By Jonathan Kim, M.D.
Case #1: A 55-year-old female triathlete self-refers herself to your clinic complaining of exertional dyspnea on exertion. She has been a high-level recreational endurance athlete for the last 25 years, competing in 25 marathons and 8 Ironman triathlons. At baseline, she runs 40 miles per week when not training for competition. She states that for the last six to nine months, she feels excessively fatigued and more short of breath during her long runs. You are the third cardiologist she has seen. She brings previous records demonstrating a “normal” 2-D trans-thoracic echocardiogram and standard Bruce protocol exercise treadmill test. The stress test was stopped because she achieved maximum heart rate; she was asymptomatic at the time. She was told nothing was wrong with her because “you run marathons and run 50 miles per week”.
Case #2: An 18-year-old female soccer player is referred to your clinic for an “abnormal ECG” obtained during a pre-season sports physical. It shows an incomplete right bundle branch block and voltage criteria for left ventricular hypertrophy. She has no symptoms and a normal physical exam. The referring physician believes the athlete needs an echocardiogram.
These hypothetical cases are, in fact, descriptions of common referrals and self-referred patients seen in general cardiology clinics across the country. They are examples of why sports cardiology is becoming an integral and essential component of preventive cardiology. Without sports cardiology expertise and significant exposure to athletic patients, one may agree that the patient described in Case #1 is truly “fine.”
How could someone this fit have significant exertional dyspnea and fatigue? Didn’t she have a normal echo and stress test? For Case #2, it is not surprising there was concern about the presence of high voltage on the ECG. Who wants to miss a case of hypertrophic cardiomyopathy?
The story of Hank Gathers resonates with all physicians who care for athletes. Perhaps Case #2 requires more testing, and Case #1 is an example of wasted resources and too much testing. The answer is actually the exact opposite.
To start, however, it is important to first look at the tremendous rise in sports participation in the United States. Since the 1990s, the number of women and men who participate in recreational running events in the U.S. has skyrocketed, and now women sign up for long-distance road races more than men.1 In fact, it is estimated that in 2012 almost 9 million road race finishers in the U.S. were women.1 These striking trends indicate that female participation in these endurance exercise events will continue to rise over the coming years.
So why is there so much interest in recreational running? In part, people are well aware of the beneficial effects of exercise. It has long been established that exercise decreases cardiovascular morbidity and mortality.2 More exercise lowers blood pressure, improves cholesterol levels and decreases the overall cardiovascular risk profile. In addition, we know a graded exercise program is a significant part of the standard medical regimen post myocardial infarction and other cardiac surgeries and percutaneous procedures. But there is more to the story than just achieving cardiovascular health. Whether for charity, embracing the challenge, relief of stress or achieving personal milestones, people are signing up for these events in record numbers.
The “boom” in exercise participation has fueled the emergence of sports cardiology. Sports cardiology addresses cardiovascular issues for all those who place a high premium on exercise or athletic performance. From recognizing occult cardiovascular structural pathology in young athletes to evaluating the perceived loss of exercise tolerance in veteran endurance exercisers, the sports cardiologist must address, evaluate and manage these issues while taking into consideration the premium on athletic performance. With the proportion of women engaging in running events climbing at a record pace, it is critical that active women are aware this specialized medical and cardiac care exists.
The recognition that cardiovascular disease is the No. 1 cause of death in women highlights the need for better gender-specific preventive cardiovascular care and research. Unfortunately, as more women engage in strenuous exercise, women currently remain underrepresented within sports cardiology research. I would expect significant increases in the number of studies focused on female athletes over the coming years and substantial gains in our understanding of cardiovascular issues in female athletes.
Specific to running, there are several controversial issues regarding the effects of endurance exercise on the heart. The core of these issues centers on the hypothesis of a “dose-response” and exercise. Recent studies have suggested that long-term ultra endurance exercise may be linked to early plaque build-up in the coronary arteries and also the development of an “exercise-induced” right ventricular cardiomyopathy.3,4
It is important to emphasize that, to date, there are no definitive data implicating marathon running or ultra-endurance exercise as pathologic in the general population. There are data associating endurance exercise and the development of atrial fibrillation, but even these data lack formal insight into prognosis, additional risk factors and mechanisms.5 The data regarding endurance exercise and the development of an exercise-specific cardiomyopathy suggest this is extremely rare in occurrence and limited to a very small, at-risk portion of the ultra-endurance athletic population.
Exactly who is at risk is unknown and an important area of current research. The association between ultra-endurance exercise and accelerated coronary atherosclerosis remains inconclusive and based on weak and poorly controlled observational data. There is simply more we need to understand before any conclusions can be made. Moreover, there are studies that have demonstrated improved mortality in ultra-endurance athletes,6 the safety of marathon running7 and the beneficial effects on cardiovascular health from marathon training.8 Current advice for those concerned would be to consult a sports cardiologist before embarking on an ultra-endurance training regimen.
A second and more publicized controversy poses the question, should all competitive athletes be screened with a 12-lead ECG prior to sports participation? At the forefront of this controversy are highly visible, albeit rare, tragedies of sudden cardiac death on the playing field and data from Italy demonstrating a 90 percent reduction in athlete sudden cardiac death events through the use of a nationally mandated ECG screening program.9 Indeed, because of these data, Europe mandates the use of a pre-participation ECG, while the U.S. (American Heart Association) does not.10
Although it seems logical to implement this same requirement in the U.S., there are many valid issues with this proposed mandate. For one, there remains no definitive evidence that the addition of a pre-participation ECG reduces mortality compared to the current practice of only a pre-participation history and physical. However, recent data have also demonstrated higher-risk of sudden cardiac death in some U.S. collegiate athlete groups.11
At this point, this controversy remains far from resolved. For now, I believe there is a role for more in-depth pre-participation screening (utilizing ECG and/or echocardiography) in certain athlete groups if the infrastructure is in place to support this practice and the physicians, both internists and cardiologists, have the experience and expertise to adequately interpret the data obtained. Further, I believe ongoing research efforts designed to improve the interpretation of the athlete ECG are paramount and will continue to improve the specificity and false positive rates of the screening athlete ECG.
It is critical for all cardiologists and internists to educate our patients about the benefits of exercise, to not discourage strenuous exercise in those healthy enough and invested to do so, and to be aware of these current controversies within sports cardiology. For the sports cardiologist, we must be aware of the current limitations within sports cardiology research and recognize there is still much to understand. Because of this, we must be cautious of science that may garner headlines and critically analyze all new sports-specific research.
Going back to the initial cases: Case #1 illustrates the important point that symptoms experienced by even the most fit ultra-endurance athlete should not be ignored and that appropriate testing is critical to the evaluation and work-up of the endurance athlete. Although this triathlete had previous “normal” testing, the Bruce protocol is not adequate for an elite endurance athlete. Moreover, the functional capacity of this athlete was not assessed properly.
The more appropriate test of choice would have been a cardiopulmonary exercise test, using some sort of ramp exercise protocol in attempts to replicate the training conditions experienced by the athlete. From an echocardiographic standpoint, the use of speckle-tracking techniques may detect early forms of cardiomyopathy not readily evident using standard 2-D echocardiography. Thus, the work-up in Case #1 remains incomplete and inadequate.
Case #2 illustrates the importance of being familiar with normal athletic “training-related” ECG patterns. Voltage consistent with left ventricular hypertrophy, but without additional abnormal ECG findings (ex. left axis deviation, q-waves, ST-segment abnormalities, etc.), is completely normal in a young, competitive athlete. This young athlete did not require a cardiology referral and certainly does not require further testing.
This is an exciting time in the field of sports cardiology. The American College of Cardiology has endorsed exercise and sports cardiology as an important and growing field in cardiology.12 The sports cardiologist has an important role in the individualized medical care of all athletic patients. Research possibilities in sports cardiology are also endless in today’s climate, and it is essential we include female athletes in the design of new studies. As current research efforts provide evidence-based insight into the current controversies present in sports cardiology, it is paramount for the sports cardiologist to responsibly disseminate this knowledge to the general public.
- Pate RR, Pratt M, Blair SN, et al. Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA 1995;273:402-7.
- Möhlenkamp S, Lehmann N, Breuckmann F, et al. Running: the risk of coronary events : Prevalence and prognostic relevance of coronary atherosclerosis in marathon runners. Eur Heart J 2008;29:1903-10.
- La Gerche A, Burns AT, Mooney DJ, et al. Exercise-induced right ventricular dysfunction and structural remodelling in endurance athletes. Eur Heart J 2012;33:998-1006.
- Andersen K, Farahmand B, Ahlbom A, Held C, et al. Risk of arrhythmias in 52 755 long-distance cross-country skiers: a cohort study. Eur Heart J 2013;34:3624-31.
- Farahmand BY, Ahlbom A, Ekblom O, et al Mortality amongst participants in Vasaloppet: a classical long-distance ski race in Sweden. J Intern Med 2003;253:276-83.
- Kim JH, Malhotra R, Chiampas G, et al; Race Associated Cardiac Arrest Event Registry (RACER) Study Group. Cardiac arrest during long-distance running races. N Engl J Med 2012;366:130-40.
- Zilinski JL, Contursi ME, Isaacs SK, et al. Myocardial adaptations to recreational marathon training among middle-aged men. Circ Cardiovasc Imaging 2015;8:e002487.
- Corrado D, Basso C, Pavei A, et al. Trends in sudden cardiovascular death in young competitive athletes after implementation of a preparticipation screening program. JAMA 2006;296:1593-601.
- Maron BJ, Friedman RA, Kligfield P, et al. Assessment of the 12-lead ECG as a screening test for detection of cardiovascular disease in healthy general populations of young people (12-25 Years of Age): a scientific statement from the American Heart Association and the American College of Cardiology. Circulation 2014;130:1303-34.
- Harmon KG, Asif IM, Klossner D, et al. Incidence of sudden cardiac death in National Collegiate Athletic Association athletes. Circulation 2011;123:1594-600.
- Lawless CE, Olshansky B, Washington RL, et al Sports and exercise cardiology in the United States: cardiovascular specialists as members of the athlete healthcare team. J Am Coll Cardiol 2014;63:1461-72.