When the Heart's Electrical System Goes Haywire: The Congenital Long QT Syndrome

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The summary below is from the full report titled "Novel Insights in the Congenital Long QT Syndrome." It is in the 17 December 2002 issue of Annals of Internal Medicine (volume 138, pages 981-992). The authors are XHT Wehrens, MA Vos, PA Doevendans, and HJJ Wellens.

What is the problem and what is known about it so far?

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.

Why did the authors do this review?

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.

How did the authors do this review?

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.

What did the authors find?

Patients with symptoms require treatment. Patients with LQT1 and LQT2 typically benefit from drugs called ß-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.

What are the implications of this review?

Researchers are developing specific treatments for each form of this sometimes life-threatening condition.