Aortic Morphologic Changes During Lethal Hemorrhage Characterized by Intravascular Ultrasound

Noncompressible torso hemorrhage is the leading cause of potentially survivable battlefield death. In far-forward environments, rapid localization of aortic injury is limited by lack of fluoroscopy and advanced imaging. Intravascular ultrasound (IVUS) may enable identification of arterial injury and support targeted endovascular hemorrhage control, but quantitative physiologic data are needed to guide its use and inform development of realistic hemorrhage simulation models.

Twenty Yorkshire-Landrace swine (70-90 kg) underwent supraceliac aortic arteriotomy to induce lethal hemorrhage. IVUS pullbacks (0.018-inch and 0.035-inch systems) were performed preinjury and postinjury to measure aortic diameter and cross-sectional area (CSA). Continuous hemodynamic data, including mean arterial pressure (MAP), heart rate, and hemorrhage flow, were recorded throughout exsanguination.

Eighteen animals had analyzable IVUS measurements. No significant differences were observed between IVUS platforms in preinjury or postinjury diameter or CSA (all P > 0.30). Mean aortic diameter decreased from 13.3 ± 1.8 mm to 11.0 ± 1.2 mm, and CSA decreased from 142 ± 37.2 mm² to 95.8 ± 20.4 mm², representing reductions of 16.4% and 28.7%, respectively (both P < 0.001). Mean time to cardiovascular collapse was 12.2 ± 5.2 min. Hemorrhage demonstrated a reproducible triphasic flow pattern. Mixed-effects modeling showed a strong linear association between MAP and CSA (β = 0.747 mm²/mmHg, P < 0.001).

IVUS reliably detects aortic collapse during uncontrolled hemorrhage and demonstrates a quantifiable MAP-dependent relationship between vascular caliber and shock progression. These data provide essential parameters for hemorrhage interpretation and development of biomimetic noncompressible torso hemorrhage simulation models.