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Show Figure 1: Autosomal dominant Pedigree. Autosomal dominant Pedigree 1° 1 o o : gene earners = non - earners metabolic demands. Typical symptoms include exertion related shortness of breath, chest pain, dizziness or syncope. Many patients never have symptoms and are not at risk for sudden death. Others have no symptoms until later in life when the condition becomes more severe. Other HCM patients do have symptoms and some, but certainly not all, experience sudden death, including at a young age. The diagnosis may be difficult in the absence of any history of events or family history to raise suspicion. Characteristic physical findings occur in only a minority of young patients with HCM. In the absence of these characteristic findings, more subtle findings may be difficult to identify on routine physical examination. Consequently, many patients are not detected early, yet because the risk of heart rhythm problems and sudden death are not completely correlated with either prior symptoms or the degree of hypertrophy, they may still be at risk for sudden death. The diagnostic test for HCM is the echocardiogram. It demonstrates the presence, distribution, and magnitude of the hypertrophy and also defines the function of the heart. There are a number of treatments for HCM. The need for treatment, and the specific type, are determined by each patient's circumstances. Long QT syndrome Long QT syndrome is inherited by autosomal dominant transmission, and it is estimated to be present in 1:7000 persons. It is thought to be the most common cause of unexpected sudden death in children and young adults when no structural heart disease is identified at autopsy and no drugs or medications are involved. The prevalence of Long QT syndrome is higher in Utah than most other areas, and the Utah population and our medical and scientific professionals have contributed very importantly to the study and understanding of this disease, including the genetics, the diagnosis and the treatment. The first gene responsible for a primary cardiac arrhythmia was identified in Long QT syndrome, by Utah scientists, in Utah families. Long QT syndrome is the prototype disease for the "'primary cardiac electrical diseases" and study of this disease has provided very important insights into the causes and mechanisms of heart rhythm problems in general. Six genes with many mutations have been identified in LQTS, causing three typical forms of the disease, named LQT1, LQT2 and LQT3. The only typical symptom is syncope, the sudden loss of consciousness. This usually occurs precipitously and without warning, most commonly during physical exertion or with sud- den emotional stimuli such as startle, fright or loud noise. In a minority of cases, the sudden death occurs during sleep or at rest. These characteristics usually differentiate LQTS induced syncope from other more common causes of syncope such as the 'common faint', known as vasovagal syncope, or from seizures. These syncopal episodes are due to a characteristic, very fast heart rhythm known as torsade de pointes. It often reverts spontaneously to the normal heart rhythm, in which case the patient recovers consciousness and has just a syncopal spell. In a minority of cases, the torsade de pointes changes to ventricular fibrillation and the patient has sudden death. The diagnosis is made by analysis of the electrocardiogram by the finding of a prolonged QT interval. Effective treatments are available, predominantly medications, with pacemakers and implantable defibrillators in some cases. Acquired, medication induced Long QT syndrome About 50 prescription medications have the side effect of prolonging the QT interval. In a very small percent of patients who take these medications the QT prolongation causes the torsade de pointes heart rhythm and syncope or sudden death. Although the percent of patients experiencing this side effect is small, millions of persons per year take these medications, so the absolute number of patients having the side effect is high enough to be of concern. Women, the elderly, those on multiple medications, those on two or more of these QT prolonging drugs, and those with underlying heart, liver and kidney disease are at greater risk of an adverse event. Medical professionals and the public can access a list of these medications at www,qtdmgs.org by clicking on the "View QT drugs list" link. There are many resources available for more information on these conditions, and a number can be accessed on the Internet. The Sudden Arrhythmia Death Syndromes (SAPS) Foundation is a Salt Lake City based non-profit, charitable foundation dedicated to these genetic causes of sudden cardiac death in the young. Their web site, vvwvv^ad^otg, contains a great deal of information, particularly about the Long QT syndrome. The website of the Hypertrophic Cardiomyopathy Association W53QVi4feS.m,p_rg is one source of information for hypertrophic cardiomyopathy. Other web sites for these and the other disorders can be found by searching with your web browser for the name of the condition. 54 Utah's Health: An Annual Review Volume DC |
