The Wall Street Journal
January 6, 2023
The phenomenon named as the leading explanation for Damar Hamlin’s cardiac arrest after an on-field hit is notorious but rare in sports—and considered even more rare in football.
Medical experts were quick to recognize signs on Monday night of commotio cordis—Latin for “agitation of the heart”—and NFL Players Association officials said on Thursday it was “the presumptive working diagnosis.” In the intervening days, a previously obscure condition became a widely discussed topic: how prevalent it is, and whether it can be prevented.
Commotio cordis is caused by “blunt force trauma to the chest wall that affects the electrical system of the heart,” causing an arrhythmia and cardiac arrest, said Dr. James Borchers, an Ohio State professor of sports medicine who is also chief medical officer for the Big Ten Conference.
What is commotio cordis?
In a normal heartbeat, the sinus node sends out an electrical signal triggering the start of the pumping cycle.
The right ventricle sends blood to the lungs to get oxygen.
The oxygenated blood returns to the heart’s left ventricle before being pumped out to the body.
The heart then relaxes before the sinus node sends the signal to start a new beat.
A Sudden Blow
In commotio cordis, however, a blow to the heart area of the chest during a short window — as short as 30 milliseconds — as the heart begins to relax throws the cycle into chaos.
The blow causes the ventricles to start beating in a rapid and uncoordinated way, overwhelming the electrical system of the heart. The sinus node is no longer able to send a signal triggering another heartbeat, which stops the heart from effectively sending blood out to the body, including critical organs such as the brain.
It’s essentially a confluence of really unfortunate events, said Dr. Christopher Madias, director of the New England Cardiac Arrhythmia Center at Tufts Medical Center: “just the right amount of force, within the right location overlaying the heart, in this critical period of vulnerability within the cardiac cycle, or within the heartbeat.”
That worst possible moment in the heart’s electrical cycle is also exceptionally narrow, lasting approximately 30 milliseconds, said Dr. Barry Maron, a cardiologist and professor of medicine at the Lahey Hospital and Medical Center who has researched sudden death in athletes.
“These are rare events,” Maron said. “I never thought I’d ever see one on TV.”
Because a key factor in commotio cordis is extremely bad timing, the blow to the chest can even be relatively innocuous when compared with the kind of trauma in a car crash, which instead causes structural cardiac damage, Maron said.
“It’s a very strange thing,” he said, adding: “and probably why all those tackles in football didn’t result in that, and this one did.”
The most compelling diagnostic evidence for the people who have spent years studying commotio was the video replay showing the hit to Hamlin’s chest, from which he initially got up, before collapsing.
The only remaining question to them was whether there had been any underlying disease to cause the cardiac arrest, which would have had to have evaded the NFL’s combine screening, among other tests.
“This video is really typical of commotio: someone gets struck, they have about five seconds of lucidity, and then they collapse,” said Dr. Mark Link, a professor in the Department of Internal Medicine at UT Southwestern Medical Center and a member of its division of cardiology who has investigated commotio, including with Maron, since the mid-1990s.
“It looked like every commotio event we have on camera.”
That was also the conclusion of the NFL Players Association’s chief medical director, Dr. Thom Mayer, and its chief health equity officer, Dr. Sidney Hinds.
“This is information that we’ve gleaned through watching the video and talking with the medical staff at UC,” said Hinds, referring to the University of Cincinnati Medical Center where Hamlin is being treated. “Like most physicians we work on what we call a differential diagnosis: what is the most likely cause?”
Mayer said that preliminary testing on Hamlin had shown no evidence of myocarditis, an inflammation of the heart that has been linked to Covid infection, in particular. He also said that despite a lot of research into whether an effective chest protector could be developed for athletes, “nothing has been fruitful so far.”
Of greater reassurance, Mayer said, was the statistical improbability of the conditions to create commotio—and the emergency treatment that followed and has been widely credited for saving Hamlin’s life on the field.
“The good news is that if indeed that continues to be the presumptive working diagnosis, that is so exceedingly rare that someone who had it wouldn’t be at risk for it in the future,” Mayer said.
“And if indeed that turns out to be the final diagnosis, then there has been 24,000 men who’ve played this game in the National Football League, and this has never occurred before,” he added
Even one case in professional football came as a shock to some doctors, though.
“It’s primarily a hockey, baseball, lacrosse problem,” caused by a ball or a puck hitting an athlete’s chest, said Dr. Aaron Baggish, a professor at the University of Lausanne, and a member of the faculty at Harvard University, who also sits on the NFL’s cardiovascular task force.
“It’s relatively uncommon for commotio to happen from a body-to-body contact,” said Baggish.
Commotio cordis occurs when the heart receives a strong impact during a 30 millisecond window of time as the heart begins to relax, near the end of the heart’s pumping cycle.
Baggish also said he did not know of any previously confirmed case of commotio in the NFL. As a result, he said, it had not been considered a top priority for concern even among the doctors who focus on NFL players’ hearts—although he emphasized that those doctors had been focused on the emergency action plans that got Hamlin treated rapidly and effectively on the field.
“Whenever an athlete or anyone goes down and doesn’t have a pulse, it doesn’t matter what got them there,” Baggish said. “At that point the treatment is identical, it’s CPR and early defibrillation.”
Link and Maron have written of seeing descriptions of commotio going back centuries, typically in accounts of workplace accidents. But the overwhelming number of recent examples they have to draw on from recent decades involve sports.
In a 2010 review article published in the New England Journal of Medicine, Maron looked at 224 cases listed in a national registry of commotio cordis events from the previous 15 years. Some 122 cases were in competitive sports, and 48 in recreational sports.
Baseball accounted for 63 of the cases, including a chilling incident in which a baseball pitcher struck in the chest was able to retrieve the ball at his feet and throw out the baserunner before collapsing.
There were also 14 football cases, Maron found.
“Commotio cordis has been described in nearly all sports. In those sports in which there is no solid hard ball, commotio occurs secondary to impacts with elbows, fists, and helmets,” Link wrote in a paper of his own.
“It’s not unheard of in football,” Link said. “It’s there. It’s been there all along.”