Commotio cordis

Image:Heart-thorax-gray.gif Commotio cordis (from Latinheart commotion, also called myocardial contusion) is a sudden and unexpected cardiac arrestobserved mostly in young people during participation in sports. It occurs as the result of a blunt, apparently innocuous, non-penetrating traumato the precordial region, due to the strong impact of a ball, a bator other projectile. The impact is transmitted to the heart muscle, and depending on the precise timing in relation to the cardiac cycle, it will disrupt the heart's electrical conduction system, causing an arrhythmia, such as ventricular fibrillation. Pre-existing conditions, such as undetected electrical or structural abnormalities in the heartof these individuals, may render them more vulnerable thus exacerbating any potential injury. The phenomenon was confirmed experimentally in 1932, with research in large rabbits.

Incidence

Commotio cordis is a very rare event, but nonetheless it is the second leading cause of sudden death in young athletes, predominantly male. Some of the sports which have a risk for this cause of trauma are baseball, soccer, ice hockey, polo, rugby, cricket, softball, pelota, fencing, lacrosse, boxing, karate, kung fuand other martial arts. Childrenare especially vulnerable due to their more fragile thoracic skeleton. The USACommotio Cordis Registry had more than 130 cases recorded by September 2001, with most of the cases occurring in Little Leaguebaseball, lacrosse and softball. The real number of cases may be much larger.

Other situations

Commotio cordis may occur also in other situations, such as in children who are punished with blows over the precordium, cases of torture, frontal collisions of motor vehicles(the impact of the direction wheel against the thorax, although this has decreased substantially with the use of safety beltsand air bags).

Cases of commotio cordis have been recorded in people who were shot by firearmsover the precordium and were using body armour(Cannon, 2001), thus stopping the bullet but causing a high energy mechanical impact to the thorax (the so-called Behind Armour Blunt Traumaor BABT); or after being hit by non-lethal crowd controlfirearm shots using rubber bulletsor plastic bullets(Hiss et al., 1997).

The precordial thump(hard blows given over the precordium with a closed fist in order to revert cardiac arrest) is very dangerous and controversial, and may cause the opposite effect, i.e., a commotio cordis, when given by unskilled or untrained personnel, or with the wrong indication. A recent study showed that large discrepancies in the clinical usefulness and incidence of adverse effectsof the precordial thump may be attributed to the extent of trainingalone (Kohl, 2005).

Mechanism of injury

Image:Commotio-cordis-ecg.jpg

The following factors increase the chance of commotio cordis:

• Direction of impact over the precordium (precise area, angle of impact)
• Total applied energy (area of impact versus energy, i.e., speed of the projectile multiplied by its mass)
• Impact occurring within a specific 10-30 millisecond portion of the cardiac cycle. This period occurs in the ascending phase of the T wave, when the left ventricle mass is repolarizing in the diastole(relaxation).

The small window of vulnerability explains why it is a rare event. Considering that the total cardiac cycle has a duration of 1000 milliseconds (for a base cardiac frequency of 60 beats per minute), the probability of a mechanical trauma within the window of vulnerability is 1 to 3% only. That explains also why the heart becomes more vulnerable when it is physically strained by sports activities:

1. The increase in heart frequency (exercise tachycardia) may double the probability above (e.g., with 120 beats per minute the cardiac cycle shortens to 500 milliseconds without fundamentally altering the windows of vulnerability size);
2. Relative exercise-induced hypoxiaand acceleration of the excito-conductive system of the heart make it more susceptible to stretch-induced ventricular fibrillation.

The cellularmechanisms of commotio cordis are still poorly understood.

It is estimated that an impact with an energy of 50 joulesis sufficient to cause cardiac arrest when applied in the right time and spot of the precordium of an adult. Impacts of up to 130 joules have already been measured with hockey pucksand lacrosse balls, 450 joules in karate punches and an incredible 1028 joules in boxer Rocky Marciano's punch [1]. The 50 joules threshold, however, can be considerably lowered when the victim's heart is under ischemicconditions, such as in coronary arteryinsufficiency (Kohl, 2005).

Outcome and treatment

Fulminantdeath is the most common outcome, because cardiopulmonary resuscitationrequires quick action by a specialized medical team, using a defibrillatorand cardioactive drugs, and these are rarely on hand in sports arenas. Due to the significant danger to children (death by commotio cordis is the first cause of fatalities in youth baseball in the US, with 2 to 3 deaths per year, Abrunzo, 1991), it has been recommended that "communities and schooldistricts reexamine the need for accessible automatic defibrillators and cardiopulmonary resuscitation-trained coachesat organized sporting events for children." (Salib et al., 2005).

Prevention

Image:Sports-dress-codes.jpg

The mandatory use of heavily padded special vests in front of the thorax is generally sufficient to prevent high energy impacts to the precordium. The problem with many sports such as soccer, baseball and karate is that, despite the danger posed by a multitude of punches, kicks, pads, mallets, bats, pucks and balls moving at high speeds, etc., their dress codesrepresent an obstacle to the use of mechanical protection to the precordium for all players, or at least for goalkeepers, batters, ball catchers, etc. For example, boxing traditionally requires a naked chest, cricket gear protects the legs but not the chest, and soccer has practically no protection gear at all; although the ball weights 450 grams, may reach speeds of 30 meters per second [2], and barrier defenses actually encourage the reception of the ball against the chest.

Parents of children active in these sports are advised to adopt simple protective measures, particularly in informal "backyard" games, which are often much more dangerous than formal ones, which require some protection.

Legal issues

Several people have been convicted of involuntary manslaughterin cases involving insufficient and slow medical help to athletes who underwent commotio cordis during sports events (Maron et al., 2002), as well as in cases of intentional delivery of contusive blows. In one such case, a man was sentenced to 18 years of prison for killing his own son with a blow to the chest.

References

• Abrunzo TJ. Commotio cordis. The single, most common cause of traumatic death in youth baseball. Am J Dis Child. 1991 Nov;145(11):1279-82. Review. PMID 1951221
• Cannon L. Behind armour blunt trauma--an emerging problem. J R Army Med Corps. 2001 Feb;147(1):87-96. Review. PMID 11307682
• Geddes LA, Roeder RA. Evolution of our knowledge of sudden death due to commotio cordis. Am J Emerg Med. 2005 Jan;23(1):67-75. Review. PMID 15672341
• Hiss J, Hellman FN, Kahana T. Rubber and plastic ammunition lethal injuries: the Israeli experience. Med Sci Law. 1997 Apr;37(2):139-44. PMID 9149508
• Kohl P, Sachs F & Franz M (eds): Cardiac Mechano-Electric Feedback and Arrhythmias: from Pipette to Patient. Elsevier (Saunders), Philadelphia 2005.
• Kohl P, Nesbitt AD, Cooper PJ, Lei M. Sudden cardiac death by Commotio cordis: role of mechano-electric feedback. Cardiovasc Res. 2001 May;50(2):280-9. Review. PMID 11334832
• Maron BJ, Mitten MJ, Greene Burnett C. Criminal consequences of commotio cordis. Am J Cardiol. 2002 Jan 15;89(2):210-3. Review. PMID 11792344
• Salib EA, Cyran SE, Cilley RE, Maron BJ, Thomas NJ. Efficacy of bystander cardiopulmonary resuscitation and out-of-hospital automated external defibrillation as life-saving therapy in commotio cordis. J Pediatr. 2005 Dec;147(6):863-6. Review. PMID 16356450

External links

• Yabek, S.M. Commotio cordis. eMedicine, September 2005.
• Sports Sciences Feature: Commotio Cordis: Sudden death following chest wall trauma. ACC.
• Mechanical effects on heart rhythm: from commotio cordis to pre-cordial thump. PowerPoint slides, by P. Kohl. Sept. 2005 (n PDF).

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Commotio+cordis Wikipedia article Commotio cordis.