Understanding HLHS

Once you have been given a diagnosis, there are two schools of thought. One is that ignorance is bliss and finding out too many details about your baby's condition can cause you to spiral, while the second is that knowledge is power and the more you know the better you will be equipped for most eventualities.

A has openly acknowledged that the world of congenital heart defects ("chds") in babies is one he has, to this point, been completely oblivious about. Having a baby is such a complex and delicate matter that there are a million things that have to occur in perfect sequence to have a healthy child. Yet thousands and thousands of perfectly healthy babies are born each day and most people can take for granted how complicated a baby's development really is.

I've known about CHDs through personal experience as one of my closest friends was born with a CHD and had her first open heart surgery when she was 5 months old. Yet I still wasn't aware of just how complex heart defects in newborns can be.

So for all our friends and families who have ever been curious about our baby's diagnosis or just want to know a little bit more, I thought this post could help outline what we are facing.

Congenital Heart Defects

Congenital heart disease means a heart condition or defect that develops in the womb, before a baby is born. There are many different types of congenital heart disease. For example, a baby’s heart valves may not be properly formed or there may be holes between the chambers of their heart.

For many babies diagnosed with congenital heart disease, their condition is a minor problem which either doesn’t need any treatment, or can be successfully corrected with surgery. Other conditions are more serious and sadly, some children do not survive. However, thanks to advances in early diagnosis and treatment, most children will grow up to become adults and lead full and active lives.

Congenital Heart Defects kill more children each year than all childhood cancers combined. 1 in 100 babies born in the UK has a CHD. 

In most cases, something has gone wrong in the early development of the foetus. Some heart conditions are due to faulty genes or chromosomes. But often we don’t understand why the baby’s heart hasn’t developed normally. 

As a heart mum, you panic and wonder if it was that dodgy sandwich you ate or perhaps a too-hot bath you took, unsuspecting and without awareness. In fact I've been categorically told that HLHS has no known cause or environmental factor. It is just one of those things that can happen. 

The Normal Heart 

In order to understand what a complex heart condition means, it is helpful to understand what the normal heart does, so a little biology is in order here. 

The heart’s job is to pump blood around the body. There are two separate circulations; the first takes blood to the lungs (the right side of the heart), and the second takes blood to the body (the left side of the heart).

This is how the journey begins: blood returns from the body, via veins, to the right side of the heart into a collecting chamber called the right atrium. This blood has a bluish tinge (blue blood) because the body has extracted oxygen from it (deoxygenated blood).

The blood is then passed through a valve (Tricuspid) to a pumping chamber (Right Ventricle), which pumps the blood to the lungs via the lung arteries (Pulmonary Arteries).

The blood picks up oxygen as it passes through the lungs which turns the blood a red colour (oxygenated blood). This blood then returns to the left collecting chamber (Left Atrium) and it then passes through the Valve (Mitral) to the left pumping chamber (Left Ventricle). The Left Ventricle then pumps blood to the body through a Valve (Aortic) and to the body via the body artery (Aorta). The body uses the oxygen from the blood turning it blue again. And the journey starts again.

While a baby is in its mother's womb, the umbilical cord helps with its heart function by working in a special and wondrous way, enabling most babies with even complex CHDs to thrive and grow as normal. That explains all of our baby's kicking then!

Hypoplastic Left Heart Syndrome

Now we know what a normal heart should look and act like, a HLHS heart can be better explained. 

Hypoplastic Left Heart Syndrome is a congenital heart condition that is made up of a collection of problems on the left side of the heart. The pumping chamber (Left Ventricle) is small (Hypoplastic) and the Mitral and the Aortic valve may be narrow, blocked or not formed at all. The body artery (Aorta) is often small (Hypoplastic) and there is a hole (Atrial Septal Defect) between the two collecting chambers.

The blood’s journey through the heart is very different from normal. The blue (deoxygenated) blood flows into the right collecting chamber (Right Atrium), through the valve (Tricuspid) into the right pumping chamber (Right Ventricle). From there it is pumped up to the lungs where the blood receives oxygen. The red oxygen-filled blood then flows from the lungs into the collecting chamber (Left Atrium) in the left side of the heart, but it will be unable to then pass into the left pumping chamber (Left Ventricle). As the valve will be blocked, it therefore passes through the hole between the two collecting chambers into the right side, where it mixes with the blue blood and follows the normal path to the lungs.

Whilst the Ductus Arteriosus (a hole between the right and left sides of the heart that all babies are formed and born with) is still open, the blood will pass from the lung artery into the body artery and then around the body. When the duct closes, as it naturally does in normal babies within a few days after birth, the baby will no longer have oxygen flowing to their body. Without intervention, gradually they become sicker and die. 

Prognosis and the future

HLHS is one of the most complex and severe CHDs around. Around 1 in 5000 babies is born with this condition and it accounts for approximately 1% of all CHDs in babies.

Due to the severity of the condition, one of the most important things to understand is that HLHS is never going to be fully cured. There is no known cure yet- just a series of treatment options which may or may not prolong life.

Most children go through a series of three open heart surgeries over the first three years of their life. Even after all the surgery has been performed our baby's heart will not look normal or work normally, and it may be that it will gradually fail to function. If this occurs our doctors may suggest heart transplantation as the only possible final option. 

As the long-term outcome is unknown and some children’s conditions are extremely severe, it may not be possible or advisable to put the child forward for surgery. The baby would be allowed to die peacefully either in the hospital or at home; the family would be fully supported by the hospital and community care team.

Transplantation, in the case of non-correctable heart disease is offered in a few centers around the world. It involves replacing the malformed heart with a donated one. This again is a high-risk treatment and does not provide a cure. At present in Great Britain this would not be commonly offered as a treatment as there are very few baby size hearts available.

So far, all we know is that our baby has HLHS and that he will be assessed at birth to examine the condition in more detail and determine if he will be a candidate for surgery. If yes, the first open heart surgery will be carried out as soon as possible after birth and if not, our only other option is compassionate care until our baby will eventually lose heart function and pass away. 

The open heart surgeries themselves are very complex procedures and extremely risky with several post-surgical complications present which means the first few months of our baby's life are likely to be spent in hospital, in an ICU, even in the best possible case scenario. 

The hopeful news is that there are some young and inspiring children who have survived all three operations and for all intents and purposes are living healthy, comfortable lives into their late teens. The oldest known HLHS survivor in the UK is 18, as the Norwood procedure was first performed in the late 80s. Of course having HLHS means they will never truly be "normal" and will always have the threat of heart failure looming so special precautions are necessary for them, along with lifelong medication and appointments. 

Links for further information/support/research

If you or a family or friend find yourself in the position of needing to understand more about CHDs or HLHS, the best place to start is British Heart Foundation which has some really handy fact sheets and diagrams. For single ventricle conditions like HLHS specifically, there is a fantastic charity called Little Hearts Matter which offers support for parents who find themselves in a similar position to ours.

There are of course heaps more wonderful charities and organisations dedicated to every element of heart babies and parents, from helping you understand your initial ante natal diagnosis to caring for a child with a heart defect in a practical sense, but the above two are great places to start.

The work BHF do is particularly fantastic in the field of research. 30 years ago, a HLHS baby would never be able to live if it hadn't been for the constant medical developments so raising awareness and donating to the research is a fantastic way of getting involved.

A is running the Virgin London Marathon on behalf of the BHF and although I'll be getting him to do a guest heart dad post on the blog soon to discuss the marathon in a bit more detail, I'm shamelessly plugging his fundraising link here.