About cardiomyopathy in children

Cardiomyopathy is a disease of the heart muscle. (‘Cardio’ means heart, ‘myo’ means muscle and ‘pathy’ means disease.) 

It isn’t a single condition but a group of conditions with different causes, that each affects the heart muscle. It can affect the shape of the heart, the size and thickness of the muscle walls, and how
messages are sent through the heart. This affects how the heart works, reducing its ability to pump blood around the body. How the heart is affected depends on the type of cardiomyopathy the person has.

To understand cardiomyopathy and how it affects the heart, it is helpful to know a little about the heart and how it works.

The heart: its structure and how it works

The heart is the centre of our circulatory system. It pumps blood around the body, carrying oxygen and energy sources to all cells and organs of the body to ‘power’ them so that they can work effectively. 

The heart is a powerful muscular pump. It has four chambers: two on the right side and two on the left side. These pairs of chambers are separated by a wall called the septum.

  • The two atria (top chambers) collect blood coming into the heart. The right receives blood coming from the body, and the left receives blood from the lungs. The walls of the atria are thin and elastic.
  • The two ventricles (bottom chambers) receive blood from the atria above. They pump the blood out of the heart: the right side pumps blood to the lungs, and the left side pumps blood to the body. The walls of the ventricles are thick and strong and can force the blood out of the heart as they contract. The left ventricle has the thickest wall, as it has to pump blood all around the body. It is the ventricles of the heart that are often affected by cardiomyopathy.
  • The heart also has four sets of valves, which help to ensure that blood flows in the right direction through the heart and that it doesn’t leak or flow backwards.

The heart pumps blood around the body by relaxing and contracting the muscle walls of the chambers. For the heart to pump, it relies on electrical messages to be created and relayed around the heart, in a regular, rhythmical and ordered way. This ensures that the different chambers of the heart contract and relax in order, which makes blood flow in the right direction: from the heart to the lungs to pick up oxygen, and back to the heart to be pumped to the rest of the body.

When a condition such as cardiomyopathy affects how well the heart works to pump blood around the body, this affects how much blood is delivered to the cells and organs. And it also affects how ‘waste’ products such as carbon dioxide and fluid are removed from the body. This can cause a number of symptoms such as tiredness, shortness of breath, a build up of fluid on the lungs or around the ankles, and heart rhythm disturbances. (See page 13 for more about symptoms). 

Read more about how the heart works.

Types of cardiomyopathy

The different types of cardiomyopathy are described by how they affect the heart muscle.

Dilated cardiomyopathy (DCM) – the muscle of the left ventricle becomes enlarged (dilated) and stretched. The muscle becomes bigger, thinner and weaker and less able to pump blood out of the heart. 

Hypertrophic cardiomyopathy (HCM) – the muscle of the ventricle thickens (called ‘hypertrophy’), making the ventricle smaller. The thickening of the muscle is not related to any increased workload on
the heart, but due to changes caused by the cardiomyopathy. If the thickening is in the septum (see page 5), it can affect the flow of blood out of the heart (called hypertrophic obstructive cardiomyopathy or ‘HOCM’).

Arrhythmogenic right ventricular cardiomyopathy (ARVC, also known as arrhythmic cardiomyopathy) – the heart muscle cells do not join together properly, and so they die and get replaced by scar tissue or
fat. This makes the heart muscle stretched, thinner and weaker, making it less able to pump blood out of the heart.

Restrictive cardiomyopathy (RCM) – the heart muscle becomes stiff and cannot relax properly, which makes it harder for the top chambers to fill with blood. The chambers then become enlarged
and blood cannot flow properly.

Left ventricular non-compaction (LVNC) – the heart muscle doesn’t develop normally in an unborn baby. The muscle cells do not compact (tightly pack) together as normal, which causes small indentations in the muscle and it appears spongy. This affects how the heart works.

Takotsubo or ‘broken heart’ syndrome – this rare cardiomyopathy usually happens during a time of extreme stress (which gives it the name ‘broken heart’). The left ventricle becomes enlarged and
weakened. It is often only temporary and gets better with time.

Although different types of cardiomyopathy affect the heart in different ways, the symptoms can be similar.

Who gets cardiomyopathy?

Cardiomyopathy can affect anyone, at any age. It is thought to affect around 160,000 people in the UK, which is around 1 in 500 people. Although many people are born with cardiomyopathy, the symptoms
may not develop until adulthood, and some people can have the condition and never develop symptoms.

Why has my child got cardiomyopathy?

There are many different causes of cardiomyopathy, and it may not always be possible to say why someone has developed it.

Cardiomyopathy is often a genetic condition. This means that it is
caused by a mutation (a change) in the person’s DNA which affects how the heart develops and how it works. Some mutations happen spontaneously as a baby is developing in the womb, and some are
passed on (inherited) from parent to child. As cardiomyopathy can be inherited, in some families several members will have the condition. For this reason, if someone’s cardiomyopathy is thought to be genetic, it is recommended that their close family members such as parents, siblings and children (known as first-degree relatives) are tested for the condition too.

Other causes of cardiomyopathy include:
• viral infections which affect the heart;
• autoimmune diseases (which affect the immune system); and
• some medications (including those used to treat cancer) or toxins (such as alcohol or drug use).

Doctors will ask questions about the persons own and their family’s medical history, as well as doing several tests, to try and work out why someone has cardiomyopathy.

©Cardiomyopathy UK. May 2017.