Sports Sciences Feature: Commotio Cordis
March 1, 2005
Michael A. Yorio, MD and Tom Maino, MD
Lacrosse is a high-speed sport that can lead to a number of different injuries, and most would be considered relatively minor. It is a contact sport with various impacts from body contact, stick checks, or the ball, which can travel at very high speeds. Thankfully, fatalities are very rare in lacrosse and sports. A recent tragedy in NCAA men's lacrosse has raised discussions regarding a traumatic cause of sudden death due to cardiac arrest, known as commotio cordis.
What is Commotio Cordis?
By definition, commotio cordis involves sudden cardiac death after a chest blow without physical damage to the heart. The blunt trauma to the chest is transmitted to the heart and disrupts the heart's electrical system. In some cases the impact seems relatively benign.
Studies on animals and data from human victims have determined that four factors influence the chance an impact will induce commotio cordis. Factors increasing the likelihood of commotio cordis include:
The timing of the impact is the most critical factor.
The actual number of cases of commotio cordis is unknown. According to the US Commotio Cordis Registry, which published their data in the Journal of the American Medical Association in 2002, there were 128 documented cases of commotio cordis as of September 2001. Since that time there have been a number of high profile cases reported in the news. The mean age of victims was 13.6 years (range was 3 months to 45 years). 88 percent of cases were younger than 18 years, and 95 percent of the victims were males. The softer chest wall of children is thought to make them particularly susceptible to commotio cordis.
The majority of cases documented during organized sports involved baseball or softball games. Sudden death after chest impact has also been seen in hockey, football, lacrosse, soccer, karate, cricket, and rugby. In sports with high-speed projectiles spectators or reserves on the sidelines or in the baseball dugout have also been hit and suffered sudden death. Most occur in young individuals and the vast majority of documented cases have been males. 28 percent of these victims were wearing commercial chest protectors (although only 30 percent of these involved a direct blow to the protector). 2.5 percent were using special baseballs designed to prevent commotio cordis. The non-sporting events included assaults and accidental blows. Several incidents involved impacts that would usually be considered trivial. A plastic baseball bat struck one child and the head of the family dog butted another. There have been murder and manslaughter prosecutions after cases of commotio cordis. These have involved child abuse, accidental blows to the chest and deliberate beatings.
Diagnosis and Treatment
Recognition of commotio cordis is critical. Any person who is struck in the chest and becomes unconscious should be evaluated immediately. Some commotio cordis victims may remain conscious for a few seconds after the blow, but the majority pass-out immediately.
However, not all arrhythmias respond to defibrillation. The majority of commotio cordis events in animal models produced ventricular fibrillation, and this rhythm can be returned to a normal rhythm with defibrillation. However, ventricular fibrillation is not the only arrhythmia seen in commotio cordis, and not all arrhythmias respond well to defibrillation.
The success in resuscitation of commotio cordis is estimated to be about 15 percent, but recovery seems to be linked to early defibrillation in animal models.
Prevention is the Best Treatment
The best treatment for commotio cordis is to prevent it from occurring. There are two ways that the incidence of an injury in sports can be reduced. The first is through the development of protective equipment. The second is through activity modification, which can be initiated by rule changes or coaching techniques.
The protective equipment must meet certain safety standards; it has to reduce the incidence of the injury it is intended to prevent without increasing the risk for other injuries. Having every lacrosse player wear chest protectors or changing the ball to a "softer" projectile may seem like good ideas, but a scientific approach to the development of safety equipment is critical to ensure risk reduction. There is some basic science evidence that safety baseballs may reduce the incidence of sudden death from chest wall impacts in low velocity sports (T-ball, little league baseball). But deaths have still occurred when the ball has been altered.
Protective equipment changes the way that an athlete plays the game. A chest protector on a defenseman or midfielder would likely lead to more players jumping in front of attackers in an attempt to block high speed shots, which could lead to more tragic events if the equipment does not significantly reduce the risk of commotio cordis. A review article by MS Link (2003) cited 3 lacrosse goalies, 2 baseball catchers, and 2 hockey goalies who were all wearing chest protection during a chest wall impact and sudden death occurred. In theory, a light weight shoulder pad or chest protector with a hard protective shell and a soft padding undersurface over the front of the chest would spread the force of an impact on the chest wall over a wider surface area, thus reducing amount of energy transmitted to the heart after a chest blow. This could reduce the risk of commotio cordis, but good scientific studies would be necessary before a claim like that can be made. Any safety equipment recommended must not effect the player's movement or the ability to pass and shoot with both hands.
The purpose of rule changes would hopefully reduce the amount of chest wall impacts that occur in lacrosse. A rule to discourage defenseman and midfielders from intentionally stepping in front of shooters as they shoot or penalizing shooters who shoot directly at a stationary defensive player could achieve the goal of lowering the risk of commotio cordis. Teaching proper defensive technique and positioning, instructing athletes to turn one's chest away from a shot, or training those in the line of a shot to bring their arms across their chest may also be helpful.
The sudden death of an athlete is always a shock to the individual's family, friends, teammates and community. Participants in sporting events are traditionally seen as the "healthiest of the healthy" portion of our society, and a tragedy affecting an athlete highlights all of our vulnerability. In commotio cordis a fairly benign chest wall impact can trigger sudden death, and at autopsy there are typically no significant abnormalities of the heart. Prompt diagnosis, CPR and defibrillation are critical, but resuscitation results have been disappointing. A number of preventative measures can be explored in lacrosse to reduce the incidence of this rare, but catastrophic event.
Chen RL, Penny DL, Greve G, Lab MJ. Stretch-induced regional mechanoelectric dispersion and arrhythmia in the right ventricle of anesthetized lambs. Am J Physiol Heart Circ Physiol. 2004 Mar; 286(3): H1108-14
Kohl P, Nesbitt AD, Cooper PJ, Ming L. Sudden cardiac death by commotio cordis: role of mechanoelectric feedback. Cardiovasc Res. 2001 May; 50(2):280-9
Link MS. Mechanically induced sudden death in chest wall impact (commotio cordis). Prog Biophysics & Molecular Bio. 2003; 82: 175-86
Link MS, Maron BJ, Wang PJ, et al. Reduced risk of sudden death from chest wall blows (commotio cordis) with safety baseballs. Pediatrics. 2002; 109: 873-77
Maron BJ, Gohman TE, Kyle SB, Estes NA 3rd, Link MS. Clinical profile and spectrum of commotio cordis. JAMA. 2002 Mar 6; 287(9):1142-6
Maron BJ, Mitten MJ, Greene-Burnett C. Criminal consequences of commotio cordis. Am J Cardiol. 2002 Jan 15;89(2):210-3