Commotio Cordis- Can it be Prevented?
ABSTRACT & COMMENTARY
Synopsis: Relatively low-energy anterior chest impact can produce life-threatening arrhythmias if the effect is delivered at precise points during the cardiac cycle.
Source: Link MS, et al. N Engl J Med 1998;338: 1805-1811.
Commotio cordis is the name given to the syndrome of sudden death in young sports participants who are struck in the chest and then collapse. Although few victims have survived, when electrocardiograms have been obtained, either ventricular fibrillation, heart block, or idioventricular rhythms have been documented. In this paper, Link and colleagues describe an animal model of commotio cordis. They studied young domesticated pigs weighing between 8 and 12 kg. The animals were struck on the anterior chest wall with a wooden object similar in size, shape, and weight to a regulation baseball. The timing of the impact was carefully controlled so that it could be delivered at precise points during the electrocardiographic cycle. Myocardial perfusion images were obtained using technetium-99m sestamibi both before and after the chest blows. After an initial series of tests, repeat experiments using baseballs with four degrees of hardness were used. The wooden object and the baseballs struck the chest perpendicularly directly over the left ventricle at a velocity of 30 mph.
Chest wall impact produced ventricular fibrillation when delivered in the time period of 30 to 15 msec before the peak of the T wave. Nine of 10 blows delivered during this 15 msec window produced ventricular fibrillation. When impacts were delivered during the QRS complex, transient complete block was observed in four of 10 animals. In these animals, when sinus rhythm returned, ST segment elevation and left bundle branch block were noted.
Coronary angiography immediately after impact in 14 animals showed no abnormalities. However, myocardial perfusion defects after impact were noted in three of 12 animals studied. Nine of the 19 impacts that resulted in either ventricular fibrillation or ST segment elevation resulted in apical or septal hypokinesis on left ventriculography. Pathologic and histologic examination revealed mild hyperemia of the myocardium in all animals and moderate degrees of hemorrhage in the anterior left ventricle in three of 18. One animal had marked hemorrhage in the region of the atrial ventricular bundle and proximal His Purkinje system.
When the baseballs with various hardness were tested, there was a significant reduction in the prevalence of ventricular fibrillation after impact with the softest balls.
Link et al conclude that relatively low-energy anterior chest impact can produce life-threatening arrhythmias if the impact is delivered at precise points during the cardiac cycle. The timing of the impact determines the type of arrhythmia that is initiated. Athletic equipment that would cushion the impact received from a blow to the chest seems to be protective.
COMMENT BY JOHN P. DiMARCO, MD, PhD
Commotio cordis is usually considered rare, but cardiologists may be aware of one or two cases in their community in which a young individual dies suddenly after receiving some type of impact to the chest. Although this scenario has most commonly been reported in individuals who are struck by a baseball, similar sudden deaths have occurred during football, hockey, fist fights, and other sports activities. Often, there is not an unusually severe injury, and, prior to this paper, the mechanism for sudden death was unexplained. This interesting paper by Link et al gives us a plausible mechanism for sudden death in these individuals by showing that, at least in young swine, timed chest wall impact can produce truly life-threatening arrhythmias.
In their experiments, Link et al were able to produce life-threatening arrhythmias with a high frequency. Commotio cordis is a relatively rare clinical event, and its low incidence in humans is probably not explained just by the narrow timing window required for arrhythmia after a blow to the chest. Certainly, thousands, if not millions, of episodes of low-impact chest wall trauma must occur for every case of sudden death. Differences between young swine and humans may explain this difference. Swine are often used in animal experiments of fibrillation, cardiac arrest, and defibrillation. The pig has an unusual electrocardiogram and, frequently, has a long QT interval. Therefore, they are relatively easy to fibrillate and also fairly easy to maintain in fibrillation. Healthy humans are more difficult to fibrillate and, frequently, will spontaneously convert after only a few beats of polymorphic ventricular tachycardia. The animals used in these experiments were also small, weighing only 8-12 kg, and it is likely that a 30 mph impact with a baseball produces a greater shock to the heart than would be seen even in a child. It is likely, however, that the same basic mechanism is responsible for the rare deaths that have been clinically described. However, we should wonder whether there are also individual factors that predispose to these arrhythmias or whether everyone is potentially susceptible to this type of response to chest wall impact.
The data in this paper suggest that use of softer baseballs would decrease the risk of death from chest wall impacts. Particularly for very young individuals, the use of softer baseballs may be reasonable. However, more data about the prevalence of commotio cordis in the general population will be needed before more extensive changes in sports and sporting equipment can be justified.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content