SUDDEN CARDIAC DEATH IN YOUNG ATHLETES
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Sudden cardiac deaths in young athletes are uncommon events [1-25]. Of the nearly 500,000 sudden cardiac deaths in the United States each year, it is estimated that only 20 to 30 of these occur in young, competitive athletes [2]. In a review of nine studies on sudden death in young patients, including athletes and non-athletes, an incidence of 1.3 to 8.5 deaths in 100,000 patient-years was described [3]. The majority of cases of sudden death in athletes under 30 occur in individuals with inherited structural cardiac anomalies. In the athlete over the age of 30, sudden death is more common and generally due to coronary artery disease [3]. Sudden deaths in young athletes are thought to be the result of ventricular arrhythmias. The evidence to support this is scant because these individuals are rarely monitored by ECG at the time of death. A study investigating the presence of cardiac anomalies in 16 athletes who survived cardiac arrest found that: 2 had long QT syndrome (LQTS), 5 had Wolff-Parkinson-White syndrome (WPW), 8 had ventricular tachycardia (VT) or ventricular fibrillation (VF), and 1 athlete had atrial fibrillation with heart block[5-8]. However, there may be instances where factors other than ventricular arrhythmia may cause sudden death. For instance, in HCM, sudden death has also been reported with supraventricular arrhythmias. In IDCM, sudden death has been reported to be due to bradyarrhythmias or electromechanical dissociation in up to 50% of patients [3]. Sudden death in this unique patient population usually occurs in the presence of structural heart disease. In 158 young competitive athletes with sudden death, Maron et al. found a cardiovascular cause in 85%. Of the 134 athletes with a cardiovascular cause of death, structural heart disease was found in 97%. The most common structural heart disease was hypertrophic cardiomyopathy (36%). Coronary artery anomalies were the second most common cause of death (24%). Various other conditions were also contributory, such as aortic stenosis, dilated cardiomyopathy, myocarditis, ARVD, and congenital heart disease [4]. Many of the congenital heart diseases such as Ebstein Anomaly, Tetralogy of Fallot, and other stenotic or regurgitant valvular heart disease put the athlete at a higher risk of life-threatening arrhythmic events. Idiopathic dilated cardiomyopathy and acute myocarditis are also rare causes of sudden death. [5]. Exertion during athletic events may precipitate the fatal arrhythmias. Exertion is associated sudden cardiac deaths in nearly half of the patients with diagnosed HCM. Arrhythmias in ARVD and right ventricular outflow tract VT are experienced during exertion. In LQTS, sudden death and syncope is associated with exercise, especially swimming. In patients with congenital abnormalities of the coronary arteries, almost all deaths are associated with exertion [7-15]. The symptoms of arrhythmias in athletes are similar to that of the non-athlete. Symptoms include brief palpitations, syncope and resuscitated sudden death. The investigation of athlete experiencing the symptoms of arrhythmias should be similar to that of non-athletes with signs and symptoms of dysrrhythmias. Syncope during exercise is much more worrying than non-exercised induced syncope. It is recommended that athletes with cardiac symptoms that are experienced during exertion should receive a resting 12-lead electrocardiogram and an echocardiogram. In the athlete over age 30 and the athlete with syncope during exertion, an evaluation for cardiac ischemia should also be performed [5]. Sudden death is rare in athletes with structurally normal hearts. Therefore, assessment for structural heart disease is also an important aspect in the evaluation athletes with possible cardiac symptoms. Attention should be particularly to patients with resuscitated sudden death and no structural heart disease, those patients with syncope and a family history of sudden death, and those patients with syncope at peak exercise. Structural heart disease may be diagnosed by an electrocardiogram, an echocardiogram, and an exercise stress test in patients over 30 years old. However, the diagnosis of anomalous coronary arteries may require cardiac catheterization. Anomalous coronary arteries can be suggested by syncope at peak exercise, or ischemia on exercise testing. Because many of the cardiac diseases that predispose to sudden death in athletes are genetic in origin, the family medical history is also important. These genetic disorders include HCM, LQTS, CAD, the Brugada syndrome, and even some types of ARVD and IDCM. Therefore, a history of early sudden death or hereditary cardiac abnormality in the family of an athlete should prompt a thorough cardiac workup regardless of the presenting symptoms [5]. Of particular interest, a number of additional conditions associated with sudden cardiac death are being discussed with greater frequency in the medical literature [6-25]. Some of these include Brugada syndrome, Long QT syndrome and Commotio cordis. These are interesting in that they are observed in individuals with apparently structurally normal hearts, making the diagnosis and evaluation of risk for sudden cardiac death in the athlete a challenge. The investigation of Brugada syndrome and Long QT syndrome are being advanced by the development of experimental molecular biology techniques, which may in the future move to the bed-side. This is important in that in the future it may be possible to genetically screen families in order to evaluate risk of sudden cardiac death.
