Sudden death in sports impacts, mechanism, prevention and treatment.

Principal Investigator: Mark S. Link, M.D.

Institution: The New England Medical Center Hospital

Title: Sudden death in sports impacts, mechanism, prevention and treatment.

Abstract: Sudden death due to minor chest wall trauma, commotio cordis, is increasingly reported in young athletes aged 3 to 18. We have recently developed a swine model of this entity using low energy chest wall impact gated tot he cardiac cycle. With this model we have found that if a baseball impact occurs during a 20-millisecond window on the up-slope of the T-wave, ventricular fibrillation (VF) can result. We have also evaluated other variables including energy (velocity) and site of impact. We have also used this model to demonstrate that safety baseballs (softer than standard baseballs) decrease the risk of commotio cordis. Whether and what type of chest wall devices will protect youths from commotio cordis is not known.

Over the next two years, our aim is to evaluate the influence of the animal’s size, weight, and chest wall compliance in the risk of developing VF after chest wall impact. Based on data from this experiment, we will use this model to evaluate commercially available chest wall protectors to prevent or lower the risk of sudden death with chest wall impact. Furthermore, we will ascertain the sensitivity and specificity of automated external defibrillators (AEDs) in the recognition of VF in animals weighing from 10 to 50kgs, data that will be important in the ongoing debate about arrhythmia recognition by AEDs in the pediatric population.

Domesticated anesthetized swine 4 to 15 weeks old are used in our study. Millarâ mikrotip pressure catheters are inserted into the left ventricle, right atrium and esophagus for pressure monitoring. Animals are placed in a sling to approximate physiologic anatomy and cardiac hemodynamics. Animals will be grouped in 10kg increments from 10 to 50kg. Chest wall compliance will be assessed with well-established techniques prior to impact. Chest impacts will be given at velocities of 30, 40, 50 and 60mph. Variables collected will include the incidence of VF, ST elevation, heart block and the acute intra thoracic and intra cardiac pressure rises. Defibrillation will be accomplished with an AED utilizing the commercially available marketed algorithm. Using our model we propose to compare 5 different commercially available chest wall protectors. Protective chest devices will be placed on the chest wall directly over the center of the left ventricle, and impacts will be given at escalating velocities beginning at 30mph impacts.

With this study we will more fully understand the mechanism, prevention and treatment of commotio cordis. The knowledge gained will add to our understanding of not only commotio cordis, but also of ventricular fibrillation in other conditions. Finally, we hope to ascertain whether AEDs may be appropriate for use in the pediatric population. This study will add much needed public health information regarding the utility of chest wall protectors and AEDs in pediatric sports.