Published online August 1, 2008
PEDIATRICS Vol. 122 No. 2 August 2008, pp. 437-439 (doi:10.1542/peds.2007-2054)

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COMMENTARY

Protecting Our Children From the Consequences of Chest Blows on the Playing Field: A Time for Science Over Marketing

Mark S. Link, MD^a, Cynthia Bir, PhD^b, Nathan Dau, BA^b, Christopher Madias, MD^a, N.A. Mark Estes, III, MD^a and Barry J. Maron, MD^c

^a Cardiac Arrhythmia Center, Tufts Medical Center, Boston, Massachusetts
^b Bioengineering Center, Wayne State University, Detroit, Michigan
^c Minneapolis Heart Institute Foundation, Minneapolis, Minnesota

COMMOTIO CORDIS IS the devastating consequence of otherwise innocent-appearing chest-wall blows, with sudden cardiac death often resulting from projectiles striking the precordium.^1,2 This phenomenon occurs most commonly in sports when a baseball, lacrosse ball, or hockey puck strikes the chest directly over the cardiac silhouette and triggers ventricular fibrillation.³ During the past several years, the number of documented commotio cordis events reported to our registry has risen to almost 200, more likely a result of enhanced awareness rather than a true increase in incidence. Commotio cordis has now been cited as the second leading cause of sudden death in young athletes⁴ and is a uniquely pediatric problem, with an average age of only 14 years for the victims (Fig 1).

View larger version (26K): [in this window] [in a new window]   FIGURE 1 Age at which commotio cordis occurred in cases reported to the Commotio Cordis Registry. The median age was 14 years; 90% of case-patients were younger than 21 years. (Reproduced with permission from Maron BJ, Gohman TE, Kyle SB, Estes NAM III, Link MS. JAMA. 2002;287(9):1143.)

 
Among the reported commotio cordis cases, nearly 50% occurred during competitive sports.^1,2 Of particular note, some form of chest-wall protection was worn by almost 40% of the athletes who incurred fatal or nonfatal events.⁵ In these cases, sudden death resulted directly from chest blows as a result of either inadequate chest-barrier composition (ie, with direct precordial impact) or inadequate design (ie, failure to cover the precordium during all bodily movements). In some circumstances, such as with those chest protectors used in lacrosse and baseball, the ball struck the chest barrier directly but did not attenuate the transmission of energy from the blow.⁵ Furthermore, cardiopulmonary resuscitation after collapse with ventricular fibrillation attributable to commotio cordis has proved disappointing, with only 15% survival, and even prompt defibrillation may not always be effective for commotio cordis.⁶ All these factors and observations underscore the importance of developing an effective and practical chest protector that is tested to document its efficacy in preventing ventricular fibrillation and designed specifically for use in those sports associated with frequent chest blows, such as baseball, lacrosse, hockey, football, and karate.

In this regard, our experimental swine model replicating commotio cordis has been the source of important insights regarding the pathophysiology of sudden death resulting from chest blows over the past 10 years.⁷ In this biological model, ventricular fibrillation has occurred when blows directly over the heart⁸ were critically timed to the most vulnerable phase of repolarization at the upslope of the T wave.⁷ Other variables that promote ventricular fibrillation are impact velocity optimal at 40 mph⁹ and greater stiffness¹⁰ and smaller diameter¹¹ of the impact object. Chest-wall blows do not seem to produce ventricular fibrillation by converting mechanical to electrical energy but, rather, by myocardial stretch produced by increased left ventricular pressure after impact, which activates ion channels.^12–14

In addition to defining mechanism, this biological model also affords an opportunity to evaluate the efficacy of chest-wall barriers in protecting against commotio cordis. Indeed, we have reported that 12 commercially available chest-wall protectors used in lacrosse or baseball offer virtually no protection against ventricular fibrillation and sudden death produced by chest blows (Figs 2 and 3). ¹⁵ Some of the products we systematically evaluated (eg, chest protectors made for baseball catchers) failed to prevent commotio cordis, which was not surprising given their soft-foam composition that collapses immediately on impact and allows the projectile nearly unimpeded access to the chest wall. Furthermore, other chest barriers (eg, for lacrosse goalies), composed of stiffer foam and certain plastic materials, also do not afford protection against chest-blow–induced ventricular fibrillation.

View larger version (33K): [in this window] [in a new window]   FIGURE 2 Incidence of ventricular fibrillation (VF) with baseball precordial blows for each of 8 commercially available chest-protector materials and for controls without chest protectors. P values above the bars are calculated for each chest protector versus the controls. (Reproduced with permission from Weinstock J, Maron BJ, Song C, Mane PP, Estes NAM III, Link MS. Pediatrics. 2006;117(4):e656.)

 

View larger version (34K): [in this window] [in a new window]   FIGURE 3 Incidence of ventricular fibrillation (VF) with lacrosse-ball precordial blows for each of 7 commercially available lacrosse chest-protector materials and for controls without chest barriers. P values above the bars are calculated for each chest protector versus the controls. (Reproduced with permission from Weinstock J, Maron BJ, Song C, Mane PP, Estes NAM III, Link MS. Pediatrics. 2006;117(4):e656.)

 
These observations have created a dilemma for all interested parties, particularly the parents of children who participate in competitive sports for which there is a risk of chest blows. Although the mechanisms and epidemiology of commotio cordis have now been extensively studied and reported in a series of articles, a practical strategy for prevention remains lacking. Indeed, the chest barriers that are commercially available, although perceived as protective, do not seem to be reliable in either the human experience or in the experimental laboratory. Therefore, the development of a more effective chest-wall protector targeted to prevent commotio cordis events for young sports participants is crucial.

Recent and currently unpublished data from our laboratory (using high-speed cinematography at 4500 frames per second) has demonstrated that the plastics used in commercially available products are not sufficiently stiff to prevent the transmission of energy to the heart after a direct blow. Indeed, it is the composition and stiffness of the plastic component that seems to be the most important, exceeding the value of the soft-foam elements. On the basis of these preliminary data, we are confident that creation of a more effective chest protector should be feasible in the near future.

In addition to the development of a chest protector, we believe that it is also critical to establish industry-wide standards for assessing the potential efficacy of current and future chest-barrier products without the need for continued testing in the animal laboratory. Therefore, a reliable, reproducible, and readily available surrogate mechanical testing model is an important component in the reduction of commotio cordis events. Indeed, such models and standards exist for other sporting equipment including football helmets (National Operating Committee on Standards for Athletic Equipment), bicycle helmets (Snell and American National Standards Institute), and lacrosse eye gear (American Society for Testing and Materials). However, no such standards currently exist for chest-wall protection in sports. Development of this standard must be based on reproducible and scientifically valid data, not on emotion or market-driven claims.

Consequently, in our view, there are 2 prerequisites for eliminating or minimizing the occurrence of commotio cordis: (1) development of a chest-wall protector, demonstrable under experimental conditions to abolish ventricular fibrillation triggered by precordial blows, and (2) transition from a biological model to a surrogate mechanical model that is readily available for the testing of potentially protective materials.

Until the time comes when chest-wall barriers can eliminate the risk of commotio cordis, simple coaching techniques with baseball (eg, avoiding turning into an inside pitch) and rules changes to prohibit shot-blocking with the chest in lacrosse should be implemented. In addition, while we await more efficacious chest-wall protectors, the use of age-appropriate softer-than-standard baseballs should be encouraged. These safety baseballs have been developed and seem to reduce (although not eliminate) the risk of commotio cordis.

In conclusion, the safety of the athletic field and protection of children during competitive sports is of vital importance, and abolishing or minimizing the risk of commotio cordis is clearly part of that mandate. Current commercially available chest barriers are not sufficiently effective in preventing chest-blow–induced sudden cardiac death and, in fact, probably offer only a false sense of security to athletes, families, and the general public. Therefore, the efforts described herein to produce an effective chest barrier to prevent commotio cordis deserve our attention and support.

	FOOTNOTES

 
Accepted Nov 12, 2007.

Address correspondence to Mark S. Link, MD, Tufts Medical Center, NEMC Box 197, 750 Washington St, Boston, MA 02111. E-mail: mlink{at}tufts-nemc.org

Financial Disclosure: Dr Link is working on the development of a chest protector and a mechanical model of commotio cordis, and Dr Bir and Mr Dau are working on the development of a mechanical model of commotio cordis; Drs Madias, Estes, and Maron have indicated they have no financial relationships relevant to this article to disclose.

	REFERENCES

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PEDIATRICS (ISSN 1098-4275). ©2008 by the American Academy of Pediatrics

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