Current Concepts
Cardiovascular Disease in Athletes
Frederick C. Basilico MD
Am J Sports Med
27:108-21
W. T. Nessa, MD, Center for Sports Cardiology, New England Baptist Hospital, Boston, Massachusetts
Address correspondence and reprint requests to Frederick C. Basilico, MD, Chief, Section of Cardiology,
New England Baptist Hospital, 125 Parker Hill Avenue, Boston, MA 02120.
Neither the author nor his related institution has received any financial benefit from research in this study.
As a physician, coach, or trainer, we see athletes as healthy, physically fit, and able to
tolerate extremes of physical endurance. It seems improbable that such athletes may
have, on occasion, underlying life-threatening cardiovascular abnormalities. Regular
physical activity promulgates cardiovascular fitness and lowers the risk of cardiac
disease. However, under intense physical exertion and with a substrate of significant
cardiac disease--whether congenital or acquired--athletes may succumb to sudden
cardiac death. The deaths of high-profile athletes receive much attention through the
national news media, but there are also deaths of other athletes. With repetitive,
intense physical exercise, the heart undergoes functional and morphologic changes.
Knowledge of those changes may help one identify cardiovascular abnormalities that
can cause sudden death from the heart known as an "athlete's heart." This article will
review cardiovascular diseases that may limit an athlete's participation in sports and
that may put an athlete at risk for sudden cardiac death. It also reviews the extent and
limitations of the cardiovascular preparticipation screening examination. Team
physicians, coaches, and trainers must understand the process of evaluation of a
symptomatic athlete that may indicate significant cardiac abnormalities. Finally,
guidelines to determine eligibility of athletes with cardiovascular disease to return to
sports will be reviewed.
SUDDEN CARDIAC DEATH
The death of an athlete from sudden cardiac collapse is a tragic event and has great impact
on the family, the community, and the medical establishment. The deaths of Hank Gathers,
[33] a college basketball player, of Sergei Grinkov, a former Olympic gold medal skater, of
Reggie Lewis, a professional basketball player, and of Jim Fixx, a long-distance runner and
fitness advocate, have great public interest and have generated public debate. Sudden
cardiac death related to sports can involve any athlete from the older, highly trained, elite
athlete to the young, school-aged athlete. In each instance, the question always arises as to
how someone who is physically fit and who has seemingly been screened to participate in
sports can die from a cardiac abnormality.
"Sudden death is defined as a witnessed or unwitnessed natural death resulting from sudden
cardiac arrest occurring unexpectedly within 6 hours of a previously normal state of
health." [35] Other definitions limit the time frame of sudden cardiac death in athletes, such as
during or 1 hour after supervised or unsupervised exercise. [12]
For the purpose of this discussion, a competitive athlete is considered to be a person who
participates in an organized team or individual sport in which regular competition is a
component. A high priority is placed on excellence and achievement in the sport. Vigorous
training in a systematic fashion is required for the sport. [35] [40] [48]
Epidemiology
The origin of sudden cardiac death in athletes is influenced by the intensity of competition.
Those sports that involve particularly high levels of exertional intensity may provide an
intense triggering factor for cardiac arrest. [51] [52] Sports such as basketball, football, track,
and soccer have the highest incidence of sudden death in young athletes. [43] The common
denominator of all sudden death events is the development of electrical instability leading
to a fatal arrhythmia. It is the combination of exercise and underlying heart disease, rather
than exercise alone, that usually leads to the final common pathway of lethal arrhythmia. [26]
[52] [53] In the older athlete (age >40), coronary artery disease is the most common cause of
sudden death among athletes. Intense physical activity can lead to atherosclerotic
109
plaque rupture, reducing coronary blood flow and producing ischemia and electrical
instability. In the younger athlete, multiple causes, including congenital abnormalities, may
lead to electrical instability during intense exercise. [61]
The estimated risk of sudden death among high school and college athletes ranges between
1 in 100,000 and 1 in 300,000. [43] [64] There are approximately 50 sudden cardiac deaths per
year among athletes, and there is a preponderance among male athletes. The incidence of
sudden cardiac death increases with age. [42] Estimates of sudden cardiac death among
people who exercise vigorously, such as joggers, in the older population ranges from 1 in
15,000 to 1 in 18,000. [58] [62] The incidence of cardiovascular collapse as the cause of athletic
fatalities in high school and college athletes outnumbers death caused by trauma nearly 2 to
1. [9]
Causes
There are different causes of sudden cardiac death in athletes in two major age groups. The
dividing age is 35: causes affecting younger athletes (<35 years old) are different from
those affecting older athletes (>35 years old). In the younger age group, over 40% of all
sudden deaths are due to hypertrophic cardiomyopathy (Table 1) . [7] [35] [43] [64] Approximately
10% of these deaths are due to idiopathic left ventricular hypertrophy, which is defined as
an unexplained increase in cardiac mass and does not meet the criteria for the diagnosis of
hypertrophic cardiomyopathy. Diseases of the myocardium, including myocarditis (usually
virus-related), dilated cardiomyopathy, and arrhythmogenic right ventricular dysplasia
account for 8% of deaths. Infrequent causes include ruptured aorta, congenital prolonged
QT syndrome, mitral valve prolapse, sarcoidosis, aortic valve stenosis, and atherosclerotic
coronary artery disease. In older athletes, the most frequent cause (>75%) of sudden cardiac
death is coronary artery disease. Infrequent causes in this age group include mitral valve
prolapse, hypertrophic cardiomyopathy, and acquired valvular heart disease. [35]
TABLE 1 -- Causes of Sudden Cardiac Death in 288 Young Competitive Athletesa a
Cause of death
%
Hypertrophic cardiomyopathy
42
Increased LV Mass/Possible HCM
Anomalous coronary artery
9
17
Other CAD
9
Myocarditis
5
Dilated cardiomyopathy
4
Ruptured aortic aneurysm
3
Aortic valve stenosis
3
ARVD
2
MVP
2
Unknown/other
4
Data derived from Burke et al., [7] Maron et al., [35] [43] and Van Camp et al. [64] LV, left ventricular; HCM,
hypertrophic cardiomyopathy; CAD, coronary artery disease; ARVD, arrhythmogenic right ventricular
dysplasia; MVP, mitral valve prolapse.
a
THE ATHLETIC HEART
Intense and repetitive physical exercise causes the heart to undergo functional and
morphologic adaptations that may distinguish it from what is considered a "normal" heart.
This morphologic adaptation is considered a normal myocardial variant and is the result of
changes produced by the response of the myocardium to pressure or volume, or both,
overload. [21]
Physiologically, the heart maintains its ability to function as a pump by altering heart rate
and contractility when under increased demand. [21] The left ventricular cavity may dilate
under an increased volume demand, such as that needed for aerobic (dynamic) exercise as
in running or cross-country skiing. Left ventricular mass increases to normalize wall stress,
as evidenced by increased left ventricular septal and free wall thickness. This adjustment is
in keeping with Laplace's law, which explains the equilibrium relationship in a concave
surface (wall stress = pressure × radius/[wall thickness × 2]). [67] Although both wall
thickness and left ventricular end-diastolic dimension increase, the mass-to-volume ratio
remains constant. [66] This increase in volume and wall thickness is considered a normal
adaptation for athletes who require increased cardiac output during exercise. [21]
In athletes who require significant pressure overload during isometric (static) exercise, such
as weightlifters and rowers, there is a significant increase in myocardial mass without an
increase in left ventricular volume. This type of activity can require tremendous, brief
increases in cardiac output against the increased resistance of an extremely high systolic
blood pressure, which may sometimes reach 300 mm Hg. [21] These athletes demonstrate
significant wall thickening that normalizes wall stress at high afterload. [21] [66] Therefore, the
hallmark feature in the heart of the isometric (static) athlete is an increased mass-to-volume
ratio. Physiologic hypertrophy is usually symmetric; asymmetry should make one suspect
pathologic hypertrophy.
Electrocardiogram
When evaluating an athlete, it is important to be aware that substantial variability may
appear on an electrocardiogram (ECG). Rhythm disturbances as well as voltage and
repolarization changes are common. The majority of abnormal ECG findings are due to
increased vagal tone, reduced sympathetic tone, and physiologic hypertrophy. [21] The most
common finding on the resting ECG of an athlete is sinus bradycardia, which is sometimes
accompanied by heart rates as slow as 25 beats per minute. [21] [67] Atrioventricular block-including first-, second- (usually Mobitz type I), and, rarely, third-degree atrioventricular
block--can be found. A higher incidence of atrial arrhythmia, wandering atrial pacemaker,
junctional rhythm, and atrial fibrillation, compared with controls, has been reported. [67]
The ECGs of well-conditioned athletes may have a vertical shift of the QRS axis and
increased QRS voltage. The ECG findings for left ventricular hypertrophy have been
110
documented in 10% to 80% of athletes. [67] [69] An ST segment elevation with narrow T
waves (early repolarization) is present in up to 50% of athletes' ECGs. [67] [69] Additionally,
30% of athletes' ECGs may demonstrate inverted T waves (Fig. 1) . [69] Because these ST
segment and T wave changes are presumed to be vagally induced, the changes often
normalize with exercise as vagal tone becomes inhibited. [67] These changes should resolve
with cessation of regular exercise. [67] [69]
Echocardiogram
The echocardiogram of a highly trained or elite athlete can be variable. Studies have shown
that athletes competing in a variety of sports demonstrate an increase of left ventricular
mass, with an average increase of 46% compared with control subjects. [4] [5] [33] Left
ventricular end-diastolic volume is increased in athletes who participate in aerobic
(dynamic) sports by approximately 10% compared with matched sedentary controls, or an
approximate 33% increase in left ventricular volume. [33] Left ventricular septal and posterior
wall thicknesses often increase in male athletes and not in female athletes. [53] In most cases,
wall thickness is usually not greater than 13 mm, and the ratio of septal to posterior wall
thickness is usually less than 1.3:1. [33] Wall thickness between 14 and 16 mm and ratios
greater than 1.3:1 may fall into a gray zone and may be secondary to intense conditioning
or part of a mild pathologic process of hypertrophic cardiomyopathy. Left ventricular
hypertrophy can occur at an early stage of intense conditioning, and has even been
documented to occur after 1 week of training. [32] Conversely, deconditioning can lead to
loss of left ventricular mass noted on repeat echocardiogram as early as 1 week after
cessation of exercise. [32] In certain instances, echocardiogram after deconditioning may help
distinguish athletes with borderline abnormal increase in left ventricular wall thickness.
Significant left ventricular hypertrophy that does not diminish with deconditioning may
indicate pathologic hypertrophy.
Figure 1. The ECG of 22-year-old professional basketball player demonstrating left ventricular
hypertrophy, ST segment elevation, and T wave inversion (arrow) in precordial leads consistent with an
athletic heart. Echocardiogram and exercise test were normal.
SPECIFIC CARDIAC ABNORMALITIES
Hypertrophic Cardiomyopathy
Hypertrophic cardiomyopathy is a disorder of the cardiac muscle that is revealed in many
different ways. The estimated prevalence of hypertrophic cardiomyopathy in the general
population is about 1 in 500. The disease has a familial transmission as an autosomaldominant trait with variable expression, so not all people with the gene trait will have the
disease. Molecular studies demonstrate the heterogeneity of this disease, which can be
caused by mutations in the cardiac sarcomere (the beta myosin heavy chain, cardiac
troponin T, alpha tropomyosin, and myosin-binding protein C gene). [59] The cellular
architecture of the left ventricle is characteristically disorganized. Myocardial cells appear
bizarre in shape with multiple intracellular connections arranged in chaotic patterns. [31] Left
ventricular wall thickening may appear in multiple patterns. Left ventricular hypertrophy
involving the septum is the predominant type of hypertrophy. [13] Left ventricular wall
thickness can vary from mild (13 to 15 mm; normal, <12 mm) to massively increased,
including the most substantial hypertrophy observed in any cardiac disease (>30 mm). [25] [31]
It may be difficult to distinguish mild hypertrophic cardiomyopathy from normal left
ventricular hypertrophy in the highly trained athlete. [41] In general, wall thickness greater
than 13 mm is very uncommon in highly trained athletes, found usually only in athletes
training in rowing sports, and is associated with left ventricular cavity dilation. [41] [54] Left
ventricular outflow tract obstruction is usually associated with hypertrophic
cardiomyopathy (Fig. 2) .
Most athletes who have hypertrophic cardiomyopathy have no symptoms. [38] Some athletes
may develop lightheadedness, syncope, shortness of breath, or chest pain. Abrupt changes
in left ventricular filling, such as caused by dehydration or vasodilation, may lead to
decreased left ventricular filling, increased outflow tract obstruction, and abrupt decrease in
blood pressure that results in lightheadedness or syncope. Left ventricular wall stiffness can
increase left ventricular filling pressure causing dyspnea. The demand of a large left
ventricular mass is greater than the supply of coronary blood flow, and may lead to
increased pressure, tightness, or pain in the chest.
The first clinical manifestation of hypertrophic cardiomyopathy may be sudden cardiac
death. The mortality rate of hypertrophic cardiomyopathy is approximately 2% to 4% in
young adults. No symptom has been shown to be a reliable predictor of sudden cardiac
death except repetitive syncope. However, other disease variables may be associated with a
high risk of sudden death: young age, massive left ventricular hypertrophy (>30 mm),
family history of unusually frequent sudden death, and nonsustained ventricular tachycardia
as determined by Holter monitoring. [36] [37]
111
Figure 2. Echocardiogram of a 24-year-old former collegiate hockey player with hypertrophic
cardiomyopathy. A, two-dimensional, echo, apical, four-chamber view demonstrating marked
hypertrophy of the septum and lateral wall; B, two-dimensional, echo, short axis view; C, Doppler
study demonstrating a peak velocity of 5 m/sec consistent with a 100 mm Hg outflow tract gradient; D, Mmode echocardiogram demonstrating systolic anterior motion of mitral leaflet (arrow). AP, apical; LV, left
ventricular cavity; LAT, lateral; IS, interventricular septum; RV, right ventricle; ANT, anterior; POST,
posterior wall.
Idiopathic Left Ventricular Hypertrophy
This condition accounts for approximately 10% of all sudden cardiac death in young
athletes. The autopsy findings reveal an unexplained increase in cardiac mass and mild left
ventricular wall thickening, but without the clinical or characteristic morphologic fiber
disarray that characterizes hypertrophic cardiomyopathy. It may be difficult to distinguish
between idiopathic left ventricular hypertrophy, hypertrophic cardiomyopathy, and athletic
heart syndrome. In the absence of other clinical findings, such as family history and serum
markers of hypertrophic cardiomyopathy and hypertension, left ventricular wall thickness
of 13 to 14 mm is of intermediate diagnostic value and often included as idiopathic left
ventricular hypertrophy.
Coronary Artery Abnormalities
Anomalous origin of the coronary artery is the most common coronary abnormality leading
to sudden cardiac death and is often first discovered at autopsy. The first indication of this
congenital abnormality may be an athlete who has symptoms of dyspnea or chest pain,
pressure, or tightness; such symptoms should alert the evaluating physician to consider this
diagnosis. [11] Echocardiography can sometimes demonstrate the origin of the left main
coronary artery, and sometimes the right coronary artery if the echo window is satisfactory.
The anomalous artery can be of two types: the left coronary artery arises from the right
sinus of Valsalva, or the right coronary artery arises from the left sinus of Valsalva. [11] The
ostium of the anomalous artery is often slitlike and makes an acute bend between the
ascending aorta and the pulmonary trunk. [43] Coronary ischemia during exercise is produced
by this narrow ostium or by the impingement of the coronary artery as it traverses between
the aorta and the pulmonary trunk (Fig. 3) .
Other coronary anomalies include hypoplasia (small size and short course), aneurysm, and
acute angle take-off of the left main coronary artery. [43]
The incidence of atherosclerotic coronary vascular disease increases with advancing age.
This disease is characterized by formation of the cholesterol- and fat-laden plaque within
the coronary circulation. Supply-demand
112
and
Figure 3. Diagram showing proposed mechanism of ischemia of anomalous right (upper panel)
left (lower panel) coronary arteries. With exercise, the aorta and pulmonary trunk dilate,
producing torsion and additional narrowing of the ostium of the anomalous artery. (Adapted from
Waller.[65] )
mismatch in the coronary circulation can lead to ischemia and the development of
arrhythmia. Abrupt plaque rupture during intense physical exertion can produce acute
coronary occlusion, acute myocardial infarction, and sudden cardiac death. Such death from
atherosclerotic coronary vascular disease is extremely rare in the high school or college
athlete. If premature atherosclerotic coronary vascular disease is diagnosed, a search for
causes such as familial hypercholesterolemia or arteritis should be initiated. [63]
Arrhythmogenic Right Ventricular Dysplasia
Arrhythmogenic right ventricular dysplasia is a relatively rare cause of myocardial disease
in North America; however, it is the most common cause of sudden cardiac death in
northern Italy. [12] This disease is characterized by the fatty infiltration and fibrosis of
primarily the right ventricle, but occasionally the left ventricle may be involved. This
infiltration may lead to right or, less commonly, left ventricular dysfunction. An athlete
with this disease may have an arrhythmia, especially ventricular arrhythmia with left
bundle-branch block pattern. [68] Diagnosis may sometimes be difficult. An ECG may reveal
abnormal T waves in the precordium. Although rarely found, a characteristic epsilon wave
is a sure diagnostic sign of this disease (Fig. 4) . If echocardiography does not demonstrate
right ventricular dilation and dysfunction, an MRI can sometimes be diagnostic in
demonstrating fatty infiltration of the myocardium. [30]
Abnormalities of the Cardiac Conducting System
Wolff-Parkinson-White syndrome is an abnormality of the cardiac conduction system
whereby an additional electrical pathway can lead to tachycardia and, rarely, sudden
cardiac death. [17] [24] This conduction abnormality is relatively rare, affecting only 0.15% to
0.20% of the general population, and has a very small risk of sudden cardiac death (less
than 0.1%). [68] The resting ECG demonstrates an initial slurred QRS complex upstroke,
which is the delta wave (Fig. 5) . Persons may have various symptoms including
palpitations, lightheadedness, and syncope. The mechanism of sudden cardiac death is the
development of atrial fibrillation with rapid atrioventricular conduction via the bypass tract,
resulting in rapid ventricular response (at rates of 300 beats per minute) and subsequent
ventricular fibrillation. [24] Athletes with evidence of Wolff-Parkinson-White syndrome
should be screened with exercise testing and 24-hour arrhythmia monitoring to monitor
development of atrial fibrillation. [70]
Long QT syndrome is a congenital abnormality of the electrical conduction system
characterized by prolonged repolarization of the ventricle, and there is an associated
113
Figure 4. Diagram of leads V1 and V2 of normal (left) and abnormal (right) ECG depicting
epsilon wave (arrow) in a patient with arrhythmogenic right ventricular dysplasia (ARVD).
Figure 5. An ECG (recorded at twice the standard) of a 17-year-old asymptomatic high school lacrosse
and football player with Wolff-Parkinson-White syndrome type B. Note the short PR interval and delta
wave (arrows). Subsequent exercise tolerance test and 24-hour monitoring (including during sports
practice) were negative for arrhythmia. The athlete was allowed to participate in sports without restriction.
high risk of sudden cardiac death. Most life-threatening arrhythmias in long QT syndrome
occur during emotional stress and physical activity. Mutations that cause the congenital
long QT syndrome have been identified in three genes, each involving a cardiac ion
channel. [1] [49] [55] The mechanism of sudden cardiac death is the development of wide,
polymorphic tachycardia, that is, torsades de pointes. [60]
The QT interval prolongation may be secondary to a variety of conditions, including
reactions to drugs such as antiarrhythmics, antibiotics, antidepressants, and certain
nonsedating antihistamines, as well as with hypokalemia and hypomagnesemia (Table 2) .
As in the congenital syndrome, delayed repolarization may cause polymorphic ventricular
tachycardia, torsades de pointes, and sudden cardiac death. [49]
TABLE 2 -- Causes of the Long QT Syndrome (LQTS) a
Inherited
Romano-Ward (autosomal dominant, normal hearing)
Jervell and Lange Nielson (autosomal recessive, sensorineural hearing loss)
LQTS with syndactyly
Sporadic
Acquired
Drugs
Antiarrhythmics
Class IA
Quinidine
Procainamide
Disopyramide
Class III
Sotalol
Dofetilide
Bretylium
Amiodarone (rare)
Antidepressants
Tricyclics (e.g., amytriptyline)
Tetracyclics
Antifungals
Itraconazole
Ketoconazole
Antihistamines
Astemizole
Terfenadine
Antimicrobials
Erythromycin
Chloroquine
Neuroleptics
Phenothiazines
Haloperidol
Organophosphate insecticides
Promotility agents (cisapride)
Electrolyte derangement
Hypocalcemia
Hypokalemia
Hypomagnesemia
Medical conditions
Arrhythmias
Cardiac
Myocarditis
Tumors
Neurologic
Cerebrovascular accident
Encephalitis
Head trauma
Subarachnoid hemorrhage
Endocrine
Hypothyroidism
Pheochromocytoma
Nutritional
Alcoholism
Anorexia nervosa
Liquid-protein diet
Starvation
a
Data derived from Ackerman. [1]
114
Aortic Rupture
Weakening of the wall of the aorta due to Marfan's syndrome or cystic medial necrosis can
lead to aortic aneurysm and abrupt rupture of the aorta, which may result in sudden cardiac
death. [58] Athletes with Marfan's syndrome have skeletal defects such as arachnodactyly
(long fingers), scoliosis, ectopic lens, elevated hard palate, and wingspan greater than
height. [68] Echocardiographic findings may include mitral valve prolapse, aortic root
dilation, and aortic regurgitation. The underlying mechanism of aortic root dilation is cystic
necrosis of the medial layer of the aorta, which leads to weakening and potential rupture of
the aorta. Occasionally, the cardiac manifestations may be present without the skeletal
manifestations (forme fruste). [13]
Mitral Valve Prolapse
Mitral valve prolapse is a common occurrence in the general population but is an infrequent
cause of sudden cardiac death. Most athletes with mitral valve prolapse are totally
asymptomatic. Occasionally, athletes may experience chest pressure or pain, palpitations,
lightheadedness, or dyspnea. Physical examination may reveal the characteristic
midsystolic click and late systolic murmur. Further evaluation may be required in persons
with moderate-to-severe mitral regurgitation or with symptoms of dyspnea. If an athlete has
syncope, a family history of sudden cardiac death, exertional chest pain, or moderate or
severe mitral regurgitation, it is recommended that athletic participation be restricted. [37]
Myocarditis and Cardiomyopathy
Inflammation of the heart muscle, or myocarditis, has rarely been associated with sudden
cardiac death. The most likely cause of myocarditis is acute viral infection of the
myocardium by either Coxsackievirus or echovirus. Illicit drug (for example, cocaine) use
can also cause myocardial inflammation. Sudden cardiac death may occur in persons with
healed as well as active myocarditis and may be due to the development of electrical
instability in the left ventricle. [37] Athletes with active myocarditis should not engage in
sports and may require up to 6 months of convalescence before returning to sports. [37]
Prolonged myocardial inflammation may lead to weakening of the heart muscle, or
cardiomyopathy. Most diffuse cardiomyopathies are idiopathic and are presumed to be
viral-related. However, ethanol and infiltrative processes such as amyloid or
hemachromatosis may be causes. The development of myocardial scarring can provide a
focal point for development of ventricular arrhythmia and the potential for sudden cardiac
death.
Valvular Heart Disease
Aortic stenosis in the athlete is usually congenital and is characterized by a bileaflet valve
instead of the normal trileaflet aortic valve. In severe aortic stenosis, the valve cusps are
fused, which causes doming of the valve and a significantly increased pressure between the
left ventricle and aorta. This pressure overload of the left ventricle can produce chest
pressure or pain, lightheadedness, syncope, or dyspnea. On physical examination, an early
ejection click and a loud ejection systolic murmur at the base of the heart is heard, and there
is a delayed and slow upstroke of the carotid pulse. Because it is relatively easy to search
for this abnormality on the physical examination, it is an infrequent cause of sudden cardiac
death. The degree of severity of aortic stenosis can often be determined during the physical
examination and by echocardiography. However, the distinction between moderate and
severe stenosis may be difficult by noninvasive methods, and cardiac catheterization may
be required. Because the lesion may progress in severity over time, periodic reevaluation
may be necessary. [19]
Aortic regurgitation has multiple causes, including 1) congenital bicuspid aortic valve, 2)
rheumatic heart disease, 3) infectious endocarditis, and 4) aortic root diseases such as
Marfan's syndrome, ascending aortic aneurysm, aortic dissection, systemic hypertension,
and rheumatoid spondylitis. [10] Aortic regurgitation, when severe, leads to left ventricular
volume overload and, ultimately, congestive heart failure. Physical examination and
Doppler echocardiogram can be very sensitive in determining the degree of aortic
regurgitation. [10]
Mitral stenosis is usually of rheumatic origin. Mitral stenosis rarely causes sudden cardiac
death because most patients with severe cases of this disease have dyspnea on minimal
exertion and therefore do not wish to engage in sports. [10] Exercise in these patients
produces significant increase in left atrial pressure and pulmonary capillary wedge pressure
causing dyspnea and congestive heart failure. Echocardiography with Doppler analysis can
determine the severity of stenosis.
Mitral regurgitation has a variety of causes, including 1) mitral valve prolapse, 2) rheumatic
heart disease, 3) infectious endocarditis, 4) coronary heart disease, 5) Marfan's syndrome,
and 6) dilated cardiomyopathy. [10] The severity of mitral regurgitation is related to the
degree of regurgitant volume within the left atrium, which leads to diastolic left ventricular
volume overload. Severe mitral regurgitation can cause congestive heart failure.
Determination of the severity of mitral regurgitation can sometimes be difficult by physical
examination and by Doppler echocardiography. Doppler may underestimate the severity of
mitral regurgitation when the regurgitation flow is off-center and hugs the atrial wall
instead of the center of the left atrium.
Congenital Heart Disease
Atrial septal defect is characterized by a persistent opening in the wall between the right
and left atria. A systolic ejection murmur that is best heard at the base of the heart and a
fixed split to the second heart sound is characteristic. Such defects in childhood are usually
asymptomatic and, when corrected in childhood, they do not lead to development of
complications such as pulmonary hypertension
115
or arrhythmias that may limit participation in sports. The ECG and echocardiogram must
be performed to determine the degree of shunt, the degree, if any, of pulmonary
hypertension, and the coexistence of supraventricular or ventricular arrhythmia to
determine eligibility to play or return to sports. [19]
Ventricular septal defect is characterized by a persistent opening in the wall between both
ventricles and may be categorized as small, moderate, or large. The holosystolic murmur at
the midparasternal area is a definitive sign of ventricular septal defect. If physical
examination and ancillary studies indicate normal heart size and normal pulmonary artery
pressure in patients with a clinically suspected small ventricular septal defect, then further
evaluation is not required. [19] A patient with a ventricular septal defect that does not readily
fit into the small defect category requires further investigation, usually by
echocardiography. [19]
CARDIOVASCULAR PREPARTICIPATION SCREENING
EXAMINATION
Goal of Preparticipation Examination
The goal of the preparticipation cardiovascular screening examination is to identify athletes
with unsuspected heart disease. The extent of the preparticipation cardiovascular screening
examination continues to be debated [2] [6] [14] ; however, guidelines for accepted criteria have
been established for the team physician. [18] [44] [46] These guidelines were developed to provide
prudent, practical, and effective screening procedures. Because of the budgetary constraints
of most athletic programs, especially at the high school and college levels, cost-effective
screening is necessary. Extensive, multisystem preparticipation cardiovascular screening
examinations have been developed for athletes of professional teams, which are not under
significant financial constraint. [57] The team physician must be aware of the limitations of
the preparticipation cardiovascular screening examination as part of their ethical obligation
to ensure that athletes are not subjected to unacceptable medical risk. [45]
Guidelines
The American Heart Association, the American Academy of Pediatrics, and the American
College of Cardiology have endorsed the following guidelines for the preparticipation
cardiovascular screening examination. [45]
1. All high school and college athletes should undergo a routine preparticipation
screening examination.
2. The examination is to be performed by a health care worker (preferably a licensed
physician) who has the medical skills, background, and training to perform a
reliable history examination and physical examination and to recognize heart
disease.
3. The evaluation should include a complete medical history and physical
examination, including brachial artery blood pressure measurement.
4. The examination is considered mandatory and should be performed before
participation in high school and collegiate sports.
5. In the high school athlete, screening must occur every 2 years, with an interim
history in intervening years.
6.
For the collegiate athlete, a comprehensive history and physical examination must
be performed in the 1st year on entering the institution and before training and
competition. In each of the subsequent years, an interim history and blood pressure
measurement should be obtained. Any significant change may constitute evidence
that another examination and possible further testing should be performed.
Although the guidelines recommend that a licensed physician perform the examination,
under certain circumstances a trained registered nurse or physician's assistant may perform
screening examination. A standardized form that outlines a detailed history and physical
examination should be used. [18]
A thorough cardiac history should include a history of 1) chest pain or chest tightness,
especially with exertion; 2) dyspnea at rest or mild exertion, or with less than expected
activity; 3) palpitations or irregular heart beat; and 4) lightheadedness or syncope. Previous
medical history should include prior heart murmur, rheumatic fever, or cardiac surgery. The
family history is extremely important in eliciting the risk of diseases with familial
transmission such as hypertrophic cardiomyopathy, Marfan's syndrome, and congenital
prolonged QT syndrome. Sudden cardiac death of a family member under age 40 may be
the only finding that may identify a person at risk of having a potentially serious cardiac
abnormality (such as hypertensive cardiomyopathy, Marfan's syndrome, or prolonged QT
syndrome). Whenever possible, parental involvement with the history questionnaire can be
helpful. An athlete's use of cocaine or anabolic steroids should be reviewed, although an
athlete is often not forthcoming in admitting illicit drug use.
Because careful cardiac auscultation is required, the examination should be performed in an
area that has minimal background noise. The evaluation includes brachial artery blood
pressure and evaluation of pulses, specifically the carotid pulse for delayed upstroke (aortic
stenosis), spike and dome pattern (hypertrophic cardiomyopathy), and radial-to-femoral
pulse delay (coarctation of the aorta). Abnormal body habitus should be noted, especially
that seen with Marfan's syndrome, such as an unusually tall person with wide wingspan,
pectus excavatum, myopia, and displaced lenses. Cardiac auscultation should be performed
to determine the presence of a heart murmur and to distinguish benign flow murmurs from
pathologic disease. Familiarity with maneuvers such as handgrip (increased intensity of
mitral regurgitation murmur) and Valsalva (increased intensity of systolic murmur due to
hypertrophic cardiomyopathy) can be helpful in this regard.
The high cost of noninvasive testing and the low yield of a positive test result in this
relatively healthy population makes mandatory noninvasive testing unfeasible. [45] The
debate, however, continues over the cost-effectiveness of ECG [16] [27] [56] and
echocardiography [50] as useful screening
116
tools. Although ECG alone is a relatively low-cost procedure (approaching $10 per test
when performed on a large scale), the cost of screening a large number of athletes and the
cost of follow-up of abnormal ECGs is substantial. The ECG has not been demonstrated to
effectively enhance the screening guidelines. In a recent study by Fuller et al., [16] 16 of
5615 athletes screened (0.03%) were not approved for athletics because of the ECG
obtained during screening. However, the authors do not comment on the follow-up studies
that finally determined the athletes' eligibility to participate in sports. If most athletes were
ultimately deemed eligible to play, the yield of the ECG during preparticipation
cardiovascular screening examination is negligible and costly. Maron et al. [34] studied 501
college athletes by means of routine history, physical examination, and ECG. Ninety (18%)
of these athletes with abnormal findings also had echocardiography. No athlete was
disqualified from competition. Multiple studies evaluating the usefulness of
echocardiography during screening examinations have been performed, including studies in
black collegiate populations and in using low-cost, limited echocardiography. [15] [28] [50] [66]
Although up to 10% of the athletes in the combined studies demonstrated mild cardiac
abnormalities (including mitral valve prolapse, bicuspid aortic valve, and valvular
regurgitation), no athlete was found to have a significant cardiac abnormality such as
hypertrophic cardiomyopathy, Marfan's syndrome, or a severe and previously undetected
valvular disease that precluded participation in sports.
For the older athlete (over age 35), evaluation should focus on possible underlying coronary
artery disease. A history of risk factors, including a family history of premature
atherosclerotic cardiovascular disease, should be part of the preparticipation cardiovascular
screening examination in this age group. It is prudent to perform medically supervised
exercise stress testing in men older than 40 and women older than 50 in whom the
physician suspects occult coronary artery disease based on two or more risk factors, other
than age or sex, or based on a single but markedly abnormal risk factor. [45] Older athletes
should be warned of prodromal cardiovascular symptoms such as chest pain or chest
pressure. [45]
Limitations of Preparticipation Screening
It is important to understand the limitations of the preparticipation cardiovascular screening
examination in detecting athletes who are at risk for sudden cardiac death. In the series by
Maron et al., [43] 134 athletes were identified to have died suddenly. Of these, 130 (97%)
underwent preparticipation medical evaluations; 19 of these athletes were identified as
having cardiac abnormalities. Only two athletes, however, were disqualified from
participation in sports based on their preparticipation medical evaluation. Therefore, only 2
of 134 athletes (1%) who died suddenly were disqualified because of findings during
preparticipation screening.
THE ATHLETE WITH SYMPTOMS
The fact that the currently recommended preparticipation screening guidelines are limited
in their ability to accurately predict athletes at risk places a significant burden on the team
physician, coach, and trainer to be vigilant in watching for athletes who develop symptoms
that may herald underlying cardiac abnormalities. An athlete who develops unexplained
chest pain, chest tightness, lightheadedness, syncope, or palpitations requires immediate
cardiovascular evaluation by a professional who is specifically trained to screen for
cardiovascular abnormalities in an athlete. This evaluation should include a complete
history, physical examination, and an ECG. Additional testing based on symptoms and
examination findings may be necessary.
Syncope
Syncope is the sudden loss of consciousness for a brief duration but with subsequent
complete recovery. Syncope usually occurs as a result of the sudden drop of cerebral blood
flow. Occasionally, other causes such as hypoglycemia, seizures, or, rarely, hypoxia may be
the cause of syncope. Long-term recurrent syncope usually has a benign cause; however,
recurrent syncope over a short duration has an increased likelihood of organic heart disease.
[8] Intense physical activity in extreme heat may lead to dehydration and hyperthermia and
the resultant loss of consciousness. In such a situation, evaluation of the athlete's state of
hydration and body temperature is mandatory. These athletes slowly improve with
hydration and body cooling. Syncope associated with chest discomfort, palpitations, or
occurring without premonition such as yawning, nausea, or epigastric discomfort, or
occurring during physical exercise requires further investigation for a possible cardiac
cause of syncope (Table 3) . [22] [29]
Echocardiography is a valuable diagnostic tool in the evaluation of the young athlete
because it can be used to screen for myocardial diseases such as hypertrophic and
congestive cardiomyopathy as well as valvular heart disease. A 24-hour Holter monitor or
an event monitor is useful for screening for cardiac arrhythmia. Tilt-table testing may be
helpful to diagnose neurocardiogenic syncope in an athlete with unexplained syncope [20]
and without evidence of structural cardiac disease. Caution must be raised in the
interpretation of findings from an abnormal tilt-table test because conditioned athletes may
have a false-positive test result because of high vagal tone. Exercise testing is often
combined with echocardiography before and immediately after exercise (stress
echocardiography), or with nuclear myocardial scanning, and can be used to screen for
coronary artery disease and for an anomalous coronary artery. In athletes who are thought
to be at risk for arrhythmogenic right ventricular dysplasia, MRI scanning can be
diagnostic. Invasive cardiac testing, including electrophysiologic studies for arrhythmia
evaluation and cardiac catheterization for coronary artery evaluation, can provide useful
diagnostic information in
117
TABLE 3 -- Causes of Syncope a
Cardiovascular
Reflex
Vasovagal
Vasovagal (situational)
Micturition
Defecation
Cough
Swallow
Oculovagal
Diving
Weight lifting
Orthostatic hypotension
Jacuzzi
Carotid sinus syncope
Cardiac
Obstruction to flow
Obstruction to left ventricular outflow
Aortic stenosis
Hypertrophic cardiomyopathy
Mitral stenosis
Left atrial myxoma
Obstruction to pulmonic outflow
Pulmonic stenosis
Pulmonary embolism
Tetrology of Fallot
Pulmonary hypertension
Right atrial myxoma
Pump failure: myocardial infarction
Aortic dissection
Arrhythmias
Bradyarrhythmias
Sick sinus syndrome
Atrioventricular block
Pacemaker malfunction
Tachyarrhythmias
Ventricular tachycardia
Supraventricular tachycardia
Pacemaker malfunction
Noncardiovascular
Neurologic
Vertebrobasilar insufficiency
Subclavian steal syndrome
Seizure
Metabolic
Hypoxia
Hypoglycemia
Hyperventilation
Drug induced
Psychiatric
Panic disorder
Major depression
Hysteria
Unexplained
a
Data derived from Kapoor [22] and Manolis et al. [29]
the appropriately selected athlete as determined by the cardiology consultant.
Palpitations
Palpitation is a common symptom characterized as an unpleasant awareness of the forceful
or rapid beating of the heart. It is usually produced by cardiac rhythm disturbances such as
premature or ectopic beats, bradyarrhythmia, or tachyarrhythmia. Careful history-taking
may help characterize the arrhythmia. Episodes that last for an instant or that are described
as a "skipped" or "floppy sensation" are usually due to isolated premature beats and most
often are benign. The sensation of "rapid heart beat" or documentation of an unexplained
rapid pulse that does not resolve at rest can herald significant tachyarrhythmia such as
supraventricular tachycardia, atrial flutter, ventricular tachycardia, or atrial fibrillation.
Testing usually includes an ECG to evaluate for conduction abnormality or for the presence
of preexcitation. Exercise tolerance testing is valuable to attempt to reproduce an exerciseinduced arrhythmia. A potentially troublesome but not usually fatal form of exerciseinduced tachyarrhythmia is right ventricular outflow tract arrhythmia, a benign form of
ventricular tachycardia that is evaluated with electrophysiologic testing and amenable to
transcatheter ablation (Fig. 6) . Cardiac event monitoring with cardiac loop-cycle recorders
(that can record 1 to 5 minutes of heart beat initiated by patient activation) and with
practice-site telemetry can detect arrhythmia as well as determine if the arrhythmia has
been satisfactorily controlled or terminated with appropriate treatment.
of
Figure 6. Two ECGs of a 34-year-old competitive bicyclist with history of recurrent
lightheadedness and palpitations with exercise. A, at rest; B, during exercise, demonstrating runs
ventricular tachycardia. Subsequent electrophysiologic study demonstrated a right ventricular
outflow tract origin of ventricular tachycardia, which was treated with transcatheter ablation. Follow-up stress
test was normal. Athlete was asymptomatic at 2 years after transcatheter ablation.
118
Chest Pain
The sensation of chest pressure or pain during exertion--other than the sensation of chest
discomfort associated with extreme shortness of breath from intense activity--is an
abnormal symptom that requires cardiac evaluation for myocardial ischemia. The
pathophysiologic mechanism is due to a supply-demand mismatch from either obstruction
to coronary blood flow or from inadequate blood flow to a hypertrophied myocardium. The
usual location of this symptom is either substernal or over the precordium. In rare cases,
neck tightness, arm tightness, or jaw discomfort with exercise may be an equivalent
symptom. In the older athlete (over age 35), exercise tolerance testing, possibly with
nuclear or with stress echocardiographic evaluation, is necessary to screen for coronary
artery disease. In the young athlete, myocardial disease (hypertrophic cardiomyopathy) as
well as coronary artery anomalies are added to the differential diagnosis in examining for
chest pain.
ELIGIBILITY FOR COMPETITION
Once a diagnosis of cardiac disease is made, the physician must make an eligibility
recommendation to the athlete and the team physician. Guidelines for eligibility have been
established. In 1994, the 26th Bethesda Conference--a consensus meeting of cardiologists
cosponsored by the American College of Cardiology and the American College of Sports
Medicine--developed recommendations for determining eligibility for competition in
athletes with cardiovascular abnormalities. [39] This document provides guidance to
physicians, athletes, team officials, and athletic governing bodies regarding the acceptable
medical risk of athletes with known cardiovascular abnormalities who want to participate in
sports. [40] These guidelines review the types of exercise (static versus dynamic) for each
sport and specific cardiac abnormalities, the severity of which will determine an athlete's
eligibility to participate.
Exercise can be defined by two types: dynamic and static. Dynamic exercise involves a
change in muscle length and joint movement that creates a small intramuscular force. Static
exercise involves little movement of muscle and joint and creates a large intramuscular
force. [47] For example, weight lifting is considered a high static and low dynamic exercise,
whereas long-distance running is considered a low static and high dynamic exercise (Table
4) .
Based on the task force recommendation of the 26th Bethesda Conference, athletes with
specific cardiac abnormalities can be determined to be ineligible for certain sports. For
example, younger athletes (<30 years) with evidence of hypertrophic cardiomyopathy are
considered ineligible for all sports except those that involve low static and low dynamic
exercise (such as golf, billiards, and
TABLE 4 -- Types of Exercise by Sport a
A. Low dynamic
I. Low static
B. Moderate
dynamic
C. High dynamic
Billiards
Baseball
Badminton
Bowling
Softball
Cross-country skiing
(classic technique)
Cricket
Table tennis
Field hockey *
Curling
Tennis (doubles)
Orienteering
Golf
Volleyball
Race walking
Riflery
Racquetball
Running (long
distance)
Soccer *
Squash
Tennis (singles)
II. Moderate static
Archery
Fencing
Basketball *
Auto racing *
Field events
(jumping)
Ice hockey *
Diving *
Figure skating *
Cross-country skiing
(skating technique)
Equestrian *
Football (American) Football (Australian
*
rules) *
Motorcycling *
Rodeoing *
Lacrosse *
Rugby *
Running (middle
distance)
Running (sprint)
Swimming
Surfing *
Team handball
Synchronized
swimming
III. High static
Bobsledding *
Body building *
Boxing *
Field events
(throwing)
Downhill skiing *
Canoeing/kayaking
Gymnastics *
Wrestling *
Cycling *
Karate/judo *
Decathlon
Luge *
Rowing
Sailing
Speed skating
Rock climbing *
Waterskiing *
TABLE 4 -- Types of Exercise by Sport a
A. Low dynamic
B. Moderate
dynamic
C. High dynamic
Weight lifting *
Windsurfing *
Reprinted with permission from the American College of Cardiology (Mitchell et al., J Am Coll Cardiol 28:
845-899, 1994).
* Danger of bodily collision.
a
Increased risk if syncope occurs.
119
[37]
riflery).
Athletes with asymptomatic mild aortic stenosis may participate in all sports.
[19]
Athletes with Wolff-Parkinson-White syndrome require noninvasive tests including
ECG, 24-hour Holter monitor recording during athletic activity, exercise test, and
echocardiogram to exclude associated cardiac abnormalities. If these test are negative and
the athlete is asymptomatic, full participation in all sports is allowed. [70] Athletes with
presumed myocarditis should be considered ineligible for all competitive sports and should
be advised to undergo convalescence of at least 6 months. Cardiac evaluation by stress
echocardiography or radionuclide angiography should be performed before return to
competition to confirm that left ventricular function has returned to normal and there is no
evidence of significant ventricular or supraventricular arrhythmia. [37]
CARDIOPULMONARY RESUSCITATION AND AUTOMATIC
EXTERNAL DEFIBRILLATORS
Athletes who are at significant risk for sudden cardiac death may not be detected by the
preparticipation examination and may not develop symptoms while participating in sports.
Their first manifestation can be a life-threatening or lethal cardiac arrhythmia. Some
athletic programs, especially at the professional level, have required training in
cardiopulmonary resuscitation (CPR) and in the use of automatic external cardiac
defibrillators for support staff, including trainers, coaches, and team physicians.
Automatic external cardiac defibrillators are devices that accurately analyze cardiac
rhythms and, if appropriate, advise and deliver electric countershock. [23] These devices, at a
cost of approximately $3000, are small, compact, and portable. They have been used by
emergency personnel, have been proven to be accurate and effective, and have become the
essential link in the "chain of survival" as defined by the American Heart Association. [23]
The use of automatic external defibrillators has now been extended to nonmedical,
minimally trained personnel. It has become part of the Basic Life Support (CPR) program
taught by the American Heart Association.
No study has been performed to evaluate the success of early-access defibrillation in the
athlete population. It is known that early defibrillation improves the likelihood of survival
from sudden cardiac death. This method has been shown to be equally effective in the adult
as well as the adolescent and preadolescent populations. [3]
Because of the potential for an athlete to develop a cardiac emergency during practice or
competition, it is advisable that a team's support staff be trained in CPR and in the use of
automatic external defibrillators. Definitive recommendations regarding the necessity of
defibrillators for high school or collegiate athletic programs will require future research.
SUMMARY
The incidence of cardiac disease in young athletes is low and mostly attributable to
congenital abnormalities. For the older athlete, the incidence of coronary artery disease
increases with each decade of life. The risk of sudden cardiac death in young athletes is
rare, approximately 1 in 100,000 to 300,000, as compared with the older athlete, whose risk
is 1 in 15,000 to 18,000. There are multiple causes for cardiac disease in young athletes,
with approximately 40% attributable to hypertrophic cardiomyopathy and an additional
25% attributable to coronary artery abnormalities. The cardiovascular preparticipation
screening examination is mandatory for all athletes and every effort must be made by the
team physician, coach, and trainer to adhere to established guidelines for this examination.
A detailed history and physical examination, including the use of a standardized form,
should be part of the preparticipation cardiovascular screening examination. The American
Heart Association has proposed 13 items to be used as minimum components of the
preparticipation cardiovascular screening examinations. Additional testing such as ECG or
echocardiography as part of the preparticipation examination is costly and beyond the
budgets of most high school and collegiate athletic programs. The findings of important
cardiac abnormalities by these additional tests is extremely low. It is imperative for
physicians to watch for the athlete who develops significant symptoms during the course of
training or competition. An athlete who develops unexplained lightheadedness, syncope,
palpitations, or chest pain requires immediate medical evaluation by a physician
knowledgeable in those cardiac conditions that may limit athletic participation.
The team physician, coach, and trainer should be prepared to handle a cardiac emergency
during practice and competition. It is advisable that staff members be trained in basic CPR
and in the use of automatic external cardiac defibrillators. The availability of these
defibrillators at the professional sport level is becoming more common as these teams can
afford the cost of these devices (approximately $3000). Currently, the more extended use of
automatic external cardiac defibrillators is being evaluated. Therefore, no specific
recommendation can be made as to their necessity for high school or college athletic
programs. Future research is required to evaluate the cost, complications, and success of the
widespread use of defibrillators for athletic programs.
ACKNOWLEDGMENTS
I am grateful to Justin Basilico, Gary Epler, MD, Arnold Scheller, Jr., MD, and Judith
Waligunda, MD, for their assistance in the preparation of this manuscript.
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