Upper and lower limits of vulnerability to sudden arrhythmic death with chest-wall impact (commotio cordis).

OBJECTIVES: In an animal model of commotio cordis, sudden death with chest-wall impact, we sought to systematically evaluate the importance of impact velocity in the generation of ventricular fibrillation (VF) with baseball chest-wall impact.

BACKGROUND: Sudden cardiac death can occur with chest-wall blows in recreational and competitive sports (commotio cordis). Analyses of clinical events suggest that the energy of impact is often not of unusual force, although this has been difficult to quantify.

METHODS: Juvenile swine (8 to 25 kg) were anesthetized, placed prone in a sling to receive chest-wall strikes during the vulnerable time window during repolarization for initiation of VF with a baseball propelled at 20 to 70 mph.

RESULTS: Impacts at 20 mph did not induce VF; incidence of VF increased incrementally from 7% with 25 mph impacts, to 68% with chest impact at 40 mph, and then diminished at >/=50 mph (p < 0.0001). Peak left ventricular pressure generated by the chest blow was related to the incidence of VF in a similar Gaussian relationship (p < 0.0001).

CONCLUSIONS: The energy of impact is an important variable in the generation of VF with chest-wall impacts. Impacts at 40 mph were more likely to produce VF than impacts with greater or lesser velocities, suggesting that the predilection for commotio cordis is related in a complex manner to the precise velocity of chest-wall impact.