Commotio cordis--sudden cardiac death with chest wall impact

The Effects of Cardiac Implantable Electronic Device Personal Protective Equipment Use in Patients with Pediatric and Adult Congenital Heart Disease

Pediatric and adult congenital heart disease (ACHD) patients encounter physical and emotional barriers. Cardiac implantable electronic devices (CIEDs), including pacemakers and implantable cardiac defibrillators (ICD) often compound these issues. Patient fear associated with damaging the CIED system can lead to avoidance of physical activity and reduced quality of life (QOL). CIED personal protective equipment (PPE) is a potential treatment for decreasing this fear. We sought to determine the effects of CIED PPE use in the pediatric and ACHD population. Patients 5 years or older with a CIED at a single pediatric and ACHD heart rhythm center received a CIED protector and customized athletic shirt. QOL was assessed using the PedsQL TM 4.0 SF15 prior to and after 6-12 months. Of the 77 patients enrolled, 26 completed repeat assessment. The mean age at enrollment was 15.6 years (range 5-36) with a mean device age of 2.2 years (< 1-10 years). Pacemakers were present in 77% and 23% had ICDs. The PPE was used in 92% with no PPE malfunction. Fear associated with physical activity was reduced, z = - 4, p < 0.001, with a large effect size (r = 0.55). There was a trend toward increased physical activity. Total QOL scores improved, z = - 2.771, P < 0.05, with a medium effect size (r = 0.4). This first study of CIED PPE in children shows that providing CIED PPE to pediatric and ACHD patients may decrease their fear of damaging their device system, increasing physical activity levels, and improving quality of life.

Sudden cardiac death in the young: A consensus statement on recommended practices for cardiac examination by pathologists from the Society for Cardiovascular Pathology

Sudden cardiac death is, by definition, an unexpected, untimely death caused by a cardiac condition in a person with known or unknown heart disease. This major international public health problem accounts for approximately 15-20% of all deaths. Typically more common in older adults with acquired heart disease, SCD also can occur in the young where the cause is more likely to be a genetically transmitted process. As these inherited disease processes can affect multiple family members, it is critical that these deaths are appropriately and thoroughly investigated. Across the United States, SCD cases in those less than 40 years of age will often fall under medical examiner/coroner jurisdiction resulting in scene investigation, review of available medical records and a complete autopsy including toxicological and histological studies. To date, there have not been consistent or uniform guidelines for cardiac examination in these cases. In addition, many medical examiner/coroner offices are understaffed and/or underfunded, both of which may hamper specialized examinations or studies (e.g., molecular testing). Use of such guidelines by pathologists in cases of SCD in decedents aged 1-39 years of age could result in life-saving medical intervention for other family members. These recommendations also may provide support for underfunded offices to argue for the significance of this specialized testing. As cardiac examinations in the setting of SCD in the young fall under ME/C jurisdiction, this consensus paper has been developed with members of the Society of Cardiovascular Pathology working with cardiovascular pathology-trained, practicing forensic pathologists.

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.

Mechanoelectric coupling and arrhythmogenesis in cardiomyocytes contracting under mechanical afterload in a 3D viscoelastic hydrogel

The heart pumps blood against the mechanical afterload from arterial resistance, and increased afterload may alter cardiac electrophysiology and contribute to life-threatening arrhythmias. However, the cellular and molecular mechanisms underlying mechanoelectric coupling in cardiomyocytes remain unclear. We developed an innovative patch-clamp-in-gel technology to embed cardiomyocytes in a three-dimensional (3D) viscoelastic hydrogel that imposes an afterload during regular myocyte contraction. Here, we investigated how afterload affects action potentials, ionic currents, intracellular Ca2+ transients, and cell contraction of adult rabbit ventricular cardiomyocytes. We found that afterload prolonged action potential duration (APD), increased transient outward K+ current, decreased inward rectifier K+ current, and increased L-type Ca2+ current. Increased Ca2+ entry caused enhanced Ca2+ transients and contractility. Moreover, elevated afterload led to discordant alternans in APD and Ca2+ transient. Ca2+ alternans persisted under action potential clamp, indicating that the alternans was Ca2+ dependent. Furthermore, all these afterload effects were significantly attenuated by inhibiting nitric oxide synthase 1 (NOS1). Taken together, our data reveal a mechano-chemo-electrotransduction (MCET) mechanism that acutely transduces afterload through NOS1-nitric oxide signaling to modulate the action potential, Ca2+ transient, and contractility. The MCET pathway provides a feedback loop in excitation-Ca2+ signaling-contraction coupling, enabling autoregulation of contractility in cardiomyocytes in response to afterload. This MCET mechanism is integral to the individual cardiomyocyte (and thus the heart) to intrinsically enhance its contractility in response to the load against which it has to do work. While this MCET is largely compensatory for physiological load changes, it may also increase susceptibility to arrhythmias under excessive pathological loading.

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.

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.

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.

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.

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.

Control of cardiac alternans in an electromechanical model of cardiac tissue

Electrical alternations in cardiac action potential duration have been shown to be a precursor to arrhythmias and sudden cardiac death. Through the mechanism of excitation-contraction coupling, the presence of electrical alternans induces alternations in the heart muscle contractile activity. Also, contraction of cardiac tissue affects the process of cardiac electric wave propagation through the mechanism of the so-called mechanoelectrical feedback. Electrical excitation and contraction of cardiac tissue can be linked by an electromechanical model such as the Nash-Panfilov model. In this work, we explore the feasibility of suppressing cardiac alternans in the Nash-Panfilov model which is employed for small and large deformations. Several electrical pacing and mechanical perturbation feedback strategies are considered to demonstrate successful suppression of alternans on a one-dimensional cable. This is the first attempt to combine electrophysiologically relevant cardiac models of electrical wave propagation and contractility of cardiac tissue in a synergistic effort to suppress cardiac alternans. Numerical examples are provided to illustrate the feasibility and the effects of the proposed algorithms to suppress cardiac alternans.

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.

A fatal case of commotio cordis caused by an accidental fall on the beach

Sudden cardiac death is a major health problem and a recurring issue in forensic medicine. Most cases are attributed to congenital heart disease, cardiomyopathy, myocarditis, pathology of the coronary arteries, long or short QT interval syndromes, Brugada syndrome or secondary toxic effects of cardioactive drugs. Sudden death caused by Commotio cordis after an accidental fall is very rare in women. Victims are essentially young people who die following a direct blow to the chest sustained during physical activity. In the following, we report a case of an adult with no significant past medical history, walking on the beach with friends, who died from commotio cordis following an accidental fall on the wet sand. This article deals with post-mortem diagnosis, and demonstrates the importance of a detailed understanding of the circumstances surrounding the death, as well as systematic histological examination of the heart, as the heart will generally appear normal under macroscopic examination. It is important to note that commotio cordis can also occur in adults.

Sudden cardiac death in athletes: where do we stand

We aimed to review the literature to explore the magnitude of sudden cardiac death (SCD) in young athletes. Although SCD in athletes is not a common event, it represents a tragedy of the apparently fit young population. SCD varies according to countries, age groups, and sex. In addition, it varies in the underlying causes and the screening tool. Therefore, we are in need for further research efforts. Guidelines, public and physician awareness, and education regarding the warning signs are integral part in the strategy to reduce SCD tragedy. However, all these requirements raise concern for cost-effectiveness in some countries for proper implementation.

Commotio cordis, therapeutic hypothermia, and evacuation from a United States military base in Iraq

BACKGROUND

Therapeutic hypothermia (TH) has been demonstrated to improve clinical outcomes after out-of-hospital ventricular fibrillation (VF) cardiac arrest. It remains unclear if TH can be safely and effectively used in the setting of traumatic arrest. Furthermore, the use of TH methods in the pre-hospital and transport environments remain poorly established and a domain of active investigation.

OBJECTIVES

To describe a case of successful TH utilization after blunt trauma with commotio cordis and pulmonary contusion, and to describe the continuation of TH during international fixed-wing aeromedical transport.

CASE REPORT

A 33-year-old active duty soldier suffered blunt chest trauma and immediate VF arrest. He was successfully resuscitated with cardiopulmonary resuscitation and defibrillation attempts. Given his ensuing comatose post-arrest state, he was therapeutically cooled and subsequently evacuated from Iraq to Germany, with cooling maintenance established in flight without the availability of training or commercial cooling equipment. The patient exhibited an eventual excellent neurologic recovery. To utilize TH for this patient, military physicians with limited local resources employed a telemedical approach to obtain a hypothermia protocol to develop a successful treatment plan.

CONCLUSIONS

The patient's successful resuscitation suggests that care should not be withheld for blunt trauma patients without vital signs in the field if VF is present, until the differential diagnosis of commotio cordis has been considered.

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.

Sudden cardiac death in young athletes; a literature review and special considerations in Asia

Sudden cardiac death (SCD) in a young athlete is rare, but catastrophic. Exercise acts as a risk factor for SCD in people with cardiovascular disease. A diversity of cardiovascular disorders including hypertrophic cardiomyopathy, congenital coronary anomalies, arrhythmogenic right ventricular dysplasia, dilated cardiomyopathy, aortic rupture due to Marfan syndrome, myocarditis, valvular disease and electrical disorders (Wolff–Parkinson–White syndrome, long QT syndrome, Brugada syndrome), as well as commotio cordis represent the common causes of SCD in young athletes.

As the outcome of lethal cardiovascular disorders is not reversible except in few cases, effective measures should be addressed to reduce the burden of sudden cardiac death in young athletes. Currently, two types of recommendations are proposed by American and European countries.

It seems that there are some special considerations in Asia, entirely different from North America or Europe, which warrant more comprehensive research on epidemiology and etiology of SCD in young Asian athletes by country and evaluation of current national preventive strategies and their achievements in decreasing the risk. Using these data and considering regional restrictions, an expert group will be able to plan a practical and feasible preventive strategy.

Primary cardiac arrest following sport or exertion in children presenting to an emergency department: chest compressions and early defibrillation can save lives, but is intravenous epinephrine always appropriate?

OBJECTIVES

The objective of this study was to describe the characteristics and outcome of pediatric patients presenting to an emergency department (ED) following out-of-hospital primary cardiac arrest (OHPCA), to determine if long-term survival is influenced by specific resuscitation interventions.

METHODS

This was a prospective observational study of cases of OHPCA during sport or exertion in young patients presenting to an ED over a 5-year period. Cases were identified from a resuscitation database, which documented patient demographics, nature of event, emergency treatment, response times, and clinical progress. These data were analyzed to determine outcomes.

RESULTS

Nine children were identified who presented following OHPCA during the study period. The mean age was 10.7 (±4.2) years. All were subsequently diagnosed with an underlying primary cardiac disorder. Six patients (66.6%) survived to make a full recovery. All patients who survived had received early chest compressions (within 5 minutes) and early defibrillation (within 10 minutes). The initial cardiac arrest rhythm in all survivors had been an electrically cardiovertable rhythm. Five (83%) of the 6 survivors did not receive epinephrine during resuscitation.

CONCLUSIONS

The importance of early chest compressions and defibrillation in collapsed young athletes is highlighted in this report. These interventions can result in full long-term neurological recovery. Use of epinephrine in these patients may be dangerous. We suggest that special consideration should be given to this subgroup of patients in the development of future resuscitation guidelines.

Cardiac changes after simulated behind armor blunt trauma or impact of nonlethal kinetic projectile ammunition

BACKGROUND

Cardiac-related injuries caused by blunt chest trauma remain a severe problem. The aim of this study was to investigate pathophysiological changes in the heart that might arise after behind armor blunt trauma or impacts of nonlethal projectiles.

METHODS

Sixteen pigs were shot directly at the sternum with "Sponge Round eXact I Mpact" (nonlethal ammunition; diameter 40 mm and weight 28 g) or hard-plastic ammunition (diameter 65 mm and weight 58 g) to simulate behind armor blunt trauma. To evaluate the influence of the shot location, seven additional pigs where exposed to an oblique heart shot. Physiologic parameters, electrocardiography, echocardiogram, the biochemical marker troponin I (TnI), and myocardial injuries were analyzed.

RESULTS

Nonlethal kinetic projectiles (101-108 m/s; 143-163 J) did not cause significant pathophysiological changes. Five of 18 pigs shot with 65-mm plastic projectiles (99-133 m/s; 284-513 J) to the front or side of the thorax died directly after the shot. No major physiologic changes could be observed in surviving animals. Animals shot with an oblique heart shot (99-106 m/s; 284-326 J) demonstrated a small, but significant decrease in saturation. Energy levels over 300 J caused increased TnI and myocardial damages in most of the pigs.

CONCLUSION

This study indicates that nonlethal kinetic projectiles "eXact iMpact" does not cause heart-related damage under the examined conditions. On impact, sudden heart arrest may occur independently from the cardiac's electrical cycle. The cardiac enzyme, TnI, can be used as a reliable diagnostic marker to detect heart tissue damages after blunt chest trauma.

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.

Overview of sudden cardiac death in young athletes

Sudden cardiac death is the leading cause of nontraumatic mortality in young athletes. The estimated incidence varies; however, recent studies have provided more accurate data. Most cases are attributed to silent hereditary or congenital cardiac disorders, many of which may be detected through preparticipation screening programs. This article provides a comprehensive review of the incidence and etiology of sudden cardiac death in young athletes, with practical advice regarding evaluation and management in light of a large number of recent advances. A brief outline of current perspectives on preparticipation screening programs and prevention is included.

Increased short-term variability of the QT interval in professional soccer players: possible implications for arrhythmia prediction

Background

Sudden cardiac death in competitive athletes is rare but it is significantly more frequent than in the normal population. The exact cause is seldom established and is mostly attributed to ventricular fibrillation. Myocardial hypertrophy and slow heart rate, both characteristic changes in top athletes in response to physical conditioning, could be associated with increased propensity for ventricular arrhythmias. We investigated conventional ECG parameters and temporal short-term beat-to-beat variability of repolarization (STV_QT), a presumptive novel parameter for arrhythmia prediction, in professional soccer players.

Methods

Five-minute 12-lead electrocardiograms were recorded from professional soccer players (n = 76, all males, age 22.0±0.61 years) and age-matched healthy volunteers who do not participate in competitive sports (n = 76, all males, age 22.0±0.54 years). The ECGs were digitized and evaluated off-line. The temporal instability of beat-to-beat heart rate and repolarization were characterized by the calculation of short-term variability of the RR and QT intervals.

Results

Heart rate was significantly lower in professional soccer players at rest (61±1.2 vs. 72±1.5/min in controls). The QT interval was prolonged in players at rest (419±3.1 vs. 390±3.6 in controls, p<0.001). QTc was significantly longer in players compared to controls calculated with Fridericia and Hodges correction formulas. Importantly, STV_QT was significantly higher in players both at rest and immediately after the game compared to controls (4.8±0.14 and 4.3±0.14 vs. 3.5±0.10 ms, both p<0.001, respectively).

Conclusions

STV_QT is significantly higher in professional soccer players compared to age-matched controls, however, further studies are needed to relate this finding to increased arrhythmia propensity in this population.

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.

Causes of sudden cardiac arrest in young athletes

Knowledge of sudden cardiac death in young athletes is imperative for all physicians and allied health professionals. The complete differential diagnosis of a young patient with sudden cardiac arrest will result in proper work-up and treatment. In this article, we review several etiologies of sudden cardiac death, including hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, Wolff-Parkinson-White syndrome, long QT syndrome, Brugada syndrome, and commotio cordis. Clinical findings, work-up, treatment, long-term management, and athlete preparticipation screening guidelines are discussed.

Emergent precordial percussion revisited--pacing the heart in asystole

Precordial percussion is a technique by which a manual force is applied repeatedly to the chest of a patient experiencing an unstable bradycardic or asystolic rhythm. The force is used not to defibrillate the myocardium as is the case with the "precordial thump" in pulseless ventricular tachycardia/ventricular fibrillation but rather to initiate a current through the myocardium in the form of an essentially mechanically paced beat. In this review, we discuss the physiology and utility of precordial percussion, or precordial thump, in the emergency setting as a very temporary bridge to more effective and permanent pacing techniques.

Safety baseballs and chest protectors: a systematic review on the prevention of commotio cordis

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.

Basketball injuries in children

Basketball is a popular, worldwide sport played outdoors and indoors year-round. Patterns of injury are related to abrupt changes in the athlete's direction, jumping, contact between athletes, the hard playing surface and paucity of protective equipment. Intensity of play and training in the quest of scholarships and professional careers is believed to contribute to an increasing occurrence of injury. Radiologists' appreciation of the breadth of injury and its relation to imaging and clinical findings should enhance the care of these children. Some of the patterns of injury are well known to radiologists but vary due to age- and size-related changes; the growing skeleton is affected by differing susceptibilities from biomechanical stresses at different sizes. Beyond screening radiographs, the accuracy of MRI and CT has improved diagnosis and treatment plans in this realm. Investigations to detect symptoms and signs in an attempt to prevent the tragedy of sudden cardiac death in basketball players may lead to MRI and CTA studies that compel radiologists to evaluate cardiac function along with myocardial and coronary artery anatomy. Worthy of mention also is the female athlete triad of disordered eating, amenorrhea, and osteoporosis that is observed in some young women participating in this and other sports.

Precordial thump for cardiac arrest is effective for asystole but not for ventricular fibrillation

BACKGROUND

Precordial thump for cardiac arrest remains controversial. Although precordial blows can trigger ventricular fibrillation (VF) (i.e., commotio cordis), they paradoxically have been regarded as potential therapy for cardiac arrest. In commotio cordis, impact energy and resultant peak left ventricular (LV) pressure are important variables in VF initiation.

OBJECTIVE

The purpose of this study was to assess the relationship between LV pressures generated by thumps and their effectiveness in defibrillation of VF or resuscitation of asystole after defibrillation.

METHODS

After induction of VF, 10 swine each received 18 chest thumps; two sets of three thumps each with a clenched fist, a 30-mph lacrosse ball, and a 40-mph lacrosse ball. If asystole followed defibrillation, manual thumps were given to induce ventricular depolarizations until resumption of spontaneous rhythm.

RESULTS

During VF, generated LV pressure (mmHg) was 263 +/- 52 with manual thumps, 392 +/- 179 with 30-mph ball thumps, and 616 +/- 182 with 40-mph ball thumps (P <.001). None of the 180 thumps terminated VF. All episodes required electrical defibrillation. During asystole, generated LV pressures were greater for thumps that induced ventricular depolarizations than for those that did not (111 +/- 27 mmHg vs 73 +/- 23 mmHg, P <.001). A significant association was observed between induction of ventricular depolarizations and thump-generated LV pressures (odds ratio 2.0 per 10 mmHg rise in LV pressure, 95% confidence interval 1.8-2.1).

CONCLUSION

Despite generating high LV pressures, precordial thumps were not effective in terminating VF. Based on these data, precordial thump for VF in cardiac arrest victims cannot be recommended but for asystolic victims might be beneficial.

Cardiovascular screening of athletes

<Zakljucak> Sprovodjenje kardiovaskularnog skrining programa ima za cilj smanjenje ucestalosti iznenadne srcane smrti kod sportista. Potrebno je doneti nacionalne preporuke koje bi trebalo da jasno definisu obim, organizaciju i sprovodjenje skrininga i redovnih sistematskih pregleda sportista. U medjuvremenu, dok se ne donesu posebne nacionalne preporuke, smatramo da je neophodno da se svi klinicki lekari koji se bave sportskom medicinom detaljno upoznaju sa vazecim evropskim i americkim preporukama, a za prakticnu primenu u svakodnevnoj rutinskoj klinickoj praksi predlazemo primenu modifikovanog americko-evropskog skrining programa koji bi se sastojao od 12 tacaka iz americkih preporuka (navedeno u tabeli 2) i obaveznog 12- kanalnog EKG-a.

Cell membrane stretch and chest blow-induced ventricular fibrillation: commotio cordis

INTRODUCTION

Commotio cordis, sudden cardiac death secondary to blunt nonpenetrating chest blows in sports, is reported with increasing frequency. In a swine model, ventricular fibrillation (VF) is induced by a baseball blow to the chest, and the initiation of VF is related to the peak left ventricular (LV) pressure produced by the blow. LV pressure changes likely result in cell membrane stretch and mechanical activation of ion channels. Disruption of cell cytoskeleton that anchors the cell membrane prior to precordial blows offers the opportunity to explore whether cell membrane deformation is critical to commotio cordis.

METHODS AND RESULTS

Twelve juvenile swine (mean 12.7 +/- 1.6 kg) were randomized to intravenous normal saline (control, n = 6) or 10 mg of intravenous colchicine (n = 6), which is known to depolymerize microtubules. Animals were given up to six blows timed to the vulnerable portion of the cardiac cycle with a 30 mph baseball on the chest directly over the cardiac silhouette. VF was initiated by 14 of the 29 (48%) impacts in the colchicine-treated animals compared with only 3 of 28 (11%) in the controls (P = 0.002). The peak generated LV pressure did not differ between colchicine animals (405 +/- 61 mmHg) and controls (387 +/- 115) (P = 0.47). However, animals administered colchicine were more likely to have VF generated by the chest blow at all pressures.

CONCLUSION

The initiation of VF by chest blows is significantly increased by selective disruption of the cytoskeleton, suggesting that mechanical deformation of the cell membrane is fundamental to the activation of ion channels and underlies the mechanism of VF in commotio cordis.