Exercise is commonly recommended as a way to reduce cardiovascular risk factors such as obesity, hypertension, dyslipidemia, and type 2 diabetes. While athletes do have a lower rate of adverse cardiovascular events, they are not immune to them. This topic was a point of discussion at Care of the Athletic Heart, a forum recently presented by the American College of Cardiology.
Traditional risk factors
Conditions such as type 2 diabetes, hypertension, dyslipidemia, and obesity are not only dangerous on their own – they also increase an individual’s risk of developing cardiovascular disease (CVD) and having an adverse cardiovascular event. These disorders tend to appear less frequently in athletes and people who routinely engage in exercise, but there are certainly still some active people who also have these risk factors. Tobacco use, a lifestyle factor especially detrimental to cardiovascular wellness, is also less common – but not absent – in active individuals such as endurance athletes. Consequently, it makes sense that the incidence of CVD and related adverse events are lower in active individuals, but not completely absent.
One important risk factor highly correlated with CVD that isn’t affected by exercise, is age. Age is referred to in clinical practical guidelines as a nonmodifiable risk factor for cardiovascular conditions such as atherosclerosis. While other risk factors such as systolic blood pressure, type 2 diabetes, smoking, cholesterol, and body mass index can be altered with lifestyle and pharmacological interventions, age cannot. Not surprisingly, most sports-related cardiac deaths occur in individuals over the age of 40.
Active people generally have better cardiorespiratory fitness (CRF), a measure of how well the body takes in and delivers oxygen to muscles and organs during physical exertion. A doctor can measure CRF during a standard exercise stress test, but individuals can get an idea of their own CRF outside of the clinic using the 12-minute run test. This method has been relied on for decades in military training to measure aerobic health. To test CRF using this method, a healthy adult runs as fast as they can comfortably manage for 12 minutes. They then compare the resulting distance to the U.S. Department of Defense chart ranking CRF based on age and miles run. The link between CRF and cardiovascular health informed the American Heart Academy’s 2016 recommendation to assess CRF during routine checkups because:
- Low CRF is linked to CVD and a higher likelihood of a CVD-related hospitalization
- Low CRF is a strong predictor of stroke
- Optimal CRF is linked to improved post-surgery outcomes, including reduced mortality
The link between athletic performance and better CRF, therefore, is a good indicator that active individuals will have markedly fewer complications, hospitalizations, and mortality related to CVD.
Atherosclerotic coronary artery disease
While it is true that the risk of CVD is lower for athletes, it is still present. When adverse cardiovascular events and deaths in athletes do happen, most are attributed to atherosclerotic coronary artery disease (CAD). Although CAD is the most frequently observed CVD in athletes who experience symptoms or death, the event rate for CAD is still significantly higher in sedentary individuals than active ones. Researchers are exploring the incidence of CAD in athletes, particularly endurance or “master” athletes who engage in long-distance or extended periods of exertion such as marathoners, ultramarathoners, or triathletes.
Coronary artery calcium
Recent studies have shown that coronary artery calcium (CAC) in certain athletes, particularly males, is higher than in age-matched controls. The mechanisms underlying this phenomenon remain unclear because the pathophysiology of CAC deposition, composition and impact on CVD risk in sedentary versus active individuals hasn’t been explored. Possibly, the endothelial injury occurring during rigorous exercise is being repaired with calcium deposition, but it’s unclear from prior studies if the calcium deposits collect in the endothelium, smooth muscle, or both. Further research to identify potential mechanisms of action of increased CAC in athletes is needed to better elucidate this phenomenon.
CVD screening and management in athletes
Screening for CVD in athletes includes obtaining a detailed medical history, performing a physical exam, electrocardiogram, and exercise stress test. Identifying athletes who require assessment is often difficult because they are asymptomatic at rest, and their overall health may be such that they don’t present as a typical patient at risk of CVD. Given the demonstrated correlation between CAC and CVD in athletes, providers may also take a measure of CAC for athletes who are believed to be at intermediate risk.
As with any patient, athletes who have experienced an adverse cardiovascular event should be treated with conventional medical therapy and followed for a few months post-event. Then, the provider and patient can proceed with shared decision-making about a return to activity. Low-risk, asymptomatic athletes with normal cardiac function and rhythm can usually return to all sports or activities. Athletes with any abnormal findings or cardiac scarring would likely be considered high risk and restricted to low-intensity static and dynamic exercise. Any patient athlete on dual antiplatelet therapy for CVD should avoid contact sports.
Athletes have a lower risk of CVD and adverse CV events such as stroke or cardiac arrest because they tend to have better CRF and fewer risk factors such as tobacco use, obesity, hypertension and dyslipidemia. However, when adverse CV events do happen to athletes they usually are mid-activity and older than 40 years old. Two conditions most commonly found in athletes with CVD are atherosclerotic CAD and higher-than-average CAC, although the mechanisms of these correlations are unclear.