Genetic testing for inherited heart disease.

M edical conditions that run in a family are inherited or genetic, meaning they are caused by changes in genes that are passed from generation to generation. Many different types of heart disease can be inherited. Some conditions like high blood pressure or coronary artery disease (blockages in the arteries that supply the heart with blood) run in families but probably result from a number of different genetic changes that individually have a subtle effect but work collectively in a complex manner to cause disease. In these situations, genetic testing is not yet available. There are other less common inherited heart diseases that are caused by just 1 or very few genetic changes that have a very strong effect in causing disease. These are called mono-genic conditions. In this Cardiology Patient Page, we describe our approach to monogenic inherited heart conditions and genetic testing. Examples include conditions that affect the heart muscle, called inherited cardiomyopa-thies, such as hypertrophic cardiomy-opathy, dilated cardiomyopathy, and arrhythmogenic right ventricular car-diomyopathy. There are also inherited heart conditions that affect the electric system of the heart, causing abnormal heart rhythms called arrhythmias. Examples of inherited arrhythmias include the long-QT syndrome and Brugada syndrome. Some of these conditions may require changes in lifestyle or medical therapy. All inherited heart diseases require special attention not only for the individual patient but also for their family to see if other relatives are in need of medical care. Genes are the basic units of inheritance and are made up of chemicals called DNA. Genes provide instructions for cells to make proteins that carry out all body functions and form our physical characteristics. We each have more than 20 000 genes, and each gene is present in 2 copies. One copy is inherited from your mother and 1 copy is inherited from your father. Genetic conditions are caused by a change (or mutation) in 1 or more genes passed from generation to generation. Most genetic heart conditions are inherited in an autosomal dominant pattern. Autosomal means that both men and women are equally affected. Dominant means that although there are 2 copies of each gene, a mutation in just 1 copy is enough to cause disease. Therefore, a person with an autosomal dominant condition has 1 normal copy of the gene and 1 copy with a mutation. The chance of passing the abnormal copy of the gene to a child is …