Watching the Super Bowl a few months ago, I was reminded of another topic I’ve been meaning to talk about. It’s a condition called commotio cordis, and it’s received a lot of attention due to several high-profile sports incidents recently. A number of my readers asked me about it after the drama that took place during a prime-time NFL game last fall when one of the Buffalo Bills defensemen, Damar Hamlin, suffered a cardiac arrest on the field. In a true testament to the expertise and professionalism of medical crews from both teams, he was resuscitated, made a full recovery, and is playing again this year. Last month Damar was nominated for the “NFL Comeback Player of the Year” award. He came in second but I would have voted for him—quite a comeback from lying dead on the football field getting CPR to starting DB for a Super Bowl contender. My readers’ questions dealt with their concern for their own kids playing contact sports—so let’s take a look at what’s up with this fortunately rare occurrence.
Commotio cordis is a Latin phrase that means “agitation of the heart.” The condition is appropriately named, as it describes the mechanism of this disorder that’s caused by a sudden, mechanical distortion of the heart. The impact can spark a burst of energy that disrupts the normal electrical conduction of signals passing through the heart muscle that normally drives coordinated contraction. If the sudden strike to the chest happens during a specific time of the cardiac electrical cycle it can set off a chaotic, dysfunctional cardiac rhythm called “ventricular fibrillation,” a fancy term for cardiac arrest. There’s no blood pressure generated by the heart, and the victim passes out within seconds and soon after dies unless there is immediate aid. It is known that the eliciting factor to Damar Hamlin’s fatal arrhythmia was a premature heartbeat (called PVC—premature ventricular contraction), which I talked about at length a few months ago. The initial trigger to the early beat is the focal force of the direct impact to the heart. The American Heart Association published a good overview a few years ago that dates the first descriptions way back in the late eighteenth century occurring in chest trauma among construction workers.
There are no known predisposing conditions for commotio cordis, so a definitive diagnosis can be really hard to establish. Docs call it a “diagnosis of exclusion”—when all other possible reasons have been ruled out the diagnosis falls to this one. There’s no way to know in advance that someone might be susceptible to this condition. There may be a genetic abnormality making commotio cordis possible that scientists have found in the lab. It’s a rare alteration in the chemical channels that conduct electricity into heart cells that might make it easier to set off this chaotic electrical storm and lead to sudden death. Fortunately, it doesn’t happen very often, but commotio cordis is still the second leading cause of sudden death among young, otherwise healthy athletes. Other things can trigger it also. Assault is the second most common cause (and the leading non–sports-related inciting factor), but any chest trauma like a blunt strike on the steering wheel to an unbelted driver during a motor vehicle accident can set it off.
Commotio Cordis is rare—there are probably less than 100 cases a year in the United States—yet there could be many other cases that just are not identified. Commotio cordis primarily affects young individuals, generally in adolescence. There is a registry of known cases and the average age is 15 years with few commotio cordis victims over the age of 20 years. The going theory on why the incidence decreases with age is that the bone and cartilage structure of the chest wall stiffens as we get older and that offers more protection to the heart. It’s not surprising that victims are usually male since males participate much more frequently in contact sports and there are obvious anatomical chest wall differences between men and women that add protection for women.
Even though the most recent notoriety comes from football players, baseball is actually the most common sport in which commotio cordis occurs, caused by a direct baseball strike to the left side of the chest over the heart. The risk of commotio cordis can be reduced in some circumstances, but can’t be eliminated entirely. Engineering improvements in chest protectors are a possibility, and the use of safety baseballs with different degrees of hardness also offers promise. In the lab, investigators were able to set off commotio cordis ventricular fibrillation with a 30-mph baseball pitch in 7% of impacts with kids’ T-balls compared to 22% with intermediate grades of baseballs and 35% with a regulation baseball. At 40 mph, the softest safety baseballs triggered ventricular fibrillation in 11% of impacts compared to 19% with safety baseballs of intermediate hardness, and 69% with standard baseballs. To improve safety, the Consumer Product Safety Commission has recommended the use of age-appropriate baseballs to decrease the risk of injury to kids playing the sport.
Since the risk is not going away, rapid intervention is crucial to reducing the risk for death. This is exactly what we saw in prime time last fall during the Buffalo Bills football game. Survival after commotio cordis has improved over the years. Back in 1970 the survivorship was only 10% but it’s up to more than 60% today since the majority of commotio cordis incidents during sporting events are witnessed. Combine that with increased training, quick recognition and treatment, and widespread cardiopulmonary resuscitation skills among coaches, officials, the general population, and medical personnel. In addition, the widespread availability of automatic external defibrillators at sports arenas and practice fields has contributed to survivability of this condition. An additional benefit is that defibrillators, which you can find all over public places these days, have improved survival for much more common events like heart attacks in older individuals that also lead to ventricular fibrillation and sudden death.
Another reason commotio cordis is so rare is that it requires multiple unlikely variables to occur nearly simultaneously. The inciting impact must be forceful enough to cause that electrical spark and delivered to just the right spot on the anterior chest wall directly over the heart. It also has to happen during a tiny window of only 20 msec (0.00033 minutes) during a very specific time of the cardiac electrical sequence. This brief time is only 1% of the cardiac cycle. A vigorously exercising athlete has a heart rate about 100–120 beats/minute so his total cardiac cycle lasts a little more than 0.5 seconds. Doing the math—1% of half a second—the time window of vulnerability for a strike in the right place at just the wrong time of the cardiac cycle is only about 0.005 seconds. The overwhelmingly statistical improbability of these events ever happening even once, let alone twice, to the same person is why a vigorous athlete like Damar Hamlin with a structurally normal heart could safely return to the game after his recovery.
The boatload of bad luck it takes to suffer this fate reminds me of my absolutely favorite Dr. Seuss quote from Did I Ever Tell You How Lucky You Are? I used to read the book to my kids at bedtime and preach this lesson to them all day:
When you think things are bad, when you feel sour and blue,
When you start to get mad... you should do what I do!
Just tell yourself, Duckie, you’re really quite lucky!
Some people are much more... oh, ever so much more...
Oh, muchly much-much more unlucky than you!
That’s pretty good advice to all of us throughout our lives; cherish all your blessings and offer comfort and aid to those who are less fortunate. Make sure your harness is tight in the air and your seat belts are secured on the ground, and as always—fly safe!
