Protecting Athletes From Sudden Cardiac Death

Although incidence rates are low — 1 in 15,000-1 in 100,000 — a sudden cardiac death (SCD) of an athlete is one of the most devastating and traumatic events in sports.

Sanjay Sharma, BSc (Hons), MD, FRCP (UK), FESC, a professor of cardiology at Cleveland Clinic London, believes that more can be done to facilitate better screening and gain more insight into proactive strategies.

Part of what makes screening and prevention so challenging is that athletes are often asymptomatic, and there is a diverse set of conditions that can contribute to SCD, i.e., there is not a single test that could identify all conditions.

The epidemiological characteristics of SCD indicate that males are affected at much higher rates (male-to-female ratio of 9:1) and the mean age at death is approximately 19 years. Incidence rates for Black athletes are also much higher and may be up to five times higher than their White counterparts. The risk also appears to vary by sport, and sports that have a higher degree of stop-start dynamics, such as basketball, football and American football appear to carry greater risk.

“There’s a bit of a paradox when it comes to exercise in these situations,” says Prof Sharma. “We know cardio-focused exercise is beneficial, but in at-risk patients, exercise can actually trigger a myocardial infarction and promote fatal arrhythmias in predisposed individuals. Perhaps, what’s most alarming is that 80% of individuals who succumb to SCD are asymptomatic prior to the event, so screening based on symptoms is incredibly limited.”

Prof Sharma and his colleagues recently published a review article in the Indian Pacing and Electrophysiology Journal, which looked at the causes of SCD, current screening practices, diagnostic challenges and potential ways to mitigate risk.

Understanding the underlying factors contributing to SCD

“The first step in our research was determining the variance between the various SCD causes,” says Prof Sharma. “The most common cause was cardiomyopathies, specifically, hypertrophic cardiomyopathy. Congenital coronary artery disease and aortopathy were the second-most common. The most common of this group was congenital coronary artery anomalies.”

Acquired disease (myocarditis, other and Kawasaki disease), valvular heart disease (mitral valve prolapse and aortic stenosis), ion channel and electrical disorders (ion channel disorder, Wolff-Parkinson-White, conduction system disease) and coronary artery disease were the other most common causes, respectively.

“In terms of prevention, there is a real balance at play,” says Prof Sharma. “Because there is so much heterogeneity involved with these various causes, there is not a single screening test that could identify all individuals at risk. Furthermore, because of the relatively low incidence rates of SCD, any proposed screening programme must balance sensitivity and specificity. Accessibility, scalability and cost-effectiveness must all be considered.”

Current screening methods

Despite these challenges, Prof Sharma highlights two screening models. An American one, endorsed by the American Heart Association, relies on a 14-point evaluation centered around a physical examination and personal and family history. Conversely, the European screening model advocates for the inclusion of a 12-lead electrocardiogram (ECG).

“The differences in these strategies reflect how these groups interpret or prioritize the different trade-offs between sensitivity, specificity and resource allocation,” says Prof Sharma. “But in reality, implementation ultimately relies on governing sports bodies since their policies tend to vary depending on regional healthcare infrastructure and cultural attitudes toward risk tolerance.”

Prof Sharma notes that prior studies have indicated that ECG screening has demonstrated sensitivity of up to 94% for detecting high-risk cardiovascular conditions. This number is much higher than the diagnostic performance of history (20%) and physical examination (9%) alone.

“This is an important consideration since we’re often focusing on young athletes, the majority of whom are asymptomatic and display unremarkable findings on examination,” says Prof Sharma. “As such, relying solely on patient history and examination leaves the vast majority of at-risk individuals unidentified.”

However, Prof Sharma notes that while EGG is considered standard screening among elite sporting organisations, it is not without limitations. There are several relevant causes of SCD — anomalous coronary arteries, myocarditis, commotio cordis, and ion channelopathies — that can escape detection via ECG. False negatives can also result from incomplete or evolving cardiomyopathy phenotypes.

Looking beyond adolescent athletes

Of note, Prof Sharma explains that while instances of SCD are typically associated with younger athletes, incidence rates are actually much higher among middle-aged athletes, particularly men between 45 and 55 years. Among this demographic, the most common underlying pathology is atherosclerotic coronary artery disease (CAD), which is a condition that is frequently undetected through ECG. Intense physical exercise can acutely precipitate plaque rupture and ventricular arrhythmias, leading to myocardial infarction (MI) or SCD.

“The risk of MI during exercise for this age group is estimated to be six times greater than at rest, and the risk of sudden death up to sixteen times higher,” says Prof Sharma. “However, the long-term benefits of regular physical exercise are still substantial. In fact, we’ve seen studies indicating that individuals with the highest levels of habitual exercise have a 50-fold lower risk of exertion-related MI compared with sedentary counterparts. So, screening for this demographic must go beyond ECG and focus more on integrated cardiovascular risk profiling.”

Ways to help all athletes reduce SCD risk

In their published paper, Prof Sharma and his research group explain that while there is not a single test that could detect all contributing disorders of SCD, there are ways to mitigate risk. While not perfect, ECG is an inexpensive method that can still detect both electrical disorders and structural cardiomyopathies with electrical expression. In instances of potential SCD, early Cardiopulmonary Resuscitation and the application of an automated external defibrillator can improve survival rates by up to 5-fold.

“Improving education as it relates to SCD and its prevention and treatment can significantly improve an athlete’s survival in these instances,” says Prof Sharma. “We know that survival rates from SCD in the community are around 10%. But that survival number increases to the range of 24-49% in sporting events equipped with defibrillators. That’s a huge increase in survivorship likelihood. But time is of the essence in these situations, and action needs to be taken quickly. Active cardiopulmonary resuscitation needs to be initiated within one minute, and the application of an external defibrillator within two minutes and twenty seconds.”

Prof Sharma also stresses that athlete education is equally important. Athletes should be advised about the cardinal symptoms of cardiac disease. They should be advised about the dangers of vigorous exercise during febrile episodes, lower respiratory tract infections and diarrheal illnesses. Athletes need to recognize the cardiovascular dangers of performance-enhancing agents, like anabolic steroids. These drugs can contribute to pathological left ventricular hypertrophy and accelerated coronary atherosclerosis.

Looking ahead

At a more macro level, genetic testing could also play a role in prevention. In the current era, there are several barriers to implementation, for example, low diagnostic yield, uncertainties related to variants of undetermined significance and cost. However, genetic testing could be useful in cases with indeterminate or borderline phenotypes. Prof Sharma suggests that while integration into population-level pre-participation screening for SCD in athletes is impractical, it could be helpful to cascade testing when a pathogenic variant has already been identified in a family member of an athlete.

Ultimately, SCD prevention in athletes is multifaceted. Guidelines provide direction for best practices, but there is variance between European and American associations. ECG screening has demonstrated a high sensitivity for detecting high-risk cardiovascular conditions, but there are limitations since not all causes of SCD are detected. Other methods of reducing risk exist, but cardiopulmonary resuscitation requires knowledge and timeliness, as does defibrillation, which also requires access.

“We know that regular exercise is beneficial, but it can also be a risk factor for myocardial infarction and sudden cardiac arrest,” says Prof Sharma. “We also know that a large proportion of adolescent and adult athletes with serious cardiac diseases can be identified by relatively simple screening methods. As healthcare professionals, it is our responsibility now to thoroughly screen and educate every athlete to help prevent such tragedies from occurring.”