Long Qt Syndrome
Long Qt Syndrome and Prolong Qt Syndrome.
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Many females with RS live well into adulthood. However, sudden or unexplained, life-threatening complications may develop. Increased risk of sudden death may be due to abnormalities in the transmission of electrical impulses that coordinate contractions of the heart (cardiac conduction system). For example, studies have demonstrated that girls with RS may have significantly longer "corrected QT intervals" compared with other girls of the same age. The QT interval, as seen on an electrocardiogram, represents the time required for "recharging" of the heart's electrical system following each heart beat. Thus, in those with an elongated QT interval, sometimes referred to as "long QT syndrome," there is prolongation of the resting pause of the heart. Long QT syndrome may lead to irregular heart rhythms (arrhythmias), potentially resulting in a sudden loss of consciousness (or syncope) due to insufficient blood supply to the brain and sudden death. Evidence of longer corrected QT intervals in RS patients suggests that cardiac electrical instability or dysfunction may play some role in the sudden death that may sometimes occur in association with RS. In addition, in some RS patients, life-threatening complications may occur as a result of weakened lung function (e.g., due to pneumonia, scoliosis, etc.), malnutrition, or other associated abnormalities.
THE LONG QT SYNDROME Thanks for visiting the IHC web site on long QT syndrome. We hope this information will be of assistance to you. The following pamphlet is prepared from information developed by the SADS Foundation. The material was updated on November 18, 1996. If you require more material, please call the Foundation and request additional information. Sudden Arrhythmia Death Syndromes Foundation 540 Arapeen Drive, Suite 207 Salt Lake City Utah, 84108 (800) STOP SAD Fax: (801) 582-1941 http://www.sads.org
WHAT IS THE LONG QT SYNDROME?
The Long QT Syndrome (LQTS) is an abnormality of the heart electrical system. The mechanical function of the heart is entirely normal. The electrical problem is due to defects in heart muscle cell structures called ion channels.These electrical defects predispose affected persons to a very fast heart rhythm (arrhythmia) called torsade de pointes which leads to sudden loss of consciousness (syncope) and may cause sudden cardiac death. The QT refers to an interval measured on the electrocardiogram (ECG). The syndrome may be inherited (the genetic form) or acquired. The SADS Foundation is especially concerned with the inherited form. INHERITED: The inherited Long QT Syndrome was first clearly described in 1957. There are two variants, the autosomal dominant Romano-Ward type and the autosomal recessive Jervell, Lange-Nielsen type. Even though LQTS was described almost 40 years ago, the syndrome is still not a well known or recognized entity. ACQUIRED: Acquired LQT is most often due to the administration of medications. These medications are contraindicated in patients with the Long QT Syndrome, and a subsequent section will identify these drugs.
HOW COMMON IS INHERITED LQTS? The frequency is unknown but it appears to be a common cause of sudden and unexplained death in children and young adults. It is certainly much more common than previously thought. It may be as frequent as 1 in 5,000, and may cause 3,000-4,000 sudden deaths in children and young adults each year in the United States. The Jervell, Lange-Nielsen form is associated with congenital deafness and is rare, but the Romano-Ward variant, with normal hearing, is being recognized with increasing frequency.
WHAT ARE THE SYMPTOMS? The usual symptoms are syncope (sudden loss of consciousness) or sudden death, typically occurring during physical activity or emotional upset. These most commonly begin in pre-teen to teen-age years, but may present from a few days of age to middle age. The syncopal episodes are often misdiagnosed as the common faint (vasovagal event) or a seizure. Actual seizures are uncommon in long QT syndrome. Sudden loss of consciousness during physical exertion or during emotional excitement should strongly raise the possibility of the Long QT Syndrome. A family history of unexplained syncope or sudden death in young people should also raise suspicion. Importantly, about one third of individuals who have the Long QT Syndrome never exhibit symptoms, and therefore, the lack of symptoms does not exclude a person or family from having LQTS. Any young person that has an unexplained cardiac arrest should be considered for LQTS,as well as those with unexplained syncope.
WHAT CAUSES THE SYMPTOMS? Patients with long QT syndrome develop a very fast heart rhythm disturbance known as 'Torsade de pointes'. This is a form of ventricular tachycardia. This rhythm is too fast for the heart to beat effectively, so the blood flow to the brain falls precipitously causing the sudden loss of consciousness. In most instances, there is no warning prior to syncope.
COMMON TRIGGERS AND CONSEQUENCES OF THE ARRHYTHMIAS TRIGGERS
Swimming, running Startle:
An alarm clock, a loud horn,
a ringing phone Anger, crying,
test taking or other stressful situations.
Sudden death may occur during sleep CONSEQUENCES Car accidents Apparent drowning Dizziness or near fainting after exercise or sports
HOW IS THE SYNDROME DIAGNOSED? The diagnosis is commonly suspected or made from the ECG. All children and young adults should have an ECG as part of their evaluation for an unexplained loss of consciousness episode. Sometimes no testing, or only neurological testing with an electroencephalogram (EEG) is done. If necessary, therefore, request that an ECG be done and specifically evaluated for QT prolongation. In about 10% of LQTS patients the QT interval on the initial ECG is normal, and in another 30% the QT interval is only borderline prolonged, not prolonged enough to clearly make the diagnosis. In these cases, an exercise ECG will usually assist in clarifying the diagnosis. The exercise test is preferably a low level, somewhat protracted exercise test, which allows the individual to exercise for 10 or more minutes without reaching a heart rate much in excess of 150-160 beats per minute. This prevents the T wave from merging with the P wave in normal subjects and simplifies the measurement of the QT interval. The principle abnormality to be identified is a prolonged QT interval relative to the heart rate, determined by an increase in the calculated QTc interval, and the appearance of bifidT-waves.
HOW IS THE SYNDROME INHERITED? It is commonly inherited by autosomal dominant transmission. This means that it affects boys and girls equally, and that each child of an affected parent has a 50% chance of inheriting the gene. In a large family approximately 50% of the children would inherit the gene. In usual size families it can range from all to none as each child has an independent 50/50 chance of inheriting the gene. It is extremely important that all family members be tested for the syndrome once a family member is identified as a Long QT Syndrome patient. The testing should include the parents, all siblings, any children of the affected individual, and all relatives of the affected parent. It is extremely important that all patients be identified early in order to prevent the tragic and unnecessary sudden deaths that may occur. Please see the legend at the bottom of this pedigree for interpretation of this figure. In this family pedigree, a young male (arrow) died on the basketball court. Afterwards, his sister was found to have the Long QT Syndrome. Family evaluation revealed 7 additional affected members (one deceased). One of the great grandparents (generation I) had to be a gene carrier. The pedigree should be even further expanded by identifying the brothers and sisters of the affected great-grandparent and his/her offspring. Screening of these individuals would likely reveal many more members with LQTS. This example of a typical family with LQTS demonstrates the importance of pedigree expansion and family screening.
MOLECULAR GENETICS OF THE LONG QT SYNDROME Little is known about the Jervell, Lange-Nielsen form. It is rare and there have been no reports yet on any genes for this form. In the Romano-Ward form, four genes have been found, KVLQT1, on chromosome 11 (LQT1), HERG on chromosome 7 (LQT2), SCN5A on chromosome 3 (LQT3), and Min K on chromosome 21 (LQT5), which interacts with KVLQT1 to produce long QT syndrome. Another gene is known to be located on chromosome 4 (LQT4), but the gene has not yet been identified. Probably other genes exist in addition to these. The symptoms, signs and treatment of the disease vary somewhat depending on the gene involved. Genetic testing will become available for diagnosis of the Long QT Syndrome sometime in the future. It is available now on a limited basis in certain research laboratories, and it takes a number of months at the quickest to get back the results. Fortunately, in most cases the diagnosis can be accurately made in the absence of the genetic tests.When all the genes are identified, genetic testing will become the standard test and will markedly improve the ability to make the correct diagnosis in those patients with atypical symptoms or borderline QT intervals.
WHAT IS THE TREATMENT? Beta blocker medications are the mainstay of therapy for most patients with the Long QT Syndrome. These medications are effective in about 90% of affected subjects. New information regarding the genetics of the syndrome suggests that a subset of patients might be treated with other drugs, either instead of or in addition to the beta blocker medications. This can be discussed with your physician and it depends upon the gene type which you have. In patients who do not respond to medication, the insertion of a pacemaker or the automatic defibrillator, or the surgical cutting of certain nerves in the neck, called cervico-thoracic sympathectomy, can be utilized. All patients with symptoms should be treated, and because it is not possible to predict which patients are vulnerable to the syncope and sudden death, and sudden death often occurs with the first episode, asymptomatic patients, especially children, should also be treated.
SHOULD ACTIVITY BE RESTRICTED? Since the symptoms are often precipitated by physical exertion or emotional upset, it is appropriate to restrict physical activity in symptomatic individuals and reasonable even in those without symptoms. For most individuals, this only requires refraining from competitive and vigorous sports. Recreational activities are often allowable . The "buddy system" is a wise strategy for Long QT patients. In individuals with continued symptoms, further restriction of activity may be necessary.
WHAT ABOUT PREGNANCY & SURGERY? Although labor and delivery and surgical procedures are stressful and physically exacting events, it is uncommon for Long QT Syndrome patients to experience symptoms during these times. It is important to be sure that the blood potassium is maintained. It may be reduced if diuretic (water) medications are used or if there is sweating, vomiting or diarrhea, and potassium supplementation may be necessary during these times.
OTHER RESOURCES SADS SCIENTIFIC ADVISORY COMMITTEE In addition to the SADS office, Scientific Committee members can assist with care, questions and referrals. Peter J. Schwartz, M.D.Chair, Scientific Committee Milan, Italy William J. Mandel, M.D Los Angeles, California Jeffrey L. Anderson, M.D. Salt Lake City, Utah Arthur J. Moss, M.D. Rochester, New York Charles Antzelevitch, Ph.D. Utica, New York Dan M. Roden, M.D. Nashville, Tennessee Richard S. Crampton, M.D. Charlottesville, Virginia Jeffrey A. Towbin, M.D. Houston, Texas Arthur Garson, Jr., M.D. Houston, Texas Dan Tzivoni, M.D. Jerusalem, Israel Kunitake Hashiba, M.D. Nagasaki, Japan Victoria L. Vetter, M.D. Philadelphia, Pennsylvania Mark T. Keating, M.D. Salt Lake City, Utah Raymond L. Woosley, M.D. Washington, D.C. Thomas S. Klitzner, M.D. Los Angeles, California INTERNATIONAL LONG QT SYNDROME REGISTRY We encourage those with LQTS to enroll in the Long QT Syndrome Registry for research purposes. LQTS REGISTRY University of Rochester Medical Center P.O. Box 653 Rochester, NY 14642-8653 TEL: 716-275-5391 FAX: 716-473-2751 Director: Arthur J. Moss, MD Study Coordinator: Jennifer Robinson, MS FURTHER INFORMATION ABOUT LQTS Moss AJ, Schwartz PJ, Crampton RS, Tzivoni D, Locati EH, MacCluer J, Hall WJ, Weitkamp L, Vincent GM, Garson A, Robinson JL, Benhorin J, Choi S. The long QT syndrome: prospective longitudinal study of 328 families. Circulation. 1991:84:1136-1144. Schwartz JP, Moss AJ, Vincent GM, Crampton RS. Diagnostic criteria for the long QT syndrome: An update. Circulation. 1993;88:782-784. Vincent GM, Timothy KW, Leppert M, Keating M: The spectrum of symptoms and QT intervals in carriers of the gene for the long QT syndrome. New England Journal of Medicine. 1992;327:846-852
DRUGS TO AVOID There are a number of drugs which are known to prolong the QT interval and to cause heart rhythm abnormalities, particularly in patients with the Long QT Syndrome. You should always inquire of your physician or other health care provider about the risk of any medication suggested or prescribed for you. Always inform them of your Long QT Syndrome and make sure they know there are many medications which are contraindicated in this condition. The Foundation will be happy to provide you and your physician with a list of medications to be avoided.
This list is also contained in our newsletter, for additional reference, and is updated on a regular basis.
Drug name Chemical name General use ANESTHETICS / ASTHMA Adrenaline Epinephrine Local anesthetics, or as an asthma medication ANTIHISTAMINES Seldane Hismanal Benadryl Terfenadine Astemizole Diphenhydramine allergies allergies allergies ANTIBIOTICS E-Mycin, EES,EryPeds, PCE etc. Bactrim, Septra Pentam intravenous Erythromycin Trimethoprim & Sulfamethoxazole Pentamidine Infections: lung, ear throat Infections: urinary, ear, lung Lung infections HEART MEDICATIONS Quinidine, Quinidex, Duraquin, Quiniqlute, etc. Pronestyl Norpace Betapace Lorelco Vascor Quinidine Procainamide Disopyramide Sotalol Probucol Bepridil Heart rhythm abnormalities Heart rhythm abnormalities Heart rhythm abnormalities Heart rhythm abnormalities High triglycerides, cholesterol Chest pain (angina) GASTROINTESTINAL Propulsid Cisapride For esophageal reflux, acid ANTIFUNGAL DRUGS Nizoral Diflucan Sporanox Ketoconazole Fluconazole Itraconazole Fungal infections Fungal infections Fungal infections PSYCHOTROPIC DRUGS Elavil, Norpramine, Viractil Compazine, Stelazine, Thorazine Mellaril,Etrafon, Trilafon, others Haldol Risperdal ORAP Amitriptyline (Tricyclics) Phenothiazine derivatives Haloperidol Risperidone Pimozide Depression Mental disorders Mental disorders Mental disorders Mental disorders DIURETICS Lozol Indapamide Water loss, edema POTASSIUM LOSS In addition, many diuretics cause loss of potassium, as does extensive vomiting and diarrhea, and low potassium levels in the blood can aggravate the symptoms of the Long QT Syndrome.
Sudden Arrhythmia Death Syndromes Foundation
540 Arapeen Drive, Suite 207
Salt Lake City Utah, 84108
(800) STOP SAD
Fax: (801) 582-1941
http://www.sads.org
WHAT IS THE SADS FOUNDATION? The SADS Foundation is a 501 (c)(3) tax exempt public charitable Foundation. It was developed to assist patients, physicians, families and others concerned with sudden and unexpected death in children and young adults, and particularly the inherited Long QT Syndrome (LQTS).
The SADS Foundation is funded entirely by charitable contributions from individuals and private organizations. SADS has four principle goals: EDUCATION Lay Public Newsletters Publications Electronic Media Medical Professionals Publications Seminars RESEARCH Case and family identification Genealogy and pedigree development Genetic studies Research grant awards PATIENT SERVICES Family pedigree development and diagnostic screening Consultation services Care coordination Physician referral services FAMILY SUPPORT Local SADS Groups Networking service Board of Trustees G. Michael Vincent, M.D., Chairman David E. Salisbury, Vice Chairman Katherine W. Timothy, Secretary and Treasurer Ralph W. Hardy, Jr. Richard G. Hinckley Linda Shockley, M.D. President and Medical Director G. Michael Vincent, M.D. Office Personnel Katie Roberts Lynne Godfrey The SADS Foundation is pleased to provide information about the inherited Long QT Syndrome. We hope that this will be of benefit to you.
Please contact us with comments, suggestions, or to receive our newsletter at 1-800-STOP-SAD. The Sudden Arrhythmia Death Syndromes (SADS) Foundation, a nonprofit 501(c)(3) charitable organization, was established on December 12, 1991 by G. Michael Vincent, M.D. and several dedicated co-founders for the purpose of helping prevent sudden and unexpected cardiac death in children and in young adults.
The SADS Foundation is dedicated to providing information, assistance & hope. More Information on this Please go their web site at www.sads.org or click on the photo above.
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