Selective activation of the K(+)(ATP) channel is a mechanism by which sudden death is produced by low-energy chest-wall impact (Commotio cordis)

Sudden cardiac death in athletes

Sudden cardiac death in athletes is an uncommon but extremely visible event because of the high profile of amateur and professional athletes and the expected excellent health of these athletes. However, paradoxically, athletic performance may immediately increase the risk of ventricular arrhythmias and sudden cardiac death while run reducing atherosclerosis, which thus improves cardiovascular health and longevity. In athletes younger than 30 years, the most common underlying causes are due to inherited heart disease. In the older athletes, sudden death is generally due to arrhythmias in the context of coronary artery disease. Many athletes with aborted sudden death, arrhythmia-related syncope, or high-risk genetic disorders benefit from therapy with implanted cardioverter/defibrillators (ICDs) . Although ICD therapy can effectively abort sudden death, implantation of an ICD generally prohibits an individual from all competitive athletics except low-intensity sports. The screening of athletes has been notoriously inadequate; however, the optimal screening strategies have yet to be determined. Recommendations for participation in competitive athletics generally follow the recently published 36th Bethesda Conference Eligibility Recommendations for Competitive Athletes with Cardiovascular Abnormalities.

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.

Hypertrophic cardiomyopathy and other causes of sudden cardiac death in young competitive athletes, with considerations for preparticipation screening and criteria for disqualification

Cardiovascular disease is the most frequent cause of death in young athletes, and hypertrophic cardiomyopathy (HCM) is the single most common condition responsible for these tragedies. Detection of diseases such as HCM can be achieved in general athlete populations through preparticipation screening, and most effectively if testing with electrocardiography or echocardiography is incorporated into the process. Criteria for disqualification and eligibility, based on identified cardiovascular abnormalities, are available in consensus panel guidelines for both United States and European athletes. Removal from intense training and competition is recommended for athletes with HCM, some of whom may ultimately be judged to be at unacceptably high risk for sudden death and eligible for prophylactic defibrillator implantation.

Commotio cordis--sudden cardiac death with chest wall impact

Commotio cordis (CC), sudden death as a result of a blunt, often innocent-appearing chest wall blow, is being reported with increasing frequency. The clinical spectrum is diverse; however, a substantial number of cases occur in youth athletics. In events that occur during sport, victims are struck by projectiles regarded as standard implements of the game. Sudden death is instantaneous and victims are most often found in ventricular fibrillation (VF). Overall survival is poor; however, successful resuscitation can be achieved with early defibrillation. Autopsy is notable for the absence of any significant cardiac or thoracic injury. Development of an experimental model has allowed for substantial insights into the underlying mechanisms of sudden death. In anesthetized juvenile swine, induction of VF is instantaneous following chest wall blows occurring during a vulnerable window before the T wave peak. Crucial variables including the velocity of impact, impact location, and hardness of the impact object have been identified. Rapid left ventricular (LV) pressure rise following chest impact likely results in activation of ion channels via mechano-electric coupling. The generation of inward current via mechano-sensitive ion channels likely results in augmentation of repolarization and nonuniform myocardial activation, and is the cause of premature ventricular depolarizations that are triggers of VF in CC. While softer-than-standard safety baseballs reduce the risk of CC, commercially available chest protectors are ineffective in preventing CC. The development of more effective chest protectors and more widespread use of automated external defibrillators at youth sporting events are needed.

Ventricular Fibrillation Induced by Stretch Pulse: Implications for Sudden Death Due to Commotio Cordis

INTRODUCTION

Nonpenetrating chest wall impact (commotio cordis) may lead to sudden cardiac death due to the acute initiation of ventricular fibrillation (VF). VF may result from sudden stretch during a vulnerable window, which is determined by repolarization inhomogeneity.

METHODS

We examined action potential morphologies and VF inducibility in response to sudden myocardial stretch in the left ventricle (LV). In six Langendorff perfused rabbit hearts, the LV was instrumented with a fluid-filled balloon. Increasing volume and pressure pulses were applied at different times of the cardiac cycle. Monophasic action potentials (MAPs) were recorded simultaneously from five LV epicardial sites. Inter-site dispersion of repolarization was calculated in the time and voltage domains.

RESULTS

Sudden balloon inflation induced VF when pressure pulses of 208-289 mmHg were applied within a window of 35-88 msec after MAP upstroke, a period of intrinsic increase in repolarization dispersion. During the pressure pulse, MAPs revealed an additional increase in repolarization dispersion (time domain) by 9 +/- 6 msec (P < 0.01). The maximal difference in repolarization levels (voltage domain) between sites increased from 19 +/- 3% to 26 +/- 3% (P < 0.05). Earliest stretch-induced activation was observed near a site with early repolarization, while sites with late repolarization showed delayed activation.

CONCLUSIONS

Sudden myocardial stretch can elicit VF when it occurs during a vulnerable window that is based on repolarization inhomogeneity. Stretch pulses applied during this vulnerable window can lead to nonuniform activation. Repolarization dispersion might play a crucial role in the occurrence of fatal tachyarrhythmias during commotio cordis.

Dysrhythmia and electrocardiographic changes in diabetes mellitus: pathophysiology and impact on the incidence of sudden cardiac death

BACKGROUND

The incidence of sudden cardiac death (SCD) is increasing in diabetes mellitus. Susceptibility to dysrhythmias and the reliability of an electrocardiogram in diabetic hearts are debatable issues.

OBJECTIVES

To highlight the underlying mechanism of dysrhythmia and electrocardiographic changes in diabetic patients and the impact on the incidence of SCD.

METHODS

Most the pertinent articles (English and non-English) published in Medline, Scopus and EBSCO Host research databases have been reviewed.

RESULTS AND CONCLUSION

In the absence of systematic reviews, susceptibility to dysrhythmias and electrical instability in diabetic patients are underestimated. This susceptibility has been found to be enhanced, unchanged or reduced in different studies. To find a link between SCD and diabetes, the published studies provide controversial results; however, the majority of studies with a long-term follow-up support this link. The role of hyperglycemia, autonomic neuropathy and anti-diabetic agents as predisposing factors deserve more attention to fortify the clinical judgment and decrease the incidence of SCD.

Failure of commercially available chest wall protectors to prevent sudden cardiac death induced by chest wall blows in an experimental model of commotio cordis

OBJECTIVE

Sudden cardiac death that results from chest wall blows (commotio cordis) the second leading cause of death in young athletes. Most events are caused by blows from projectiles, such as baseballs or lacrosse balls, with a substantial proportion occurring despite the use of a chest protector. In the present experiment, we tested the effectiveness of commercially available chest protectors in preventing ventricular fibrillation (VF) that results from chest wall strikes with baseballs and lacrosse balls.

METHODS

Twelve different baseball or lacrosse chest protectors were evaluated in juvenile swines that 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. Seven baseball chest protectors were hit by regulation baseballs, and 5 lacrosse chest protectors were tested by blows with standard lacrosse balls. Each animal received 2 chest blows for each protector and 2 control impacts without a chest protector, with the sequence of impacts assigned randomly.

RESULTS

VF was elicited by 12 (32%) of 37 strikes in control animals without baseball chest protectors. None of the baseball chest wall protectors tested were shown to decrease significantly the occurrence of VF when compared with controls. VF was elicited by 11 (46%) of 24 strikes in control animals without lacrosse chest protectors. None of the lacrosse chest wall protectors tested decreased significantly the occurrence of VF when compared with controls.

CONCLUSION

In our experimental animal model of commotio cordis, commercially available baseball and lacrosse chest wall protectors were ineffective in protecting against VF that was triggered by chest blows and, by inference, sudden cardiac death. Improvements in materials and design of chest wall barriers are necessary to reduce the occurrence of these tragic events and make the athletic field safer for youths.

K(ATP) channel current increases in postinfarction remodeled cardiomyocytes

Adenosintriphosphate-sensitive potassium channels (K(ATP) channels) are an important linkage between the metabolic state of a cell and electrophysiological membrane properties. In this study, K(ATP) channels were studied in myocytes of normal and remodeled myocardium of the rat. Myocardial infarction was induced by ligature of the left anterior descending artery. Remodeled myocytes were obtained from the hypertrophied posterior left ventricular wall and interventricular septum 3 months after infarction. The current through K(ATP) channels was measured in whole-cell and inside-out patches by using the patch-clamp technique. After myocardial infarction, the heart weight/body weight ratio was doubled and the myocytes were hypertrophied yielding a cell capacitance of 266+/-16 pF compared to 122+/-12 pF in control cells. The amount of Kir6.2 protein was indistinguishable in corresponding regions of control and remodeled hearts. The ATP sensitivity of K(ATP) channels in remodeled cells was significantly lower than in control cells (half maximum block at 115 micromol/l ATP in remodeled and at 71 mumol/l ATP in control cells). The maximum I (KATP) density induced by metabolic inhibition was higher in small remodeled (176+/-15 pA/pF) than in control cells (127+/-11 pA/pF), but was unchanged in large remodeled cells. Both, the higher I (KATP) density and the lower sensitivity of the K(ATP) channels to ATP suggest that remodeled cardiomyocytes develop an improved tolerance to ischemia by stabilizing the resting potential and decreasing excitability.

Effects of mechanosensitive ion channels on ventricular electrophysiology: experimental and theoretical models

The heart is an electrically driven mechanical pump, somewhat like an electric motor. Interestingly, like an electric motor in 'dynamo mode', the heart can also convert mechanical stimuli into electrical signals. This feedback from cardiac mechanics to electrical activity involves mechanosensitive ion channels, whose properties and pathophysiological relevance are reviewed in the context of experimental and theoretical modelling of ventricular beat-by-beat electromechanical function.

Effect of stretch-activated channels on defibrillation efficacy

OBJECTIVES

This study aims to explore whether defibrillation threshold elevation could be caused by sustained recruitment of stretch-activated channels (SACs) and, if so, what are the underlying mechanisms.

BACKGROUND

Clinical studies have demonstrated that patients with dilated and overloaded ventricles have elevated defibrillation threshold. Prolonged ventricular stretch has been suggested as a possible factor in defibrillation threshold elevation; however, its role remains unclear.

METHODS

A two-dimensional finite-element bidomain model of ventricular defibrillation was used in the study. Retaining the geometrical parameters in the model, defibrillation dose-response curves were constructed with and without SACs to isolate the effect of stretch on shock outcome.

RESULTS

Simulations demonstrate that SAC activation leads to flattening of dose-response curve and increases in defibrillation threshold and effective dose for defibrillation by 31.4% and 18.8%, respectively. Examination of the electrophysiologic properties associated with sustained SAC recruitment pinpointed the main mechanisms responsible for the decrease in defibrillation efficacy. The lower conduction velocity of the shock-induced break excitations and the more positive transmembrane potential at the end of the effective refractory period in the tissue with SACs are proposed as main reasons for defibrillation threshold elevation.

CONCLUSIONS

Demonstrating the contribution of SACs to defibrillation threshold elevation identifies SACs as an attractive pharmaceutical target to reduce defibrillation threshold in patients with dilated cardiomyopathy.

Successful resuscitation after sudden death in a one year old infant who sustained a blunt chest injury after a fall from 10 m

Sudden cardiac arrest due to blunt anterior chest wall impact (Commotio Cordis) usually occurs in young athletes who are struck by a baseball or other projectile in the precordium. Survival is extremely rare if the induced ventricular fibrillation (VF) is not defibrillated immediately at the scene. We report here a rare case of a one-year-old infant survivor of cardiac arrest caused by blunt chest impact during an accidental fall from a fourth story window. Eye witnesses reported to have seen him land on the front of his chest directly onto the plastic rain cover on the ground floor. He was transferred to a nearby hospital within minutes, where ventricular fibrillation was recorded. Immediate cardiopulmonary resuscitation and defibrillation and was successful. He recovered without any subsequent sequelae. To the best of our knowledge, this rare incident represents the first time that an infant has survived such cardiac arrest in these circumstances that has been recorded in the literature. This has implications for the management of paediatric fall injuries.

Role of Streptomycin-Sensitive Stretch-Activated Channel in Chest Wall Impact Induced Sudden Death (Commotio Cordis)

INTRODUCTION

Deaths secondary to low-energy impacts to the precordium in young individuals (commotio cordis) have been reported with increasing frequency. In a swine model, baseball impacts induce ventricular fibrillation when directed at the center of the left ventricle during the vulnerable portion of repolarization just prior to the T-wave peak. It has been hypothesized that activation of stretch-sensitive channels could be crucial for this electrophysiological phenomenon. In this study, a nonselective stretch-activated cation channel was pharmacologically blocked prior to chest blows to determine whether this channel represents a possible pathway by which commotio cordis events occur.

METHODS

In a randomized and blinded experiment, 12 swine (mean 17.1 +/- 2.5 kg) received either 2-g streptomycin intramuscularly (mean serum concentration 115 +/- 18 muM) or sterile water prior to chest impact. Each animal received six precordial impacts with a baseball propelled at 40 mph.

RESULTS

There was no significant difference in the frequency of induced VF in the animals administered streptomycin (10 of 19 impacts: 53%) compared to those control animals receiving only sterile water (10 of 31: 32%) (P = 0.15). However, the magnitude of ST segment elevation was less in the streptomycin-treated animals (19 +/- 19 mV) versus controls (61 +/- 46 mV) (P = 0.015).

CONCLUSION

Streptomycin did not alter the frequency of ventricular fibrillation in our commotio cordis model, indicating that the stretch-activated channel is not implicated in the genesis of chest blow-induced cardiac arrest. However, streptomycin did reduce ST elevation following impact suggesting that the stretch-activated channel may play a role in ST segment elevation following chest wall blows.

Induction of ventricular arrhythmias following mechanical impact: a simulation study in 3D

Commotio cordis, mechanical induction of heart rhythm disturbances, including sudden cardiac death, in the absence of corresponding structural damage, has been reported with increasing frequency in young individuals participating in sporting activities. Recently, the electrophysiological changes during c. cordis have been attributed to mechano-electric feedback, and particularly, to the recruitment of stretch-activated ion channels. The underlying mechanisms, however, by which a mechanical impact results in ventricular fibrillation, remain unknown. This study employs a 3D realistic model of rabbit ventricular geometry and fiber orientation to elucidate the electrophysiological mechanisms involved in arrhythmia induction following acute mechanical stimulation of the heart. Impact effects are modeled through stretch-activated ion channel activation in a 3D region of the ventricles representing the impact profile. Both cation-nonselective and potassium-selective stretch-activated ion channels are recruited upon mechanical impact. The impact is administered at various coupling intervals following pacing at the apex. To aid in the interpretation of results, the effect of mechanical stimulation on single cell action potentials is also examined. The results demonstrate that the region of impact is characterized by different types of cellular responses, including generation of a new action potential, shortening, or lengthening of action potential duration. The impact induces sustained reentry only when (1) a new activation is elicited by mechanical stimulation (caused by activation of cation-nonselective stretch-activated ion channels), and (2) upon return to the original region of impact, this activation does not encounter an extension of action potential duration (prevented by activation of potassium-selective stretch-activated ion channels).

Commotio cordis?A report of three cases

Commotio cordis is a recognised cause of sudden death in which an apparently minor blow to the chest causes ventricular fibrillation and cardiac arrest. It is best known for causing death during games of youth baseball in the United States, but individual cases have been recorded as a result of a wide range of activities, principally sporting. The underlying biochemical and mechano-electric causes have been well documented. However, there are few reported cases where commotio cordis is implicated as the cause of death in homicide cases. We present three cases from the north-east of England where an assault caused death by this mechanism.

Commotio cordis

Commotio cordis is ventricular fibrillation that results from blunt chest trauma and is a life threatening condition; early resuscitation and defibrillation are critical. This may occur during sporting events or from child abuse and most patients are boys who are younger than 16 years. Commotio cordis' prognosis depends on the availability of cardiac defibrillation. Automatic defibrillators at convenient locations near sporting events, combined with improved cardiopulmonary resuscitation education, may improve chances of survival after this rare phenomenon. Transient cardiac conduction abnormalities and arrhythmias have been observed in survivors; therefore, cardiac clearance before resumption of sports is indicated.

Mechanical induction of arrhythmias during ventricular repolarization: modeling cellular mechanisms and their interaction in two dimensions

Nonpenetrating mechanical stimulation of the precordial chest is particularly likely to instantaneously induce sustained rhythm disturbances if timed to coincide with ventricular repolarization. A number of possible mechanisms have been proposed, including mechanoelectric feedback acting via stretch-activated ion channels. The cellular effects of such channel activation have been studied and mathematically modeled in great detail. In this study, we investigate their dynamic interaction with the trailing wave of action potential repolarization in a two-dimensional model of ventricular tissue. The model identifies how stretch activation of cation-nonselective ion channels causes ectopic excitation in fully repolarized tissue and functional block of conduction at the intersection of the mechanical stimulus and the repolarization wave end, which may give rise to both trigger and sustaining mechanisms of ventricular arrhythmia. Simulation of stretch activation of K(+)-selective ion channels alone is insufficient in causing instantaneous arrhythmia, although it may, via action potential shortening, contribute to its sustenance.

Sulfonylureas attenuate electrocardiographic ST-segment elevation during an acute myocardial infarction in diabetics

OBJECTIVES

The aim of this study was to determine whether sulfonylureas attenuate ST-segment elevation in diabetics during acute myocardial infarction (AMI).

BACKGROUND

Sulfonylureas block adenosine triphosphate-sensitive potassium channels found in the pancreas and heart. Animal studies have demonstrated that opening of these cardiac channels results in ST-segment elevation during AMI, and pretreatment with sulfonylureas blunts these ST-segment changes.

METHODS

We performed a retrospective study of diabetic patients hospitalized with AMI over a four-year period in Framingham, Massachusetts. Electrocardiograms obtained on arrival were analyzed for standard ST-segment criteria for thrombolytic therapy (>1 mm in two or more contiguous leads). Results were compared between the study group (40 patients taking sulfonylureas) and control group (48 patients taking alternative hypoglycemic agent).

RESULTS

Demographics were similar for both groups apart from a female preponderance in the study group. A significantly higher percentage of patients in the study group did not meet ST-segment criteria for thrombolytic therapy as compared with the control group (53% vs. 29%, p = 0.02). This difference was most prominent in patients with peak creatinine phosphokinase levels between 500 and 1,000 mg/dl (86% vs. 22%, p = 0.04). The magnitude of ST-segment elevation and the frequency of thrombolytic therapy were significantly lower in the sulfonylurea group than in the control group (1.1 +/- 1.0 mm vs. 2.1 +/- 2.7 mm, p = 0.02 and 20% vs. 40%, p = 0.04, respectively).

CONCLUSIONS

Sulfonylurea therapy appears to attenuate the magnitude of ST-segment elevation during an AMI, resulting in failure to meet criteria for thrombolytic therapy and as a consequence leading to inappropriate withholding therapy in this subset of diabetic patients.

Differential effects of stretch and compression on membrane currents and [Na+]c in ventricular myocytes

Mechano-electrical feedback was studied in the single ventricular myocytes. A small fraction (approximately 10%) of the cell surface could be stretched or compressed by a glass stylus. Stretch depolarised, shortened the action potential and induced extra systoles. Stretch activated non-selective cation currents (I(ns)) showed a linear voltage dependence, a reversal potential of 0 mV, a pure cation selectivity, and were blocked by 8 microM Gd(3+) or 30 microM streptomycin. Stretch reduced Ca(2+) and K(+) (I(K)) currents. Local compression of broadwise attached cells activated I(K) but not I(ns). Cytochalasin D or colchicin, thought to disrupt the cytoskeleton, suppressed the mechanosensitivity of I(ns) and I(K). During stretch, the cytosolic sodium concentration increased with spatial heterogeneities, local hotspots with [Na(+)](c)>24 mM appeared close to surface membrane and t-tubules (pseudoratiometric imaging using Sodium Green fluorescence). Electronprobe microanalysis confirmed this result and indicated that stretch increased total sodium [Na] in cell compartments such as mitochondria, nuclear envelope and nucleus. Our results obtained by local stretch differ from those obtained by end-to-end stretch (literature). We speculate that channels may be activated not only by axial but also by shear stress, and, that stretch can activate channels outside the deformed sarcomeres via second messenger.

Mechanically induced sudden death in chest wall impact (commotio cordis)

Sudden death due to nonpenetrating chest wall impact in the absence of injury to the ribs, sternum and heart is known as commotio cordis. Although once thought rare, an increasing number of these events have been reported. Indeed, a significant percentage of deaths on the athletic field are due to chest wall impact. Commotio cordis is most frequently observed in young individuals (age 4-18 years), but may also occur in adults. Sudden death is instantaneous or preceded by several seconds of lightheadedness after the chest wall blow. Victims are most often found in ventricular fibrillation, and successful resuscitation is more difficult than expected given the young age, excellent health of the victims, and the absence of structural heart disease. Autopsy examination is notable for the lack of any significant cardiac or thoracic abnormalities. In an experimental model of commotio cordis utilizing anesthetized juvenile swine, ventricular fibrillation can be produced by a 30 mph baseball strike if the strike occurred during the vulnerable period of repolarization, on the upslope of the T-wave. Energy of the impact object was also found to be a critical variable with 40 mph baseballs more likely to cause ventricular fibrillation than velocities less or greater than 40 mph. In addition, more rigid impact objects and blows directly over the center of the chest were more likely to cause ventricular fibrillation. Peak left ventricular pressure generated by the chest wall blow correlated with the risk of ventricular fibrillation. Activation of the K(+)(ATP) channel is a likely cause of the ventricular fibrillation produced by chest wall blows. Successful resuscitation is attainable with early defibrillation.

Is ATP-sensitive K+ channel (K+ATP) recruitment a common mechanism for ECG-ST segment depression and elevation?

ATP sensitive (K(+)(ATP)) potassium cardiac channels are recruited when ATP levels are low as in ischemic injury and acute trauma. Such activation results in ECG-ST elevation and cardiac arrhythmias. K(+)(ATP) channel recruitment may be blocked by the sulfonylurea glibenclamide, permitting a wide variety of animal experimentation designed to test the genesis of ECG-ST segment elevations and depressions in diverse conditions including digitalis effect, acute arterial occlusion, tachycardias, and acute pericarditis. A specific series of animal experiments designed to test this hypothesis is proposed. Clinical implications are discussed.

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

OBJECTIVES

In an animal model of commotio cordis, sudden death with chest-wall impact, we sought to systematically evaluate the importance of impact velocity in the generation of ventricular fibrillation (VF) with baseball chest-wall impact.

BACKGROUND

Sudden cardiac death can occur with chest-wall blows in recreational and competitive sports (commotio cordis). Analyses of clinical events suggest that the energy of impact is often not of unusual force, although this has been difficult to quantify.

METHODS

Juvenile swine (8 to 25 kg) were anesthetized, placed prone in a sling to receive chest-wall strikes during the vulnerable time window during repolarization for initiation of VF with a baseball propelled at 20 to 70 mph.

RESULTS

Impacts at 20 mph did not induce VF; incidence of VF increased incrementally from 7% with 25 mph impacts, to 68% with chest impact at 40 mph, and then diminished at >/=50 mph (p < 0.0001). Peak left ventricular pressure generated by the chest blow was related to the incidence of VF in a similar Gaussian relationship (p < 0.0001).

CONCLUSIONS

The energy of impact is an important variable in the generation of VF with chest-wall impacts. Impacts at 40 mph were more likely to produce VF than impacts with greater or lesser velocities, suggesting that the predilection for commotio cordis is related in a complex manner to the precise velocity of chest-wall impact.

Automated external defibrillator arrhythmia detection in a model of cardiac arrest due to commotio cordis

INTRODUCTION

Cardiac arrest due to chest wall blows (commotio cordis) has been reported with increasing frequency in children, and only about 15% of victims survive. Automated external defibrillators (AEDs) have been shown to be life saving in adults with cardiac arrest, but data on their use in children are limited. In a swine model of commotio cordis designed to be most relevant to young children, we assessed the efficacy of a commercially available AED for recognition and termination of ventricular fibrillation.

METHODS AND RESULTS

Ventricular fibrillation was produced in anesthetized juvenile swine by precordial impact from a baseball under controlled conditions. Animals were randomized to defibrillation after 1, 2, 4, or 6 minutes of ventricular fibrillation. Twenty-six swine underwent 50 ventricular fibrillation inductions. Sensitivity of the AED for recognition of ventricular fibrillation was 98%, and specificity for nonshockable episodes was 100%. All episodes of ventricular fibrillation were successfully terminated by the AED.

CONCLUSION

In this experimental model of commotio cordis, the AED proved to be highly sensitive and specific for recognition of ventricular fibrillation and effective in terminating the arrhythmia and restoring sinus rhythm. These findings suggest that early defibrillation with the AED could save young lives on the athletic field.

Commotio cordis

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Reduced risk of sudden death from chest wall blows (commotio cordis) with safety baseballs

OBJECTIVES

In an experimental model of sudden death from baseball chest wall impact (commotio cordis), we sought to determine if sudden death by baseball impact could be reduced with safety baseballs.

BACKGROUND

Sudden cardiac death can occur after chest wall impact with a baseball (commotio cordis). Whether softer-than-standard (safety) baseballs reduce the risk of sudden death is unresolved from the available human data. In a juvenile swine model, ventricular fibrillation (VF) has been shown to be induced reproducibly by precordial impact with a 30-mph baseball 10 to 30 ms before the T-wave peak, and this likelihood was reduced with the softest safety baseballs (T-balls). To further test whether safety baseballs would reduce the risk of sudden death at velocities more relevant to youth sports competition, we used our swine model of commotio cordis to test baseballs propelled at the 40-mph velocity commonly attained in that sport.

METHODS

Forty animals received up to 3 chest wall impacts at 40 mph during the vulnerable period of repolarization for VF with 1 of 3 different safety baseballs of varying hardness, and also by a standard baseball.

RESULTS

Safety baseballs propelled at 40 mph significantly reduced the risk for VF. The softest safety baseballs triggered VF in only 11% of impacts, compared with 19% and 22% with safety baseballs of intermediate hardness, and 69% with standard baseballs.

CONCLUSION

In this experimental model of low-energy chest wall impact, safety baseballs reduced (but did not abolish) the risk of sudden cardiac death. More universal use of these safety baseballs may decrease the risk of sudden death on the playing field for young athletes.

Commodio cordis: an underappreciated cause of sudden cardiac death in young patients: assessment and management in the ED

Commotio cordis is the condition of sudden cardiac death or near sudden cardiac death after blunt, low-impact chest wall trauma in the absence of structural cardiac abnormality. Ventricular fibrillation is the most commonly reported induced arrhythmia in commotio cordis. Blunt impact injury to the chest with a baseball is the most common mechanism. Survival rates for commotio cordis are low, even with prompt CPR and defibrillation.

Impact directly over the cardiac silhouette is necessary to produce ventricular fibrillation in an experimental model of commotio cordis

OBJECTIVES

In an experimental model of sudden death from chest wall impact (commotio cordis), we sought to define the chest wall areas important in the initiation of ventricular fibrillation (VF).

BACKGROUND

Sudden death can result from an innocent chest blow by a baseball or other projectile. Observations in humans suggest that these lethal blows occur over the precordium. However, the precise location of impact relative to the risk of sudden death is unknown.

METHODS

Fifteen swine received 178 chest impacts with a regulation baseball delivered at 30 mph at three sites over the cardiac silhouette (i.e., directly over the center, base or apex of the left ventricle [LV]) and four noncardiac sites on the left and right chest wall. Chest blows were gated to the vulnerable portion of the cardiac cycle for the induction of VF.

RESULTS

Only chest impacts directly over the heart triggered VF (12 of 78: 15% vs. 0 of 100 for noncardiac sites: p < 0.0001). Blows over the center of the heart (7 of 23; 30%) were more likely to initiate VF than impacts at other precordial sites (5 of 55; 9%, p = 0.02). Peak LV pressures generated instantaneously by the chest impact were directly related to the risk of VF (p < 0.0006).

CONCLUSIONS

For nonpenetrating, low-energy chest blows to cause sudden death, impact must occur directly over the heart. Initiation of VF may be mediated by an abrupt and substantial increase in intracardiac pressure. Prevention of sudden death from chest blows during sports requires that protective equipment be designed to cover all portions of the chest wall that overlie the heart, even during body movements and positional changes that may occur with athletic activities.

Commotio cordis: an underappreciated cause of sudden death in athletes

Over the last few years, the recognised cardiovascular risks of sporting activities have been extended to include cardiac arrest resulting from low-energy precordial chest impact produced by projectiles (e.g. baseball) or bodily contact, in the young, healthy and active athlete [also known as commotio cordis (CC)]. However, case reports of CC in European medical literature can be traced back for at least 130 years. CC accounts for a small, but important, subset of sudden death during sporting activities. It is a devastating electrophysiological event in the young athlete, and one which has generated considerable concern, both in the medical profession as well as in the public. The mechanism of sudden death appears to be caused by ventricular fibrillation, which occurs when the chest impact is delivered within a narrow, electrically vulnerable portion of the cardiac cycle, that is, during repolarisation, just before the peak of the T wave. Resuscitation of these victims is possible with prompt cardiopulmonary resuscitation and defibrillation. Preventive measures, such as the use of age-appropriate safety baseballs and suitably designed chest wall protection, may reduce the risk of sudden death and, thus, make the athletic field a safer place for young athletes.