Cardiac Risk in Athletes

Gordo Byrn asked on Twitter a few days ago: "What are the top markers for preventable early death in athletic populations?" I offered some off-the-cuff thoughts about cardiac risk....and heard some thoughts by other EC folks on Twitter.

There have been a couple notable medical problems among elite triathletes in the past couple months.

We recalled the recent death of Steve Larsen who died earlier this year, collapsing during a workout. Initial reports suggested heart disease, but follow-up reports noted that an autopsy failed to demonstrate a cardiac cause of death.

More recently, Torbjorn Sinballe retired from triathlon when he and his physicians decided that further training would be detrimental because of his underlying cardiac conditions (bicuspid aortic valve and enlargement of the ascending aorta).

Gordo's question is a good one. It gets at the very important issue of preventable death in athletes of all types. I've done a little reading over the past few days and I'll offer my findings here. I'll continue to do some more reading/research and report back with any new, useful information that I dig up. I've borrowed the pictures....and listed some references for the material I present.

How big is the problem of nontraumatic death in athletes?

This is a rare event. A recent study reported <100>

This is not something new. Recall that in 490 BC, the young Greek soldier, Phidipides, ran from Marathon to Athens and fell dead at the finish.

But there are some sobering observations.... Sudden death occurs instantaneously and usually occurs during training or competition, suggesting that exercise plays a causative role. More than 90% of events occur in men. Warning signs are seldom present and a correct diagnosis is rarely made before death.

Van Camp et al. studied the issue of nontraumatic deaths in high school and college athletes in the U.S. based on information at the National Center for Catastrophic Sports Injury Research during 1983 to 1993. There were 126 deaths among high school athletes and 34 among college athletes. The authors estimated death rates at 7.47 per million for men and 1.33 per million for women (1).

Maron et al. examined sudden death due to cardiovascular disease among Minnesota high school athletes from 1985 to 1997. There were 1,453,280 sports participations and 651,695 student participants. There were 3 sudden cardiac deaths, yielding a calculated risk for sudden cardiac death of 1 per 500,000 participants or 1 per 217,400 participants per academic year. This would translate to a risk of 1 per 72,5000 for a typical 3-year student athlete over his/her high school career (2).

What are the causes of sudden death in athletes?

A variety of studies have tried to answer this question. The following is a list of the most common cardiovascular abnormalities found in young athletes with sudden cardiac death, in decreasing order of frequency (3):

1. Hypertrophic cardiomyopathy(HCM) (in 36%): Hank Gathers, Reggie Lewis

2. Unexplained increase in cardiac mass (in 10%)

3. Aberrant coronary arteries (in 13%): Pete Marovich

4. Other coronary anomalies (in 6%)

5. Ruptured aortic aneurysm (all others, <=5%)

6. Tunneled LAD coronary artery

7. Aortic valve stenosis

8. Lesion consistent with myocarditis

9. Idiopathic dilated cardiomyopathy

10. Arrhythmogenic right ventricular dysplasia

11. Idiopathic myocardial scarring

12. Mitral valve prolapse

13. Atherosclerotic coronary artery disease: Jim Fixx

14. Other congenital heart disease

15. Long QT syndrome

16. Sarcoidosis

17. Sickle cell trait

18. "Normal" heart

What is noteworthy is that this list would look very similar to the list of causes of sudden cardiac death in a similarly young but NONATHLETIC popoulation.

How do we screen for athletes at risk for sudden cardiovascular death(4)?

There have been 2 sets of recommendations for proper preparticipation physical examinations for young athletes: 1 ) A monograph (5) from 5 medical specialties (Aerican Medical Society for Sports Medicine, American Academy of Family Physicians, American Academy of Pediatrics, American Orthopaedic Society for Sports Medicine, American Osteopathic Academy of Sports Medicine); and 2) A consensus statement (6) from the American Heart Association (AHA). Often, the preparticipation physical examination takes place before participation in school athletics, but this examination can be a portion of an annual examination for athletes outside of the school setting.

The AHA guidelines suggest that the examination include:

1. Detailed cardiovascular history with attention to:

a. Exertional chest pain or discomfort

b. Syncope or near syncope

c. Excessive, unexpected and unexplained shortness of breath with exercise

d. The past detection of a heart murmur or elevated blood pressure

e. A family history of premature death (sudden or otherwise)

f. Significant disability from cardiovascular disease in close relatives younger than 50 years

g. Specific knowledge of the occurence of hypertrophic cardiomyopathy, Marfan syndrome, arrhythmias, long QT syndrome, or dilated cardiomyopathy

2. Cardiac physical examination with attention to:

a. Femoral artery pulses to exclude coarctation of the aorta

b. Precordial auscultation in the supine and standing positions to identify heart murmurs consistent with dynamic left ventricular outflow obstruction
c. Recognition of the stigmata of the Marfan syndrome

d. Brachial blood pressure measurement in the sitting position

Unfortunately, there are no prospective studies on whether the preparticipation physical examination effectively screens out conditions that predispose the young athlete to sudden cardiac death. The AHA admits, though, that screening by history-taking and physical examination alone (without additional testing) is not sufficient to guarantee detection of many cardiovascular conditions responsible for sudden cardiac death in athletes.

Is additional noninvasive testing helpful?

Some authorities have suggested the addition of noninvasive testing (eg, electrocardiogram and/or echocardiography) to help identify young athletes at risk for sudden cardiac death.

It seems almost intuitive that one or the other of these noninvasive tests might identify some underlying cardiac conditions.

Unfortunately, there are few data to suggest that either of these tests, when incorporated with the physical examination, results in a lower rate of sudden cardiac death among athletes. Moreover, the tests are (relatively) expensive and the AHA suggests that they are not cost-effective. As an example.....if the underlying prevalence of hypertrophic cardiomyopathy among young athletes is 1 per 500, and if an echocardiogram cost $500, it would cost $250,000 to detect a single unsuspected case of HCM.

Recommendations

I'd like to do some additional reading....and I promise to report back. From what I've learned so far, though, I would suggest that adult triathletes have an annual physical examination with attention to the cardiac issues listed above. I would also lean toward recommending an ECG and an echocardiogram, despite their cost, and despite a lack of evidence to confirm their effectiveness.

Some References

1. Van Camp SP et al. Med Sci Sports Exerc 1995; 27:641-647.

2. Maron BJ et al. J Am Coll Cardiol 1998; 32:1881-1884.

3. Maron BJ. Cardiac Electrophys Rev 1997; 1/2:274-277.

4. Mick TM et al. Cleveland Clin Rev 2004; 71:587-597.

5. Am Acad of Family Physicians et al. Preparticipation Physical Evaluation, 2nd ed. New York: McGraw-Hill, 1996.

6. Maron BJ et al. Circulation 1998; 97:2294.

7. Maron BJ et al. Circulation 2009; 119:1085-1092.