protocol in more detail, below

2. Cardiac anomalies - when to refer?
An abnormal view may be due to disproportion or structural or extra-cardiac anomalies, or multiple soft markers. 

Departmental protocols should tell you what to do if a normal view cannot be seen.

We recommend: (a) perform a manoeuvre to improve the view, if you do not have a good fetal lie;  (b) ask a colleague to help. 
After this, if a normal view still cannot be seen, consider referring the patient immediately for full fetal echo.

We do NOT recommend that you ask the patient to come back for a repeat scan 2 weeks later, as the view may still be obscure and the delay can be crucial.  Most referral centres would rather see a suspicious case, rather than miss an abnormality.

3. Is the "5 Views" a sweep or 5 discrete views?
It is a sweep and with training and practice, a sonographer will be able to establish fetal lie, find abdominal situs and perform a sweep that shows all 5 views.

The connections & relationships that are seen in a sweep are important, particularly for detecting abnormal connections or relationship.

The reason we call the protocol the "5 Views" is simply that it is difficult to describe a continuous sweep and much easier to break it down into 5 stages. 

Getting the correct "plane" of view is important.  Each view should be a cross-section so that the relative sizes of each vessel, are seen without distortion, so that real disproportion will be apparent.

4. How important is the 4-chamber view?
The 4-chamber view is still the most crucial view, as it takes into account the heart's size/position and examines in detail the chambers (for disproportion), walls & septum.  The "4-chamber" view will generally pick up about half of fetal cardiac anomalies.

However, just looking at the 4-chamber view can result in missing important problems such as Tetralogy of Fallot, "hidden" septal defects, Transposition of the Great Arteries (TGA) and arch defects such as Coarctation.

Some of these "outflow tract" heart conditions have excellent outcomes if detected antenatally.
Detection of Transposition of the Great Arteries in Fetuses Reduces Neonatal Morbidity and Mortality, Bonnet et al., Circulation. 1999;99:916-918

Historically, the 4-chamber view, which is the traditional method of screening for congenital heart disease at about 20-weeks, is about 15-20 years old.  At that time it was intended to revolutionise fetal heart screening and increase detection, but this did not happen - possibly due to the lack of suitable equipment at that time. 

Today, modern equipment is able to examine the tiny, fast moving structures of the fetal heart with greater clarity and it is time to go beyond the limitations of the 4-chamber view. 

In summary, the 4-chamber view has been used for 20 years as the prime means of detection, yet "widespread improvements in detection rates were not achieved."  Ref: R. Chaoui, The four chamber view, Ultrasound Obstet Gynecol 2003; 22:3-10 

5. Modern Equipment
There have been major advances in ultrasound technology in the last few years and there is little doubt that modern ultrasound equipment (less than 5 years old), with the right probes and fetal echo settings is superior to older equipment in achieving better quality images more swiftly.  The benefit of this is greater speed and accuracy, so that more patients can be screened more thoroughly and more quickly.

6. Colour Doppler (colour flow mapping)
This technique is useful for checking for reversal of flow through valves & in the arterial duct in View 5 (3 vessel view) and can assist the detection of subtle heart disease.  As soon as sonographers are imaging the 5 transverse views consistently, we recommend the use of colour flow mapping.

7. What can the "5 View" protocol miss?
Rare conditions associated with anomalous pulmonary vein connections (TAPVC) can still be missed, as they lie away from the heart. 
Subtle, mild or late-developing congenital heart disease can also be missed at 20-weeks.

The "needle in a haystack" problem:  most fetal heart scans will be normal (in about 99% of cases*), so it can be hard to maintain alertness for the relatively small number of cases that will occur randomly throughout a year. 

* At 20 weeks' gestation, congenital heart disease occurs in approximately 7 babies per 1,000 and it is more likely that half will have major CoHD, as there is a higher proportion of serious defects in fetal life compared to postnatal.

It is encouraging to remember the benefits of early detection both to doctors, parents and babies themselves.

8. Other, non-transverse views (& false negatives)
Non-transverse views are often used for diagnosis, but are not recommended for detection.  In some cases they may give a false negative.

An example is the Sagittal view of the Aortic Arch.  Whilst this view looks impressive, it can often give the impression that there is no coarctation, when a transverse view has shown significant disproportion.  In our experience, the transverse view is more trustworthy.

Is this your experience?  We would like to hear your views & experiences.

9. Early (11-14 week) scan
Nuchal Translucency, which can be elevated at this gestational age, is an effective way of determining babies at risk of Down syndrome, provided that gestational age has been correctly established.  Down syndrome in turn has associated cardiac anomalies.

However, most congenital heart disease occurs without aneuploidy and screening at 18-23 weeks' gestation is optimum, due to the relative size and development of the fetal heart.

10. Late (3rd trimester) scans
If a late scan is performed to check growth, we advise that the 5 views be imaged to look for late-developing congenital heart disease.  This does not take much time and many important conditions may been found.

11. Post-delivery scans
A post-delivery scan would also aid the detection of subtle or late developing heart disease, but this is rarely offered to parents and has the disadvantage that heart damage may already have occurred.

Link: Guidelines on Ultrasound Screening, 2008: what they mean for fetal heart screening

The "5-view" Protocol in more detail

Note:  This is a guide to the protocol and does not replace 'hands-on' training by an experienced Trainer.

Preparation:  Establish fetal lie - which way up is the baby & on which side?  This is very important in identifying isomerism, especially in View 1.

Imaging: Sweep up the fetal chest, establishing a normal image of each of the 5 transverse views and checking connections & relationships at the same time.  With experience you will be able to perform this sweep within a few minutes.

You may need to tilt the transducer slightly and move around each view to properly trace connections.

Is the heart normal?
At each view, try to establish normal images of:
1. normal abdominal situs (see picture on right)
2. a) normal 4-chamber (distant for size/position);   
    b) zoom in to examine chambers, walls & septum
3. normal aortic root/aorta
4. normal pulmonary artery
5. normal 3 vessel view

If you do not see a "normal" view when a baby is in a good position, you must suspect an anomaly.

Each view in detail

VIEW 1: Abdominal situs (see first picture above) An important and overlooked view, that checks the relative position of descending Aorta, spine, stomach, IVC & umbilical vein.	VIEW 2: 4-chamber The classic view where about 50% of heart defects will be found. (a) Distant view to check size & position of heart (cardio-thoracic ratio & apex) (b) Zoom in to examine chambers, walls & septum, tilting to spot 'hidden' VSDs or AVSDs.	VIEW 3: Aortic root (left outflow tract) The aortic valve & ventricles (assuming there is no Transposition)
		This image is just to illustrate Colour Doppler which can be applied in all views, but especially Views 2 and 5 where it can identify abnormal flow
VIEW 4: Pulmonary artery (right outflow tract) The main & branching pulmonary arteries, ascending (& descending) aorta	VIEW 5: 3 vessel view The ductal arch & transverse aortic arch.	VIEW 5+CFM: 3 vessel view with colour flow mapping (Colour Doppler) Colour Doppler can be used to check for reversal of flow etc.

Note:  If you spot an anomaly in one view, other views may have signs of the same anomaly, such as disproportion.

5 View Poster

Our A3 "fetal echo 5-view poster" illustrated the 5 transverse views* with ultrasound images and labelled diagram for each view.

Availability
About 2,000 copies of the poster were distributed in the UK, Europe and around the world.  A new poster is in planning, but until then we are making an electronic version available for download.

Cost?  The poster was free to registered UK sonographers and equivalent health professionals in Europe.  All posters were subject to availability.

Does this replace 'hands-on' training?
This poster is a useful reminder of the 5 view protocol, but it cannot replace the personal experience of 'hands-on' scanning.

Acknowledgements
Thanks to Siemens Medical Solutions UK (Ultrasound department) who helped to design, print and distribute the poster, A91100-M2430-C630-1-7600 (Siemens reference).  We also gratefully acknowledge the help of sonographers and mums who allowed us to scan them.

Further reading

The benefits of early detection of congenital heart disease (2001):  "There is now good evidence, based on prospective data, that the early recognition of cardiac malformations before birth can significantly alter the prevalence of complex congenital heart disease."
Source:  Hunter S., Cardiac ultrasound and congenital heart disease. Heart Dec. 2001; 86(Suppl II):ii1-ii2

"Reverberations" from UKAS
Our article on detection and intervention was featured in the Summer 2002 edition.  A further article on the 5 Views was published in late 2004.

"Ultrasound" from BMUS
August 2005 issue of BMUS Ultrasound featured the article: Antenatal detection of heart defects is important and achievable and was accompanied by our fetal heart scan CD, illustrating the normal fetal heart in 5 Transverse Views.

Follow-up article: Examination of the fetal heart – making a diagnosis and avoiding pitfalls (May 2007)

Also see ... Questions and Answers on our Fetal Heart Scan Training

Link to Guidelines: Guidelines on Ultrasound Screening, 2008: what they mean for fetal heart screening