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DOI:10.1542/peds.109.5.8732002;109;873-877Pediatrics

VanderBrink and N. A. Mark Estes, IIIMark S. Link, Barry J. Maron, Paul J. Wang, Natesa G. Pandian, Brian A.

Safety BaseballsReduced Risk of Sudden Death From Chest Wall Blows (Commotio Cordis) With

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reserved. Print ISSN: 0031-4005. Online ISSN: 1098-4275.Village, Illinois, 60007. Copyright © 2002 by the American Academy of Pediatrics. All rightstrademarked by the American Academy of Pediatrics, 141 Northwest Point Boulevard, Elk Grove

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Reduced Risk of Sudden Death From Chest Wall Blows(Commotio Cordis) With Safety Baseballs

Mark S. Link, MD*; Barry J. Maron, MD‡; Paul J. Wang, MD*; Natesa G. Pandian, MD*;

Brian A. VanderBrink, BA*; and N. A. Mark Estes III, MD*

ABSTRACT. Objectives. In an experimental model ofsudden death from baseball chest wall impact (commotiocordis), we sought to determine if sudden death by base-ball impact could be reduced with safety baseballs.

Background. Sudden cardiac death can occur afterchest wall impact with a baseball (commotio cordis).Whether softer-than-standard (safety) baseballs reducethe risk of sudden death is unresolved from the availablehuman data. In a juvenile swine model, ventricular fi-brillation (VF) has been shown to be induced reproduc-ibly by precordial impact with a 30-mph baseball 10 to 30

ms before the T-wave peak, and this likelihood wasreduced with the softest safety baseballs (T-balls). Tofurther test whether safety baseballs would reduce therisk of sudden death at velocities more relevant to youthsports competition, we used our swine model of commo-tio cordis to test baseballs propelled at the 40-mph ve-locity commonly attained in that sport.

Methods. Forty animals received up to 3 chest wallimpacts at 40 mph during the vulnerable period of repo-larization for VF with 1 of 3 different safety baseballs ofvarying hardness, and also by a standard baseball.

Results. Safety baseballs propelled at 40 mph signif-icantly reduced the risk for VF. The softest safety base-balls triggered VF in only 11% of impacts, compared with

19% and 22% with safety baseballs of intermediate hard-ness, and 69% with standard baseballs.

Conclusion. In this experimental model of low-en-ergy chest wall impact, safety baseballs reduced (but didnot abolish) the risk of sudden cardiac death. More uni-versal use of these safety baseballs may decrease the riskof sudden death on the playing field for young athletes.Pediatrics 2002;109:873–877; sudden death, ventricular fi-brillation, athletes, commotio cordis, baseball.

ABBREVIATIONS. VF, ventricular fibrillation; RIF, Reduced In- jury Factor; N/cm; newtons/centimeter; ECG, electrocardiogram.

Sudden death from relatively innocent chest

blows (commotio cordis) has been reportedwith increasing frequency in youth sports.1–4

Although once thought to be a rare event, it is nowapparent that these tragedies are underreported andprobably far more common than once considered;indeed, a significant proportion of sudden deaths onthe athletic field are attributable to chest wall blows.The clinical spectrum of commotio cordis has now

been well-documented in 128 cases by the Commotio

Cordis Registry.4

Victims are usually young maleswho incur ventricular fibrillation (VF) when struckon the chest wall overlying the heart. It is thoughtthat young individuals are uniquely susceptible tothis phenomenon because of the compliance of theirthoracic cage, which allows more energy to be trans-mitted by the impact object directly to the heart.5 Themost common projectiles responsible for commotiocordis are baseballs (approximately 60% of the re-ported cases), but commotio cordis also occurs re-sulting from hockey pucks, lacrosse balls and soft-

balls, fistfights, or virtually any circumstanceinvolving precordial blows. Successful resuscitation

is more difficult than expected given the youthfulage and excellent health of the victims, and also theabsence of structural heart disease. Autopsy exami-nation is notable for the absence of significant cardiacor thoracic abnormalities.

Safety baseballs with rubber cores of different de-grees of hardness, have been advocated to reduce therisk of traumatic injury to young athletes.5,6 Al-though there is agreement that safety baseballs re-duce the risk for head and bodily injury,5–7 contro-versy persists regarding whether such balls will alsoreduce the risk of commotio cordis.8–10

We have developed an experimental model of commotio cordis in juvenile swine in which a chest

blow from a baseball during the vulnerable time-window of repolarization triggers VF.11 This modelhas permitted definition of the variables responsiblefor commotio cordis, including the precise locationson the chest wall that are susceptible,12 the impactvelocities most critical for these events,13 and theimportance of the activation of the autonomic ner-vous system in generating VF.14

Using our animal model, we sought to define therisk of commotio cordis-related sudden death with

baseballs of varying degrees of hardness. In a previ-ous experiment we reported that the softest safety

baseballs, intended for 5- to 7-year-olds, delivered at

From the *Center for the Cardiovascular Evaluation of Athletes, the Cardiac

Arrhythmia Center, New England Medical Center, Tufts University School

of Medicine, Boston, Massachusetts; and the ‡Cardiovascular Research

Division, Minneapolis Heart Institute Foundation, Minneapolis, Minnesota.

The opinions expressed in this article are those of the authors and do not

necessarily reflect the opinions of the National Operating Committee on

Standards for Athletic Equipment or the Paul G. Allen Foundations.

Received for publication Oct 22, 2001; accepted Feb 8, 2002.

Reprint requests to (M.S.L.) New England Medical Center, Box 197, 750

Washington St, Boston, MA 02111. E-mail: [email protected]

PEDIATRICS (ISSN 0031 4005). Copyright © 2002 by the American Acad-

emy of Pediatrics.

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the relatively low velocity of 30 mph decreased therisk of VF.11 However, for 11- to 12-year-olds, theaverage velocity of a pitched baseball is about 40mph.15 Therefore, we sought to replicate such cir-cumstances of youth baseball with our animal modelof commotio cordis, and assess the consequences of chest blows from safety baseballs propelled at thesevelocities.

METHODS

Experimental Model Juvenile domesticated swine, 6 to 8 weeks old and weighing 8

to 12 kg (mean 10.1 Ϯ 1.5 kg), were used in this study. Theresearch protocol was approved by the Animal Research Commit-tee of the New England Medical Center in conformity with theregulations of the Association for Assessment and Accreditation of Laboratory Animal Care. Animals were sedated with 12 mg/kgintramuscular ketamine and then anesthetized with inhaled 1% to2% isoflurane mixed with oxygen and nitrous oxide. Anesthesiawas maintained with isoflurane. Animals were then placed pronein a sling to approximate physiologic blood flow and cardiachemodynamics.11,16

Chest wall impact was produced by a baseball mounted on alightweight (20-g) aluminum shaft. A chronograph (Oehler Re-search, Austin, TX), modified for low velocity, assessed the speedof the baseball. The impact object was propelled by a spring and

directed, with echocardiographic guidance, to strike the animalperpendicular to the chest wall, directly over the center of theheart.12 At the time of impact the baseball and shaft were in freeflight. The timing of the impact was accomplished using a com-mercially available cardiac stimulator (EP-2, EP Medical, Inc,Budd Lake, NJ) triggered from a surface electrocardiographicinput from the swine. With a known and consistent 120-ms delay

between the release of the object and the subsequent chest impact,precordial blows could be delivered during the vulnerable periodfor initiation of VF, 10 to 30 ms before the T-wave peak.11,16

Impacts occurring outside of this time window were excludedfrom the analysis.

Baseballs Tested

Baseballs used in this experiment represented 4 degrees of hardness but were of similar masses. The safety baseballs used

(Reduced Injury Factor [RIF], Worth Inc, Tullahoma, TN) werecomposed of a rubber core varying in hardness and covered by aleather exterior; the standard baseball (Rawlings Little League,

LLB-1, St. Louis, MO) had a rubber core covered by wound yarnand a leather exterior. The softest ball (RIF 1) marketed for use inT-ball for youths aged 5 to 7 years, has a stiffness of 213 Ϯ 36newtons/cm (N/cm) (1 newton ϭ 0.225-lb force).17 Medium-soft

balls (RIF 5), marketed for children 8 to 10 years old, have astiffness of 353 Ϯ 18 N/cm. Safety balls with hardness closest tothe standard baseball (RIF 10, for youths 11–13 years old) have astiffness of 1114 Ϯ 36 N/cm. Standard baseballs had a hardness of 2533 Ϯ 108 N/cm. The mass of the RIF 1 was 151 g, while the RIF5, RIF 10, and standard baseballs weighed 149, 149, and 147 g,respectively.

ProtocolAnimals were randomized to receive chest blows by 1 of the 4

baseballs delivered at 40 mph, with each receiving up to 3 impacts.When VF was triggered by chest impact from the baseball, theanimal was defibrillated immediately. Blood pressure, left ventric-ular function, and electrocardiograms (ECGs) were assessed andobserved over a period of 20 minutes. If blood pressure, leftventricular ejection fraction, and ECG pattern returned to normal,additional chest impacts were delivered. If these parameters didnot return to normal, no additional chest impacts occurred and theanimal was euthanized, and an autopsy performed.

Statistical Analysis

Data are given as mean Ϯ standard deviation. The statisticalsignificance of differences between groups was analyzed with a

2-sided Fisher exact test and 2

test for trend. P values of Ͻ

.05were considered significant.

RESULTS

VF

Forty animals underwent 83 chest impacts with baseballs propelled at 40 mph. Risk of VF (Fig 1) waslinearly correlated with hardness of the baseball (Fig2 and Table 1). With the softest ball (RIF 1), 10animals received 26 impacts and VF was producedonly 3 times (11%). With the medium-soft ball (RIF5), 10 animals received 23 strikes and VF occurred 5times (22%). With the hardest safety ball (RIF 10), 21

impacts in 10 animals resulted in 4 episodes of VF(19%).In contrast, with a standard baseball, 13 impacts in

Fig 1. Six-lead surface ECG shows immediate initiation of VF with a chest wall blow from a 40-mph baseball in an 8-kg swine.

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10 animals resulted in 9 episodes of VF (69%). Dif-ferences in the incidence of VF between the standard

baseball and each safety ball were statistically signif-icant (P Ͻ .01 for comparison between each safety

ball and the standard ball). No differences were ev-ident among the safety baseballs of different hard-

ness.There was no significant difference between the

probability of VF with respect to the number of thestrike (35% of the first strike, 18% of the second, and22% of the third), body weight of the animal or the

baseline ECG pattern.

Other Electrophysiologic Changes

In the 62 40-mph chest impacts that did not pro-duce VF, including all balls tested, ST segment ele-vation occurred in 65% but did not significantly dif-fer relative to the hardness of the baseball (Table 1).Transient complete heart block was observed in 7

(11%) of 62 impacts, and occurrence did not differsignificantly between the baseballs. Transient bundle

branch block occurred in 44 (71%) of the 62 impactsand the occurrence did increase relative to the hard-ness of the baseball.

Pathologic Analysis

Postmortem study demonstrated only superficial bruises at the point of impact in all animals withoutevidence of rib fractures, hemothorax, or hemoperi-cardium. Two animals showed small myocardialcontusions caused by impact with a medium-soft

baseball in one and by a standard baseball in the

other (Pϭ

not significant). No animal showed sig-nificant structural damage involving the myocar-dium or valves.

Comparison Between 40- and 30-mph Impacts

At both 40 mph and 30 mph, chest wall blows byeach of the 3 safety baseballs (RIF 1, 5, and 10) lessfrequently triggered VF than did standard baseballs(Table 1; Fig 2). These differences between the safety

balls and the standard baseball were much morepronounced at 40 mph because of the marked differ-ence in incidence of VF with standard baseballs at 40mph (69%) compared with 30 mph (35%) (P ϭ .046).There was no significant difference in the occurrence

of VF between the 3 safety baseballs when propelledat 40 or 30 mph.

In contrast to 40-mph impacts in which the hard-ness of the ball did not alter the incidence of STsegment elevation and transient heart block, in 30-mph impacts, safety baseballs produced significantlyless of these abnormalities (P ϭ .0004 and 0.008,respectively). Safety baseballs thrown at both 40 and30 mph produced less bundle branch block (Table 1).

DISCUSSION

Sudden death attributable to chest wall impact has been reported with increasingly frequency in youthsports, and consequently there is considerable inter-est in strategies to prevent these tragic events.10 Base-

ball chest impact is the most common cause of com-motio cordis; thus, prevention in this sport wouldhave the largest impact on saving lives in sportingactivities. Several approaches have been consideredfor prevention of commotio cordis, including the useof softer-than-normal baseballs, development of ef-fective chest wall barriers, and improved coachingtechniques.10 Softer baseballs and chest wall barriershave been proposed to potentially decrease the trans-mission of energy to the heart from the chest impactand thereby prevent VF. Better coaching techniqueswould include preventing chest wall blows fromoccurring by instructing children to turn away fromthe ball while batting or fielding. These alternativestrategies may well prove to be effective in reducingthe risk for commotio cordis, although the presentinvestigation focuses on the benefits of altering thecomposition of the baseball.

In our experimental model of commotio cordis,safety baseballs reduced the incidence of VF withchest impact at 40 mph, a velocity commonly respon-sible for fatal commotio cordis events in youth base-

ball. Of note, with 40-mph impacts, the incidence of VF decreased sixfold with the softest safety ball and3.5 times with balls of intermediate hardness whencompared with a standard baseball.

Our data seemingly contrast with the findings re-ported with testing of safety baseballs in a 3-ribdummy model and in swine struck with baseballs ata particularly high velocity of 95 mph.18 Safety-base-

ball chest impacts in these animals were associatedwith reduction in fatal arrhythmias; however, with95-mph Hybrid III dummy impacts, some safety

baseballs failed to show reduced values for force andmomentum transfer. In a later study, using a 3-rib

dummy model impacted at velocities of 40 to 60mph, investigators found that values for force andmomentum transfer with baseball impact were notsurprisingly directly related to the velocity of im-pact.19 For baseballs of the same weight (similar tothose assessed in our current study) thrown at thesame velocity, the values for force and momentumtransfer were lower with softer baseballs, supportingour conclusions that reducing the hardness of the

baseball will reduce the risk of injury.19 Furthermore,theoretic computations by another investigator haveconfirmed that both the weight and hardness of the

baseball are significant factors in the risk of injurywith head and chest wall impacts.20 In our current

Fig 2. Incidence of VF with chest wall impacts to 8- to 12-kgswine by baseballs differing in hardness. Data are from both thecurrent experiment with 40-mph chest blows and an experimentpreviously reported with 30-mph impacts.11

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study, we chose projectiles of equivalent weight totest only the variable of hardness of the impact ob-

ject.There is a large measure of consensus among re-

searchers, coaches, and parents that softer baseballsreduce the risk of serious blunt head and bodilyinjury.5–7,21 Recommendations for reduction of riskof sudden death from chest wall blows have beenlimited by the absence of a credible biological modelfor commotio cordis. However, with our experimen-tal swine model, which replicates the clinical syn-drome of commotio cordis,11,12,16 we have been ableto convincingly show that safety baseballs reduce therisk of VF and sudden death attributable to chest

wall blows. The results of the present study alsosupport the view that more widespread use of safety

baseballs will significantly decrease (although prob-ably not abolish) the occurrence of commotio cordis-related sudden death in youth baseball. Indeed, rarecases of sudden death associated with chest blows bysafety baseballs have been reported,3 underlining theneed for complementary strategies for reducing therisk of sudden death from chest wall blows such asimproved coaching techniques and protective chestwall barriers.

Obstacles to more widespread introduction of safety baseballs into organized youth sports include

negative attitudes of coaches, administrators, andeven some parents, who note that the nontraditionalsafety baseball alters the fundamental nature of thegame because of unpredictable and exaggerated

bounce, and insufficient velocity when struck by the bat.8,9,22,23 For these reasons, the softest baseballs,marketed for T-ball use in children under age 7, may

be inappropriate for older players. However, safety baseballs of intermediate grades of hardness arelargely indistinguishable from the standard baseballwhile in play, and would appear to be reasonableand safer options for play in older age groups.

Others have raised the theoretical possibility thatsafety balls might paradoxically enhance risk for

sudden cardiac death.10,18,19 However, evidence forthis hypothesis is lacking. In fact, the results of thepresent experimental study show that projectiles of this design may significantly reduce risk (relative tostandard baseballs) and are therefore potentially life-saving. Our observations regarding commotio cordisand safety balls, in combination with the universalagreement that these projectiles cause less traumaticinjury to the head and other body parts,5–7,21 supportmore universal use of such baseballs in organizedyouth baseball as well as informal play around thehome.

ACKNOWLEDGMENTS

This work was supported by a grant from the National Oper-ating Committee on Standards for Athletic Equipment, OverlandPark, Kansas, and the Paul G. Allen Foundations, Seattle, Wash-ington (to Dr Maron).

REFERENCES

1. Maron BJ, Poliac LC, Kaplan JA, Mueller FO. Blunt impact to the chest

leading to sudden death from cardiac arrest during sports activities.

N Engl J Med. 1995;333:337–342

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motio cordis: an under-appreciated cause of sudden death in the young

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3. Maron BJ, Gohman TE, Estes NAM III, Link MS. The clinical spectrum

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6. Kyle SB. Youth Baseball Protective Equipment Project Final Report. Wash-

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Hoerner EF, ed. Head and Neck Injuries in Sports (ASTM STP 1229).

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8. Granberry M. ’Safety baseball’ strikes out in Laguna Niguel. Los Angeles

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9. Carroll M. Many leagues resist soft, safer baseballs. Boston Globe. May

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TABLE 1. Electrophysiologic Consequences of Baseball Impacts at 40 (and 30) mph to the Chest Wall of 8- to 12-kg Swine During theVulnerable Time Window for VF

RIF 1‡ RIF 5‡ RIF 10‡ Standard‡

VF 40 mph 3/26␤ 5/23␤ 4/21␤ 9/13§(Pϭ .0009*) (11%) (22%) (19%) (69%)

30 mph† 2/26␤ 6/27 6/21 8/23(Pϭ .03*) (8%) (22%) (29%) (35%)

40 mph 15/23§ 16/18 15/17§ 3/4ST segment elevation (Pϭ .20*) (65%) (89%) (88%) (75%)

30 mph 4/24␤ 16/21 6/15 8/15(Pϭ .0004*) (17%) (76%) (40%) (53%)

40 mph 1/23 3/18 3/17 0/4Transient heart block (Pϭ .42*) (4%) (17%) (18%) (0%)30 mph 1/24 0/20␤ 5/15 3/15

(Pϭ .008*) (4%) (0%) (33%) (20%)40 mph 8/23␤,§ 15/18§ 17/17§ 4/4§

Bundle branch block (PϽ .0001*) (35%) (83%) (100%) (100%)30 mph 0/24␤ 8/21 3/15 4/15

(Pϭ .006*) (0%) (38%) (20%) (27%)

* 2 for trend comparing incidences among the different baseballs at the given velocity.‡ Data are presented as number of events/number of impacts (%).† VF data for 30-mph baseballs previously reported.11

␤ 2 P value of Ͻ.05 comparing safety balls to standard ball at the identical velocity of impact.§ 2 P value of Ͻ.05 comparing 40-mph to 30-mph impacts.

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11. Link MS, Wang PJ, Pandian NG, et al. An experimental model of

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413– 418

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various baseballs. J Appl Biomech. 1998;14:390 – 400

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19. Janda DH, Bir CA, Viano DC, Cassatta SJ. Blunt chest impacts: assessing

the relative risk of fatal cardiac injury from various baseballs. J Trauma.

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Exerc. 1997;29:26 –3621. Vinger PF, Duma SM, Crandall J. Baseball hardness as a risk factor for

eye injuries. Arch Ophthalmol. 1999;117:354 –358

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THE PATIENT’S TAKE

“Doctors are a strange breed. They nibble at an overwhelming amount of information in medical school. They are too bright to miss the incredible distance

between what they know and what there is to know. They dedicate their wakinghours to memorizing droplets from a great ocean of information. They learn trivialanatomic structures and then promptly forget them. They stand with groups of more experienced physicians and are asked questions they don’t know the answersto. They shake the sleep from their eyes and walk down neon-lit halls feelinginadequate and small . . . Inevitably, they lose their empathy for pain. The waterfallof pain they hear from countless patients wears them down to smooth rock. Afterall, they have had to deny themselves so much to succeed. They have endured theirown painful humiliation. They have learned that pain is simply a warning mech-anism; it isn’t real. Is it any wonder that our painful cries empty into a vacuumwhen doctors are in the room?”

Shapiro D. Mom’s Marijuana. Nevada City, CA: Harmony Books; 2000

Submitted by Student

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DOI:10.1542/peds.109.5.8732002;109;873-877Pediatrics

VanderBrink and N. A. Mark Estes, IIIMark S. Link, Barry J. Maron, Paul J. Wang, Natesa G. Pandian, Brian A.

Safety BaseballsReduced Risk of Sudden Death From Chest Wall Blows (Commotio Cordis) With

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