This chapter is dedicated to the memory of Fran Crippen (April 17, 1984–Oct. 23, 2010). Fran attended the University of Virginia, where he was an All-American swimmer and went on to earn six national titles. We honor and remember Fran as a student athlete whose character and commitment were commensurate with his remarkable athletic ability.
Historical Perspective
The elite athlete has enjoyed a celebrated status within our culture since ancient times. The Olympic Games solidified that status as early as 776 BC, and it was amplified by Pheidippedes, a legendary Greek Olympic champion in 500 BC. Ten years later, when the Persians arrived at the plains of Marathon and threatened to conquer Athens, Pheidippedes was dispatched from Athens to seek the assistance of the Spartans. Although he was remembered most for his 26-mile run from Marathon to Athens to announce the Greek victory, this run was only part of a remarkable triathlon of events for this Greek athlete. He began the first leg of his journey with a 145-mile run over mountains and plains that included swimming across the aquatic obstacles on his way to reach Sparta in only 2 days and without sleep. The second leg included travel by boat from Sparta to Marathon, where he joined in the victorious battle against the Persians. Only then did he embark upon his now infamous run back to Athens, where he proclaimed victory before dying suddenly in front of his fellow Greek citizens. The remarkable athletic accomplishments of Pheidippedes emphatically etched the Marathon run into sports modernity and deeply engraved the tragic event of athletic sudden death (SD) into our cultural consciousness. The Oxford poet and scholar A.E. Housman captured the effect of the SD of an athlete in the poem, To An Athlete Dying Young (1896):
The time you won your town the race We chaired you through the market place;
The metaphor of the winning athlete on the shoulders of the townspeople is an image we have all witnessed in some form many times. With the unexpected death of the athlete, Housman brings the same metaphor full circle from celebration to sadness, with the athlete’s coffin resting upon the shoulders of those same townspeople:
Shoulder-high we bring you home, And set you at your threshold down, Townsman of a stiller town.
Estimates of the incidence of athletic SD reassure us that this event is rare. The consequences of athletic SD, however, resound far beyond the persons who are directly affected by it. The advent of continuous media coverage through television, radio, and the Internet that is now further augmented by social media has created instant access to any adverse event involving a previously healthy and seemingly invincible athlete. Accordingly, a tragic athletic SD immediately affects family, friends, fellow athletes, students, coaches, and administrators, and that effect can rapidly ripple into the minds of sports fans anywhere in the world. The SDs on the soccer pitch of Marc Vivien Foe (a Cameroon national player with hypertrophic cardiomyopathy [HCM]) in 2003 and Fabrice Muamba (a player for Bolton in the English Premier league) in 2012 illustrate the magnitude of the amplification of modern information. Disturbing videos of both events are widely available on the Internet and have been viewed by millions of fans around the world.
The SD of Hank Gathers in 1990 had a seminal impact on the landscape of sports cardiology in the United States. Gathers played Division I college basketball for Loyola Marymount on a team that had realistic aspirations for a national championship. The previous season he had become the second player in NCAA history to lead the nation in scoring and rebounding. Gathers fainted on the court, and both sustained and nonsustained ventricular arrhythmias were documented, most likely as a result of underlying myocarditis. With the extraordinary success of this team from a small university, there was tremendous pressure for Gathers to continue to play. He ultimately returned to play later in the season and died tragically on the court during a tournament game. This case illustrates the entwined complexity inherent to any cardiovascular diagnosis in an elite athlete. Gathers was admittedly noncompliant with his propranolol. The reluctance to disqualify him under the circumstances was profound. The emotional cost to Gather’s family, friends, teammates, and the Loyola Marymount community at large is beyond measure. There was also a profound financial impact, with judgments and settlements against the physician and the university.
Now that we are more than 20 years removed from this event, it is reasonable to assume that Loyola Marymount is still suffering beneath the dark cloud of this occurrence. Death during competition would intercede as “the most unwelcome spectator” (Jim Murray, The Los Angeles Times ) for other notable athletes as well, including Tom Simpson, an English cyclist who died on Mont Ventoux in the 1967 Tour de France (likely from use of amphetamines); Flo Hyman, an Olympic volleyball player who died of aortic dissection as a result of Marfan syndrome 4 years before Gathers; basketball players Pete Maravich (as a result of an anomalous coronary artery), Reggie Lewis, and Jason Collier; Sergei Grinkov (ice skating); Jiri Fischer (hockey); Thomas Herrion (football); and Fran Crippen (swimming). Furthermore, SD has not only occurred in elite athletes with national and international notoriety. It has also had a profound impact on communities around the world that have had to cope with unexpected deaths of athletes of all ages and levels of ability.
The amplification of athletic SD into our cultural consciousness has stimulated considerable research and medical practice interest into the causes of SD in athletes, potential preventive measures inclusive of screening, and the development of care and management guidelines for athletes with known cardiovascular abnormalities. In practice, the prevention of SD represents only a part of the comprehensive cardiovascular care of the elite athlete. In this chapter we will discuss the current state of practice, controversy with regard to screening, and the detection and management of cardiovascular disorders with particular emphasis on the normal physiologic cardiovascular remodeling that can occur with elite levels of training.
A Medical Home for the Elite Athlete
It is imperative for the elite athlete to have a medical home, ideally with a primary care sports medicine provider. Athletic trainers are a vital part of this medical home as well and bring a rapidly evolving expertise involving the overall health and wellness of the athlete. Trainers are keenly aware of the importance of cardiovascular health and are now familiar with a wide array of useful technology and equipment including blood pressure cuffs, stethoscopes, automatic external defibrillators (AEDs), and electrocardiogram (ECG) machines. It is very helpful for trainers to accompany athletes to subspecialty encounters because the trainers can reliably relay important information to personnel on the practice and playing field and report back on the development of any important signs, symptoms, or physical findings that may place the athlete at risk.
Preparticipation Physical Evaluation
The initial history and physical examination performed by the primary care sports medicine provider now includes the fourth edition of the Preparticipation Physical Evaluation (PPE-4) and has evolved to include a somewhat more reliable process to detect familial cardiovascular abnormalities that might increase the risk of SD. The PPE-4 was adopted by the American Heart Association consensus panel for preparticipation cardiovascular screening. However, the current initial evaluation of the athlete has significant limitations. Wide variation exists from state to state with regard to the type of provider performing the PPE-4, as well as the content of the PPE-4. Furthermore, this process has a poor sensitivity for the detection of cardiovascular disorders. Indeed, in a retrospective look at SD in athletes who had participated in preparticipation screening, only 3% were thought to have potential cardiovascular abnormalities, and none was restricted from participation. According to the PPE-4, an athlete should be referred for more advanced cardiovascular care or evaluation in the event of an abnormal physical finding, a family history of premature sudden death, or the development of new symptoms that elicit concern.
Many of the most dangerous cardiovascular conditions that could threaten an athlete are asymptomatic, with no physical findings that would trigger a referral. Such conditions include HCM, arrhythmogenic right ventricular cardiomyopathy (ARVC), congenital long QT and Brugada syndromes, Wolff-Parkinson-White (WPW) syndrome, and the anomalous coronary artery. The absence of a positive family history for SD can be falsely reassuring in persons with autosomal-dominant familial conditions (e.g., HCM, ARVC, long QT syndrome, and Marfan syndrome) because up to 25% to 33% of affected persons will have new spontaneous mutations with no previously affected family members. Accordingly, the current state of evaluation of the elite athlete in the United States is unlikely to detect most threatening cardiovascular conditions.
Furthermore, the normal physiologic adaptations of hypertrophy of the left ventricle (LV) to rigorous isometric training (often referred to as the “athlete’s heart”) can very closely mimic HCM, which is the most prevalent and dangerous cardiovascular disease in young athletes. In addition, physiologic changes in LV and right ventricular (RV) cavity size and systolic function can be difficult to distinguish from forms of dilated cardiomyopathy and ARVC. Perhaps nowhere else in medicine does normalcy mimic disease as it does in this circumstance. As a result, further screening or evaluation of elite athletes requires a sophisticated and programmatic approach that is designed to avoid the pitfall of potentially life-changing false-positive results that will be the inherent weakness in the evaluation of large populations of athletes with a low prevalence of disease. Because of these inherent complexities, expert consensus in the United States has not recommended routine evaluation of the athlete beyond the PPE-4. Although this recommendation is well wrought and reasonable, evidence is lacking regarding the efficacy of the PPE-4 in the prevention of morbidity and mortality in athletes. In addition, these recommendations have created an unanticipated consequence in the field of sports cardiology.
The United States has a paucity of well-trained and knowledgeable cardiovascular providers who are familiar with the nuances of normal physiologic adaptations to elite training and know how to differentiate normalcy from disease. Encounters with elite athletes are uncommon for most practicing cardiologists. Accordingly, athletes who undergo more extensive testing and evaluation by inexperienced providers are commonly sidelined unnecessarily, subjected to overtesting, relegated to the emotional consequences of concern for survival, and undergo temporary or permanent disqualification from sports. Cardiovascular care must be incorporated into the medical home of the athlete very carefully with knowledgeable providers who are dedicated to understanding the complex world of the athlete.
Cardiovascular Adaptations and Remodeling Associated with Rigorous Athletic Training
The earliest recognition of the physiologic changes commonly referred to as “athlete’s heart” were astutely described in 1899 by a Swedish physician who detected cardiac enlargement in elite Nordic skiers through use of remarkably accurate skills of auscultation and percussion. That same year these findings were reinforced in a study of Harvard University rowers. It is not surprising that the earliest descriptions of cardiac enlargement were made in Nordic skiers and elite rowers, because these disciplines include extreme combinations of endurance training (isotonic, dynamic, and aerobic) and strength training (isometric, static, and anaerobic) that lead to more striking combinations of both LV cavity dilation and hypertrophy. A few years later, Paul Dudley White strengthened the legacy of sports cardiology in Boston by observing pulses in endurance-trained runners participating in the Boston Marathon and later described bradycardia associated with this level of endurance training. The evolution of more sophisticated technology would allow for the complex assessment of the electrophysiologic and structural cardiovascular adaptations to varying degrees and types of athletic training.
Accordingly, any cardiovascular evaluation of an athlete inclusive of electrocardiography or any form of cardiovascular imaging must be undertaken with in-depth knowledge of the training-specific changes in cardiac structure and function. Pure endurance training involves prolonged activities with sustained increases in cardiac output without significant elevation in mean arterial pressure. This type of volume load can lead to dilation of all four chambers of the heart and to some degree the great vessels as well. Strength training subjects the heart to more brief but dramatic increases in mean arterial pressure that in turn leads to an increase in myocardial muscle hypertrophy. Marathon running is a good example of pure endurance training, and weightlifting is an example of pure strength training. Most sports, however, have varying degrees of both types of training that will also vary with the approach of the individual athlete. Therefore the heart of any athlete may manifest changes across a broad spectrum of physiologic adaptation.
Structural Adaptations to Rigorous Training
Left Ventricle
The effects of training on the LV are routinely detected on ECGs, and increases in voltage have been documented for decades. Athletes who undergo endurance training that also incorporates increasing degrees of isometric/strength training (e.g., cycling, rowing, cross country skiing, and canoeing) are more likely to demonstrate these manifestations on the resting ECG. Transthoracic echocardiography (TTE) has been used extensively to document the spectrum of LV cavity dilation and the increase in LV wall thickness/left ventricular hypertrophy (LVH) associated with rigorous training. LV cavity size across a large variety of sports is larger than in sedentary control subjects and ranges from 43 to 70 mm (mean, 55 mm) in men and 38 to 66 mm (mean, 48 mm) in women. LV wall thickness is generally less than 13 mm in elite athletes, but larger increases in wall thickness (1.3 to 1.5 mm) that stray into the “gray zone” with HCM are more commonly seen in older elite athletes (rowers) who train with large degrees of static and dynamic exercise. LV systolic function as measured by TTE is usually normal in elite athletes.
It is important to recognize, however, that LV systolic function can be low-normal to mildly depressed (mimicking mild forms of dilated cardiomyopathy), as shown in some of the fittest athletes in the world participating in the Tour de France. These adaptive changes in cavity dimension, wall thickness, and the associated increase in LV mass have also been demonstrated in magnetic resonance imaging (MRI) studies and have recently been reviewed in depth. LV diastolic function is usually normal in elite athletes and can be improved with endurance training, leading to more robust early diastolic filling. Less is known about the effects of strength training on diastolic function, but evidence shows that diastolic function may be impaired, which could be an untoward long-term effect of hypertrophy that warrants further study.
Right Ventricle
Sustained increases in cardiac output have a similar effect on the RV compared with the LV, particularly with regard to cavity dilation. Older M-mode and two-dimensional TTE studies in endurance-trained athletes showed symmetrical dilation in both the RV and the LV. The unique geometry of the RV makes it difficult to assess RV size and function with echocardiography, and cardiac MRI has greatly enhanced our ability to evaluate the RV. More recent MRI studies in elite endurance athletes have reinforced the balanced dilation of the RV and LV, demonstrating increases in LV and RV mass, diastolic volumes, and stroke volumes. Abnormalities in systolic function in endurance athletes also can be abnormal and generally are seen in athletes with more extensive RV dilation. The impact of strength training on the RV is less clear but is likely to be a topic of future clarification through use of TTE and cardiac MRI.
Atria
As expected, increased right and left atrial volumes and sizes are also seen in endurance athletes, with more numerous studies evaluating the left atrium. A large volume of data supports the physiologic effects of sustained endurance volume loading on all four cardiac chambers, including the atria. In the largest Italian series, 20% of athletes had left atrial dimensions of greater than 40 mm measured by TTE, and supraventricular arrhythmias were not common in this group.
Great Arteries and Veins
The great arteries and veins are subject to the physiologic effects of endurance training. The aorta is of particular interest with regard to strength training, because extraordinary increases in both systolic and diastolic blood pressure (up to 480/350 mm Hg!) have been documented in weight lifters. Studies have documented somewhat inconsistent aortic root dilation with regard to specific types of sports and training regimens. Strength-trained athletes have been shown to have larger dimensions of the aorta measured by TTE at the aortic annulus, the sinuses of Valsalva, the sinotubular junction, and the proximal aortic root when compared with control subjects, and this effect increased with the duration of training. Aortic root size was greater in taller athletes and typically measured between 3.0 and 4.0 cm, only rarely measuring greater than 4.0 cm. Although aortic regurgitation was not found in any of the control subjects, 9% of the strength-trained athletes had mild (n = 5) or moderate (n = 4) aortic regurgitation.
Another large trial comparing strength-trained and endurance-trained athletes supported these findings. In a large trial of athletes participating in a wide range of sports in Italy, the largest measurements were found in endurance-trained athletes, particularly in the disciplines of cycling and swimming. This apparent inconsistency may be attributed to the sustained combination of isometric and isotonic exercise associated with these sports. Accordingly, rigorous training, particularly strength training, has an impact on aortic root size but rarely causes degrees of dilation that are dangerous or a cause for concern.
Taller athletes (such as basketball and volleyball players, for example) may be expected to push the envelope of “normal” aortic root size, and more data are expected in this area in the future. The effects of training are also seen on a wide range of great vessels in endurance athletes and taller athletes, including larger caliber carotid arteries, branch pulmonary arteries, superior and inferior vena cavae, and abdominal aortas as shown in cyclists, long-distance runners, and volleyball players. It has been our observation that the inferior vena cava is routinely larger than normal in endurance-trained athletes and that published estimates of right atrial pressure based on vena cava size and inspiratory collapse do not apply to the elite athlete.
The Athlete’s ECG and Electrophysiologic Adaptations to Rigorous Training
Training-induced alterations in cardiac structure and autonomic regulation are reflected on the ECG of the athlete in many ways, and the resting ECG will have a range of well-documented variations compared with normal control subjects in most cases. Common training-related findings on the athlete’s ECG include sinus bradycardia, first-degree atrioventricular (AV) block, incomplete right bundle branch block, early repolarization, and voltage criteria for LVH ( Fig. 15-1 ). Electrophysiologic aberrations, like their structural counterparts, are more common in endurance sports that include a significant amount of strength training as well (e.g., cycling, rowing, canoeing, and cross-country skiing).
Gender, Genetics, and Race
Gender, genetics, and race have a pronounced influence on the structural and electrophysiologic adaptations to rigorous athletic training. Abnormal findings on the athlete’s ECG are more common in men and in athletes of African or Caribbean descent. Dramatic examples of LVH by voltage with markedly abnormal T waves and repolarization abnormalities are commonly seen in elite African athletes ( Fig. 15-2 ) and should not be mistaken for HCM. In 1962, these findings were described in the Bantu and Nilotic people of Africa, and in the case of an Olympic boxer, an ECG performed after prolonged detraining demonstrated complete regression of the ECG findings of LVH and T-wave abnormalities.
Gender and ethnicity have a similar impact on imaging studies (i.e., TTE). A study of 600 elite female athletes undergoing TTE screening demonstrated a low incidence of LV cavity dilation, and not one female athlete had an LV wall thickness greater than 12 mm. Black female athletes show a modest but more pronounced tendency toward hypertrophy, with LV wall thickness measuring 6 mm greater when compared with white female athletes. In a study of elite rowers, a familial genetic influence was suggested when Baggish et al. found that athletes with a family history of hypertension developed a more pronounced increase in LV mass when compared with rowers without a family history of hypertension. The pattern of hypertrophy was different as well, with concentric hypertrophy more commonly seen in rowers with a family history of hypertension and eccentric hypertrophy seen in control subjects. In addition, angiotensin-converting enzyme gene polymorphisms have been shown to predispose athletes to more pronounced remodeling, with increases in both LV mass and LV wall thickness. These studies underscore the complexity of the process of training-induced cardiac remodeling. This process is influenced by the type and duration of training, the gender, and the genetic heterogeneity of the individual athlete.
Cardiovascular Screening of Athletes
Because of the devastating consequences of unexpected athletic SD, a wide array of approaches have been developed outside of recommended guidelines by individual universities, countries, and professional athletic teams to more reliably identify potential life-threatening and asymptomatic abnormalities that would not be detected on the PPE-4. The modern elite athlete stresses the cardiovascular system to remarkable levels of both strength and endurance. The examples of Pheidippedes and Fran Crippen, who died in a 10-km open water swim in extreme heat in 2010 in the United Arab Emirates, may both be examples of athletic SD occurring as a result of heroic athletic effort in the absence of any underlying cardiovascular abnormality. Accordingly, any undiagnosed cardiovascular abnormality could expose the athlete to distracting symptoms, impaired performance, and ultimately athletic SD.
Landmark articles on the causes of SD in athletes younger than 35 years are well established. In the United States, athletic SD occurs at a rate of approximately 125 per year, and HCM accounts for more than one third of these tragic occurrences. Other congenital cardiac anomalies constitute the majority of the other causes of athletic SD, including the anomalous coronary artery, congenital aortic stenosis, ARVC, and ruptured aorta as a result of Marfan syndrome or related vascular disorders. A much smaller percentage of athletic SD in young athletes results from acquired heart diseases such as myocarditis and coronary artery disease (CAD). In addition to serious cardiovascular disorders, many other less threatening congenital and acquired abnormalities exist that are often asymptomatic and may have subtle if any physical findings that could affect the future of the athlete’s health, cause symptoms in the athlete, or impair performance ( Box 15-1 ). Accordingly, any programmatic attempt to screen athletes for potential cardiovascular abnormalities beyond the PPE-4 will require the ability to reliably distinguish training-related remodeling from real disease, familiarity with the congenital anomalies that will be found, and the ability to distinguish benign from more serious disorders.
- 1.
Bicuspid aortic valve—functionally normal or mild valve disorder
- •
Fifty percent will have an associated abnormality of the ascending aorta (congenital aortopathy)
- •
- 2.
Atrial septal defect (ASD)/left to right shunts
- •
Secundum ASD, which includes atrial septal aneurysm with small or multiple ASD/patent foramen ovale
- •
Venosus ASD
- •
Coronary sinus ASD
- •
Partial anomalous pulmonary venous return
- •
- 3.
Hypertrophic cardiomyopathy
- 4.
Anomalous coronary arteries, coronary artery fistulae
- 5.
Marfan syndrome and related disorders
- •
Ehlers-Danlos syndrome
- •
Loeys-Dietz syndrome
- •
Mitral valve prolapse, aortic root diameter at upper limits of normal for body size, stretch marks of the skin, and skeletal conditions similar to Marfan syndrome (MASS) phenotype
- •
- 6.
Wolff-Parkinson-White syndrome
- 7.
Long QT syndrome
- 8.
Brugada syndrome
- 9.
Ventricular tachycardia, pathologic premature ventricular contractions
- 10.
Arrhythmogenic right ventricular cardiomyopathy
- 11.
Coarctation of the aorta (particularly milder forms)
- 12.
Pulmonary hypertension (particularly mild to moderate forms)
- 13.
Myocarditis (acute or with chronically impaired ventricular function)
- 14.
Congenital cardiomyopathy (including congenital noncompaction)
- 15.
Mitral valve prolapse
Because screening must remain noninvasive and pose no risk to the athlete, ECG and TTE are the most widely used modalities. Unless exercise-induced arrhythmias or CAD are suspected, routine stress testing is of little value, whereas computed tomography (CT) and MRI expose the athlete to radiation (CT) and, at times, intravenous contrast media (CT and MRI). These tests, along with Holter monitoring and genetic testing, should be performed only when significant cardiovascular disease is strongly suspected, and the test results should be interpreted by providers knowledgeable in sports cardiology issues.
Electrocardiographic Screening in Athletes
The ECG is a widely available screening tool that can provide valuable information regarding cardiac structure and function. Accordingly, the ECG is the most frequently used diagnostic test for screening athletes above and beyond the PPE-4. Mandatory ECG screening has been in place in the Veneto region of Italy since 1971. The Medical Protection of Athletes Act mandates that ECGs be performed for Italian athletes ages 12 to 35 years. Corrado et al. have published an extensive 25-year experience with athlete ECG screening in a variety of sports, and from the Italian perspective, this testing has been shown to be cost-effective. Investigators argue that the data from Italy support ECG screening, and that has led to the disqualification of Italian athletes at risk (particularly with HCM), thereby shifting the demographics of athletic SD in Italy away from HCM as the most common cause of SD and toward ARVC. As a result of these findings, the International Olympic Committee supported ECG screening of Olympic athletes in 2004, and the following year a similar recommendation emerged from the European Society of Cardiology.
ECG screening has also been shown to more reliably identify college athletes with cardiovascular disorders in the United States, albeit with an increase in false-positive results, but because of the inherent interpretive complexity of this process, the proposed routine addition of the ECG to athletic screening has generated considerable controversy. The use of ECGs has been advocated in the United States by persons who support the European approach, whereas the cost and inherent limitation of widespread ECG screening has been elegantly argued and it has even been discouraged. Widespread ECG screening has not been endorsed by the U.S. Olympic Committee, the American Heart Association, or the American College of Cardiology, and it was not incorporated into the most recent 36th Bethesda Conference on Eligibility Recommendations for Competitive Athletes with Cardiovascular Disorders. We believe that the ECG has considerable value, particularly when applied with a comprehensive understanding of normal adaptations associated with training and the effects of race and gender and when it is supplemented by available on-site high-quality TTE, which can limit the number of false-positive results (particularly with regard to HCM) and thereby reduce the incidence of unnecessary withdrawal from participation. Regardless, the controversy will undoubtedly continue in the United States, and institutions and team physicians will need to decide what type of screening is feasible and affordable and what level of risk is acceptable.
Incorporation of an ECG into the screening process can borrow heavily from the extensive data available to assist in interpretation. Corrado and colleagues offer important evidence to distinguish normal adaptation from “uncommon and training un-related ECG changes.” Uncommon findings include ST segment depression, pathologic q waves, left atrial enlargement, left axis deviation/left anterior hemiblock, right axis deviation/right posterior fascicular block, RV hypertrophy, ventricular preexcitation/WPW syndrome, complete right and left bundle branch block, long ( Fig. 15-3 ) and short QT, and Brugada-like early repolarization ( Fig. 15-4 ). Training-related remodeling typically results in increased QRS amplitude alone and does not include significant QRS widening or ST depression. Although T-wave inversion is regarded as an uncommon finding in the Italian database, providers who see larger volumes of athletes of African descent will be exposed to a much wider range of repolarization abnormalities (such as ST elevation and biphasic T waves) associated with dramatic increases in voltage, as shown in Figure 15-2 and Figure 15-5, A . Accordingly, incorporation of ECG screening alone in conjunction with the PPE-4 will likely lead to unnecessary sidelining of athletes, particularly athletes of African and Caribbean descent, with further testing being performed at the expense of the athlete in question. Therefore any consideration of the cost-effectiveness of ECG screening alone must incorporate the added and often unnecessary cost of downstream imaging (e.g., TTE) generated by false-positive results of a screening ECG.
TTE Screening in Athletes
TTE screening for athletic preparticipation has not been formerly included in any guidelines or recommendations in Europe or the United States except when the abnormalities found during the PPE-4 or screening ECG or the development of new symptoms indicate the need for additional testing. TTE is far more expensive and logistically challenging compared with an ECG, and it is accompanied by similar challenges with regard to the definition of acceptable limits of normal remodeling and the presence of true disease. Accordingly, TTE also poses the important problem of false-positive results exceeding the detection of real disease states.
Performance of TTE as a screening tool or as a consequence of concern for disease places the sports cardiologist in and around the “gray zone,” defined by Maron as the overlap area between training-related hypertrophy and HCM. This overlap area presents a strong challenge; however, tools are available to sharpen our discernment, allowing more precise separation of the two entities. The autosomal-dominant mutation of the cardiac sarcomere known as HCM is phenotypically a very heterogeneous condition, with LV wall thickness ranging from normal (<12 mm) to severe hypertrophy (30 to 50 mm); furthermore, the hypertrophy can be focal or symmetric, obstruction may be present or absent at rest or with exercise, and symptoms are highly variable. Training-related remodeling can induce degrees of hypertrophy that frequently exceed the upper limit of normal and stray into the “gray zone” (13 to 15 mm) and occasionally beyond to mimic the most feared condition any athlete could have: HCM. Features on TTE can help distinguish between athletic remodeling and HCM. LV end-diastolic cavity size tends to be larger in trained athletes and is often more than 55 mm, whereas LV end-diastolic cavity size in athletes with HCM tends to be smaller. Examples of athletic remodeling and HCM are provided in Figure 15-5 . As discussed, abnormalities of diastolic Doppler indices are not typically seen in athletes and are more suggestive of HCM, as is systolic anterior motion of the mitral valve or evidence of LV outflow tract obstruction. Focal hypertrophy of the septum or apex that is localized is also much more suggestive of HCM and can be missed by routine or screening TTE and is more readily detected by cardiac MRI ( Fig. 15-6 ). Late gadolinium enhancement on MRI provides additional information with regard to the presence of early scar formation and fibrosis in persons with HCM and also may be of prognostic value ( Fig. 15-7 ).
Application of TTE can be very useful in the diagnosis of a host of disorders that may not immediately threaten the athlete ( Box 15-1 ). However, because of the “gray zone” mimicry of HCM, in addition to previously discussed milder forms of dilated cardiomyopathy and ARVC, application of TTE is not for the faint hearted. Clearly, some cases will challenge our diagnostic certainty and may require more extensive testing or detraining. It is common practice to perform “limited” TTE in screening programs; this limited TTE often is performed by fellows in training, without recording or digital storing of the images. Although we applaud the interest and the effort, we discourage this practice because once the screening process has been initiated, physicians assume liability related to the accuracy of the test. “Limited” screening TTE that focuses primarily on HCM is less likely to detect focal HCM, the anomalous coronary artery, or more subtle abnormalities of the ascending aorta (particularly those associated with the bicuspid aortic valve). Furthermore, limited TTE screening will be less discerning with regard to remodeling versus real disease and could trigger unnecessary testing and anxiety over a false-positive diagnosis that is unnecessary and costly. For this reason, to best serve the athlete, at the initiation of the evaluation we recommend incorporation of high-quality and thorough TTE (which, we have found, can be performed in the screening setting in <10 minutes) that ideally would include the knowledge of congenital anomalies.
Structural and Congenital Disease States in Elite Athletes
It is prudent for the sports cardiologist to proceed with great caution and a meticulous approach before establishing a concrete diagnosis of a structural abnormality in any elite athlete, particularly when the diagnosis overlaps with the previously discussed remodeling changes that mimic real disease. When a structural abnormality is diagnosed in an elite athlete, the most recent expert consensus from the 36th Bethesda Conference provides us with general guidelines for management, particularly with regard to eligibility for athletic participation. Each athlete must be considered individually and thoroughly, and the sports cardiologist may be confounded by the overall lack of data that support any survival benefit derived from restriction from participation. Providers will also struggle to maintain equipoise during this process, with competing interests vying for influence, including the strong desire of the athlete to continue competing; pressure from parents, fans, administrators, teams, and schools; a shared loyalty to the athlete/patient and the institution or team that employs or consults the provider; the athlete seeking multiple opinions until a provider acquiesces and allows participation; and concern for adverse publicity or medical-legal repercussions that can have a profound impact on any individual physician managing a celebrated athlete. The cases of basketball players Hank Gathers and Reggie Lewis are dramatic examples of the difficult and damaging nature of this process.
Hypertrophic Cardiomyopathy
HCM occurs in approximately 1 in every 500 persons in the general population and is the most common cause of athletic SD in the United States. A British pathologist initially described HCM in 1958 in a very high-risk family with dramatic asymmetric LVH ; HCM would be further evaluated in major referral centers, creating a significant referral bias and exaggerating the true risk of SD faced by persons with the diagnosis. Indeed, we have more recently understood HCM to be a condition with a widely variable phenotypic expression ranging from significant risk of SD to a benign clinical course with unusual longevity in persons with the condition. In many ways, the only consistency with regard to HCM is inconsistency.
Some data suggest that an increased risk of athletic SD in persons with HCM is associated with race, young age, and vigorous physical activity ; however, except for an inference from the Italian experience, data are lacking to support the existence of a survival benefit in athletes as a result of withdrawal from participation in sports. Because the safest course of action is probably withdrawal of all athletes with the confirmed diagnosis of HCM from all but low-intensity sports, this recommendation was adopted by the 36th Bethesda Conference in 2005 and integrated again by expert consensus on HCM in 2011. Disqualified athletes and sports cardiologists both will be affected by the lack of compelling data when complying with these guidelines, with the knowledge that low-risk athletes will be unnecessarily sidelined from competition. Accordingly, individual cardiologists may decide to challenge these recommendations and allow participation. In 1990, Division I college basketball player Monty Williams was diagnosed with HCM his sophomore year at Notre Dame, the same year that Hank Gathers died. Initially he was disqualified and was told he would never play basketball again. Two years later he sought another opinion, and after a battery of tests, he was cleared to compete in a controversial decision by his consulting cardiologist, and he went on to play in the NBA. Other persons have advocated for individualized participation for athletes with defibrillators (i.e., implantable cardioverter-defibrillators [ICDs]), but this process is very complex without strong data to support it. The effects of extreme motion and bodily contact could disrupt function of the ICD, and thus managing physicians must rely on the athlete to frequently check the device remotely and respond immediately to any alerts signaling malfunction.
Nicholas Knapp, a 17-year-old high school senior who had accepted a basketball scholarship at Northwestern University, experienced cardiac arrest while playing informally, and ventricular fibrillation (VF) was documented. He was resuscitated and recovered completely. He was subsequently found to have mild asymmetric LVH localized to the septum with hyperdynamic LV systolic function and mild systolic anterior motion of the mitral valve and diffuse T-wave inversion on his resting ECG. He was diagnosed with HCM, and after a negative electrophysiology study, an implantable defibrillator was inserted. Knapp matriculated at Northwestern the following year and was declared medically ineligible to play but was allowed to maintain his full scholarship. Despite the profile of serious risk that had been established, Knapp pursued his right to participate in intercollegiate basketball in federal district court (Knapp v. Northwestern University ), arguing that restricting him from playing was a violation of his rights as established in the Rehabilitation Act of 1973. The federal district court initially ruled in favor of Knapp, but this ruling was overturned in the U.S. Court of Appeals.
Athletes who are disqualified because of suspected HCM and who are within the “gray zone” should be subjected to a period of detraining and then reevaluated. In an interesting case report, investigators describe a 17-year-old male swimmer who underwent vigorous training (14 hours per week/16 miles per week) and was shown to have LVH by voltage on his ECG, along with inverted and biphasic T waves, LV wall thickness of 14 mm, and an end-diastolic LV cavity size of 48 mm according to TTE. The athlete was evaluated after 8 weeks of detraining, and complete regression of all training-related remodeling was found on both the ECG and TTE. Pelliccia et al. prospectively evaluated 40 elite Italian athletes with hypertrophy and cavity dilation after a more prolonged period of detraining (1 to 13 years) and found that LVH regressed to normal in all subjects, whereas LV cavity dilation persisted (>60 mm) in 22% of subjects. Accordingly, detraining is particularly helpful in the circumstance of the “gray zone,” and it would seem reasonable to reevaluate the athlete after approximately 2 months and again at around 1 year.
Genetic testing is problematic because only a positive test is helpful; a negative test does not exclude a new and private mutation. Athletes who are referred because of a family history of HCM but are not shown to be affected by ECG, TTE, or the presence of symptoms may benefit greatly from genetic testing if the affected parent/relative can have the gene identified and the athlete is subsequently tested for the presence of the same genotype. Because the timing of phenotypic development of LVH in persons with HCM is variable, a positive genetic test in the athlete would stimulate follow-up at frequent intervals and serial testing that should include yearly TTE and stress testing at a minimum, as well as consideration for disqualification depending on the risk profile of the family history and the individual athlete. In contrast, athletes with negative results of genetic testing would be free to participate and would not subjected to frequent and expensive diagnostic testing.
Congenital Anomalous Coronary Artery
The congenital anomalous coronary artery is the second most common cause of athletic SD in the United States. The left coronary arising from the right sinus is more prevalent in cases of athletic SD than is the right coronary arising from the left sinus ; however, both scenarios can be threatening. When an oblique orifice arising from the contrary sinus is subjected to aortic expansion from increased cardiac output with exercise, the slitlike narrowing can be accentuated, leading to acute ischemia and arrhythmic SD. This anomaly may be the most elusive and difficult for the sports cardiologist because symptoms are often absent, and of the athletes who experienced SD and had undergone screening, none (9/9) had abnormal ECG results, and of those who had undergone stress testing, none had abnormal findings (6 of 6).
The only opportunity to make this diagnosis prior to an event would be with a screening TTE, which can correctly identify the right and left coronary arteries in most elite athletes. However, imaging of coronary arteries is not routinely performed in standard adult TTE laboratories, whereas it is standard to assess coronary origin and course in congenital TTE laboratories. Accordingly, in any athlete undergoing TTE for screening, chest pain, or syncope with exertion, imaging of the coronaries should be undertaken. Indeed, it is recommended that coronary artery imaging be included in any TTE protocol involving elite athletes. CT angiography is the best test for athletes suspected of having this anomaly, and anatomy can be elegantly identified with this technique. When an anomaly is detected, conventional wisdom dictates at least temporary disqualification and subsequent surgical repair of the aforementioned anomalies, although no randomized data exist to support that recommendation. This recommendation is advisable and clearer in symptomatic athletes. If the anomaly is incidentally found in an asymptomatic athlete, careful stratification of risk based on the duration and nature of event-free participation and the structural appearance of the anomaly will be necessary to individualize any recommendation about whether the athlete should be able to continue to participate or should undergo surgery.
Arrhythmogenic Right Ventricular Cardiomyopathy
ARVC historically has posed a difficult diagnostic challenge, and TTE and ECG have not been ideal tools for making this diagnosis. As previously discussed, athletes may have training-related dilation and systolic dysfunction of the RV that can mimic the condition of ARVC. Diagnostic criteria for ARVC have evolved with better RV imaging with MRI ; however, we urge caution with regard to this diagnosis, particularly in the asymptomatic athlete without documentation of ventricular arrhythmia. Precordial T-wave inversion of more than 2 mm in two or more adjacent leads ( Fig. 15-8 ) is uncommon in older athletes and may warrant further evaluation with MRI. T-wave inversion in precordial leads V1 to V3 occurs in fewer than 3% of healthy persons from ages 19 to 45 years (it is more common in children) and in 87% of patients with ARVC. Therefore the diagnosis should only be made in the context of the individual patient based on age and whether premature ventricular contractions or ventricular tachycardia (VT) of left bundle branch block morphology are present. For suspected cases of ARVC, temporary disqualification is warranted and expert electrophysiologic consultation should be sought. In confirmed cases, disqualification from all but low-intensity sports may be permanent and a defibrillator may be required.
