To Run or Not to Run. The Contradiction of Cardiac Risk in Exercise

My contribution to a discussion in the SGRunners forum on the dilemma facing wannabe runners with risk factors for cardiac disease.

Given the dramatic nature of a young and apparently fit sportsperson collapsing after a race, it is understandable that the lay public may draw the wrong conclusions and become leery of exercise. Isn't exercise supposed to be good for your heart? Why are all these "fit" men running marathons and racing triathlons keeling over then? How to reconcile the apparent contradiction?

It is probably best described in the sentence below, excerpted from the article cited in the next paragraph.

"Physical exercise reduces the incidence of atherosclerotic heart disease by managing atherosclerotic risk factors such as a high heart rate and hypertension(1). Vigorous physical activity such as endurance exercise increases the risk for myocardial infarction and sudden cardiac death in patients with diagnosed and latent heart disease(2)."
Am J Cardiol. 2007 Mar 15;99(6):849-51. Epub 2007 Jan 26
Major adverse cardiac events during endurance sports. Belonje A, Nangrahary M, de Swart H, Umans V. Department of Cardiology, Medical Center Alkmaar, Alkmaar, The Netherlands.

In other words, it would appear that in the long term, exercise is a useful, and indeed, essential strategy for folk who are at risk for cardiac events to control their risk factors. A proper exercise regime has been shown to lower lipids, blood pressure, and allow the heart muscle to withstand a heart attack better. This is not to say the risk is completely eliminated. As has been amply demonstrated, extraordinarily fit folk can also be struck down. Sometimes you just can't escape genetics. It is noteworthy that the article ends with the following paragraph;

"The incidence of MACEs in well-trained marathon athletes is very low. In our series, it occurred in only 4 of 62,862 participants, and none of these participants died. All events occurred shortly after or just before the completion of the races. A rapidly available manual defibrillator is among the lifesaving medical equipment that should be on site at all major sporting events."

In the 2 references quoted above, the first describes the health benefits of long term exercise;

(1) Exercise and physical activity in the prevention and treatment of atherosclerotic cardiovascular disease. Thompson PD. Arterioscler Thromb Vasc Biol. 2003 Aug 1;23(8):1319-21.

Exerpts describe reduced blood pressure;

"A meta-analysis of 44 randomized controlled trials including 2674 participants6 demonstrated average reductions in systolic and diastolic blood pressure of 2.6 and 1.8 mm Hg in normotensive subjects and 7.4 and 5.8 mm Hg in hypertensive subjects, respectively."

delayed/reduced onset of type2 diabetes;

"In the DPP, an average 4-kg decrease in body weight and a 593-kcal increase in weekly energy expenditure (approximately 6 miles of walking) reduced the onset of type II diabetes in individuals at high risk for this disease by 58% compared with usual care. The lifestyle intervention was also significantly more powerful than the 31% reduction in the onset of diabetes produced by metformin 850 mg taken twice daily."

amongst other benefits. If you have already had a cardiac event, exercise plays a critical role in rehab;

""Total mortality decreased 27% (P[1]0.05) with the exercise only intervention, but only 13% (P NS) with the more comprehensive rehabilitation programs suggesting that the exercise training is critically important for the beneficial effect. Cardiac mortality was reduced 31% (P[1]0.05) and 26% (P[1]0.05) for the exercise only and comprehensive programs, respectively."


So, lots of pluses. What are the downsides.

Thompson PD. The cardiovascular complications of vigorous physical activity. Arch Intern Med 1996;156:2297–2302.

"The predominant causes of exercise-related cardiovascular complications are congenital abnormalities in young subjects and atherosclerotic coronary disease in adults. The absolute incidence of exercise deaths is low. Only approximately 0.75 and 0.13 per 100,000 young male and female athletes and 6 per 100,000 middle-aged men die during exertion per year. Nevertheless, exercise does acutely and transiently increase the risk of cardiac events. CONCLUSIONS: Routine cardiovascular testing to prevent exercise events (echocardiography in the young and exercise testing in adults) has limited usefulness because of the rarity of such events, the cost of screening, and poor predictive accuracy of exercise testing for exercise events. Physicians should (1) perform routine screening and cardiac auscultation in young athletes; (2) carefully evaluate exercise-induced symptoms; and (3) ensure that adults know the symptoms of cardiac ischemia."

In a nutshell, exercise is good for you, just be careful when doing it!

Cheers.