When the Heart's Electrical System Goes Haywire: The Congenital Long QT Syndrome. Ann Intern Med. 2002;137:I-43. doi: 10.7326/0003-4819-137-12-200212170-00005
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Published: Ann Intern Med. 2002;137(12):I-43.
The congenital long QT syndrome (LQT syndrome) is a rare inherited disorder of the heart's electrical system. It prolongs the time that the heart takes to electrically recharge after each heartbeat (known as the QT interval). The disorder is most often first detected during childhood or early adulthood.
Most patients never have symptoms of the disorder, but when they occur, symptoms include fainting, irregular heart rhythm, and sudden death; some people who die of the LQT syndrome have had no prior symptoms. In people with symptoms, half have a “cardiac event” by age 12 years; nearly all have one by age 40 years.
The LQT syndrome takes different forms depending on what inherited abnormality of the genetic material (gene) is present. Three forms of the syndrome are clinically important and are described in detail: LQT1, LQT2, and LQT3. Each has different symptoms and is diagnosed and treated differently. For example, in patients with LQT1, exercise and stress trigger cardiac events; in patients with LQT3, rest and sleep are triggers. In patients with LQT2, triggers include both rest and exercise, as well as loud noises, such as being awakened by an alarm clock. Since effective clinical management depends on the type of genetic abnormality, identifying the abnormality benefits the patients. If one family member has the LQT syndrome, all relatives should be tested since sudden death can occur in people with the gene abnormality, even if they don't have the disorder itself.
Advances in genetic research in the last 10 years have provided new information on this potentially deadly disorder. Discussion of the classification, symptoms, diagnosis, and treatment of different forms of the LQT syndrome may save many lives.
The authors searched the PubMed database (1966–2001) and their personal databases for research about the LQT syndrome. They used 152 articles to write their review.
Patients with symptoms require treatment. Patients with LQT1 and LQT2 typically benefit from drugs called β-blockers to prevent irregular heart rhythm. Some need surgical insertion of a pacemaker or defibrillator device. Beta-blockers don't seem to help patients with LQT3, but other drugs called sodium channel–blockers and pacemaker insertion may help. The need to treat patients with no symptoms remains controversial.
Researchers are developing specific treatments for each form of this sometimes life-threatening condition.
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Cardiology, Rhythm Disorders and Devices.
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