A novel model of blunt thoracic aortic injury: a mechanism confirmed?
BACKGROUND
There is no consensus on the mechanism of traumatic injury to the thoracic aorta and no reproducible animal model. Advances in injury scene analysis suggest that lateral and oblique force vectors cause aortic injury. We hypothesized that the spectrum of aortic injury could be reproduced in an animal model by application of an obliquely directed load to the pressurized aorta.


METHODS
Graded air impulses of 80, 100, 110, and 120 pounds per square inch (PSI) were delivered to the descending thoracic aorta of 19 swine with a novel pneumatic device. Aortic isthmus strain was recorded with microminiature probes. Gross and microscopic injury was recorded with digital photography.


RESULTS
The spectrum of human aortic injury was reproduced in this model. Deep injuries to the aortic media were common. The majority of injuries occurred within the region of the isthmus. Impulse pressure of 120 PSI caused transections, whereas lower impulse pressure resulted in less severe injuries. Aortic isthmus strain was greater in the animals exposed to 120 PSI than those receiving lower PSI (19.6 +/- 4.9% vs. 8.7 +/- 2.5%, p = 0.067).


CONCLUSIONS
Direct loading of the pressurized descending thoracic aorta causes isthmus injury secondary to aortic wall strain. Deep medial lesions are common and could propagate soon after injury to form pseudoaneurysms. A critical load is required to cause complete uncontained transection with exsanguination, which may have relevance to injury scene death.
Schmoker
Joseph D
JD
Department of Surgery, Division of Cardiothoracic Surgery, Fletcher Allen Health Care and the University of Vermont College of Medicine, Burlington, Vermont, USA. joseph.schmoker@vtmednet.org
Lee
Christopher H
CH
Taylor
Richard G
RG
Chung
Arnold
A
Trombley
Lucy
L
Hardin
Nicholas
N
Russell
Sheila R
SR
Howard
Alan
A
D000818:Animals; D001013:Aorta, Thoracic / Q000293:injuries* / Q000473:pathology; D001019:Aortic Rupture / Q000503:physiopathology*; D004195:Disease Models, Animal; D005260:Female; D007150:Immunohistochemistry; D015601:Injury Severity Score; D008297:Male; D011312:Pressure; D011336:Probability; D011897:Random Allocation; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D015996:Survival Rate; D013552:Swine; D013898:Thoracic Injuries / Q000401:mortality / Q000473:pathology* / Q000503:physiopathology; D017539:Tunica Intima / Q000473:pathology; D014949:Wounds, Nonpenetrating / Q000401:mortality / Q000473:pathology* / Q000503:physiopathology