The Physician and Sportsmedicine
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Safety Baseballs and Chest Protectors: A
Systematic Review on the Prevention of Commotio
Cordis
Justin A. Classie, Laura M. Distel & James R. Borchers
To cite this article: Justin A. Classie, Laura M. Distel & James R. Borchers (2010) Safety
Baseballs and Chest Protectors: A Systematic Review on the Prevention of Commotio Cordis, The
Physician and Sportsmedicine, 38:1, 83-90, DOI: 10.3810/psm.2010.04.1765
To link to this article: https://doi.org/10.3810/psm.2010.04.1765
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Safety Baseballs and Chest Protectors: A Systematic
Review on the Prevention of Commotio Cordis
Justin A. Classie, MD; Laura M. Distel, MD; James R. Borchers, MD, MPH
Abstract
Objective: To determine whether chest protectors and/or safety baseballs reduce the incidence of commotio cordis during sport
through a review of the best available evidence. Data sources: PubMed, Ovid Medline, and Embase databases from 1950 to 2009. We
selected articles according to “death, sudden, cardiac,” “commotio cordis,” “sports equipment,” and “protective devices.” We identified 17 articles in the systematic literature search. Of these, 7 articles met inclusion criteria. Three independent reviewers reviewed
the articles. The study results and generated conclusions were extracted and agreed on. Results: The softest safety baseball shows
statistically significant reductions in the incidence of ventricular fibrillation (VF) at all velocities compared with standard baseballs
in the 3 studies that evaluated their use. Different degrees of softness did not show statistically significant reductions in VF. In the
3 studies that evaluated the use of chest protectors against controls, there was an increase in protection against fatal arrhythmias;
however, this was only statistically significant for 1 chest protector. Conclusions: This systematic review shows strong supportive
evidence toward a decreased rate of commotio cordis with safety baseballs when compared with standard balls. Based on the results
of our systematic review, the rate of induction of VF was at its lowest when chest protection was used.
Keywords: commotio cordis; chest protectors; safety baseballs; preventive equipment; sudden cardiac death
Justin A. Classie, MD 1
Laura M. Distel, MD 1
James R. Borchers, MD, MPH 1
1
The Ohio State University Sports
Medicine Center, Columbus, OH
Correspondence: James R. Borchers,
MD, MPH,
The Ohio State University Sports
Medicine Center,
2050 Kenny Road, Suite 3100,
Columbus, OH 43221.
Tel: 614-293-3600
Fax: 614-293-4399
E-mail: james.borchers@osumc.edu
Introduction
Sudden cardiac death in a young, healthy athlete is a relatively rare but extremely tragic event that can
occur as a result of several etiologies. Underlying structural and electrical abnormalities of the heart
are often associated with sports-related cardiac arrest, but commotio cordis (CC) is now recognized as
a more common cause of sports-related death than first assumed.1,2 Defined as sudden cardiac death
due to a blunt, nonpenetrating trauma to the chest wall, CC is a phenomenon that is characterized by
a low-energy impact to the precordium in an individual lacking any underlying cardiac abnormalities.2
Often, the impact does not carry enough force to cause any significant injury to the chest wall or
myocardium, which can be demonstrated on autopsy.2 This supports the theory that the mechanism of
cardiac arrest is multifactorial and is likely an electrically induced event.1 Most of the studies involving
the pathophysiology of CC have shown that the impact must occur during a specific vulnerable moment
in the cardiac cycle, which subsequently induces ventricular fibrillation (VF) and cardiac arrest.1,2 Similar to other causes of VF, early resuscitation is crucial. Resuscitative efforts appear to be more effective
when initiated within 3 minutes of the incident; however, survival is still the exception, with only about
15% of individuals revived successfully.1
The US CC Registry has documented ⬎ 200 cases of CC since 1996; however, this is likely underreported.3 Most reported cases have occurred in white males, aged 10 to 18 years, who were participating
in sports that use a dense, projectile object, such as in baseball, softball, hockey, or lacrosse.3 Although
there have been rarer documented cases of CC in individuals aged ⬎ 18 years, it is thought that the
increased chest wall compliance of younger athletes makes them more susceptible, with higher transmission of forces to the heart.1 The blow is usually a result of routine aspects of the game. For example,
25% of CC-related deaths in baseball were the result of impact with a pitched ball, with the rest a result
of a batted or thrown ball.1
Given the increasing amount of young athletes participating in organized and recreational sports,
as well as the fatal nature of the injury and relative lack of treatment options, it seems obvious
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Classie et al
to investigate methods of preventing CC. With continued
understanding of the risk factors and pathophysiology of the
induction of VF, there have been several studies investigating
the effectiveness of protective equipment in preventing
CC. This article briefly summarizes the pathophysiology
and clinical presentation of CC, and reviews the literature
regarding the use of safety equipment, specifically chest
protectors and safety baseballs, and their effects on the
incidence of CC.
Pathophysiology
Most theories on the pathophysiology of CC originate from
experimental animal model research. The most recognized
cause of death from CC is VF secondary to a blow to the
chest wall.1,2 Experimental animal research shows that CC is
a single electrical-related event that is not caused by hemorrhage, heart block, or ischemia.2 Most studies agree that the
mechanism underlying VF is multifactorial. These factors
are all related to the blow to the chest wall. The type, location, force, and timing of impact will regulate if the potential
arrhythmia, VF, is initiated.4
The timing of the impact is the rate-limiting factor.
Research has shown that when chest wall trauma coincides
with the narrow window (10–30 msec before the peak of
the T wave) in the cardiac cycle, VF is the likely result.1 This
specific time period of repolarization within the cardiac
cycle seems to be connected with ATP-dependent potassium
channels.4 It is thought that activation of the ATP-dependent
potassium channel causes elevation of the ST-segment and
the R-on-T phenomenon in myocardial infarction, and is
an instrumental risk for progression to VF.1,2 This is because
of the similar electrical properties seen between CC and
myocardial ischemia.
Electrophysiologic changes are shown in several animal
studies in association with rapid rise in left ventricular pressure produced by the chest blow.2 These studies also showed
a direct relationship between left ventricular pressure rise
and risk for VF.2 The chest wall impact resulting in increased
left ventricular pressure leading to myocardial stretch can in
turn cause activation through mechanical-electrical coupling
of ion channels.1 A rat atrial model demonstrated that this
rise in pressure, leading to myocardial stretch, activates ATP
potassium channels which in turn leads to increased risk for
VF.2 This information may be useful when looking for ways
of prevention.
84
Clinical Presentation
Commotio cordis most commonly occurs in the setting of
an organized sporting event. There have been several other
documented cases of chest wall blows causing sudden death
in daily activities, but these are rare.5 The event is often
precipitated by a seemingly benign, blunt impact to the left
side of the chest by a dense projectile during a routine aspect
of the game.1 For example, in baseball, documented cases
have resulted from impact of pitched, batted, or thrown balls.1
In approximately one-half of cases, the individual collapses
immediately after the impact. In the other one-half of cases,
there is a brief period of consciousness prior to collapsing.6
On initial examination, the subject is often found to be unresponsive, pulseless, apneic, and possibly cyanotic. There may
be soft tissue bruising over the sternum noted on subsequent
examination, with rare damage to the underlying bony structures. When an electrocardiogram is performed prior to the
onset of asystole, the most common arrhythmia noted is VF.7
Immediate cardiopulmonary resuscitation should be
initiated; however, this is often delayed because of bystanders’
lack of awareness to the seriousness of the blow. Successful
resuscitation is often not achieved, with the survival rate
at about 15%.7 However, the chances of survival improve
significantly when cardiopulmonary resuscitation (CPR) is
initiated within 3 minutes of the event.7
Due to the poor prognosis of CC, prevention has become
a focus of research as a way to reduce the incidence of CC.
One mode of prevention is ensuring that all persons involved
in athletics are familiar with emergency protocols and correct use of an automated external-defibrillator (AED). In this
article, we chose to review the current literature on the use
of safety equipment as its use is the focus of preventing this
phenomenon.
Materials and Methods
A literature review was completed using PubMed, Ovid
Medline, and Embase database searches from 1950
through November 2009 to identify all papers that
assessed the use of chest wall protectors or safety baseballs on prevention of CC in sports involving projectiles. Several key search terms were used to narrow our
literature search. “commotio cordis” revealed no MeSH
terms—therefore, “death, sudden, cardiac” was used in
the MeSH database and revealed 7792 articles. Searching all fields with “commotio cordis” or the MeSH entry
© THE PHYSICIAN AND SPORTSMEDICINE • ISSN – 0091-3847, April 2010, No. 1, Volume 38
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Prevention of Commotio Cordis
of “death, sudden, cardiac” revealed 7848 articles. The
MeSH terms “sports equipment” or “protective devices”
were searched and yielded a total of 26 417 articles. The
term “athlete” [all fields] was searched and yielded 4757
articles. When combined with “death, sudden, cardiac”
[MeSH] or “commotio cordis” [all fields], 96 articles
were identified. However, 0 articles were found when
those 96 articles were searched with “protective devices”
[MeSH] or “sports equipment” [MeSH]. The term “athlete” in our final search was not used as it appeared to
eliminate relevant articles. A secondary bibliography
search yielded no further articles. The combination
of “sports equipment” [MeSH] or “protective devices”
[MeSH] and “death, sudden, cardiac” [MeSH] or “commotio cordis” [all fields] led to 17 articles.
In this article, we chose to specifically evaluate the
use of chest protectors and safety baseballs in the prevention of CC. Of the 17 articles reviewed, 2 were excluded
because they did not pertain to the desired topic. Two
articles were epidemiologic studies and did not specifically evaluate protective equipment. Three articles
did not meet criteria because they were case reports.
Two articles were clinical reviews that did not focus
on preventive equipment. One article was a published
commentary on the topic. Seven articles were deemed
appropriate for this review.
Table 1. Clinical Review Demographics and Methods
Study
Objective
Study Type
Population
Cohorts
Primary/Secondary
Outcomes
Drewniak et al13
To determine whether a
relationship exists between
mechanical properties of chest
protectors and occurrence
of VF
Experimental
model
Biomechanical
surrogate
Commercially
available baseball
and lacrosse chest
protectors
Primary: quasistatic mechanical
properties and VF occurrence
Secondary: relationship between
the areas of pressure distribution and the proportion of hits
resulting in VF
Doerer et al14
To evaluate the protective
nature of commercially available
chest protectors against CC
Retrospective
case series
Fatal and
nonfatal cases
of CC
Chest protector vs
no chest barrier
Primary: fatality
Secondary: use of chest
protector or not
Weinstock et al10
To evaluate the effectiveness of
chest protectors in
preventing VF
Experimental
model
Juvenile swine
Baseball and
lacrosse chest
protectors vs no
protection
Primary: occurrence of VF
Secondary: peak LV pressure,
ST-segment elevation, presence
of BBB
Viano et al11
To evaluate the effectiveness
of chest protectors and assess
fatality risk using the viscous
criterion
Experimental
model
Biomechanical
surrogate
Baseball chest
protectors vs no
protection
Primary: viscous criterion
for each chest protector
Secondary: deflection (mm)
of the surrogate
Link et al8
To evaluate the induction of VF
with chest wall impact and the
effectiveness of safety baseballs
on inducing arrhythmias
Experimental
model
Juvenile swine
Safety baseball vs
regulation baseball
Primary: occurrence of VF
Secondary: ST-segment changes,
BBB, complete heart block, myocardial perfusion/wall motion
abnormalities, pathologic findings, use of safety baseballs
Janda et al12
To evaluate various soft core
Experimental
baseballs for their ability to reduce model
the risk of fatal chest impact injury
Biomechanical
surrogate
Soft-core baseball vs
standard baseball
Primary: viscous criterion
for each baseball
Secondary: sled displacement
for all baseballs
Link et al9
To evaluate the effectiveness of
safety baseballs on inducing VF
Juvenile swine
Safety baseballs vs
regulation baseball
Primary: Occurrence of VF
Secondary: ST-segment elevation,
transient complete heart block,
transient BBB, pathologic analysis, comparison between 40- and
30-mph impacts
Experimental
model
Abbreviations: BBB, bundle branch block; CC, commotio cordis; LV, left ventricular; VF, ventricular fibrillation.
© THE PHYSICIAN AND SPORTSMEDICINE • ISSN – 0091-3847, April 2010, No. 1, Volume 38
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Results
The 7 articles included in this review are summarized in
Table 1. The studies were then grouped by the use of animal
models, biomechanical models, and epidemiologic review.
Animal Models
Using an experimental swine model to induce VF as a result
of low-energy impact to the chest, Link et al8 studied whether
the use of softer safety baseballs, projected at 30 mph, would
reduce the risk of arrhythmia compared with standard
regulation baseballs. They found that use of the softest safety
baseball significantly reduced the incidence in the induction
of VF compared with the regulation ball (P = 0.03). Although
the authors did not analyze the differences among the 3 levels
of softness, there was an apparent trend between increasing
levels of softness and decreasing incidence of VF.
Limitations identified in this study include the possibility that general anesthesia use may lower the threshold for
induced arrhythmias. Also, the smaller size of the pigs as
compared with children may have exposed the swine to
greater impact forces. The structure of the swine chest is
similar, but not identical, to the size and compliance of a
human chest. These differences can thus affect transmission
of energy. The use of a left ventricular catheter may also have
proarrhythmic potential.
Link et al9 studied 3 safety baseballs compared with
regulation baseballs, propelled at 30 and 40 mph, in reducing
incidence of VF in a swine model. The authors found that
VF was significantly reduced between the standard baseball
and each of the safety baseballs; however, no differences
were found among levels of softness. This conclusion was
consistent at both 30 mph and 40 mph.
There was no statistically significant difference in
occurrence of ST-elevation or transient complete heart
block among each of the baseballs, although the induction
of transient bundle branch block increased with the level of
hardness with each baseball. No limitations were identified
by the authors in this study.
Weinstock et al10 evaluated the effectiveness of 12 commercially available baseball and lacrosse chest protectors
in decreasing the occurrence of VF. They also utilized an
experimental swine model. Swine were subjected to 40-mph
baseball or lacrosse ball blows to the precordium during the
vulnerable period of repolarization for VF and were compared with control impacts without chest protectors. Of the
86
baseball or lacrosse chest wall protectors tested, none were
shown to prevent VF when compared with controls.
Secondary outcomes of this study included measurements
of peak left ventricular pressure, ST-segment elevation, and
bundle branch block as a result of impact. Three baseball
and 3 lacrosse chest protectors showed significantly lower
mean left ventricular pressures compared with controls. Two
baseball and 3 lacrosse chest protectors showed significantly
less ST-segment elevation when compared with controls.
Bundle branch block was significantly reduced by 6 lacrosse
chest protectors, but not by any of the baseball chest protectors.
The differences in the anatomy of the chest wall in swine
and humans were identified by the authors as a limitation
in this study. They tried to correct for this by having very
specific parameters for precordial strikes. A 4 × 4-inch section
of the chest protector was cut and used during the experiment.
Cutting may have altered the mechanical properties of the chest
protector. Results from the studies involving animal models
are summarized in Table 2.
Biomechanical Studies
Results from the studies involving biomechanical models are
summarized in Table 3.
In an experimental study by Viano et al,11 5 baseball
chest protectors were randomly tested on a 3-rib structure
and evaluated with regard to their effect on the viscous criterion (VC). In this study, only 1 chest protector, the All Star
vest (AMPAC Enterprise, Inc., Shirley, MA), significantly
decreased the VC for all speeds tested compared with the
control (unprotected 3-rib structure). Three vests, the ASP
vest, Wet Vest, and Adams vest (Adams USA, Cookeville,
TN), significantly reduced VC for at least 1 speed tested.
One vest (IPASC vest, International Protective Athletic Safety
Corp.) resulted in a statistically significantly increased VC
compared with the control.
A possible limitation in regard to one of the chest protectors tested was the way in which the sensory interface
equipment, a position transducer mounted to the biomechanical surrogate, was used to measure the velocity to the sternum.
The interface may have picked up the deformation of the vest,
which could focus the contact area and increase the energy
delivered to the chest, thus resulting in higher velocity readings from the transducer.11
Janda et al12 tested 9 soft-core baseballs by propelling them
against a 3-rib biomechanical structure at 40, 50, and 60 mph,
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CLINICAL FEATURES
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Table 2. Systematic Review Results and Conclusions (Animal Models)
Study
Results
Conclusions
Link et al
There were significant differences in the induction of VF between
the softest safety ball and the regulation ball (P = 0.03) and
between the wooden object and each of the baseballs
(P ⬍ 0.01 for all comparisons). No significant differences were
evident between the regulation baseball and the medium-soft and
the least-soft safety baseballs.
The softest baseball tested significantly reduced the
incidence of VF when compared with the regulation
baseball.
Regardless of level of softness, safety baseballs seem
to decrease incidence of ventricular fibrillation.
Differences between various levels of softness were
not analyzed.
Weinstock et al10
1. VF was elicited by 12 (32%) of 37 strikes as a result of control
impacts in animals without baseball chest protectors. With
chest protectors, VF occurred in the range of 22%–49% of
chest blows.
2. VF was elicited by 11 (46%) of 24 strikes as a result of control
impacts in animals without lacrosse chest protectors. With chest
protectors, VF occurred in the range of 21%–50% of chest blows.
None of the baseball or lacrosse chest wall
protectors tested significantly decreased the
occurrence of VF when compared with controls.
Link et al9
1. 40 animals underwent 83 chest impacts with baseballs propelled
at 40 mph.
All safety baseballs tested significantly decreased
incidence of VF compared with regulation baseballs,
but no difference existed between safety baseballs
when compared with each other, regardless of speed
at 30 or 40 mph.
8
2. With the softest ball (RIF 1), VF was produced only 3 times
(11%). With the medium-soft ball (RIF 5), VF occurred 5 times
(22%). With the hardest safety ball (RIF 10), VF occurred 4 times
(19%).
3. At both 30 and 40 mph, chest wall blows by each of the
3 safety baseballs (RIF 1, 5, and 10) triggered VF less frequently
than did standard baseballs.
Abbreviation: VF, ventricular fibrillation.
and calculating the VC to determine the risk of CC. Only one
ball, the Incrediball (Incrediball Enterprises Ltd., Langley,
British Columbia, Canada), had a significantly lower VC
value at all tested velocities when compared with the control
(standard baseball). This ball was the lightest of all the balls
tested. Five of the 9 balls tested reduced the VC significantly
for at least 1 velocity tested. One ball resulted in an increase
in VC when tested at 60 mph. No limitations were identified
by the authors in this study.
Drewniak et al 13 studied the mechanical properties
of 11 commercially available chest protectors by using a
servo-hydraulic material tester and pressure-sensitive film.
Each chest protector underwent quasistatic compression to
examine impact area, depth, volume, displacement, permanent
deformation, and stiffness properties. They found that there
was a significant decrease in the amount of hits resulting in
VF as the area of pressure distribution increased. There was
no statistically significant relationship between displacement
and the amount of hits resulting in VF. There was a slight relationship between VF and permanent deformation; however,
this was not statistically significant. When the chest protectors
were analyzed according to low- or high-stiffness regions, no
discernible relationship was found.
The fact that the findings were based on data collected quasistatically was recognized as a limitation.
The authors state that dynamic mechanical testing could
yield more effective results. In addition, some of the data
were collected at another testing facility, with analysis
and statistical relationships using some data collected
in a separate study.
Epidemiology Study
One epidemiologic study and its results are summarized
in Table 4. Doerer et al 14 reviewed past cases of reported
CC and stratified them according to the presence or
absence of chest protection. There were 182 total cases
identified, with 85 of them occurring during competitive sporting events. Thirty-two of the 85 cases (nearly
40%) occurred while the athlete was wearing a chest
protector. Ninety-seven of the cases occurred during
recreational sports or other circumstances. Although
it is unknown whether the athletes were wearing chest
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Table 3. Systematic Review Results and Conclusions (Mechanical Models)
Study
Results
Conclusions
Janda et al
1. One ball, the Incrediball (lightest ball tested), had significantly
lower VC value at all 3 velocities (P ⬍ 0.05)
2. Five of the other balls all had significant reduction in VC values
for ≥ 1 of the tested velocities
3. One ball had significantly higher VC than the standard to the
P ⬍ 0.05 level at 60 mph
Only the lightest ball tested reduced VC enough
at all speeds tested (40, 50, 60 mph) to correlate
with a possible reduction in CC
Viano et al11
1. One vest had a significantly lower VC from the standard baseball
impact of the unprotected chest (VC reduced by average of
50.6% [P ⬍ 0.05])
2. Another vest had an average of 38.1% lower VC and was
significantly different for impacts of 50 to 70 mph
3. Two other vests had significant reductions of VC
(27.7% and 18.7%) above 60 mph
4. One vest increased VC by an average of 34.2% at 40 and 50 mph
4 of the 5 protective vests tested had significant
reductions in VC in ≥ 1 of the tested velocities
Drewniak et al13
1. A significant difference was shown in the proportion of hits
resulting in VF as the area of pressure distribution increased
(R2 = 0.59; P = 0.001)
Of the measured properties, only the area of
pressure distribution was found to significantly
decrease the proportion of hits resulting in VF
12
2. Displacement of chest protectors and proportion of hits
resulting in VF showed no relationship (R2 = 0.19; P = 0.125)
3. No significant relationship between low-stiffness region
(R2 = 0.18; P = 0.13) or high-stiffness region (R2 = 0.093;
P = 0.291) of the chest protector and induction of VF
Abbreviations: CC, commotio cordis; VF, ventricular fibrillation.
protection at the time of impact, it would seem logical
to assume that most recreational participants would
not wear chest protectors. Utilizing this hypothesis, the
fraction of individuals wearing chest protection at the
time of the fatal event would be much smaller (17.5%).
leagues. Our systematic review of the current evidence has
shown that the use of commercially available chest protectors likely does offer some protection from CC, although
they do not reliably prevent all cases. Safety baseballs do
appear to reduce the incidence of CC compared with standard baseballs.
Discussion
Due to the increasing recognition of CC as a significant cause
of sports-related fatality in young athletes, there have been
recent studies evaluating the use of protective equipment,
specifically chest protectors and safety baseballs, as a mode of
prevention. The observation that death due to blunt trauma
to the chest has occurred despite the use of such equipment
has led to several experimental studies attempting to evaluate
the effectiveness of chest protectors and safety baseballs in
reducing the incidence of inducing VF.
The most recent task force on CC, which was published
in 2005 by Maron et al,15 did not make any definitive recommendations promoting the universal use of commercially
available chest protectors as an effective way to prevent CC;
however, the authors provided recommendations regarding
the use of age-appropriate safety baseballs in organized youth
88
Chest Protectors
It is generally presumed that the use of chest protectors offers
some sort of protection against the inherent risks of trauma
associated with organized sports participation. The current
task force recommendations do not include promotion of the
universal use of chest protectors to prevent CC.15 The results
of this systematic review were obtained from experimental
studies involving the use of animal and biomechanical
models that suggest a degree of protection exists, but there
is not guaranteed prevention of blunt impact-related death.
Doerer’s study14 looked at the CC Registry and found that
nearly 40% of reported cases involving an organized sports
setting had chest protection during the time of impact.
However, one could hypothesize that the cases involving
recreational sports or other circumstances were likely not
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Table 4. Systematic Review Results and Conclusions (Epidemiology)
Study
Results
Conclusions
Doerer et al14
32 of 182 reported deaths due
to commotio cordis occurred
despite the presence of a chest
protector
N/A
97 of 182 reported cases of
commotio cordis occurred
while playing recreational sports
or under other circumstances
using chest protection, making the incidence of death with
chest protection only 18%.
Overall, review of the current evidence does not reveal
reliable protection from the use of chest protectors. There does
seem to be a trend, however, toward a decrease in VF as the
velocity of the ball increases when chest protection is present.
Of the mechanical properties of chest protectors, it appears
that those capable of increasing the area of pressure distribution are also likely to decrease incidence of VF. Specifically,
chest protectors constructed from expanded polypropylene
beads, as opposed to closed-cell foam, demonstrate the lowest
occurrence of VF and the largest area of pressure distribution.
There is no evidence to suggest that a vest with a hard plastic
shell reduces the incidence of VF.
Safety Baseballs
In agreement with the current recommendations on CC
published in 2005,15 the results of our systematic review found
that safety baseballs reduce the risk of CC when compared with
the standard baseball. Although there is no identifiable cutoff for softness, it appears that softer balls have some degree
of benefit in preventing impact-related death during sport.
In the 3 experimental studies reviewed, the softest ball shows
substantially decreased rates of induction of VF compared
with the standard youth baseball. A similar effect was also seen
for varying degrees of softness, especially when propelled at
higher velocities.
Limitations
There were several limitations identified when performing this
systematic review. The aim of the article was to evaluate the
evidence for safety equipment in preventing CC in sport. Our
inclusion criteria were narrowed to only include studies that
were experimental or observational designs that specifically
evaluated safety baseballs or chest protectors. Although there
are many epidemiologic studies and case reports on the topic
of CC, we wanted to focus solely on the use of protective
equipment for prevention.
Due to the nature of the topic, there are no randomized
controlled trials available to test the clinical effectiveness of
protective equipment. Our review was consequently limited
to studies that utilized animal or biomechanical models as
subjects. There are obvious inherent differences between a
swine or biomechanical model and a young athlete that cannot
be accounted for in testing, and therefore may affect results.
It is thought that young adolescents are at higher risk of CC
because of their increased chest wall compliance. Despite best
efforts, it is nearly impossible to replicate the identical anatomic qualities of a human chest wall, i.e. in a swine model or
biomechanical structure, without actually experimenting on
human subjects. Obviously, this is a necessary limitation and
cannot be prevented.
Although our review included the highest quality of evidence
available on this topic, our conclusions are based on indirect correlations to clinical outcomes (ie, induction of VF). One example
is the use of the VC as a predictor of VF, as utilized by Viano
et al11 and Janda et al.12 The VC is a time-dependent product of
the velocity of the chest deformation and the amount of chest
compression. It was developed from automotive research and
is a measure of the risk of traumatic thoracic injury. This value
has been used to predict the occurrence of CC in a previously
published experimental study.16 Despite its validity, the VC is a
laboratory value and has innate limitations in clinical correlations. According to the hypothetical analysis by Viano et al,11
the VC is unlikely to be a sole indicator of CC. Therefore, safety
equipment may offer more protection than indicated by the VC
values alone.
Another limitation to the review is the lack of uniformity
among the methodology of the studies and their outcomes. The
data collection and outcome measures were variable among the
reviewed studies. Although the ultimate conclusion was focused
on preventing VF, it is difficult to compare animal and biomechanical studies without making hypothetical assumptions, and
therefore can affect the strength of our final conclusions.
Conclusion
Based on the results of our systematic review, we recommend the use of chest protectors during sports using a dense
projectile object. The evidence is limited, but the rate of induc-
© THE PHYSICIAN AND SPORTSMEDICINE • ISSN – 0091-3847, April 2010, No. 1, Volume 38
89
CLINICAL FEATURES
Classie et al
tion of VF was at its lowest when using chest protection. This
recommendation is further strengthened as the chest protector
is also beneficial for musculoskeletal injury prevention. The
only identifiable risk with its application is the concept that
the relationship between VF and impact speed is nonlinear.
Data from the reviewed studies support the hypothesis that
wearing a chest protector during high-speed impacts may
reduce the impact speeds and subsequent risk of VF. The evidence is not conclusive on the structure of the chest protector
worn. There does seem to be a tendency that polypropylene
may the material of choice, but more investigation into this
matter is needed.
This systematic review provides quality evidence leading
us to soundly recommend the use of safety baseballs for the
purpose of preventing CC. The trend toward preventing CC is
relatively linear with respect to degree of softness. We cannot
state that the use of softer-core objects for lacrosse, softball,
or hockey is beneficial, as we have no literature to support
that issue. However, there is controversy regarding the use of
softer-density baseballs during sport because skeptics feel it
may change the nature of the sport.
Because children wearing chest protectors have succumbed
to CC, it should be emphasized that all persons involved with
athletics should understand appropriate emergent management. Early recognition of CC, followed by calling 911, and
initiating immediate high quality CPR with early defibrillation
has resulted in improved outcomes. Automated external defibrillator programs that provide early access to defibrillation
and appropriate training by coaches, trainers, parents, and
athletes can result in improved outcomes from CC and other
cause of suddens death in athletes at athletic events.
Conflict of Interest Statement
Justin A. Classie, MD, Laura M. Distel, MD, and James R.
Borchers, MD, MPH disclose no conflicts of interest.
90
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