Can we minimize the risk of sudden cardiac deaths?

By Sabrina Gonzalez | Photo by Cooper Smith/Unsplash

Endurance exercise and physical activity are known to produce significant health benefits. However, increased participation in long endurance events and races has also been associated with rare reports of sudden death and cardiac dysfunction. This has generated a lot of concern regarding the possible risks of endurance activities. This month, let’s focus on the effects that physical activity exerts on one of the most vital muscles of the body–the heart.

Changes in Heart Structure and Function

As early as the 1890s, clinicians have been trying to determine the changes that the heart undergoes in response to exercise. Chronic endurance exercise imposes additional workload on the heart, resulting in alterations in cardiac structure commonly described as the “athlete’s heart.” Numerous researches document the occurrence of heart enlargement; the significance of this however has remained to be a hot topic of debate. Increased left ventricular volume and dimensions are likewise reported in the athletic population. Oftentimes, these changes have no associated symptoms; however, over time, these might predispose the athlete to serious, life-threatening rhythm abnormalities. In many cases, normal cardiac remodeling is difficult to differentiate from pathologic changes such as those seen in cardiomyopathies.

Incidence of Adverse Cardiac Events

The RACER study, short for Race Associated Cardiac Arrest Event Registry, is a 10-year study that looked into the occurrence of adverse cardiac events during long-distance races in the United States. Out of 10 million participants, there were 59 documented cases of cardiac arrest, an incidence of about 0.5 per 100,000 individuals. This incidence is lower than that in triathletes, where it is estimated to be one death per 52,000 participants. Most adverse cardiac events occurred in males, during marathons, and in the last mile of the race. Of the 59 patients in this study, 71 percent died.

Cause of Sudden Cardiac Death

In young athletes, sudden cardiac death during competition has been attributed to various congenital cardiac disorders. Hypertrophic cardiomyopathy, a muscular disorder of the heart characterized by left ventricular enlargement, remains to be the most common cause, responsible for approximately 33 percent of these deaths. An undiagnosed anomaly of the coronary arteries comes in second.

The RACER study looked into an older population of endurance athletes; according to this study, the most common cause of sudden cardiac death in endurance athletes remains to be hypertrophic cardiomyopathy, similar to that seen in the younger population. Other cardiac causes include arrhythmias, which are seen approximately five times more in endurance athletes training for long-distance events. Other studies point to existing coronary artery disease as the most common underlying condition responsible for sports-related sudden cardiac death, which has been previously reported to occur in as much as 80 percent of patients.

Identifying Athletes at Risk

Except for pre-existing cardiac conditions, there are no specific tell-tale signs to identify which athletes are at risk for developing cardiac dysfunction and sudden cardiac death. A high index of suspicion, along with a combination of laboratory examinations such as electrocardiography, echocardiography, Holter monitoring, and stress testing, may be necessary in order to diagnose these conditions in seemingly healthy individuals. Advanced imaging techniques such as computed tomography and cardiac magnetic resonance imaging may help identify patients with subclinical cardiac conditions; however, these examinations are too costly to be used routinely. At present, there is no standard pre-participation screening employed for endurance athletes.

Tips to Prevent Sudden Cardiac Death

Given all of this, what can an endurance athlete do to minimize the risk of sudden cardiac death? Experts suggest engaging in regular exercise and proper athletic training. Although sudden cardiac death is seen to occur during vigorous activities, individuals who do not routinely exercise have been noted to be at higher risk than those who do. The consensus by the American Heart Association is at least 150 minutes of moderate endurance training or 75 minutes of vigorous exercise per week in adults. Other international societies suggest screening for occult conditions in certain athletic populations such as coronary artery disease in the older athlete, especially in males. In individuals who have already been diagnosed with a cardiac condition or who have symptoms like chest pain on exertion or sudden loss of consciousness, it is best to consult your physician for clearance prior to engaging in endurance events or competitive sports.

Healing vs Harming

The health benefits of endurance exercise far outweigh the infrequent instances of sudden cardiac death in endurance athletes. Before engaging in long endurance events, it is advisable to obtain an adequate cardiac evaluation by a sports physician or a cardiologist. Steady, incremental training is likewise recommended. Endurance exercise may either heal or harm the heart–it is important to take necessary precautions, especially before subjecting the body to vigorous, stressful events. The heart, after all, has its limits.