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Show Unexpected Sudden Cardiac Death in the Young G. Michael Vincent, M.D. Unexpected sudden cardiac death in children and young adults is a tragic event. The causes include diseases of the heart muscle such as cardiomyopathies and myocarditis, disorders of the heart's electrical system such as Long QT syndrome, prescription medications and recreational drugs, and congenital abnormalities of the coronary arteries. Most of the causes are genetic in origin, and family history and family member screening help to define the affected members and allow institution of preventive treatment. Effective treatments are available and emphasize the need to identify families and family members at risk prior to the onset of symptoms. Most people have heard or have read of a case of unexpected sudden death of a young athlete or of the completely unexpected sudden death of a child. They are unexpected because there is no previous history or knowledge of heart disease or any other condition that would predispose them to sudden death. Anyone who has been associated with one of these tragic events is aware of the enormous consequences for the family and friends of the deceased. Those who have not had that experience can at least imagine the pain and suffering associated with such an event. These cases are categorized separately from SUDS (sudden infant death syndrome, crib death, cot death) which is restricted to unexpected death prior to 1 year of age. The causes of sudden death in SIDS versus older children and youth are different. The large majority of cases of unexpected sudden death in the young are due to an abnormal cardiac (heart) rhythm. A small percent are caused by rupture of a blood vessel in the head, or of the aorta, the large vessel that carries blood from the heart out to the body. Some of the abnormal heart rhythms are caused by diseases of the heart muscle, collectively called "cardiomyopathies," or "myocarditis" caused by inflammation of the heart muscle. In others the rhythm disturbance is unasso-ciated with structural heart disease and these conditions are called "primary electrical system diseases", meaning that the rhythm disturbance is directly due to the electrical abnormality and not secondary to any other heart disease. In both situations the end result is the predisposition to the lethal heart rhythm known as ventricular fibrillation and cardiac arrest and sudden death. The number of cases of sudden unexpected cardiac death per year is not known with certainty. There are many difficulties in diagnosis, coding of the cause of death, and reporting. There is no central database of unexpected deaths including none for sudden cardiac death in children and young adults. With these limitations it has been estimated that several thousand deaths occur each year in the USA. Of particular importance, most of these sudden deaths can be prevented if the disease is recognized and treated before any symptoms or a tragic event occur. These diseases are not common, and many physicians rarely see them in their practice. Medical professionals must concentrate on the diseases which are very common and which they see everyday, like injuries, asthma, diabetes, infections, high blood pressure, coronary artery disease and heart attacks, strokes, and others. Therefore, physicians and other health care professionals are not always familiar with nor looking for these causes of sudden unexpected death in the young, so the presenting signs and symptoms may not be recognized as risks for sudden death, and the diagnosis may be missed or mislabeled. Consequently, it is very important that parents, grandparents and the public in gen- eral be acquainted with them and able to consider and discuss these possibilities with the medical professionals if circumstances in a family member(s) raise suspicion of one of these diseases. The diseases most likely to be responsible for unexpected sudden cardiac death in the young are shown in Table 1. Most of these causes are genetic in origin and, thus, run in families. The others are caused by acquired diseases, or by the use of drugs or medications. As we all recognize, the use of recreational and addictive drugs is rampant and a major public health concern. Some of these drugs are well known to cause sudden death, drugs like heroin, methamphetamine, and cocaine. Others, such as ephedra or caffeine, which have been discussed recently in the newspaper, may cause heart rhythm disturbances, and perhaps by themselves, or in the presence of underlying heart disease, might cause sudden death. Drug abuse is often the first thought and question in the minds of investigating officers or medical examiners. These drugs, however, would not be a likely cause in young children. In the absence of recreational drugs the conditions in Table 1 are the most likely. In children as well as young adults (older adults too), a growing and also major public health issue is "acquired Long QT syndrome", due to prescription medications which alter the electrical properties of the heart and predispose those taking the medications to abnormal heart rhythms and the possibility of sudden death. This will be discussed in more detail later in conjunction with the Long QT syndrome. As noted in Table 1 many of these conditions are inherited, familial disorders. The inheritance is primarily by autosomal dominant transmission, which means that males and females inherit the condition with equal frequency, and, that each child of an affected parent has a 50% chance of inheriting the abnormal gene. Because each child has an independent 50-50 chance of getting the abnormal versus the normal gene copy, the risk in the children as a group is just like flipping a coin. If a coin is flipped many times the result will be 50% heads and 50% tails. But when flipped a few times, like the usual number of children in a family, it can be heads each time or tails each time, or usually some combination. Similarly, in a usual sized family all or none of the children can be affected, but usually there is some mixture of affected and unaffected children. This means that family member screening is critical to identify the other affected members, who may be at risk for a cardiac arrest or sudden death. The first step is to construct an extended family pedigree. Effective treatment is available for most of these disorders. Therefore the screening of members of the pedigree is quite important to detect the affected members and to begin treatment to prevent tragic events. Treatments include medications, sometimes pace- 52 Utah's Health: An Annual Review Volume IX |