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SUDDEN CARDIAC DEATH IN THE ATHLETE
EMERGENCY MANAGEMENT OF CARDIAC ARRHYTHMIAS
0733-8627/98 $8.00
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SUDDEN CARDIAC DEATH IN THE ATHLETE Earl J. Reisdorff, MD, FACEP, and Robert J. Prodinger, DO
Athletes are usually fit and healthy, especially the young athlete; therefore, the sudden, unexpected death of an athlete is a disturbing and tragic event. One of the first accounts of sudden death is the apocryphal tale of a long distance runner who brought a message from Marathon to Athens in 490 BC. On arriving in Athens and reporting the news of the military defeat of the Persian army, he fell dead. More recent accounts of athletes dying suddenly have included Loyola Marymount basketball star Hank Gathers (1990), marathon runner Jim Fixx (1984), US Olympic volleyball star Flo Hyman (1986), former professional basketball player Pete Maravich (1980), and 28-year-old Olympic figure skater Sergei Grinkov (1995). These deaths were caused by a variety of cardiovascular conditions. Sudden cardiac death (SCD) does not have a universally accepted definition. The time interval of symptoms, from initial onset to cardiac death, ranges from 1 to 24 hours. Sudden cardiac death implies an unexpected, nontraumatic death from cardiac causes, signaled by an abrupt loss of consciousness within 1 hour of the onset of acute symptoms. The term athlete implies participation in an organized team or individual sport in which regular competition.is a component; moreover, an athlete can be presumed to be involved in a regimented exercise program. Athletes known to have succumbed to SCD have been involved in a variety of sports, including basketball, football, running, soccer, hockey, and lacrosse. There is a strong male predilection in SCD cases.26
From the Michigan State University Emergency Medicine Residency, Ingham Regional Medical Center and Sparrow Hospital, Lansing, Michigan
EMERGENCY MEDICINE CLINICS OF NORTH AMERICA
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VOLUME 16 NUMBER 2 . MAY 1998
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Including both athletes and nonathletes, over 300,000 cases of SCD occur annually in the United States.20In fact, SCD accounts for approximately 50% of all cardiovascular deaths. The incidence of SCD during athletic activities is extremely low, ranging from 1 death per 13,000 hours of crosscountry skiing to 1 death per 396,000 hours of j0gging.l One cardiac arrest occurs every 33,000 to 112,600 hours in cardiac rehabilitation exercise programs.15,41 Although exercise increases the risk of a cardiac dysrhythmia, there is some reduction in risk of sudden death by becoming fit with moderate exercise, especially in the athlete with coronary artery disease (CAD). Athletes and other conditioned persons appear to have a lower risk of SCD while ~edentary.3~ Angiographic evidence does support the reduction of coronary atherosclerosis in some exercising subjects. Although patients with CAD are at increased risk for SCD while exercising, many patients can exercise with a high level of safety in a medically supervised setting. YOUNG ATHLETES
SCD occurs in young athletes (< 30 yrs) about 10 to 25 times each year. The incidence of sudden death in older athletes (> 30 yrs) is uncertain. Sudden death in young athletes is predominately due to structural (often congenital) nonatherosclerotic heart disease.25Although the underlying cardiac disease is typically unsuspected during life, up to 15% of children have a preexisting cardiac diagnosis at the time of SCD.31In the young athlete, hypertrophic cardiomyopathy (HCM) and anomalies of the coronary arteries are the most common conditions causing SCD.23In one review of young athletes (ages 13-30 yrs) with SCD, hypertrophic cardiomyopathy was the most common abnormality (48.3%),followed by idiopathic left ventricular hypertrophy (17.2%),and coronary artery anomalies (17.2%). Significant atherosclerotic CAD was present in 10.3'/0.~~ Although not competitive athletes, military recruits usually are healthy subjects undergoing vigorous physical activity. Among 19 medically screened Air Force recruits ages 17 to 28 years who died during basic training, the most common cause of death was myocarditis (8 recruits), followed by coronary artery anomalies (3 recruits), hypertrophic cardiomyopathy (2 recruits), mitral valve prolapse (1 recruit), focal subendocardial fibrosis (1 recruit), and Shone's syndrome (1 recruit).34 The abnormalities associated with Shone's syndrome are a parachute mitral valve and subaortic stenosis. No causal diagnosis was made in three subjects. MATURE ATHLETES
Mature athletes are defined as those older than 30 years of age. CAD is found in most cases of SCD in mature athletes.23,44, 48 In fact,
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atherosclerotic heart disease is the cause of SCD in as high as 94.7% of patients.35Among mature athletes, up to 80% have known cardiac disease prior to their SCD.32Even conditioned runners who run extensive distances are not protected from the effects of atherosclerotic vascular disease.4s Other causes of SCD in the mature athlete include aortic dissection, conduction system, disturbances, and hypertrophic cardiomyopathy (HCM). PATHOPHYSIOLOGY OF SUDDEN CARDIAC DEATH SCD most commonly arises from lethal arrhythmia, that is ventricular tachycardia-fibrillation (VT-VF) created by a structural or functional abn~rrnality.~~ Arrhythmogenic structural abnormalities include myocardial infarction (acute and healed), ventricular hypertrophy, and conduction pathway abnormalities. Patients with CAD who die suddenly frequently have accompanying left ventricular hypertrophy and coexistent hyperten~ion.~~ Among patients with idiopathic and hypertensive hypertrophic cardiomyopathy, VT-VF is a common mechanism of sudden cardiac death in 50% to 70% of cases.13,28 Functional (nonstructural) abnormalities include transient ischemia with or without reperfusion, hypoxia, acidosis, and cardiotoxic medications. In the presence of a structural or functional cardiac abnormality, exercise can be arrhythmogenic. Exercise causes an increase in heart rate, systolic blood pressure, and myocardial contractility, all of which increases myocardial oxygen demand. CAD from atherosclerosis, hypoplasia, or spasm can reduce regional myocardial blood flow, resulting in focal membrane instability. Increased myocardial oxygen demand in regions served by a vessel that is able to deliver only a fixed supply of blood is the probable mechanism of exercise-induced arrhythmia and SCD in athlete^.^, 23 In the case of HCM and idiopathic left ventricular hypertrophy, the mechanism of arrhythmogenesis is uncertain. With anomalous coronary arteries, a reduction in coronary artery blood flow may occur by compression of the vessel between the expanded aorta and pulmonary artery during exercise. CAUSES OF SUDDEN CARDIAC DEATH Certain conditions do contribute to sudden cardiac death, among them the following: 1. Hypertrophic cardiomyopathy 2. Idiopathic left ventricular hypertrophy 3. Right ventricular dysplasia 4. Atherosclerotic CAD 5. CAD
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6. Congenital anomolies of the coronary arteries 7. Hypoplastic coronary arteries 8. Tunneled coronary arteries 9. High-grade ventricular arrhythmias 10. Wolff-Parkinson-White syndrome 11. Prolonged QT syndrome 12. Idiopathic ventricular tachycardia 13. Severe valvular heart disease, including aortic stenosis and pulmonic stenosis 14. Congenital heart disease 15. Coarctation of the aorta 16. Acute myocarditis 17. Marfan’s syndrome 18. Competition-enhancing agents (e.g., anabolic steroids, erythropoietin) 19. Illicit drugs (e.g., cocaine, inhalants) Cardiomyopathies Hypertrophic Cardiomyopathy
HCM is associated with exercise-related SCD in the young adult.6 In fact, death from HCM is more likely to occur during exercise than at rest.6 Up to 50% of SCD cases in young athletes are due to HCM.24,25 HCM also causes SCD in athletes older than 30 years, but at a much lower incidence. The findings of HCM typically include cardiomegaly, asymmetric septal hypertrophy (ASH), and myocardial cellular disarray. With HCM, the ventricle is hypertrophied, not dilated, which causes decreased ventricular filling owing to the increased ventricular muscle m a ~ s . 4The ~ hypertrophy is idiopathic, occurring in the absence of a cardiac or systemic condition such as aortic stenosis or systemic hypertension. The interventricular septal thickness is usually 15 mm or greater with the left ventricular free-wall thickness either normal or also increased. ASH is a term used to describe an interventricular septum to left ventricular free-wall ratio of 1.3 : 1.0 or greater. Abnormally thickened intramural coronary arteries with narrow lumens are also seen with HCM. In a series of SCD occurring during exercise in patients with HCM, 35.7% had a previous cardiac evaluation for symptoms that included syncope, family history, murmurs, fatigue, or VT on exercise testingz5 The mechanism of SCD in HCM is from ventricular arrhythmias, in most cases presumably caused by abnormal conduction by malformed muscle. The systolic murmur of HCM increases with Valsalva’s maneuver, by decreasing both the venous return to the right heart and left ventricular volume. It is heard best at the left lower sternal border to the apex. Approximately 90% of patients with HCM and more than 90% of HCM victims of SCD have abnormal electrocardiogram^.^^ A normal electrocardiogram suggests that HCM is absent.
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Echocardiographic evaluation of all young athletes as a screen for detecting HCM is probably not beneficial, because incidence of HCM is low. Moreover, it is difficult to distinguish mild forms of HCM from exercise-induced cardiac hypertrophy (athlete's heart syndrome). Cardiovascular evaluation including an echocardiogram is reasonable, however, for persons who wish to embark on a strenuous exercise regimen and who have a history of syncope, arrhythmias, or a family history of SCD. The echocardiographic finding of an increased ventricular septal thickness ( 2 15 mm) is a critical diagnostic feature of HCM. Increased left ventricular mass in an athlete may result in a 14-mm but rarely a 15-mm interventricular septal thickness. A small left ventricular cavity, anterior motion of the anterior leaflet of the mitral valve in systole, discrete areas of hypertrophy, and diastolic dysfunction are other echocardiographic findings suggestive of HCM. The presence of a first-degree relative with HCM is a factor indicating the diagnosis of HCM in the subject being evaluated. The cardiomegaly of HCM is visible on chest radiograph. ldiopathic Left Ventricular Hypertrophy Compared with HCM, idiopathic left ventricular hypertrophy (ILVH) is a less common cause of SCD in athletes. Unlike HCM, there are no myocardial cellular disarray or coronary artery abnormalities. ILVH probably results from undiagnosed hypertension, or it may represent a truly different form of idiopathic hypertrophy. Over 17% of cases of SCD occur in athletes with ILVH. Because exercise can increase left ventricular wall thickness and ventricular dilatation, some changes may result from the exercise process itself and may not represent a pathologic condition. The cause-effect relationship of ILVH in SCD is poorly established. Idiopathic hypertrophy should be considered a possible cause of death in only the absence of other causes. Right Ventricular Dysplasia Right ventricular dysplasia is an idiopathic cardiomyopathy primarily involving the right it is also called right ventricular cardiomyopathy or arrhythmogenic right ven tricular dysplasia. Right ventricular dysplasia is characterized by thinning of the right ventricular wall with dilatation. There is often an intermixing of fibrous tissue, fat, and myocytes in the affected area. Ventricular arrhythmias are a common clinical manifestation of this condition. Markers for sudden death from right ventricular dysplasia include T-wave inversion in the anterior precordial leads, a bundle branch block, sustained VT, and syncope." Atherosclerotic CAD
Jim Fixx's sudden cardiac death in 1984 was surprising because of his active promotion of cardiovascular fitness. He himself, however, had severe triple vessel coronary disease, with areas of previous myocardial necrosis. He was a middle-aged man (52 years) with hypercholesterol-
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emia (cholesterol 254 mg/dl) who had smoked two packs of cigarettes a day until he started running at the age of 36 years. His father had suffered a myocardial infarction at the age of 35 years and died 8 years later. Exercise-related deaths due to atherosclerotic CAD occur in even young subjects.= Most mature victims of SCD have advanced chronic atherosclerotic lesions. Postmortem examinations found lesions (275%) in at least three major vessels in 61% of the hearts at autopsy. Two-vessel disease occurred in 15%; only 24% of the hearts had either single-vessel study, 75% of victims of disease or no significant s t e n ~ s i sIn . ~ another ~ SCD had at least one coronary artery with 90% or more stenosis in contrast with 8% of victims with sudden death from other causes.2O Often, it is not the chronic fixed coronary lesion that causes death. Acute coronary artery changes were found at 95% of the postmortem examinations of sudden ischemic death victims. Recent acute thrombi were found in 74% of the hearts. Only 44% of the hearts had 50% or greater occlusion by the recent coronary thrombi; the remaining 51% had only minor occlusive thrombi or plaque fiss~ring.~ Some of these findings are explained by rupture of atherosclerotic plaque during exer~ i s eThese . ~ observations suggest that acute intraluminal coronary artery changes have a significant role in the initiation of a terminal rhythm, and that they do so by mechanisms extending beyond strictly arterial occlusion. For example, coronary artery spasm at the site of an acute thrombus or distal to it may precipitate a terminal arrhythmia. Mature athletes often know they have CAD before exercise-related SCD. Of the 51 cases of SCD caused by atherosclerosis in British squash players (all of whom were perceived as fit or very fit by relatives) prior symptoms of chest pain and fatigue were present in nearly one In one group of 44 joggers and runners who died suddenly, 22.7% had family histories of premature heart disease, 25.0% had systemic hypertension, 22.7% had cholesterol levels at or above 200 mg/dl, and 22.7% had a known history of coronary artery atherosclerosis.43,45 Coronary Artery Abnormalities Coronary Artery Spasm
Coronary spasm at the site of an acute thrombus or distal to a thrombus may precipitate VT-VF. Persistent coronary artery spasm has been observed at Interestingly, coronary artery spasm with resolution exposes the myocardium to the double hazard of transient ischemia and subsequent reperfusion. Exercise-induced coronary artery spasm can also contribute to exertion-related cardiac events.l4e37, 51 Coronary Artery Anomalies
Following HCM, coronary artery anomalies are the second most common cause of exercise-associated SCD in young athletes. There are
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multiple possible courses for an abnormal left main coronary artery. Most cases resulting in SCD involve patients with an anomalous left coronary artery that passes posterior to the right ventricular outflow tract; the exact mechanism of SCD from this anomaly is unknown. Nonetheless, theories include compression of the artery by the right ventricular outflow tract and coronary artery spasm. Angled takeoffs of the coronary ostium may contribute to terminal arrhythmias in the absence of other coronary artery anomalies. Theoretically, as a patient survives into adulthood the degree of atherosclerosis in the coronary vessel is accelerated owing to the circulatory turbulence created by the acute angled takeoff. Another anomaly of the coronary arteries is when the left main coronary artery arises from the pulmonary trunk. Because of the severe consequences of this condition, 90% of patients become symptomatic and die during the first year of life. A less serious but rarer anomaly is that of the left anterior descending coronary trunk arising from the pulmonary trunk. These patients typically present with angina in early adulthood. Another variation is a single coronary ostium giving rise to all three major coronary arteries. Other aberrant coronary artery formations are associated with SCD, including hypoplastic coronary arteries. Hypoplastic coronary arteries are diminutive vessels with markedly diminished, almost pinpoint lumina (usually < 1.5 mm).” In 1980, former basketball star Pete Maravich died suddenly during a pickup basketball game. He was found to have a rare anomaly-the presence of a single coronary artery. In his case, a single coronary artery was the right coronary artery; the left coronary artery was totally absent. Both marked cardiac hypertrophy and myocardial fibrosis were present on postmortem examination. Coronary artery anomalies are difficult to detect in the ED. Often there is a history of prior syncope. With multiple episodes of syncope, cardiac ischemia, or severe arrhythmias, an angiogram is required. An exercise electrocardiogram (ECG) to uncover ischemia and a two-dimensional echocardiogram to define the position of the left coronary artery may be helpful. Tunneled Coronary Arteries
With a tunneZed coronary artery, the coronary artery passes under myocardial muscle-forming a ”myocardial bridge.” A tunneled epicardial coronary artery is found in a significant number of subjects dying from noncardiac causes. In fact, myocardial bridging of the left anterior descending coronary artery is found in about 30% of autopsies. The precise role of a tunneled coronary artery SCD is therefore uncertain. Nonetheless, cases of tunnels that are 2 cm or longer have been associated with angina and SCD.3 In some cases, angina is relieved after debridging techniques. Because of the prevalence of asymptomatic tunneling, one must be cautious in assigning the cause of death to myocardial bridges.
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Electrophysiologic Etiologies
A pathologic examination of the conduction system is rarely performed in the evaluation of exercise-related SCD. The incidence of terminal arrhythmias without a structural defect in athletes varies widely; it can be as high as 50% in children and as low as 3% in a retrospective study of adults.=,31 Although the heart may appear normal at postmortem examination, that finding does not exclude a disorder of the conduction system. Electrophysiologic abnormalities causing SCD are extremely difficult to detect on postmortem examination. Subtle findings may include narrowed or sclerotic sinus node arteries? Direct sclerosis and calcification of the conduction system (i.e., sinus node, AV node, and His bundle) can also O C C U ~ . ~ Other electrophysiologic possibilities in the absence of ischemia include idiopathic prolonged QT syndrome,3* Wolff-Parkinson-White syndrome, and idiopathic ventricular fibrillation Prolonged QT syndrome is characterized by a corrected QT interval of greater than 440 msec, although at times the QT interval in these patients may be normal. Persons with prolonged QT syndrome are prone to syncope and cardiac arrest because of VT-VF. Fatal rhythms can be provoked by exerciserelated tachycardia; thus, anyone with this condition should be restricted from competitive sports. Patients with Wolff-Parkinson-White syndrome also have short refractory periods involving their accessory pathway and are at risk for both syncope and SCD. Other Disorders Commotio Cordis
Collision with another player or with a projectile (e.g., baseball) may produce a force sufficient enough to induce a lethal arrhythmia in a structurally normal heart, termed commotio ~ordis.'~Often, the impact to the chest is not judged initially to be extraordinary for the particular sport nor does it appear to have sufficient force to cause death. The most commonly implicated projectiles are baseballs, softballs, hockey pucks, and lacrosse balls. Other deaths have followed a blunt collision from a football helmet, karate kick, opponent's shoulder, and a hockey stick. On impact, the transfer of kinetic energy creates electrical instability during the cardiac cycle. Unfortunately, there is a low rate of rescue following commotio cordis, even with prompt resuscitative measures. Competition-enhancing Agents
SCD has occurred in athletes (especially weightlifters) abusing anabolic steroids.21With steroid-implicated deaths, there can be cardiac hypertrophy, myocardial fibrosis, accelerated atherosclerosis, and myo-
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cardial infarction.22Anabolic steroid use by competitive athletes modifies the lipid profile, predisposing one to CAD.” l6 Other complications of steroid use include platelet hypercoagulability and coronary artery vasospasm. Erythropoietin has been implicated (although not proven) as contributing to the deaths among Dutch and Belgian bicyclists from 1987 through 1990. Erythropoietin stimulates red blood cell (RBC) production and was used to increase aerobic capacity by increasing RBC mass. Its role in exercise-related SCD may result from the polycythemic state and potential thrombotic complications, including cerebral vascular accidents, cerebral thrombosis, and myocardial infarction. These complications are more likely to occur following prolonged exercise with relative dehydration, which increases blood viscosity and thrombotic potential. Despite this speculation, these deaths remain unexplained. Valvular Heart Disease
Mitral valve prolapse is extremely common and rarely associated with malignant arrhythmias. A permissive attitude toward sports participation is advocated in patients with mitral valve prolapse unless the patient has a history of syncope, disabling chest pain, complex ventricular arrhythmias, significant mitral regurgitation, prolonged QT syndrome, or a family history of sudden death. Severe aortic stenosis is a risk factor for exercise-related sudden death and is a definite contraindication to vigorous exercise. Because aortic stenosis produces a harsh systolic ejection murmur, it is easily diagnosed. Severe mitral valve stenosis and other complications of rheumatic heart disease may cause death. Finally, Epstein’s anomaly, or atrialization of the right ventricle, may also cause death from malignant tachyarrhythmias and right heart failure. Inflammatory Disorders
Acute myocarditis is an inflammatory process of the mycardium usually caused by a viral Common viral etiologies include the enteroviruses, coxsackie viruses, influenza viruses, and cytomegalovims. Bacterial pathogens include Mycoplusma pneumoniue, Chlamydia sp., betahemolytic Streptococcus and Corynebucteriumdiphtheriue. Infectious myocarditis is suspected when a patient has chest symptoms during or soon after a flulike illness.’* Chest pain can mimic either pericarditis or angina. Palpitations from ventricular extrasystoles are common. Other symptoms include dyspnea, orthopnea, cough, and decreased exercise intolerance. An audible S3gallop or soft apical murmur may be present as well as signs of congestive heart failure. The chest radiograph may show an enlarged cardiac silhouette. The ECG may show low voltage complexes, diffuse ST-segment and T-wave changes, and sinus tachycardia. Death is usually due to ventricular arrhythmias. Exercise-related SCD secondary to inflammatory coronary artery aneurysms from Kawasaki’s disease can also occur.3o,31
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Miscellaneous Conditions Congenital Disorders. Congenital heart disease along with the corrective surgical procedures can create anatomic irregularities that predispose subjects to SCD. Congenital problems associated with death include uncorrected aortic stenosis and pulmonary vascular obstructive disease. Cardiovascular Toxins. Recreational and illicit drugs such as cocaine and abuse of inhalants can precipitate SCD during strenuous physical activities. Cocaine is primarily sympathomimetic. Volatile substances (inhalants) also cause cardiac dysrhythmias. Marfan’s Syndrome. Marfan’s syndrome may cause sudden death by aortic rupture or dissection, which is what happened to Flo Hyman, the US Olympic volleyball star, who died in January 1986 while playing volleyball in Japan. Patients with Marfan’s syndrome die from aortic dissection or rupture, with mediastinal hemorrhage, pericardial tamponade, coronary artery dissection, acute aortic insufficiency, and rapid congestive heart failure. Patients with Marfan’s syndrome should be restricted from high-impact activities. ATHLETIC HEART SYNDROME
Athletic heart syndrome (AHS) is benign syndrome characterized by physiologic adaptations for increased physical performance. Changes include cardiac chamber enlargement, increased ventricular wall thickness, and increased vagal tone. On physical examination, the athlete has bradycardia with sinus irregularity. The pulse is often strong secondary to an increased stroke volume. Auscultation discloses a normal first and second heart sound. Frequently an S, or S, gallop is heard.s,12A systolic ejection murmur results from an increased stroke volume. First-degree AV block, Mobitz type I second-degree AV block, and junctional bradycardia can be seen. Early repolarization consisting of ST elevation greater than 0.5 mm in two consecutive leads, often localized to the precordium and often with terminal slurring of the R wave, is considered benign. Lateral T wave inversion can also be seen as part of the early repolarization variant. A chest radiograph or echocardiogram can show fourchamber cardiac enlargement. Lack of recognition of these changes as probable or possible normal findings in athletes may lead to an erroneous diagnosis of a cardiovascular disorder. SCREENING EXAMINATIONS
Echocardiographic screening in young athletes is ineffective primarily because athletes can have mildly hypertrophied hearts as normal variants (AHS). Moreover, the overall incidence of structural cardiac disease is quite small, making it more likely that one would overdiagnose a patient than correctly discover disease. Among patients with
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structural disease that would be detected on echocardiogram, there are often prior symptom^.'^ Therefore, it is reasonable to conduct more thorough screening in any patient having a family history of premature sudden death, or those with a prior history of syncope, significant arrhythmias, or chest pain. Routine preparticipation stress testing is recommended for adults at risk for exercise-related death.'O Nonetheless, the infrequency of exercise deaths still limits the yield of any screening procedures. Positive results from screening examinations are often due to normal variants. In addition, SCD from CAD is often caused by an acute change in a coronary lesion, such as plaque rupture or thrombus. In one study, symptomlimited exercise stress tests were performed on 916 Indiana state policemen. Of these, 61 had an abnormal response to exercise. Of these 61 subjects, 18 went on to develop angina, one suffered a myocardial infarction, one remained asymptomatic but went on for coronary artery bypass graft, and one had SCD. Surprisingly, there were 25 myocardial infarctions, 7 SCDs, and 12 persons who developed angina all within the group with normal ECG responses (n= 855).27In the Lipid Research Clinics Primary Prevention Trial, 3617 men with baseline total cholesterol levels above 265 mg/dl and low-density lipoprotein concentration above 190 mg/dl were subjected to exercise tests to 90% of their age-predicted maximal heart rate. Of the 62 men who subsequently experienced an exercise-related cardiac event, only 11 (17.7%) had a previously positive exercise test result.40 THE ROLE OF THE EMERGENCY PHYSICIAN
The role of the emergency physician is to attempt to resuscitate those patients who have had SCD events. If resuscitation is successful, appropriate antiarrhythmic therapy and stabilization is indicated. Likewise, the physician must recognize those patients at risk for SCD, including the young athlete who has experienced syncope or cardiopulmonary complaints during exercise. In the mature athlete, the emergency physician must seek indications of dysrhythmia or ischemic CAD. Athletes should be counseled against athletic participation if certain conditions are discovered (see "Causes of Sudden Cardiac Death). One should inquire about the athlete's symptoms. The medical history includes questions about syncope, exercise tolerance, and any known cardiac (including congenital) disease. Specifically, information about exercise syncope, angina pectoris, and extreme exertional dyspnea should be gathered. One also must determine the presence of chronic disease such as diabetes mellitus and hypertension. A family history of congenital heart disease, syncope, or unexpected death at an early age should be sought. Symptoms such as chest pain, fatigue, heartburn, indigestion, and excessive breathlessness have been reported in persons prior to sudden death. The physical examination should elicit evidence of Marfan's syndrome, aortic stenosis, hypertension, and HCM. The
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physician must listen for the murmur of idiopathic hypertrophic subaortic stenosis in the young person. In mature athletes, signs and symptoms of cardiac ischemia must be reviewed. New symptoms of exercise intolerance, such as syncope, unusual dyspnea, and chest discomfort, may be symptoms of important cardiac diseases and should be carefully evaluated in athletes of all ages. Certain findings should cause concern, including profound bradycardia or high-grade AV block in an athlete not engaged in endurance training, sinus pauses longer than 3 seconds, complete heart block, and syncope or near syncope at rest or after strenuous exercise. Other conditions may predispose one to increased risk of SCD during exercise, including uncontrolled hypertension, uncontrolled atrial arrhythmias, hemodynamically significant valvular disease, and exercise-induced bronchospasm. Certain historical signs and symptoms suggest specific diagnoses. For example, a history of syncope or near syncope may suggest HCM, valvular heart disease, or idiopathic prolonged QT syndrome. Tests that may be helpful in defining disease are serum lipid profiles, resting and exercise electrocardiograms, and echocardiography. These studies should be done selectively depending on age and clinical profile of the patient. As stated before, a resting electrocardiograph or echocardiogram is not helpful in screening the apparently healthy young adults; this is also true for chest radiographs. These studies do become more and more helpful as the age of patients increase, however. STRATEGIES FOR PREVENTION OF SCD
Strategies for preventing SCD are not complex but do require knowledge of certain conditions. Coaches and trainers should observe athletes during exercise. Physicians should do screening examinations to try to assess the level of stress activity that is safe, especially in mature athletes. Athletes experiencing exertional chest discomfort, syncope, near syncope, tachyarrhythmias, and impaired performance require further evaluation. When an athlete collapses, he or she requires prompt attention because it may be cardiopulmonary arrest and not merely heat exhaustion. Emergency physicians should participate with local sport and activity programs to design a plan for immediate on site emergency treatment, including transportation to and care in the ED. References 1. Amsterdam EA, Laslett L, Holly R Exercise and sudden death. Cardiol Clin 5:337343, 1987 2. Baldo-Enzi G, Giada F, Zuliana G, et al: Lipid and apoprotein modifications in body builders during and after self-administratiin of anabolic steroids. Metabolism 39:20$ 208, 1990
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3. Bestetti RB, Costa RS, Kazava DK, et al: Can isolated myocardial bridging of the left anterior descending coronary artery be associated with sudden death during exercise? Acta Cardiol 4627-30, 1991 4. Bharati S, Bauemfeind R, Miller LB, et al: Sudden death in three teenagers: Conduction system studies. J Am Coll Cardiol 1:879-883, 1983 5. Black A, Black MM, Gensini G: Exertion and acute coronary artery injury Angiology 26~759-783,1975 6. Burke AP, Farb A, Virmani R, et al: Sports-related and non-sports-related sudden cardiac death in young adults. Am Heart J 121:568-575, 1991 7. Cobb LA, Weaver WD: Exercise: A risk for sudden death in patients with coronary heart disease. J Am Coll Cardiol 7215219, 1986 8. Crawford MH, ORourke RA: The athlete’s heart. Adv Intern Med 24311-329, 1979 9. Davies MJ, Thomas A: Thrombosis and acute coronary artery lesions in sudden cardiac ischemic death. N Engl J Med 310:1137-1140, 1984 10. Fletcher GF, Froelicher VF, Hartler LH, et al: Exercise standards: A statement for health professionals from the American Heart Association. Circulation 822286-322, 1990 11. Furlanello F, Bettini R, Bertoldi A, et al: Arrhythmia patterns in athletes with arrhythmogenic right ventricular dysplasia. Eur Heart J lO(suppl):16-19, 1989 12. Gibbons LW, Cooper KH, Martin RP, et al: Medical examination and electrocardiographic analysis of elite distance runners. Ann NY Acad Sci 301:283-296, 1977 13. Goodwin JF: The frontiers of cardiomyopathy. Br Heart J 48:l-18, 1982 14. Gordon JB, Ganz P, Nabel EG, et al: Atherosclerosis influences the vasomotor response of epicardial coronary arteries to exercise. J Clin Invest 831946-1952, 1989 15. Haskell WL: Cardiovascular complications during exercise training of cardiac patients. Circulation 57920-924, 1978 16. Hurley BF, Seals DR, Hagberg JM, et al: High-density-lipoprotein cholesterol in bodybuilders vs. powerlifters: Negative effects of androgen use. JAMA 252507-513, 1984 17. Kaplan JA, Karofsky PS, Volturo GA. Commotio cordis in two amateur ice hockey players despite the use of commercial chest protectors: Case reports. J Trauma 34:15f153, 1993 18. Karjalainen J: Clinical diagnosis of myocarditis and dilated cardiomyopathy. Scand J Infect Dis (Suppl) 88:33-43, 1993 19. Kramer MR, Drori Y, Lev 8: Sudden death in young soldiers: High incidence of syncope prior to death. Chest 93345-347,1988 20. Kulle; L; Cooper M, Perper J: Epidemiology of sudden death. Arch Intem Med 129:714-719, 1972 21. Luke JL, Farb A, Virmani R, Sample RH: Sudden cardiac death during exercise in a weight lifter using anabolic androgenic steroids: Pathological and toxicological findings. J Forens Sci 35:144-147, 1990 22. Lyngberg K K Myocardial infarction and death of a body builder after using anabolic steroids. Ugeskr Laeger 153:587-588, 1991 23. Maron MB, Epstein SE, Roberts WC: Causes of sudden death in competitive athletes. J Am Coll Cardiol 7204-214, 1986 24. Maron MB, Roberts WC, Epstein SC: Sudden death in hypertrophic cardiomyopathy: A profile of 78 patients. Circulation 65:1388-1394, 1982 25. Maron MB, Roberts WC, McAllister HA, et al: Sudden death in young athletes. Circulation 62:21&229, 1980 26. Maron MB, Shirani J, Poliac LC, et a1 Sudden death in young competitive athletes: Clinical, demographic, and pathologic profiles. JAMA 276:199-204, 1996 27. McHenry PL, O’Donnell J, Morris SN, et a1 The abnormal exercise electrocardiogram in apparently healthy men: A predictor of angina pectoris as an initial coronary event during long-term follow-up. Circulation 70:547-551, 1984 28. McLenachan JM, Dargie HJ: Ventricular arrhythmias in hypertensive left ventricular hypertrophy: Relationship to coronary artery disease, left ventricular dysfunction, and myocardial fibrosis. Am J Hypertens 3:735-740, 1990 29. Myerburg RJ, Kessler KM, Bassett AL, et al: A biological approach to sudden cardiac death: Structure, function and cause. Am J Cardiol63:1512-1516, 1989
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30. Neuspiel DR Sudden death from myocarditis in young athletes [letter]. Mayo Clin Pro 61:226-227, 1986 31. Niimura I, Maki T Sudden cardiac death in childhood. Jpn Circ J 53:1571-80, 1989 32. Northcote RJ, Ballantyne D Sudden cardiac death in sport. Br Med J Clin Res Ed 2871357-1359, 1983 33. Perper JA, Juller LH, Cooper A: Arteriosclerosis of coronary arteries in sudden, unexpected deaths. Circulation 52(Suppl):27-33, 1975 34. Phillips M, Robinowitz M, Higgens JR, et al: Sudden cardiac death in Air Force recruits: A 20-year study. JAMA 2562696-2699, 1986 35. Ragosta M, Crabtree J, Stumer WQ, et al: Death during recreational exercise in the state of Rhode Island. Med Sci Sports Exerc 16:339-342, 1984 36. Roberts WC, Curry RC, Isner JM, et al: Sudden death in Prinzmetal's angina with coronary spasm documented by angiography: Analysis of three necropsy patients. Am J Cardiol50:203-210, 1982 37. Sadaniantz A, Kitzes D, Thompson I'D: Post-exercise coronary artery spasm. Am Heart J 116866-867, 1988 38. Schwartz PJ, Periti M, Malliani A The long Q-T syndrome. Am Heart J 89:378-390,1975 39. Siscovick DS, Ekelund LG, Hyde JS, et a1 Physical activity and coronary heart disease among asymptomatic hypercholesterolemic men (the Lipid Research Clinics Coronary Primary Prevention Trial). Am J Public Health 78:1428-1431, 1988 40. Siscovick DC, Ekelund LG, Johnson JL, et al: Sensitivity of exercise electrocardiography for acute cardiac events during moderate and strenuous physical activity: The Lipid Research Clinics Coronary Primary Prevention Trial. Arch Intern Med 151:325-330, 1991 41. Van Camp SP, Peterson RA. Cardiovascular complications of outpatient cardiac rehabilitation programs. JAMA 2561160-1163,1986 42. Virmani R, Robinowitz M, Clark MA, et al: Sudden death and partial absence of the right ventricular myocardium: A report of three patients and a review of the literature. Arch Path Lab Med 106:163-167,1982 43. Virmani R, Robinowitz M, McAllister HA Jr: Exercise and the heart. Pathol Annu 20(Pt 2):431-462, 1985 44. Virmani R, Robinowitz M, McAllister HA Jr: Nontraumatic death in joggers: A series of 30 patients at autopsy. Am J Med 72:874-881, 1982 45. Virmani R, Robinowitz M.Cardiac pathology and sports medicine. Hum Pathol18493501, 1987 46. Viskin S, Belhassen B: Idiopathic ventricular fibrillation. Am Heart J 120661471, 1990 47. Voigt J, Agdal N Lipomatous infiltration of the heart: An uncommon cause of sudden, unexpected death in a young man. Arch Path Lab Med 106:497498,1982 48. Waller BF, Roberts WC: Sudden death while running in conditioned runners aged 40 years or over. Am J Cardiol45:1282-1300, 1980 49. Wigle ED, Sasson Z, Henderson MA, et a1 Hypertrophic cardiomyopathy: The importance of the site and extend of hypertrophy-a review. Prog Cardiovasc Dis 28:1-83, 1985 50. Woodward TE, Togo Y, Lee YC, et a1 Specific microbial infections of the myocardium and pericardium. Arch Intern Med 120270-279, 1967 51. Yasue HS, Omote S, Takizawa A, et al: Circadian variation of exercise capacity in patients with Prinzmetal's variant angina: Role of exercise-induced coronary arterial spasm. Circulation 59:938-947, 1979 52. Zugibe FT, Zugibe FT Jr, Costello JT, et al: Hypoplastic coronary artery disease within the spectrum of sudden unexpected death in young and middle age adults. Am J Forensic Med Pathol 14:27&283,1993
Address reprint requests to Earl J. Reisdorff, MD, FACEP Ingham Regional Medical Center Department of Emergency Medicine 401 West Greenlawn Avenue Lansing, MI 48910
0733-8627/98 $8.00
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SUDDEN CARDIAC DEATH IN THE ATHLETE Earl J. Reisdorff, MD, FACEP, and Robert J. Prodinger, DO
Athletes are usually fit and healthy, especially the young athlete; therefore, the sudden, unexpected death of an athlete is a disturbing and tragic event. One of the first accounts of sudden death is the apocryphal tale of a long distance runner who brought a message from Marathon to Athens in 490 BC. On arriving in Athens and reporting the news of the military defeat of the Persian army, he fell dead. More recent accounts of athletes dying suddenly have included Loyola Marymount basketball star Hank Gathers (1990), marathon runner Jim Fixx (1984), US Olympic volleyball star Flo Hyman (1986), former professional basketball player Pete Maravich (1980), and 28-year-old Olympic figure skater Sergei Grinkov (1995). These deaths were caused by a variety of cardiovascular conditions. Sudden cardiac death (SCD) does not have a universally accepted definition. The time interval of symptoms, from initial onset to cardiac death, ranges from 1 to 24 hours. Sudden cardiac death implies an unexpected, nontraumatic death from cardiac causes, signaled by an abrupt loss of consciousness within 1 hour of the onset of acute symptoms. The term athlete implies participation in an organized team or individual sport in which regular competition.is a component; moreover, an athlete can be presumed to be involved in a regimented exercise program. Athletes known to have succumbed to SCD have been involved in a variety of sports, including basketball, football, running, soccer, hockey, and lacrosse. There is a strong male predilection in SCD cases.26
From the Michigan State University Emergency Medicine Residency, Ingham Regional Medical Center and Sparrow Hospital, Lansing, Michigan
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Including both athletes and nonathletes, over 300,000 cases of SCD occur annually in the United States.20In fact, SCD accounts for approximately 50% of all cardiovascular deaths. The incidence of SCD during athletic activities is extremely low, ranging from 1 death per 13,000 hours of crosscountry skiing to 1 death per 396,000 hours of j0gging.l One cardiac arrest occurs every 33,000 to 112,600 hours in cardiac rehabilitation exercise programs.15,41 Although exercise increases the risk of a cardiac dysrhythmia, there is some reduction in risk of sudden death by becoming fit with moderate exercise, especially in the athlete with coronary artery disease (CAD). Athletes and other conditioned persons appear to have a lower risk of SCD while ~edentary.3~ Angiographic evidence does support the reduction of coronary atherosclerosis in some exercising subjects. Although patients with CAD are at increased risk for SCD while exercising, many patients can exercise with a high level of safety in a medically supervised setting. YOUNG ATHLETES
SCD occurs in young athletes (< 30 yrs) about 10 to 25 times each year. The incidence of sudden death in older athletes (> 30 yrs) is uncertain. Sudden death in young athletes is predominately due to structural (often congenital) nonatherosclerotic heart disease.25Although the underlying cardiac disease is typically unsuspected during life, up to 15% of children have a preexisting cardiac diagnosis at the time of SCD.31In the young athlete, hypertrophic cardiomyopathy (HCM) and anomalies of the coronary arteries are the most common conditions causing SCD.23In one review of young athletes (ages 13-30 yrs) with SCD, hypertrophic cardiomyopathy was the most common abnormality (48.3%),followed by idiopathic left ventricular hypertrophy (17.2%),and coronary artery anomalies (17.2%). Significant atherosclerotic CAD was present in 10.3'/0.~~ Although not competitive athletes, military recruits usually are healthy subjects undergoing vigorous physical activity. Among 19 medically screened Air Force recruits ages 17 to 28 years who died during basic training, the most common cause of death was myocarditis (8 recruits), followed by coronary artery anomalies (3 recruits), hypertrophic cardiomyopathy (2 recruits), mitral valve prolapse (1 recruit), focal subendocardial fibrosis (1 recruit), and Shone's syndrome (1 recruit).34 The abnormalities associated with Shone's syndrome are a parachute mitral valve and subaortic stenosis. No causal diagnosis was made in three subjects. MATURE ATHLETES
Mature athletes are defined as those older than 30 years of age. CAD is found in most cases of SCD in mature athletes.23,44, 48 In fact,
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atherosclerotic heart disease is the cause of SCD in as high as 94.7% of patients.35Among mature athletes, up to 80% have known cardiac disease prior to their SCD.32Even conditioned runners who run extensive distances are not protected from the effects of atherosclerotic vascular disease.4s Other causes of SCD in the mature athlete include aortic dissection, conduction system, disturbances, and hypertrophic cardiomyopathy (HCM). PATHOPHYSIOLOGY OF SUDDEN CARDIAC DEATH SCD most commonly arises from lethal arrhythmia, that is ventricular tachycardia-fibrillation (VT-VF) created by a structural or functional abn~rrnality.~~ Arrhythmogenic structural abnormalities include myocardial infarction (acute and healed), ventricular hypertrophy, and conduction pathway abnormalities. Patients with CAD who die suddenly frequently have accompanying left ventricular hypertrophy and coexistent hyperten~ion.~~ Among patients with idiopathic and hypertensive hypertrophic cardiomyopathy, VT-VF is a common mechanism of sudden cardiac death in 50% to 70% of cases.13,28 Functional (nonstructural) abnormalities include transient ischemia with or without reperfusion, hypoxia, acidosis, and cardiotoxic medications. In the presence of a structural or functional cardiac abnormality, exercise can be arrhythmogenic. Exercise causes an increase in heart rate, systolic blood pressure, and myocardial contractility, all of which increases myocardial oxygen demand. CAD from atherosclerosis, hypoplasia, or spasm can reduce regional myocardial blood flow, resulting in focal membrane instability. Increased myocardial oxygen demand in regions served by a vessel that is able to deliver only a fixed supply of blood is the probable mechanism of exercise-induced arrhythmia and SCD in athlete^.^, 23 In the case of HCM and idiopathic left ventricular hypertrophy, the mechanism of arrhythmogenesis is uncertain. With anomalous coronary arteries, a reduction in coronary artery blood flow may occur by compression of the vessel between the expanded aorta and pulmonary artery during exercise. CAUSES OF SUDDEN CARDIAC DEATH Certain conditions do contribute to sudden cardiac death, among them the following: 1. Hypertrophic cardiomyopathy 2. Idiopathic left ventricular hypertrophy 3. Right ventricular dysplasia 4. Atherosclerotic CAD 5. CAD
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6. Congenital anomolies of the coronary arteries 7. Hypoplastic coronary arteries 8. Tunneled coronary arteries 9. High-grade ventricular arrhythmias 10. Wolff-Parkinson-White syndrome 11. Prolonged QT syndrome 12. Idiopathic ventricular tachycardia 13. Severe valvular heart disease, including aortic stenosis and pulmonic stenosis 14. Congenital heart disease 15. Coarctation of the aorta 16. Acute myocarditis 17. Marfan’s syndrome 18. Competition-enhancing agents (e.g., anabolic steroids, erythropoietin) 19. Illicit drugs (e.g., cocaine, inhalants) Cardiomyopathies Hypertrophic Cardiomyopathy
HCM is associated with exercise-related SCD in the young adult.6 In fact, death from HCM is more likely to occur during exercise than at rest.6 Up to 50% of SCD cases in young athletes are due to HCM.24,25 HCM also causes SCD in athletes older than 30 years, but at a much lower incidence. The findings of HCM typically include cardiomegaly, asymmetric septal hypertrophy (ASH), and myocardial cellular disarray. With HCM, the ventricle is hypertrophied, not dilated, which causes decreased ventricular filling owing to the increased ventricular muscle m a ~ s . 4The ~ hypertrophy is idiopathic, occurring in the absence of a cardiac or systemic condition such as aortic stenosis or systemic hypertension. The interventricular septal thickness is usually 15 mm or greater with the left ventricular free-wall thickness either normal or also increased. ASH is a term used to describe an interventricular septum to left ventricular free-wall ratio of 1.3 : 1.0 or greater. Abnormally thickened intramural coronary arteries with narrow lumens are also seen with HCM. In a series of SCD occurring during exercise in patients with HCM, 35.7% had a previous cardiac evaluation for symptoms that included syncope, family history, murmurs, fatigue, or VT on exercise testingz5 The mechanism of SCD in HCM is from ventricular arrhythmias, in most cases presumably caused by abnormal conduction by malformed muscle. The systolic murmur of HCM increases with Valsalva’s maneuver, by decreasing both the venous return to the right heart and left ventricular volume. It is heard best at the left lower sternal border to the apex. Approximately 90% of patients with HCM and more than 90% of HCM victims of SCD have abnormal electrocardiogram^.^^ A normal electrocardiogram suggests that HCM is absent.
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Echocardiographic evaluation of all young athletes as a screen for detecting HCM is probably not beneficial, because incidence of HCM is low. Moreover, it is difficult to distinguish mild forms of HCM from exercise-induced cardiac hypertrophy (athlete's heart syndrome). Cardiovascular evaluation including an echocardiogram is reasonable, however, for persons who wish to embark on a strenuous exercise regimen and who have a history of syncope, arrhythmias, or a family history of SCD. The echocardiographic finding of an increased ventricular septal thickness ( 2 15 mm) is a critical diagnostic feature of HCM. Increased left ventricular mass in an athlete may result in a 14-mm but rarely a 15-mm interventricular septal thickness. A small left ventricular cavity, anterior motion of the anterior leaflet of the mitral valve in systole, discrete areas of hypertrophy, and diastolic dysfunction are other echocardiographic findings suggestive of HCM. The presence of a first-degree relative with HCM is a factor indicating the diagnosis of HCM in the subject being evaluated. The cardiomegaly of HCM is visible on chest radiograph. ldiopathic Left Ventricular Hypertrophy Compared with HCM, idiopathic left ventricular hypertrophy (ILVH) is a less common cause of SCD in athletes. Unlike HCM, there are no myocardial cellular disarray or coronary artery abnormalities. ILVH probably results from undiagnosed hypertension, or it may represent a truly different form of idiopathic hypertrophy. Over 17% of cases of SCD occur in athletes with ILVH. Because exercise can increase left ventricular wall thickness and ventricular dilatation, some changes may result from the exercise process itself and may not represent a pathologic condition. The cause-effect relationship of ILVH in SCD is poorly established. Idiopathic hypertrophy should be considered a possible cause of death in only the absence of other causes. Right Ventricular Dysplasia Right ventricular dysplasia is an idiopathic cardiomyopathy primarily involving the right it is also called right ventricular cardiomyopathy or arrhythmogenic right ven tricular dysplasia. Right ventricular dysplasia is characterized by thinning of the right ventricular wall with dilatation. There is often an intermixing of fibrous tissue, fat, and myocytes in the affected area. Ventricular arrhythmias are a common clinical manifestation of this condition. Markers for sudden death from right ventricular dysplasia include T-wave inversion in the anterior precordial leads, a bundle branch block, sustained VT, and syncope." Atherosclerotic CAD
Jim Fixx's sudden cardiac death in 1984 was surprising because of his active promotion of cardiovascular fitness. He himself, however, had severe triple vessel coronary disease, with areas of previous myocardial necrosis. He was a middle-aged man (52 years) with hypercholesterol-
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emia (cholesterol 254 mg/dl) who had smoked two packs of cigarettes a day until he started running at the age of 36 years. His father had suffered a myocardial infarction at the age of 35 years and died 8 years later. Exercise-related deaths due to atherosclerotic CAD occur in even young subjects.= Most mature victims of SCD have advanced chronic atherosclerotic lesions. Postmortem examinations found lesions (275%) in at least three major vessels in 61% of the hearts at autopsy. Two-vessel disease occurred in 15%; only 24% of the hearts had either single-vessel study, 75% of victims of disease or no significant s t e n ~ s i sIn . ~ another ~ SCD had at least one coronary artery with 90% or more stenosis in contrast with 8% of victims with sudden death from other causes.2O Often, it is not the chronic fixed coronary lesion that causes death. Acute coronary artery changes were found at 95% of the postmortem examinations of sudden ischemic death victims. Recent acute thrombi were found in 74% of the hearts. Only 44% of the hearts had 50% or greater occlusion by the recent coronary thrombi; the remaining 51% had only minor occlusive thrombi or plaque fiss~ring.~ Some of these findings are explained by rupture of atherosclerotic plaque during exer~ i s eThese . ~ observations suggest that acute intraluminal coronary artery changes have a significant role in the initiation of a terminal rhythm, and that they do so by mechanisms extending beyond strictly arterial occlusion. For example, coronary artery spasm at the site of an acute thrombus or distal to it may precipitate a terminal arrhythmia. Mature athletes often know they have CAD before exercise-related SCD. Of the 51 cases of SCD caused by atherosclerosis in British squash players (all of whom were perceived as fit or very fit by relatives) prior symptoms of chest pain and fatigue were present in nearly one In one group of 44 joggers and runners who died suddenly, 22.7% had family histories of premature heart disease, 25.0% had systemic hypertension, 22.7% had cholesterol levels at or above 200 mg/dl, and 22.7% had a known history of coronary artery atherosclerosis.43,45 Coronary Artery Abnormalities Coronary Artery Spasm
Coronary spasm at the site of an acute thrombus or distal to a thrombus may precipitate VT-VF. Persistent coronary artery spasm has been observed at Interestingly, coronary artery spasm with resolution exposes the myocardium to the double hazard of transient ischemia and subsequent reperfusion. Exercise-induced coronary artery spasm can also contribute to exertion-related cardiac events.l4e37, 51 Coronary Artery Anomalies
Following HCM, coronary artery anomalies are the second most common cause of exercise-associated SCD in young athletes. There are
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multiple possible courses for an abnormal left main coronary artery. Most cases resulting in SCD involve patients with an anomalous left coronary artery that passes posterior to the right ventricular outflow tract; the exact mechanism of SCD from this anomaly is unknown. Nonetheless, theories include compression of the artery by the right ventricular outflow tract and coronary artery spasm. Angled takeoffs of the coronary ostium may contribute to terminal arrhythmias in the absence of other coronary artery anomalies. Theoretically, as a patient survives into adulthood the degree of atherosclerosis in the coronary vessel is accelerated owing to the circulatory turbulence created by the acute angled takeoff. Another anomaly of the coronary arteries is when the left main coronary artery arises from the pulmonary trunk. Because of the severe consequences of this condition, 90% of patients become symptomatic and die during the first year of life. A less serious but rarer anomaly is that of the left anterior descending coronary trunk arising from the pulmonary trunk. These patients typically present with angina in early adulthood. Another variation is a single coronary ostium giving rise to all three major coronary arteries. Other aberrant coronary artery formations are associated with SCD, including hypoplastic coronary arteries. Hypoplastic coronary arteries are diminutive vessels with markedly diminished, almost pinpoint lumina (usually < 1.5 mm).” In 1980, former basketball star Pete Maravich died suddenly during a pickup basketball game. He was found to have a rare anomaly-the presence of a single coronary artery. In his case, a single coronary artery was the right coronary artery; the left coronary artery was totally absent. Both marked cardiac hypertrophy and myocardial fibrosis were present on postmortem examination. Coronary artery anomalies are difficult to detect in the ED. Often there is a history of prior syncope. With multiple episodes of syncope, cardiac ischemia, or severe arrhythmias, an angiogram is required. An exercise electrocardiogram (ECG) to uncover ischemia and a two-dimensional echocardiogram to define the position of the left coronary artery may be helpful. Tunneled Coronary Arteries
With a tunneZed coronary artery, the coronary artery passes under myocardial muscle-forming a ”myocardial bridge.” A tunneled epicardial coronary artery is found in a significant number of subjects dying from noncardiac causes. In fact, myocardial bridging of the left anterior descending coronary artery is found in about 30% of autopsies. The precise role of a tunneled coronary artery SCD is therefore uncertain. Nonetheless, cases of tunnels that are 2 cm or longer have been associated with angina and SCD.3 In some cases, angina is relieved after debridging techniques. Because of the prevalence of asymptomatic tunneling, one must be cautious in assigning the cause of death to myocardial bridges.
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Electrophysiologic Etiologies
A pathologic examination of the conduction system is rarely performed in the evaluation of exercise-related SCD. The incidence of terminal arrhythmias without a structural defect in athletes varies widely; it can be as high as 50% in children and as low as 3% in a retrospective study of adults.=,31 Although the heart may appear normal at postmortem examination, that finding does not exclude a disorder of the conduction system. Electrophysiologic abnormalities causing SCD are extremely difficult to detect on postmortem examination. Subtle findings may include narrowed or sclerotic sinus node arteries? Direct sclerosis and calcification of the conduction system (i.e., sinus node, AV node, and His bundle) can also O C C U ~ . ~ Other electrophysiologic possibilities in the absence of ischemia include idiopathic prolonged QT syndrome,3* Wolff-Parkinson-White syndrome, and idiopathic ventricular fibrillation Prolonged QT syndrome is characterized by a corrected QT interval of greater than 440 msec, although at times the QT interval in these patients may be normal. Persons with prolonged QT syndrome are prone to syncope and cardiac arrest because of VT-VF. Fatal rhythms can be provoked by exerciserelated tachycardia; thus, anyone with this condition should be restricted from competitive sports. Patients with Wolff-Parkinson-White syndrome also have short refractory periods involving their accessory pathway and are at risk for both syncope and SCD. Other Disorders Commotio Cordis
Collision with another player or with a projectile (e.g., baseball) may produce a force sufficient enough to induce a lethal arrhythmia in a structurally normal heart, termed commotio ~ordis.'~Often, the impact to the chest is not judged initially to be extraordinary for the particular sport nor does it appear to have sufficient force to cause death. The most commonly implicated projectiles are baseballs, softballs, hockey pucks, and lacrosse balls. Other deaths have followed a blunt collision from a football helmet, karate kick, opponent's shoulder, and a hockey stick. On impact, the transfer of kinetic energy creates electrical instability during the cardiac cycle. Unfortunately, there is a low rate of rescue following commotio cordis, even with prompt resuscitative measures. Competition-enhancing Agents
SCD has occurred in athletes (especially weightlifters) abusing anabolic steroids.21With steroid-implicated deaths, there can be cardiac hypertrophy, myocardial fibrosis, accelerated atherosclerosis, and myo-
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cardial infarction.22Anabolic steroid use by competitive athletes modifies the lipid profile, predisposing one to CAD.” l6 Other complications of steroid use include platelet hypercoagulability and coronary artery vasospasm. Erythropoietin has been implicated (although not proven) as contributing to the deaths among Dutch and Belgian bicyclists from 1987 through 1990. Erythropoietin stimulates red blood cell (RBC) production and was used to increase aerobic capacity by increasing RBC mass. Its role in exercise-related SCD may result from the polycythemic state and potential thrombotic complications, including cerebral vascular accidents, cerebral thrombosis, and myocardial infarction. These complications are more likely to occur following prolonged exercise with relative dehydration, which increases blood viscosity and thrombotic potential. Despite this speculation, these deaths remain unexplained. Valvular Heart Disease
Mitral valve prolapse is extremely common and rarely associated with malignant arrhythmias. A permissive attitude toward sports participation is advocated in patients with mitral valve prolapse unless the patient has a history of syncope, disabling chest pain, complex ventricular arrhythmias, significant mitral regurgitation, prolonged QT syndrome, or a family history of sudden death. Severe aortic stenosis is a risk factor for exercise-related sudden death and is a definite contraindication to vigorous exercise. Because aortic stenosis produces a harsh systolic ejection murmur, it is easily diagnosed. Severe mitral valve stenosis and other complications of rheumatic heart disease may cause death. Finally, Epstein’s anomaly, or atrialization of the right ventricle, may also cause death from malignant tachyarrhythmias and right heart failure. Inflammatory Disorders
Acute myocarditis is an inflammatory process of the mycardium usually caused by a viral Common viral etiologies include the enteroviruses, coxsackie viruses, influenza viruses, and cytomegalovims. Bacterial pathogens include Mycoplusma pneumoniue, Chlamydia sp., betahemolytic Streptococcus and Corynebucteriumdiphtheriue. Infectious myocarditis is suspected when a patient has chest symptoms during or soon after a flulike illness.’* Chest pain can mimic either pericarditis or angina. Palpitations from ventricular extrasystoles are common. Other symptoms include dyspnea, orthopnea, cough, and decreased exercise intolerance. An audible S3gallop or soft apical murmur may be present as well as signs of congestive heart failure. The chest radiograph may show an enlarged cardiac silhouette. The ECG may show low voltage complexes, diffuse ST-segment and T-wave changes, and sinus tachycardia. Death is usually due to ventricular arrhythmias. Exercise-related SCD secondary to inflammatory coronary artery aneurysms from Kawasaki’s disease can also occur.3o,31
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Miscellaneous Conditions Congenital Disorders. Congenital heart disease along with the corrective surgical procedures can create anatomic irregularities that predispose subjects to SCD. Congenital problems associated with death include uncorrected aortic stenosis and pulmonary vascular obstructive disease. Cardiovascular Toxins. Recreational and illicit drugs such as cocaine and abuse of inhalants can precipitate SCD during strenuous physical activities. Cocaine is primarily sympathomimetic. Volatile substances (inhalants) also cause cardiac dysrhythmias. Marfan’s Syndrome. Marfan’s syndrome may cause sudden death by aortic rupture or dissection, which is what happened to Flo Hyman, the US Olympic volleyball star, who died in January 1986 while playing volleyball in Japan. Patients with Marfan’s syndrome die from aortic dissection or rupture, with mediastinal hemorrhage, pericardial tamponade, coronary artery dissection, acute aortic insufficiency, and rapid congestive heart failure. Patients with Marfan’s syndrome should be restricted from high-impact activities. ATHLETIC HEART SYNDROME
Athletic heart syndrome (AHS) is benign syndrome characterized by physiologic adaptations for increased physical performance. Changes include cardiac chamber enlargement, increased ventricular wall thickness, and increased vagal tone. On physical examination, the athlete has bradycardia with sinus irregularity. The pulse is often strong secondary to an increased stroke volume. Auscultation discloses a normal first and second heart sound. Frequently an S, or S, gallop is heard.s,12A systolic ejection murmur results from an increased stroke volume. First-degree AV block, Mobitz type I second-degree AV block, and junctional bradycardia can be seen. Early repolarization consisting of ST elevation greater than 0.5 mm in two consecutive leads, often localized to the precordium and often with terminal slurring of the R wave, is considered benign. Lateral T wave inversion can also be seen as part of the early repolarization variant. A chest radiograph or echocardiogram can show fourchamber cardiac enlargement. Lack of recognition of these changes as probable or possible normal findings in athletes may lead to an erroneous diagnosis of a cardiovascular disorder. SCREENING EXAMINATIONS
Echocardiographic screening in young athletes is ineffective primarily because athletes can have mildly hypertrophied hearts as normal variants (AHS). Moreover, the overall incidence of structural cardiac disease is quite small, making it more likely that one would overdiagnose a patient than correctly discover disease. Among patients with
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structural disease that would be detected on echocardiogram, there are often prior symptom^.'^ Therefore, it is reasonable to conduct more thorough screening in any patient having a family history of premature sudden death, or those with a prior history of syncope, significant arrhythmias, or chest pain. Routine preparticipation stress testing is recommended for adults at risk for exercise-related death.'O Nonetheless, the infrequency of exercise deaths still limits the yield of any screening procedures. Positive results from screening examinations are often due to normal variants. In addition, SCD from CAD is often caused by an acute change in a coronary lesion, such as plaque rupture or thrombus. In one study, symptomlimited exercise stress tests were performed on 916 Indiana state policemen. Of these, 61 had an abnormal response to exercise. Of these 61 subjects, 18 went on to develop angina, one suffered a myocardial infarction, one remained asymptomatic but went on for coronary artery bypass graft, and one had SCD. Surprisingly, there were 25 myocardial infarctions, 7 SCDs, and 12 persons who developed angina all within the group with normal ECG responses (n= 855).27In the Lipid Research Clinics Primary Prevention Trial, 3617 men with baseline total cholesterol levels above 265 mg/dl and low-density lipoprotein concentration above 190 mg/dl were subjected to exercise tests to 90% of their age-predicted maximal heart rate. Of the 62 men who subsequently experienced an exercise-related cardiac event, only 11 (17.7%) had a previously positive exercise test result.40 THE ROLE OF THE EMERGENCY PHYSICIAN
The role of the emergency physician is to attempt to resuscitate those patients who have had SCD events. If resuscitation is successful, appropriate antiarrhythmic therapy and stabilization is indicated. Likewise, the physician must recognize those patients at risk for SCD, including the young athlete who has experienced syncope or cardiopulmonary complaints during exercise. In the mature athlete, the emergency physician must seek indications of dysrhythmia or ischemic CAD. Athletes should be counseled against athletic participation if certain conditions are discovered (see "Causes of Sudden Cardiac Death). One should inquire about the athlete's symptoms. The medical history includes questions about syncope, exercise tolerance, and any known cardiac (including congenital) disease. Specifically, information about exercise syncope, angina pectoris, and extreme exertional dyspnea should be gathered. One also must determine the presence of chronic disease such as diabetes mellitus and hypertension. A family history of congenital heart disease, syncope, or unexpected death at an early age should be sought. Symptoms such as chest pain, fatigue, heartburn, indigestion, and excessive breathlessness have been reported in persons prior to sudden death. The physical examination should elicit evidence of Marfan's syndrome, aortic stenosis, hypertension, and HCM. The
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physician must listen for the murmur of idiopathic hypertrophic subaortic stenosis in the young person. In mature athletes, signs and symptoms of cardiac ischemia must be reviewed. New symptoms of exercise intolerance, such as syncope, unusual dyspnea, and chest discomfort, may be symptoms of important cardiac diseases and should be carefully evaluated in athletes of all ages. Certain findings should cause concern, including profound bradycardia or high-grade AV block in an athlete not engaged in endurance training, sinus pauses longer than 3 seconds, complete heart block, and syncope or near syncope at rest or after strenuous exercise. Other conditions may predispose one to increased risk of SCD during exercise, including uncontrolled hypertension, uncontrolled atrial arrhythmias, hemodynamically significant valvular disease, and exercise-induced bronchospasm. Certain historical signs and symptoms suggest specific diagnoses. For example, a history of syncope or near syncope may suggest HCM, valvular heart disease, or idiopathic prolonged QT syndrome. Tests that may be helpful in defining disease are serum lipid profiles, resting and exercise electrocardiograms, and echocardiography. These studies should be done selectively depending on age and clinical profile of the patient. As stated before, a resting electrocardiograph or echocardiogram is not helpful in screening the apparently healthy young adults; this is also true for chest radiographs. These studies do become more and more helpful as the age of patients increase, however. STRATEGIES FOR PREVENTION OF SCD
Strategies for preventing SCD are not complex but do require knowledge of certain conditions. Coaches and trainers should observe athletes during exercise. Physicians should do screening examinations to try to assess the level of stress activity that is safe, especially in mature athletes. Athletes experiencing exertional chest discomfort, syncope, near syncope, tachyarrhythmias, and impaired performance require further evaluation. When an athlete collapses, he or she requires prompt attention because it may be cardiopulmonary arrest and not merely heat exhaustion. Emergency physicians should participate with local sport and activity programs to design a plan for immediate on site emergency treatment, including transportation to and care in the ED. References 1. Amsterdam EA, Laslett L, Holly R Exercise and sudden death. Cardiol Clin 5:337343, 1987 2. Baldo-Enzi G, Giada F, Zuliana G, et al: Lipid and apoprotein modifications in body builders during and after self-administratiin of anabolic steroids. Metabolism 39:20$ 208, 1990
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