Long QT syndrome

Acquired long QT syndrome can be caused by certain medicines and medical conditions. Some medications that cause long QT syndrome include antihistamines and decongestants, antibiotics, antidepressants, and cholesterol-lowering medicines. Examples of medical conditions that can cause long QT syndrome include excessive diarrhea or vomiting and certain thyroid disorders.

Inherited forms of long QT syndrome are caused by changes in genes that control the heart muscle’s electrical activity. Inherited long QT syndrome may be isolated (occur alone without other associated symptoms) or be due to a genetic syndrome, such as Romano-Ward syndrome, Jervell Lang-Nielsen syndrome, Anderson-Tawil syndrome, and Timothy syndrome.

Genetic testing for many forms of long QT syndrome is now available in a clinical setting. We recommend that you speak to a genetics professional to learn more about your testing options. The Genetic Testing Registry (GTR) provides information about the labs that offer genetic testing for this condition. The intended audience for the GTR is health care providers and researchers. Patients with specific questions about a genetic test should contact a health care provider or a genetics professional.

Genetic testing is available for celiac disease. However, genetic testing is often not required for a diagnosis of this condition.

You can find information about labs that offer genetic testing for celiac disease through the Genetic Testing Registry (GTR). The intended audience for the GTR is health care providers and researchers. Therefore, people with specific questions about genetic testing for celiac disease should speak with their health care provider or a genetics professional.

Long QT syndrome is diagnosed on the basis of electrocardiographic (EKG) findings, clinical findings such as congenital deafness or unexplained fainting, and family history of long QT syndrome or sudden cardiac death. Genetic testing is often performed in families in whom the diagnosis of long QT syndrome has been made or is suspected on clinical grounds.

We encourage you to speak with a genetics professional regarding your personal and family history of long QT syndrome. This type of professional will need to review your and your family members medical records and genetic testing results in order to help address this question. In general, genetic testing for long QT syndrome can be very complicated because there are so many different gene mutations that can cause this syndrome. When undergoing genetic testing it is important to know which genes are being tested, what method (or laboratory technique) is being used, what the detection rate of the test is, and what kind of results you might expect to receive. If you are considering genetic testing it is important to work with healthcare professionals who can accurately interpret and communicate test results, particularly making clear the significance of both a positive and negative test result. Click here to learn more about genetic consultations.

To find a genetics clinic, we recommend that you contact your primary doctor for a referral. The following online resources can also help you find a genetics professional in your community:

• The National Society of Genetic Counselors provides a searchable directory of US and international genetic counseling services.
• The American College of Medical Genetics has a searchable database of US genetics clinics.
• The University of Kansas Medical Center provides a list of US and international genetic centers, clinics, and departments.
• The American Society of Human Genetics maintains a database of its members, which includes individuals who live outside of the United States. Visit the link to obtain a list of the geneticists in your country, some of whom may be researchers that do not provide medical care.

Common symptoms of celiac disease such as diarrhea and vomiting are known to temporarily result in long QT. However, we were not able to identify information in the medical literature that suggests that there is a direct association between celiac disease and long QT syndrome. We recommend you speak to your health care provider about your concerns.

There have been many studies conducted to determine the impact of stimulant medications for attention deficit disorder and attention deficit hyperactivity disorder on the QT interval as observed by an electrocardiogram (EKG). However, we were not able to identify information in the medical literature that suggests that there is a direct association between the incidence of attention deficit disorder and long QT syndrome in an individual. We recommend you speak to your health care provider about your concerns.

The Merck Manuals offers a detailed review article on Long QT syndrome. Click on Merck Manuals to view the article.

Identification and Treatment of Sudden Death Conditions in Young Patients. A presentation by David Bradley, M.D., Director, Pediatric Heart Rhythm Service, CS Mott Children's Hospital. Assoicate Professor, Department of Pediatrics and Communicable Diseases, University of Michigan.