Short QT syndrome

Short QT syndrome is a condition that causes a disruption of the heart's normal rhythm (arrhythmia). In people with this condition, the heart (cardiac) muscle takes less time than usual to recharge between beats. If untreated, the irregular heartbeats can lead to a spectrum of signs and symptoms, from dizziness and fainting (syncope) to cardiac arrest and sudden death.

The signs and symptoms of short QT syndrome, including sudden death, can occur any time from early infancy to old age. This condition may explain some cases of sudden infant death syndrome (SIDS), which is a major cause of unexplained death in babies younger than one year. Other people with short QT syndrome never experience any health problems associated with the condition.

Fewer than 30 cases of short QT syndrome have been identified since this condition was discovered in 2000.

Mutations in the KCNH2, KCNJ2, and KCNQ1 genes cause short QT syndrome.

The KCNH2, KCNJ2, and KCNQ1 genes provide instructions for making proteins that act as channels across the cell membrane. These channels transport positively charged atoms (ions) of potassium into and out of cells. In cardiac muscle, these ion channels play critical roles in maintaining the heart's normal rhythm. Mutations in the KCNH2, KCNJ2, or KCNQ1 gene increase the activity of the channels, which changes the flow of potassium ions between cells. This disruption in ion transport alters the way the heart beats, leading to the abnormal heart rhythm characteristic of short QT syndrome.

Read more about the KCNH2, KCNJ2, and KCNQ1 genes.

Short QT syndrome appears to have an autosomal dominant pattern of inheritance, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Some affected individuals have a family history of heart problems and sudden cardiac death. Other cases are classified as sporadic and occur in people with no apparent history of short QT syndrome in their family.