- Commotio cordis is the second leading cause of cardiac death in young athletes
- Although very rare, the potential fatal injury occurs mostly in young children playing baseball 
 Biomechanical Analysis of Commotio Cordis in Children’s Baseball – A Computations Approach – Grant Dickey, et al (2021), The University of Western Ontario
According to Medscape, the instances of a sudden cardiac death from a blunt force trauma is “usually associated with previously diagnosed or un-diagnosed structural or primary electrical cardiac abnormalities”.
Though there are only 10 to 20 commotio cordis events registered each year, the actual incidence is probably much higher due to lack of recognition and under-reporting.
How Does It Happen?
All human hearts operate with a very specific and steady cardiac cycle with each cardiac having five distinct electrocardiogram phases (P-Q-R-S-T).
Commotio cordis even occurs when a blunt force trauma (usually caused by a thrown or batted baseball at around 30 to 40 mph) is struck in the precordium (sternum on the left side) “during the re-polarization phase of the cardiac cycle” 
This trauma in turn causes the heart to go into ventricular fibrillation (i.e. heart attack), often leading to death.
According to the National Institute of Health (NIH) study (Barry Maron, et. al, (2012) – link here), “the survival rate from commotio cordis has increased, likely owing to more rapid response times and access to defibrillation, as well as greater public awareness of this condition”.
In addition, there are numerous products available that are marketed generically as “heart guard” or “chest guard” to specifically address this issue.
Currently there are 2 available methods to reduce to risk of commotio cordis:
- Safety baseballs – because the majority of the injuries occur among young players, many leagues resort to using baseballs with different degrees of hardness. Many of these safety balls (primarily used in T-ball and Minor leagues) are more pliable and elastic. You can read more about safety balls in the Different Types of Baseballs for Different Age Groups article.
- Chest Guards – chest guards are another potential method that can be used to reduce the risk of injury. Unfortunately, the study has found the current line up of chest guards to be not very effective. A high-speed cinematography study has shown “that baseball penetration into the chest is not inhibited by the use of these chest protectors” 
Like helmets, baseball heart guards are designed to absorb and distribute the force from a batted or thrown baseball so that a player wearing the protective gear experiences less of an impact.
In this aspect, a properly fitted and worn heart guard can reduce the risk of traumatic structural injuries to the chest, like broken ribs and such.
However, these heart guards thus far have not been proven to be effective in preventing sudden cardiac death from commotio cordis.
BUT given the uncertainty, I believe that young players should still wear it.
I have personally purchased two different types of heart guards for my children in the past:
- Solid plate design– A simple, curved, hard-shell plate over the sternum (like this Markwort Heart-Guard) provides maximum protection against direct impact; however, my children have complained that the plate gets in the way when throwing
- Beehive plate design– composed of multiple hex pods, McDavid’s HEX Heart Guard is comfortable to wear, even for pitchers (and washable too)
New products are constantly coming out so I highly suggest that you search “heart guard for baseball” to find a suitable product for your child.
In addition to using a commercially available heart guards, I would also like to stress that proper reaction to a ball also plays a big role in reducing the injury risk:
- Batter – as soon as you recognize an inside high pitch coming in, your child should turn towards the umpire and bend over to shrink the body foot print
- Pitcher – as soon as the ball is released, he should get into a ready fielding position
- Infielders – be in the ready position when the ball is about to be thrown
Lastly, you should absolutely make sure and know where an AED (automatic external defibrillator) device is located so that during emergency you can provide aid.
- Commotio Cordis – Wikipedia.org
- Evaluation of Chest Barriers for Protection Against Sudden Death Due to Commotio Cordis – Doerer et al, 2007, American Journal of Cardiology
- Commotio Cordis – Maron, B. & Estes, M. (2010), he New England Journal of Medicine
- Clinical Cases and Images: Zidane’s headbutt
- What you need to know about young athletes, commotio cordis and sudden cardiac arrest