Upper and lower limits of vulnerability to sudden arrhythmic death with chest-wall impact (commotio cordis)

Development of the NOCSAE Standard to Reduce the Risk of Commotio Cordis

BACKGROUND

Commotio cordis, sudden cardiac death (SCD) caused by relatively innocent impact to the chest, is one of the leading causes of SCD in sports. Commercial chest protectors have not been demonstrated to mitigate the risk of these SCDs.

METHODS

To develop a standard to assess chest protectors, 4 phases occurred. A physiological commotio cordis model was utilized to assess variables that predicted for SCD. Next, a surrogate model was developed based on data from the physiological model, and the attenuation in risk was assessed. In the third phase, this model was calibrated and validated. Finally, National Operating Committee on Standards for Athletic Equipment adopted the standard and had an open review process with revision of the standard over 3 years.

RESULTS

Of all variables, impact force was the most robust at predicting SCD. Chest wall protectors which could reduce the force of impact to under thresholds were predicted to reduce the risk of SCD. The correlation between the experimental model and the mechanical surrogate ranged from 0.783 with a lacrosse ball at 30 mph to 0.898 with a baseball at 50 mph. The standard was licensed to National Operating Committee on Standards for Athletic Equipment which initially adopted the standard in January 2018, and finalized in July 2021.

CONCLUSIONS

An effective mechanical surrogate based on physiological data from a well-established model of commotio cordis predicts the reduction in SCD with chest protectors. A greater reduction in force provides a great degree of protection from commotio cordis. This new National Operating Committee on Standards for Athletic Equipment standard for chest protectors should result in a significant reduction in the risk of commotio cordis on the playing field.

Advancing Commotio cordis Safety Standards Using the Total Human Models for Safety (THUMS)

Commotio cordis is one of the leading causes of sudden cardiac death in youth baseball. Currently, there are chest protector regulations regarding the prevention of Commotio cordis in baseball and lacrosse; however, they are not fully optimized. For the advancement of Commotio cordis safety, it is vital to include various age groups and a variety of impact angles in the testing process. This study employed finite element models and simulated Commotio cordis-inducing baseball collisions for different velocities, impact angles, and age groups. Commotio cordis risk response was characterized in terms of left ventricular strain and pressure, chest band and rib deformation, and force from impact. Normalized rib and chest band deformation when correlated with left ventricular strain resulted in R2 = 0.72, and R2 = 0.76, while left ventricular pressure resulted in R2 = 0.77, R2 = 0.68 across all velocities and impact angles in the child models. By contrast, the resultant reaction force risk metric as used by the National Operating Committee on Standards for Athletic Equipment (NOCSAE) demonstrated a correlation of R2 = 0.20 in the child models to ventricular strain, while illustrating a correlation to pressure of R2 = 0.74. When exploring future revisions to Commotio cordis safety requirements, the inclusion of deformation-related risk metrics at the level of the left ventricle should be considered.

Commotio Cordis in 2023

Since the nationally televised cardiac arrest of American National Football League player Damar Hamlin in January 2023, commotio cordis has come to the forefront of public attention. Commotio cordis is defined as sudden cardiac arrest due to direct trauma to the precordium resulting in ventricular fibrillation or ventricular tachycardia. While the precise incidence of commotio cordis is not known due to a lack of standardized, mandated reporting, it is the third most common cause of sudden cardiac death in young athletes, with more than 75% of cases occurring during organized and recreational sporting events. Given that survival is closely tied to how quickly victims receive cardiopulmonary resuscitation and defibrillation, it is crucial to raise awareness of commotio cordis so that athletic trainers, coaches, team physicians, and emergency medical personnel can rapidly diagnose and treat this often-fatal condition. Broader distribution of automated external defibrillators in sporting facilities as well as increased presence of medical personnel during sporting events would also likely lead to higher survival rates.

Commotio Cordis in Non-Sport-Related Events: A Systematic Review

BACKGROUND

Commotio cordis is an increasingly recognized cause of sudden cardiac death. Although commonly linked with athletes, many events occur in non-sport-related settings.

OBJECTIVES

The goal of this study was to characterize and compare non-sport-related vs sport-related commotio cordis.

METHODS

PubMed and Embase were searched for all cases of commotio cordis from inception to January 5, 2022.

RESULTS

Of 334 commotio cordis cases identified, 121 (36%) occurred in non-sport-related contexts, which included assault (76%), motor vehicle accidents (7%), and daily activities (16%). Projectiles were implicated significantly less in non-sport-related events (5% vs 94%, respectively; P < 0.001). Nonprojectile etiologies in non-sport-related events mostly consisted of impacts with body parts (79%). Both categories affected similar younger aged demographic (P = 0.10). The proportion of female victims was significantly higher in non-sport-related events (13% vs 2%, respectively; P = 0.025). Mortality was significantly higher in non-sport-related events (88% vs 66%, respectively; P < 0.001). In non-sport-related events, rates of cardiopulmonary resuscitation (27% vs 97%, respectively; P < 0.001) and defibrillation (17% vs 81%, respectively; P < 0.001) were both lower and resuscitation was more commonly delayed beyond 3 min (80% vs 5%, respectively; P < 0.001).

CONCLUSIONS

Commotio cordis occurs across a spectrum of non-sport-related settings including assault, motor vehicle accidents, and daily activities. Both categories affected a younger and male-predominant demographic. Mortality is higher in non-sport-related commotio cordis, likely owing to lower rates of cardiopulmonary resuscitation, defibrillation, automated external defibrillator availability, and extended time to resuscitation. Increased awareness of non-sport-related commotio cordis is essential to develop a means of prevention and mortality reduction, with earlier recognition and prompt resuscitation measures.

A Soccer Shot with Lengthy Consequences—Case Report & Current Literature Review of Commotio Cordis

(1) Background: Commotio cordis, caused by objects being directly delivered to the chest, may cause cardiac arrest in young athletes, even without identifiable structural damage to the sternum, ribs or heart itself. Its prevention and management often remain suboptimal, resulting in dismal outcomes. (2) Case summary: A 32-year semi-professional goalkeeper suffered from a non-penetrating blunt thoracic trauma after being struck by a high-velocity shot during a regional league soccer game. He immediately lost consciousness, collapsed, and was successfully resuscitated through early defibrillation of ventricular fibrillation. After an uneventful follow-up for approximately 6 years, recurrent episodes of ventricular tachycardia occurred, which could ultimately only be prevented by epicardial ablation. (3) Conclusion: Very late recurrences of ventricular tachyarrhythmias may occur after ventricular fibrillation due to blunt chest trauma, even in the primary absence of evident structural myocardial damage.

Ventricular fibrillation arrest after blunt chest trauma in a 33-year-old man, commotio cordis?

Background

Commotio cordis is an event in which a blunt, non-penetrating blow to the chest occurs, triggering a life-threatening arrhythmia and often sudden death. This phenomenon is often seen in young, male athletes and has become increasingly well-known over the past few decades. We present a unique case in which ventricular fibrillation occurs in an older male athlete after blunt trauma.

Case presentation

Patient with no known medical history was brought to the ER after being found unconscious after a soccer ball kick to the chest. He was found to be in ventricular fibrillation and successfully resuscitated on the soccer field. Patient was admitted to the hospital and lab workup and initial imaging were unremarkable, except elevated troponin and lactate, which returned to normal levels. An echocardiogram showed global left ventricular systolic dysfunction with a visually estimated ejection fraction of 45–50%. Coronary showed angiographically nonobstructive coronary arteries. The patient was diagnosed with commotio cordis and discharged from the hospital in stable condition. Follow-up echocardiogram continued to show low ejection fraction and event monitor demonstrated frequent polymorphic ventricular tachycardia with periods of asystole.

Conclusion

This case is unique in that blunt trauma to the chest from a soccer ball immediately triggered ventricular fibrillation in a patient with a possible cardiomyopathy. It is possible that the blunt trauma caused primary commotio cordis that led to cardiomyopathy in a previous healthy man, or that an underlying cardiomyopathy made it more likely for this to occur. Overall, increased awareness and prevention efforts of blunt chest trauma are required to reduce the high mortality associated life-threatening arrhythmias. There is limited data regarding the interplay between these two entities.

Identifying Vulnerable Impact Locations to Reduce the Occurrence of Deadly Commotio Cordis Events in Children's Baseball: A Computational Approach

Commotio cordis is the second leading cause of sudden cardiac death in young athletes. Currently available chest protectors on the market are ineffective in preventing cases of commotio cordis in young athletes who play baseball. This study focused on using contour maps to identify specific baseball impact locations to the chest that may result in instances of commotio cordis to children during baseball games. By identifying these vulnerable locations, we may design and develop chest protectors that can provide maximum protection to prevent commotio cordis in young athletes. Simulation cases were run using the validated CHARM-10 chest model, a detailed finite element model representing an average 10-year-old child's chest. A baseball model was developed in company with the chest model, and then used to impact the chest at different locations. A 7 × 8 impact location matrix was designed with 56 unique baseball impact simulations. Left ventricle strain and pressure, reaction force between the baseball and chest, and rib deformations were analyzed. Left ventricle strain was highest from baseball impacts directly over the left ventricle (0.34) as well as impacts slightly lateral and superior to the cardiac silhouette (0.34). Left ventricle pressure was highest with impacts directly over the left ventricle (82.94 kPa). We have identified the most dangerous impact locations resulting in high left ventricle strain and pressure. This novel study provided evidence of where to emphasize protective materials for establishing effective chest protectors that will minimize instances of commotio cordis in young athletes.

Commotio Cordis Resulting from Sibling Rivalry

A 17-year-old girl with no significant medical, surgical, or family history presented to the emergency department following an episode of sudden cardiac arrest after being punched in the chest by her brother. Bystander CPR was immediately initiated, and she was found to be in ventricular fibrillation by emergency services. The patient had return of spontaneous circulation after one defibrillation event. No other significant injuries were found, and she eventually experienced a complete neurologic recovery and was discharged with no other identified cause for her arrest. The objective of this clinical case report is to highlight this unusual and rare injury to increase awareness and avoid incorrect diagnosis.

Developing commotio cordis injury metrics for baseball safety: unravelling the connection between chest force and rib deformation to left ventricle strain and pressure

Commotio cordis is a sudden death mechanism that occurs when the heart is impacted during the repolarization phase of the cardiac cycle. This study aimed to investigate commotio cordis injury metrics by correlating chest force and rib deformation to left ventricle strain and pressure. We simulated 128 chest impacts using a simulation matrix which included two initial velocities, 16 impact locations spread across the transverse and sagittal plane, and four baseball stiffness levels. Results showed that an initial velocity of 17.88 m/s and an impact location over the left ventricle was the most damaging setting across all possible settings, causing the most considerable left ventricle strain and pressure increases. The impact force metric did not correlate with left ventricle strain and pressure, while rib deformations located over the left ventricle were strongly correlated to left ventricle strain and pressure. These results lead us to the recommendation of exploring new injury metrics such as the rib deformations we have highlighted for future commotio cordis safety regulations.

Atrial Fibrillation Induced From Commotio Cordis

CASE

A 20-year-old male collegiate basketball player was evaluated for sudden chest pain, shortness of breath, dizziness, and blurry vision, following an elbow to the anterior chest by another player. His symptoms improved over 10 minutes of observation, but rhythm strip performed onsite showed atrial fibrillation, and the athlete was transmitted to the emergency department for further evaluation. Electrocardiogram in the ER confirmed atrial fibrillation with a rate of 85 bpm. Electrocardioversion was being arranged when he spontaneously converted to normal sinus rhythm, 2.5 hours from the traumatic event.

CONCLUSIONS

Our case illustrates an unusual example of atrial fibrillation induced by commotio cordis (AFCC). Although less acutely life threatening and much less frequently described than ventricular fibrillation induced by commotio cordis, AFCC should be considered in the differential after blunt chest wall trauma. Currently, there are little data regarding management of patients with AFCC.

Is Exercise Helpful or Harmful in Dealing With Specific Arrhythmia

Exercise is universally known to benefit health by lowering risk for cardiovascular disease and mortality. However, in patients with pre-existing cardiac conditions, including channelopathies, cardiomyopathies and coronary artery disease, exercise can cause sudden cardiac death (SCD). In this review, we explore exercise related risks and current recommendations for specific conditions. The risk of myocardial infarction (MI) during strenuous exercise in asymptomatic individuals with coronary artery disease is decreased with habitual exercise, especially if they have a normal ejection fraction and no ischemia. Furthermore, cardiac rehabilitation has been shown to be beneficial in heart failure. On the other hand, surgery is recommended for certain anomalous coronaries prior to engaging in vigorous activity. In addition, both exercise-induced disease progression and SCD in arrhythmogenic cardiomyopathy restrict ability to engage in competitive sports, as is the case in hypertrophic cardiomyopathy. Other diseases, like myocarditis only cause temporary risk for SCD. Previously considered benign, common conditions like early repolarization do increase SCD risk. Finally, certain gear including thicker chest protectors for athletes engaging in sports with hard, small spherical objects decrease risk of commotio cordis. While significant advances have been achieved in diagnosing and treating previously unrecognized conditions that predispose to sudden cardiac death, more research is needed to further tailor recommendations to allow beneficial exercise in those with rarer conditions that are under-represented in large systemic studies.

Cardiac Mechano-Electric Coupling: Acute Effects of Mechanical Stimulation on Heart Rate and Rhythm

The heart is vital for biological function in almost all chordates, including humans. It beats continually throughout our life, supplying the body with oxygen and nutrients while removing waste products. If it stops, so does life. The heartbeat involves precise coordination of the activity of billions of individual cells, as well as their swift and well-coordinated adaption to changes in physiological demand. Much of the vital control of cardiac function occurs at the level of individual cardiac muscle cells, including acute beat-by-beat feedback from the local mechanical environment to electrical activity (as opposed to longer term changes in gene expression and functional or structural remodeling). This process is known as mechano-electric coupling (MEC). In the current review, we present evidence for, and implications of, MEC in health and disease in human; summarize our understanding of MEC effects gained from whole animal, organ, tissue, and cell studies; identify potential molecular mediators of MEC responses; and demonstrate the power of computational modeling in developing a more comprehensive understanding of ‟what makes the heart tick.ˮ.

Size as an Important Determinant of Chest Blow-induced Commotio Cordis

PURPOSE

Commotio cordis is sudden cardiac death caused by a relatively innocent blow to the left chest wall. Adolescents account for the majority of the cases; whether this is due to the higher frequency of adolescents playing ball sports or whether there is some maturational reduction of risk is not known.

METHODS

In a swine model of commotio cordis, the effect of body weight/size (directly related to age) to the susceptibility of chest impact-induced ventricular fibrillation (VF) is examined.

METHODS

Ball impacts were delivered at escalating velocities from 48.3 to 96.9 km·h (30-60 mph) to 128 swine ranging in weight from 5 to 54 kg.

RESULTS

VF occurred in 29% of impacts to the smallest animals compared with 34% in the 14- to 239-kg group, 27% in the 24- to 33.9-kg group, 30% in 34- to 43-kg group, and 15% in the 44- to 54-kg animals. The highest-weight group was associated with a significantly lower incidence of VF compared with other weights (P = 0.002). In a multivariate logistic regression analysis, controlling for repeated measures, four variables predicted VF: body weight (P = 0.0008), velocity (P < 0.0001), distance from the center of the heart, (P < 0.0001), and peak left ventricular pressure induced by the blow (P = 0.0007).

CONCLUSIONS

In this experimental model, animals weighing <44 kg seem to have a similar susceptibility to commotio cordis, whereas animals weighing ≥44 kg have a lower susceptibility. An increase in size of the individual, rather than reduced play of ball sports, is the likely reason for the decreased commotio cordis incidence in older individuals.

Thoracoabdominal Injuries

Trauma to the thorax and abdomen can occur during participation in sports. This chapter reviews some of the more common presentations of such injuries and how such injuries should be best managed. Thoracic injuries reviewed include internal injuries such as pneumothorax, pulmonary contusion, hemothorax, commotio cordis, and cardiac contusion. Chest wall injuries are also reviewed such as rib fractures, costochondritis, and slipping rib syndrome plus sternal and scapular fractures. Abdominal injuries reviewed are focused on internal organ trauma to the spleen and liver, kidney, pancreas, and bowel. There is attention to the effect of Epstein-Barr virus and infectious mononucleosis, seen very frequently in high school and collegiate athletes. Finally, groin pain and athletic pubalgia are described.

In addition to anatomy and clinical presentation, imaging modalities that characterize such trauma are reviewed for each diagnosis. Prevention of thoracoabdominal injuries and return-to-play decisions are described at the chapter conclusion.

Mechanically Induced Ectopy via Stretch-Activated Cation-Nonselective Channels Is Caused by Local Tissue Deformation and Results in Ventricular Fibrillation if Triggered on the Repolarization Wave Edge (Commotio Cordis)

Supplemental Digital Content is available in the text.

Background—

External chest impacts (commotio cordis) can cause mechanically induced premature ventricular excitation (PVE_M) and, rarely, ventricular fibrillation (VF). Because block of stretch-sensitive ATP-inactivated potassium channels curtailed VF occurrence in a porcine model of commotio cordis, VF has been suggested to arise from abnormal repolarization caused by stretch activation of potassium channels. Alternatively, VF could result from abnormal excitation by PVE_M, overlapping with normal repolarization-related electric heterogeneity. Here, we investigate mechanisms and determinants of PVE_M induction and its potential role in commotio cordis–induced VF.

Methods and Results—

Subcontusional mechanical stimuli were applied to isolated rabbit hearts during optical voltage mapping, combined with pharmacological block of ATP-inactivated potassium or stretch-activated cation-nonselective channels. We demonstrate that local mechanical stimulation reliably triggers PVE_M at the contact site, with inducibility predicted by local tissue indentation. PVE_M induction is diminished by pharmacological block of stretch-activated cation-nonselective channels. In hearts where electrocardiogram T waves involve a well-defined repolarization edge traversing the epicardium, PVE_M can reliably provoke VF if, and only if, the mechanical stimulation site overlaps the repolarization wave edge. In contrast, application of short-lived intraventricular pressure surges neither triggers PVE_M nor changes repolarization. ATP-inactivated potassium channel block has no effect on PVE_M inducibility per se, but shifts it to later time points by delaying repolarization and prolonging refractoriness.

Conclusions—

Local mechanical tissue deformation determines PVE_M induction via stretch-activation of cation-nonselective channels, with VF induction requiring PVE_M overlap with the trailing edge of a normal repolarization wave. This defines a narrow, subject-specific vulnerable window for commotio cordis–induced VF that exists both in time and in space.

Development of a Chest Wall Protector Effective in Preventing Sudden Cardiac Death by Chest Wall Impact (Commotio Cordis)

OBJECTIVE

Commotio cordis, sudden death with chest impact, occurs clinically despite chest wall protectors worn in sports. In an experimental model of commotio cordis, commercially available chest wall protectors failed to prevent ventricular fibrillation (VF). The goal of the current investigation was to develop a chest wall protector effective in the prevention of commotio cordis.

DESIGN

In the Tufts experimental model of commotio cordis the ability of chest protectors to prevent VF was assessed. Impacts were delivered with a 40-mph lacrosse ball, timed to the vulnerable period for VF.

INTERVENTION

A chest wall protector or no chest wall protector (control) was randomly assigned to be placed over the chest. Four iterative series of 2 to 4 different chest wall material combinations were assessed. Materials included 3 different foams (Accelleron [Unequal Technologies, Glen Mills, PA], closed cell high density foam; Airilon [Unequal Technologies, Glen Mills, PA], closed cell low density soft foam; and an open cell memory foam) that were adhered to a layer of TriDur (Unequal Technologies, Glen Mills, PA), a flexible elastomeric coated aramid that was bonded to a semirigid polypropylene polymer (ImpacShield, Unequal Technologies, Glen Mills, PA).

MAIN OUTCOME MEASURE

Induction of VF by chest wall impact was the primary outcome.

RESULTS

Of 80 impacts without chest protectors, 43 (54%) resulted in VF. Ventricular fibrillation with chest protectors ranged from a high of 60% to a low of 5%. Of 12 chest protectors assessed, only 3 significantly lowered the risk of VF compared with impacts without chest protectors. These 3 chest protectors were combinations of Accelleron, Airilon, TriDur, and ImpacShield of different thicknesses. Protection increased linearly with the thicker combinations.

CONCLUSIONS

Effective protection against VF with chest wall protection can be achieved in an experimental model of commotio cordis.

CLINICAL RELEVANCE

Chest protector designs incorporating these novel materials will likely be effective in the prevention of commotio cordis on the playing field.

Cardiac Trauma

Cardiac trauma is a leading cause of death in the United States and occurs mostly due to motor vehicle accidents. Blunt cardiac trauma and penetrating chest injuries are most common, and both can lead to aortic injuries. Timely diagnosis and early management are the key to improve mortality. Cardiac computed tomography and cardiac ultrasound are the 2 most important diagnostic modalities. Mortality related to cardiac trauma remains high despite improvement in diagnosis and management.

Pediatric Cardiac Arrest Due to Trauma

Survival from pediatric cardiac arrest due to trauma has been reported to be 0.0%-8.8%. Some argue that resuscitation efforts in the case of trauma-related cardiac arrests are futile. We describe a successful outcome in the case of a child who suffered cardiac arrest caused by external traumatic airway obstruction. Our case illustrates how to deal with pediatric traumatic cardiac arrests in an out-of-hospital environment. It also illustrates how good clinical treatment in these situations may be supported by correct treatment after hospital admission when it is impossible to ventilate the patient to provide sufficient oxygen delivery to vital organs. This case relates to a lifeless child of 3-5 years, blue, and trapped by an electrically operated garage door. The first ambulance arrived to find several men trying to bend the frame and the door apart in order to extricate the child, who was hanging in the air with head and neck squeezed between the horizontally-moving garage door and the vertical door frame. One paramedic found a car jack and used it to push the door and the frame apart, allowing the lifeless child to be extricated. Basic life support was then initiated. Intubation was performed by the anesthesiologist without drugs. With FiO2 1.0 the first documented SaO2 was <50%. Restoration of Spontaneous Circulation was achieved after thirty minutes, and she was transported to the hospital. After a few hours she was put on venous-arterial ECMO for 5.5 days and discharged home after two months. Outpatient examinations during the rest of 2013 were positive, and the child found not to be suffering from any injuries, either physical or mental. The last follow-up in October 2014 demonstrated she had made a 100% recovery and she started school in August 2014.

Mechanisms and Clinical Management of Ventricular Arrhythmias following Blunt Chest Trauma

Nonpenetrating, blunt chest trauma is a serious medical condition with varied clinical presentations and implications. This can be the result of a dense projectile during competitive and recreational sports but may also include other etiologies such as motor vehicle accidents or traumatic falls. In this setting, the manifestation of ventricular arrhythmias has been observed both acutely and chronically. This is based on two entirely separate mechanisms and etiologies requiring different treatments. Ventricular fibrillation can occur immediately after chest wall injury (commotio cordis) and requires rapid defibrillation. Monomorphic ventricular tachycardia can develop in the chronic stage due to underlying structural heart disease long after blunt chest injury. The associated arrhythmogenic tissue may be complex and provides the necessary substrate to form a reentrant VT circuit. Ventricular tachycardia in the absence of overt structural heart disease appears to be focal in nature with rapid termination during ablation. Regardless of the VT mechanism, patients with recurrent episodes, despite antiarrhythmic medication in the chronic stage following blunt chest injury, are likely to require ablation to achieve VT control. This review article will describe the mechanisms, pathophysiology, and treatment of ventricular arrhythmias that occur in both the acute and chronic stages following blunt chest trauma.

L-Type Calcium Channels Do Not Play a Critical Role in Chest Blow Induced Ventricular Fibrillation: Commotio Cordis

Background. In a commotio cordis swine model, ventricular fibrillation (VF) can be induced by a ball blow to the chest believed secondary to activation of mechanosensitive ion channels. The purpose of the current study is to evaluate whether stretch induced activation of the L-type calcium channel may cause intracellular calcium overload and underlie the VF in commotio cordis. Method and Results. Anesthetized juvenile swine received 6 chest wall strikes with a 17.9 m/s lacrosse ball timed to the vulnerable period for VF induction. Animals were randomized to IV verapamil (n = 6) or placebo (n = 6). There was no difference in the observed frequency of VF between verapamil (19/26: 73%) and placebo (20/36: 56%) treated animals (p = 0.16). There was also no significant difference in the combined endpoint of VF or nonsustained VF (21/26: 81% in verapamil versus 24/36: 67% in controls, p = 0.22). Conclusions. In this experimental model of commotio cordis, verapamil did not prevent VF induction. Thus, in commotio cordis it is unlikely that stretch activation of the L-type calcium channel with resultant intracellular calcium overload plays a prominent role.

Pathophysiology, prevention, and treatment of commotio cordis

Commotio cordis is increasing described and it is now clear that this phenomenon is an important cause of sudden cardiac death on the playing field. Victims are predominantly young, male, and struck in the left chest with a ball. An animal model has been developed and utilized to explore the important variables and mechanism of commotio cordis. Impact during a narrow window of repolarization causes ventricular fibrillation. Other important variables include location, velocity, shape, and hardness of the impact object. Biological characteristics such as gender, pliability of the chest wall, and genetic susceptibility also play a role in commotio cordis. The mechanism of ventricular fibrillation appears to be an increase in heterogeneity of repolarization caused by induced abnormalities of ion channels activated by abrupt increases in left ventricular pressure. In the setting of altered repolarization a trigger of ventricular depolarization (premature ventricular depolarization caused directly by the chest blow) initiates a spiral wave that quickly breaks down into ventricular fibrillation. Prevention of commotio cordis is possible. Improved recognition and resuscitation have led to an improvement in outcome.

Atrial fibrillation induced by commotio cordis secondary to a blunt chest trauma in a teenage boy

Low-energy blunt chest trauma can cause commotio cordis and ventricular fibrillation (VF) in otherwise healthy young individuals. If the chest wall impact occurs during a narrow vulnerable window of ventricular repolarization, the generated premature ventricular impulse can lead to VF and sudden death. Atrial fibrillation (AF) in association with a blunt chest trauma has not yet been reported in a child or adolescent. Our case describes a healthy 16-year-old boy who suffered blunt chest trauma during football practice. He was found to have AF, which resolved in 3 days without any therapy. He did not have any identifiable structural or electrical cardiac abnormality and had no previous history of arrhythmia. We hypothesize that AF, similar to commotio cordis-induced VF, may occur as a result of a blunt chest trauma in healthy young individuals. Animal studies evaluating arrhythmias related to chest wall impact may elucidate the timing and mechanism of AF induced by commotio cordis.

Investigation of Sudden Death in Athletes: The Fittest Bodies in the Morgue

Sporting events are generally viewed as regulated activities with fit and healthy participants; therefore, when deaths occur, they draw considerable public interest. Athletic participants can be considered a vulnerable population based on inherent risks within certain sports and the associated physiologic stresses, which may complicate underlying medical conditions. Sudden deaths in young athletes participating in high school and collegiate organized sports occur at an average of four to six deaths per year; however, sudden deaths related to exercise outside of an organized sport setting remain unaccounted for in the overall prevalence of these deaths. A typical forensic pathology practice will see not only these higher-profile deaths occurring during an organized sporting event, but also lower-profile occurrences of individuals dying during more recreational or unstructured exercise. Sport-related deaths can essentially be categorized as those that occur due to dangers inherent in the sport itself, such as forms of heat-related illnesses, blunt force trauma, and water-related deaths, and those that occur due to susceptibilities of a given predisposed participant, including sickle cell trait, hypertrophic cardiomyopathy, and other cardiovascular diseases. This article will address both types of vulnerabilities and provide guidance for appropriate and specific medicolegal death investigation and autopsy procedures in these deaths.

Relevance of cardiomyocyte mechano-electric coupling to stretch-induced arrhythmias: optical voltage/calcium measurement in mechanically stimulated cells, tissues and organs

Stretch-induced arrhythmias are multi-scale phenomena in which alterations in channel activities and/or calcium handling lead to the organ level derangement of the heart rhythm. To understand how cellular mechano-electric coupling (MEC) leads to stretch-induced arrhythmias at the organ level, we developed stretching devices and optical voltage/calcium measurement techniques optimized to each cardiac level. This review introduces these experimental techniques of (1) optical voltage measurement coupled with a carbon-fiber technique for single isolated cardiomyocytes, (2) optical voltage mapping combined with motion tracking technique for myocardial tissue/whole heart preparations and (3) real-time calcium imaging coupled with a laser optical trap technique for cardiomyocytes. Following the overview of each methodology, results are presented. We conclude that individual MEC in cardiomyocytes can be heterogeneous at the ventricular level, especially when moderate amplitude mechanical stretches are applied to the heart, and that this heterogeneous MEC can evoke focal excitation that develops into re-entrant arrhythmias.

Biomechanical considerations for assessing interactions of children and small occupants with inflatable seat belts

NHTSA estimates that more than half of the lives saved (168,524) in car crashes between 1960 and 2002 were due to the use of seat belts. Nevertheless, while seat belts are vital to occupant crash protection, safety researchers continue efforts to further enhance the capability of seat belts in reducing injury and fatality risk in automotive crashes. Examples of seat belt design concepts that have been investigated by researchers include inflatable, 4-point, and reverse geometry seat belts. In 2011, Ford Motor Company introduced the first rear seat inflatable seat belts into production vehicles. A series of tests with child and small female-sized Anthropomorphic Test Devices (ATD) and small, elderly female Post Mortem Human Subjects (PMHS) was performed to evaluate interactions of prototype inflatable seat belts with the chest, upper torso, head and neck of children and small occupants, from infants to young adolescents. Tests simulating a 6-year-old child asleep in a booster seat, with its head lying directly on its shoulder on top of the inflatable seat belt, were considered by engineering judgment, to represent a worst case scenario for interaction of an inflating seat belt with the head and neck of a child and/or small occupant. All evaluations resulted in ATD responses below Injury Assessment Reference Values reported by Mertz et al. (2003). In addition, the tests of the PMHS subjects resulted in no injuries from interaction of the inflating seat belt with the heads, necks, and chests of the subjects. Given the results from the ATD and PMHS tests, it was concluded that the injury risk to children and small occupants from deployment of inflatable seat belt systems is low.

Commotio cordis without arrhythmic event and resuscitation: ECG, echocardiographic, angiographic and cardiovascular resonance imaging study

We describe a case of commotio cordis in which the patient had an extensive cardiac evaluation, including ECGs, a coronary angiogram, a left ventriculogram, repeated echocardiography and cardiovascular MRI (CMRI). A healthy 17-year-old boy sustained an open-handed blow to the anterior part of the chest from a friend with whom he was playing. On admission ECG was performed that showed ST-T alterations and a TNI increase, with echocardiographic evidence of a localised pericardial effusion associated with a persistent myocardial blush at selective angiography. In addition, CMRI confirmed a local delayed enhancement in the same zone. An echocardiogram examination performed 30 days after discharge showed a complete disappearance of pericardial effusion and an improvement on ECG alterations. This is the first case report of a patient with commotio cordis, who did not show any arrhythmias and did not receive any resuscitation procedure, and was extensively studied by imaging methods.

Commotio cordis

Content:

Commotio cordis is blunt, nonpenetrating trauma to the chest resulting in irregular heart rhythm and often leading to sudden death. This article presents the epidemiology, variables leading to commotio cordis, theories on predisposing factors, diagnosis, treatment, treatment outcomes, and return-to-play recommendations.

Evidence Acquisition:

A PubMed (MEDLINE) search for commotio cordis was conducted on July 1, 2008, and it yielded 106 results, of which 26 were used for this review, including experimental models, simulation studies, case analysis studies, case reports, general recommendation, review articles, and editorials.

Results:

There are more than 190 reported cases of commotio cordis in the United States. Forty-seven percent of reported cases occurred during athletic participation. Commotio cordis is the second-most common cause of sudden cardiac death in athletes. Occurrence of commotio cordis is related to time of impact during the cardiac cycle, direct impact over the heart, the hardness and speed of the projectile, and the ineffectiveness of chest barriers. As a result, the US Consumer Product Safety Commission recommends that softer “safety” baseballs be used for youth baseball. Resuscitation using defibrillation was effective in only 15% of cases. Resuscitation within 3 minutes resulted in a survival rate of 25% (17 of 68 cases). Survival drops to 3% when resuscitation is delayed beyond 3 minutes. Survival of commotio cordis has risen from 10% to 15% since 2001. Reduced ventricular ejection fraction has been identified in some commotio cordis survivors.

Conclusion:

Preventive measures, such as using soft “safety” balls and making automated external defibrillators available at sporting venues, can reduce commotio cordis morbidity and mortality. Chest protector designs can be improved to enhance protection. Return to play is best left to clinical judgment given that data are lacking with regard to susceptibility for reoccurrence.

Effect of chest compressions on ventricular activation

External mechanical forces can cause ventricular capture and fibrillation (i.e., commotio cordis). In animals, we showed that chest compressions (CCs) can also cause the phenomenon. The aim of the present study was to determine whether ventricular capture by CCs occurs in humans. Electronic rhythm strips were analyzed in 31 cases of out-of-hospital cardiac arrest. The timing of the CCs was identified from the changes in thoracic impedance between the defibrillator pads. Ventricular capture was defined as QRS complexes of similar morphology occurring intermittently but synchronized with the CC artifact and impedance waveform. Only intermittent ventricular capture was identified to avoid misclassifying constant motion artifacts or intrinsic rhythm as ventricular capture. Of the 29 patients who received CCs for ≥1 minute, minimal or stable motion artifact was present in 24. Intermittent ventricular capture was found in 7 of the 24 patients. In the patients with ventricular capture, the number of ventricular activations (from ventricular capture and native beats) was greater during the CCs than when the CCs was not being performed (18 ± 8.9 vs 9.7 ± 4.0 activations in 15 seconds, p = 0.01). However, in patients without ventricular capture, they were similar (6.8 ± 8.2 vs 7.2 ± 8.8 activations in 15 seconds, p = 0.47). Refibrillation occurred in 22 patients; it began during the CCs in 16 and closely following their initiation in 3. In conclusion, CCs during cardiopulmonary resuscitation can electrically stimulate the heart. Additional studies evaluating the effect of ventricular capture on cardiopulmonary resuscitation outcomes, its relation to refibrillation, and methods to prevent or time ventricular capture by CCs are warranted.

Evaluation of injury criteria for the prediction of commotio cordis from lacrosse ball impacts

Commotio Cordis (CC) is the second leading cause of mortality in youth sports. Impacts occurring directly over the left ventricle (LV) during a vulnerable period of the cardiac cycle can cause ventricular fibrillation (VF), which results in CC. In order to better understand the pathophysiology of CC, and develop a mechanical model for CC, appropriate injury criteria need to be developed. This effort consisted of impacts to seventeen juvenile porcine specimens (mass 21-45 kg). Impacts were delivered over the cardiac silhouette during the venerable period of the cardiac cycle. Four impact speeds were used: 13.4, 17.9, 22.4, and 26.8 m/s. The impactor was a lacrosse ball on an aluminum shaft instrumented with an accelerometer (mass 188 g-215 g). The impacts were recorded using high-speed video. LV pressure was measured with a catheter. Univariate binary logistic regression analyses were performed to evaluate the predictive ability of ten injury criteria. A total of 187 impacts were used in the analysis. The criteria were evaluated on their predictive ability based on Somers' D (D) and Goodman-Kruskal gamma (γ). Injury risk functions were created for all criteria using a 2-parameter Weibull distribution using survival analysis. The best criteria for predicting CC were impact force (D=0.52, and γ=0.52) force*compression (D=0.49, and γ=0.49), and impact power (D=0.49, and γ=0.49). All of these criteria proved significant in predicting the probability of CC from projectile impacts in youth sports (p<0.01). Force proved to be the most predictive of the ten criteria evaluated.

Sudden cardiac death in young athletes

Athletic activity is associated with an increased risk of sudden death for individuals with some congenital or acquired heart disorders. This review considers in particular the causes of death affecting athletes below 35 years of age. In this age group the largest proportion of deaths are caused by diseases with autosomal dominant inheritance such as hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, long QT-syndrome, and Marfan's syndrome. A policy of early cascade-screening of all first-degree relatives of patients with these disorders will therefore detect a substantial number of individuals at risk. A strictly regulated system with preparticipation screening of all athletes following a protocol pioneered in Italy, including school-age children, can also detect cases caused by sporadic new mutations and has been shown to reduce excess mortality among athletes substantially. Recommendations for screening procedure are reviewed. It is concluded that ECG screening ought to be part of preparticipation screening, but using criteria that do not cause too many false positives among athletes. One such suggested protocol will show positive in approximately 5% of screened individuals, among whom many will be screened for these diseases. On this point further research is needed to define what kind of false-positive and false-negative rate these new criteria result in. A less formal system based on cascade-screening of relatives, education of coaches about suspicious symptoms, and preparticipation questionnaires used by athletic clubs, has been associated over time with a sizeable reduction in sudden cardiac deaths among Swedish athletes, and thus appears to be worth implementing even for junior athletes not recommended for formal preparticipation screening. It is strongly argued that in families with autosomal dominant disorders the first screening of children should be carried out no later than 6 to 7 years of age.

Athletes and arrhythmias

Athletes are thought the healthiest segment of the population. Yet, there is a general appearance that athletes are more prone to sudden cardiac death and arrhythmias than nonathletes. Bradycardias in athletes are nearly universal, but advanced heart block is usually pathologic. Athletes may be more prone to atrial fibrillation, but not likely to other types of supraventricular tachycardias. Sudden cardiac death in athletes is rare in the absence of heart disease, with the exception of commotio cordis. Treatment strategies for athletes are focused for the return to athletics. Guidelines for treatment will be derived from the 36th Bethesda Guidelines for athletes, and the European Society of Cardiology (ESC) guidelines for athletes.

Commotio cordis - under-recognized in Europe?: a case report and review

This case and the review illustrate the induction of a sudden collapse of a football player secondary to a blow to his chest (commotio cordis) [CC]. The article argues that CC probably is under recognized in Europe and cautions that the mounting intensity and speed inherent in modern sports possibly increase the likeliness of CC in the future. If CC occurs, immediate cardiopulmonary resuscitation and automatic external defibrillator should be used.

Sudden cardiac death following blunt chest trauma: commotio cordis

BACKGROUND

There have been numerous reports of sudden cardiac death attributable to the condition of commotio cordis. Primarily, these are reports from the USA. Although three Australian cases have been mentioned in the published literature, the present case appears to be the first described Australian case.

METHODS

A man was brought to the Emergency Department after sudden collapse while playing cricket. His medical history was suggestive of hitting by a cricket ball while batting.

RESULTS

The epidemiology and mechanism of arrhythmia induction in commotio cordis are discussed. The emergency management of commotio cordis is outlined.

CONCLUSIONS

Commotio cordis is rare in sports (and Emergency Medicine). However it has a high mortality rate, and rapid recognition of the condition allows early defibrillation, generally with a good outcome. The improvement of participant care is recommended at community and other sport events.