Center for Heart & Vascular Health

Hereditary Arrhythmias

Arrhythmias are disturbances in the heart's electrical system.

The heart has a specialized network that generates electrical signals, which tell the heart muscle when to squeeze and relax. A disturbance to these impulses disturbs the heart's rhythm, resulting in an arrhythmia. Abnormal heartbeats can result in heart palpitations, lightheadedness, dizziness, fainting and sometimes death.

Long QT syndrome (LQTS)

Long QT syndrome is a rare disorder in which the lower chambers of the heart beat so fast that the heart cannot pump the blood it needs for the brain to work normally. This is called ventricular tachycardia or ventricular fibrillation. Periods of arrhythmia can occur suddenly, leading to fainting or sometimes cardiac arrest and sudden death.

Long QT syndrome can be caused by a genetic alteration in one of at least 12 genes, or it can be acquired by exposure to some medications. Most heredtary forms of the disease occur in people who inherit only a single genetic variant from one of their parents. A second form, (Jervell and Lange-Nielsen syndrome) usually occurs at a younger age, and the symptoms are more severe. These children are usually born deaf and have LQTS because they inherit two genetic changes, one from each parent.

Brugada syndrome

Brugada syndrome is an inherited condition with a specific abnormal heartbeat, called a Brugada sign, which causes the lower ventricles of the heart to beat so fast that the blood cannot circulate well in the body. This irregular heart rhythm can cause fainting or sudden cardiac arrest.

Brugada syndrome is most common in people of Asian ancestry, and it is more likely found in males. It most commonly affects otherwise healthy people 30–50 years old, but cases have been reported in people as young as infants and as old as 84. Most cases are inherited from a parent who has Brugada syndrome.

Short QT syndrome (SQTS)

Short QT syndrome is a rare hereditary condition in which the heart muscle takes less time than usual to recharge between beats, indicated by a short QT wave on an electrocardiagram. If untreated, irregular heartbeats can lead to a spectrum of signs and symptoms, from dizziness and fainting to cardiac arrest and sudden death.

Short QT syndrome usually affects young, healthy people with no structural heart disease. It may occur as an isolated case, or it may be present in families.

The genetics of hereditary arrhythmias

The majority of genetic alterations or mutations responsible for causing hereditary arrhythmias are passed through a family in an autosomal dominant pattern, with the exception of one form of long QT syndrome. In autosomal dominant patterns, a mutated gene from only one parent is needed to pass on a disorder. Autosomal dominant disorders tend to occur in every generation of an affected family, with all of the children of a parent with the genetic alteration having a 50 percent chance of inheriting the alteration.

Familial Cardiovascular Risk Assessment Program
Center for Heart & Vascular Health
4755 Ogletown-Stanton Road, Newark, DE 19718 directions
302-623-4630