Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Mao, Haojie

Abstract

Commotio cordis is the second leading cause of cardiac death in young athletes. This rare sudden-death mechanism most commonly affects young children playing baseball. It is caused by impacts to the chest during the repolarization phase of the cardiac cycle, which causes the heart to go into ventricular fibrillation, often leading to death. This study adopted the detailed and validated CHARM-10 child finite element model to replicate commotio cordis instances by simulating baseball impacts to the chest. New commotio cordis injury metrics were developed to create a more accurate prediction for chest protector effectiveness. The conventionally used injury metrics for chest protectors did not correlate strongly with left ventricle strain and pressure. This study also identified potentially vulnerable impact locations slightly lateral and above the heart that may be ignored by current commotio cordis safety regulations and commercially available baseball chest protectors.

Summary for Lay Audience

Commotio cordis is the result of a small object impacting the chest at speeds of approximately 40 mph during a vulnerable period of the cardiac cycle. In commotio cordis instances, the heart goes into ventricular fibrillation which means the heart stops pumping blood out to the body, often leading to death. These impacts typically come in the form of a baseball, lacrosse ball, or hockey puck, although it can happen in a more casual setting such as children playing around in the backyard. Commotio cordis most commonly occurs in youth males which can be explained by the abundance of males who play contact sports, as well as the weak and narrower chest walls found in children when compared to the chest walls of adults.

Currently, swine models dominate the commotio cordis research field as testing on live subjects and cadavers is not possible. Our research lab wanted to take a novel approach in analyzing commotio cordis; we used finite element modeling to replicate commotio cordis instances by simulating baseball impacts to the chest. Our study started by developing new injury metrics for commotio cordis, while also analyzing current injury metrics used by NOCSAE for chest protectors on the market today. We then identified vulnerable impact locations over the chest when considering commotio cordis. Our results from this study helped us to illustrate where future chest protectors should place protective material in order to reduce left ventricle strain and pressure, and as a result, mitigate commotio cordis in children. This thesis work finished with preliminary studies of a circular pad design in which we analyzed its ability to reduce strain and pressure in the left ventricle of the heart. We also identified preliminary results for alternative positions that youth baseball players can turn their bodies to prevent impacts over the chest if they are unable to catch the ball in time.

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