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What causes inherited cardiac conditions?

Inherited cardiomyopathy or arrhythmia is often caused by a fault or change in a specific gene. Genes control the production of proteins that have specific functions in the body, and how the body grows and develops. If a genetic change disrupts a protein which is important in the heart, this can lead to an inherited cardiac condition developing. We know that there are many genes associated with inherited heart conditions - a change in any one of those genes may be sufficient to cause the condition. 

How are cardiomyopathies and arrhythmias inherited?

Inherited cardiomyopathies and inherited arrhythmia syndromes are usually caused by a change in a single gene (‘monogenic’), which is enough on its own to cause the disorder. This is different to more common forms of heart disease such as coronary artery disease, which are caused by many different genes and are influenced by environmental factors such as diet and lifestyle.

Familial cardiomyopathies and arrhythmias are usually inherited from a parent, but can arise for the first time in an individual. When this happens there is no family history of the disorder, but the person in whom the disorder first occurs can pass it onto their children.

The pattern of inheritance for most cardiomyopathies and arrhythmias is autosomal dominant, which means that one copy of the gene fault, inherited from either parent, is enough to cause the condition.

The diagram on the left shows a family in which an inherited condition is passing in an autosomal dominant pattern.  Circles represent females, squares represent males.  Filled circles or squares represent people affected, male and female equally.  An unaffected person cannot pass the condition onto their children. 

Other patterns of inheritance can account for cardiomyopathies and arrhythmias but this is much less common.  More information about genetics can be found at www.geneticseducation.nhs.uk.