Tiny reasons to expand heart scans

Mar 17 2008 by Our Correspondent, Western Mail

Hundreds of babies are born every year with often life-threatening heart defects, but conventional pregnancy scans do not detect many of these problems. Bryan Beattie, a Welsh consultant in fetal medicine, explains why new scanning techniques are needed

EVERY year more than 5,000 babies – one in 125 – are born with significant heart abnormalities. These are more common in newborn babies than Down’s Syndrome, which occurs in around 1 in 650 newborn babies.

Around half of babies born with such abnormalities will need urgent assessment and specialised care.

But cardiac abnormalities also account for one in 10 infant deaths and nearly half of all deaths from malformations.

This means that cardiac abnormalities are both important and common, yet most are not detected during routine checks in pregnancy.

In the UK the average pick up rate is around 30% meaning around two are missed for every one that is picked up.

Most women will have a dating scan at around 12 weeks to identify that the pregnancy is viable, the age and due date, the number of babies present and some major abnormalities. A Nuchal Translucency scan measures the amount of tissue fluid at the back of the baby’s neck and, combined with a blood test, can be used to screen for Down’s Syndrome.

But if the measurement is more than 3.5mm, there is also an increased risk of cardiac abnormalities in the baby.

Around a third of babies later found to have a cardiac abnormality will have had an increased NT measurement.

Pregnant women are offered a detailed anatomy scan at around 20 weeks to screen for abnormalities in the baby – including cardiac defects – but at this time the heart is still only the size of a pea and the detection rates are poor across the UK.

Many hospitals check only one view, the “four-chamber view”, which has been around for around 20 years and looks at the four main pumping chambers – the left and right atria and the left and right ventricles.

An increasing number perform three views by also checking the left and right outflow tracts – the right ventricular outflow tract, supplies blood through the pulmonary artery to the lungs (after birth), while the left ventricular outflow tract, supplies blood through the aorta to the upper body.

The four-chamber view is still the most crucial, as it takes into account the heart’s size and position and examines in detail the four pumping chambers, walls and septum. It will generally pick up around half of all fetal cardiac anomalies.

However, just looking at the four-chamber view can result in missing important problems, including holes in the midline wall. Tiny Tickers, the UK charity which aims to improve the detection of heart disease before birth and give these babies a better start in life, advocates that all pregnant women should be offered a five-view cardiac scan.

This scan uses a conventional ultrasound probe to systematically sweep through five main views of the heart to look for any abnormalities. It includes the four-chamber view and the two outflow tract views, but two additional views add important further information about the development of the heart.

It is also able to show the flow of blood through the heart valves and can check if the flow is excessive, reduced or if there is back flow through an abnormal valve. A new cardiac screening service is being developed at the Spire Cardiff Hospital, (formerly Bupa Cardiff), which will be the first of its kind in Wales. The service will offer a five-view cardiac scan at around 24 weeks.

For more information about the five-view cardiac scan or the Nuchal Translucency scan contact Helen Dando or Dilys Gale on 0845 2303386 or email innermostsecrets@hotmail.co.uk