Multiple subfailures characterize blunt aortic injury

BACKGROUND: Blunt aortic injuries result from rapid deceleration of the thorax as may occur during automotive impacts and falls from extreme heights. Pathological findings can range from failure of specific vessel layers to immediate vessel wall rupture. The purpose of this investigation was to determine the sequence of local structural events that may lead to aortic wall disruption. METHODS: Fourteen porcine aorta specimens were opened to expose the intima and longitudinally distracted until rupture. Longitudinal mechanics were quantified and subfailures were identified. Histology was used to examine internal layer subfailure. RESULTS: Videography demonstrated that subfailures propagated into complete vessel wall rupture. Subfailures occurred before complete vessel rupture in 93% of specimens. Intimal and medial subfailures were present at 74% of the stress and 82% of the strain to rupture. Multiple subfailures were evident in 79% of specimens. CONCLUSION: Present results supported the clinical theory that nonimmediate death as a result of blunt aortic injury is commonly caused by propagation of lesser lesions, initiating on the intimal layer, into complete vessel rupture including the adventitial layer. This finding, along with histologic evidence of subfailure pathological findings, confirms the presence of an acute window during which recognition and initiation of permissive hypotension may be lifesaving.