Subcatastrophic failure characteristics of the porcine descending aorta

Failure of internal arterial layers prior to overall catastrophic vessel failure has been clinically documented and has significant clinical implications. For example, intimal failure of the internal carotid artery was associated with extremely high rates of morbidity (40-80%) and mortality (up to 40%). However, failure of internal vessel layers prior to catastrophic vessel failure has been experimentally documented in a limited number of studies and the mechanical relationship between initial and ultimate vessel failure has not been systematically explored. In the present investigation, seven porcine descending aorta specimens were mechanically tested using a novel protocol to quantify failure of internal layers relative to overall vessel failure. The protocol consisted of opening the vessel at the mid-diameter level, mechanically distracting the vessel to failure under quasi-static loading, and imaging the event from intimal and adventitial sides using a high-speed, high-resolution digital imaging system. The internal layer failed prior to catastrophic vessel failure in all specimens. Adventitial (outer) layers remained intact until ultimate failure. Initial internal layer subfailures occurred at 88% of the strain to ultimate failure. The present results demonstrate internal layer susceptibility to subcatastrophic failure without overall failure of the vessel. Although the porcine descending aorta may not be particularly susceptible to distraction failure, this vessel may be a suitable model for human arterial tissue due to similarities in geometric size and vessel structure.