Researchers explore high rate of sudden cardiac arrest in Black male athletes

The exact reasons are unclear; biological and social factors under study

The recent sudden cardiac arrests of college basketball player Bronny James and professional football player Damar Hamlin did more than shock the sports world and the nation. They brought attention to a disturbing, but little-known, fact: Sudden cardiac arrest is the number one medical cause of sudden death in young athletes in the United States and Black athletes appear to be at higher risk.   

The problem is no one knows exactly why.

In the case of James and Hamlin, quick emergency efforts saved their lives. Hamlin has recently resumed playing football and James is expected to return to the basketball court soon. But happy endings are not always the case, and some researchers are sounding the alarm. 

“Understanding why among all athletes, Black players have higher rates of sudden cardiac arrest is an important public health issue and should be an urgent focus of future research,” said Jonathan Kim, M.D., director of sports cardiology and associate professor of medicine at Emory University in Atlanta. He is also current chair of the American College of Cardiology’s Sports and Exercise Cardiology Council.

Kim, who conducts health disparities research, is doing his part. He’s among several researchers supported by the NHLBI who are studying the cardiac health of athletes and others, with an eye on better understanding why these incidents of sudden cardiac arrest, though relatively rare, occur. 

Sudden cardiac arrest happens when the heart suddenly stops beating. If intervention doesn’t happen soon enough, most often with CPR and/or a defibrillator, the condition usually causes death within minutes. Cardiac arrest is not the same as a heart attack, which happens when a blocked artery prevents blood flow to the heart.   

Each year, more than 350,000 people have an out-of-hospital cardiac arrest and about 90% them are fatal, according to the Centers for Disease Control and Prevention. Nationwide, about 1 in 50,000 to 1 in 80,000 young athletes die from the condition. For comparison, the incidence in the general population is substantially higher at about 1 in 1,000 people yearly. These risks differ by age, sex, race, sport type, and other factors.

“What we’re seeing now is not necessarily a new trend or new uptick in cases,” explained Kim, “Black individuals tend to have higher rates of sudden cardiac arrest and sudden cardiac death compared to White individuals in the general U.S. population. The trend toward those higher rates in Black athletes mirrors that disparity.” A 2015 study by NHLBI-funded researchers at the Smidt Heart Institute at Cedars-Sinai in Los Angeles found that Blacks as a group experience sudden cardiac arrest at twice the rate as White individuals.

Young Black male college basketball players are particularly at risk. A 2020 study in the British Medical Journal found that these players had an incidence of sudden cardiac arrest or death 21 times higher than the average among high school male athletes of all races. The second highest at-risk group in the study were Black male college football players.

Researchers have offered few explanations. One condition that has been linked to sudden cardiac arrest in athletes is hypertrophic cardiomyopathy, which causes the heart muscle to become larger and thicker than normal. The condition can be inherited or acquired. It has an estimated prevalence in the general U.S. population of 1 in 500, and in athletes about 1 in 2,000. Kim points out, however, that the condition has not been shown to be more prevalent in Black athletes. 

“We must also consider and assess for possible social and environmental determinants of health that affect these disparities in young athletes,” Kim said. 

His own research, for example, found that Black college football players may have an elevated risk of developing a heart change called concentric left ventricular hypertrophy or C-LVH, that causes the left side of the heart to become more thickened. Kim further showed that this condition is closely linked to lower family income levels among Black players compared to White players. More studies are needed, he said.

Patrice Desvigne-Nickens, M.D., a medical officer in the heart failure and arrhythmias branch in NHLBI’s Division of Cardiovascular Sciences, agreed that social determinants of health — the conditions and environments in which you are born, grow, live, and age — likely play a key role.

“An important contributor to health disparities among Black athletes is likely to include factors such as structural racism, impaired access to health care, distrust of the medical system, and underrepresentation in clinical trials,” Desvigne-Nickens said. “These issues are correctable. Understanding and addressing them could go a long way in preventing this life-threatening cardiac event through providing a better knowledge of susceptibility and risk predictors for the Black athlete.”

As researchers try to identify and understand the underlying causes, the sudden cardiac arrests of Hamlin and James have provided fodder for new insights. In the case of Hamlin, experts have since confirmed a diagnosis of commotio cordis, a rare condition that occurs after sudden, blunt trauma to the chest. In James’ case, his sudden cardiac arrest has been attributed to a congenital defect, according to a family spokeswoman. 

The recent incidents have also spurred calls from some schools and medical societies for improved cardiac safety measures in sports, including greater use of emergency action plans, more CPR training, and wider availability and use of defibrillators. Others are calling for increased screening and physicals of at-risk athletes, despite limited data on the exact causes. One group has developed a registry, called Outcomes Registry for Cardiac Conditions in Athletes (ORCCA), to monitor clinical outcomes in athletes diagnosed with cardiac conditions that are linked to sudden death. 

“Like most healthcare disparities, I suspect there may be many reasons why there seems to be a higher rate of sudden cardiac arrest and sudden death in young Black athletes. Because the answer is likely multifactorial, I don’t think there’s a single study or effort that will be able to provide all the answers,” said Rachel Lampert, M.D., a professor of medicine at Yale School of Medicine in New Haven, Connecticut, and an investigator with the ORCCA study. 

“It would be great to put experts thinking about this problem in the same room and discuss it in detail and try to come up with some approaches,” added Lampert, an NHLBI grantee with expertise in hypertrophic cardiomyopathy. “There are lots of pieces to this puzzle and we need to look at the problem from all angles.” 

EDITOR’S NOTE: Please see accompanying short video on this topic:

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