Blunt traumatic aortic injury

A problem presented at the UK MMSG Nottingham 2000.

Presented by:
Dr Mike Neale (Transport Research Laboratory, Crowthorne)
SJ Chapman, PD Howell, OE Jensen, JR King, M Neale, TJ Pedley, DS Riley, FT Smith, MJ Tindall

Problem Description

Blunt traumatic aortic injury (BTAI) occurs in severe vehicular impacts and is associated with a tearing of the aorta wall. In road traffic accidents, the tear tends to occur near the isthmus of the aorta, which is a slight narrowing as it begins its descent. The basic characteristics of the injury are remarkably consistent and yet the fundamental mechanism by which it occurs is not well understood. The injury is often fatal and many victims do not obviously exhibit signs of other serious injury. TRL in interested in building a finite element model of the aorta and surrounding structures (heart, spine and other main arteries), with the ultimate aim of simulating the conditions leading to rupture.

Among the rupture mechanisms that have been previously proposed are stretching or the aorta, a rise in blood pressure within the aorta, shear forces in the aorta, and pinching of the aorta against the surrounding structure, especially the spine. In order to make progress, it is important to understand the interplay between

Study Group Report

Blunt Traumatic Aortic Injury (BTAI) refers to tearing of the wall of the aorta, a serious, often fatal, injury that occurs during severe automobile collisions. BTAI is one of the most common causes of death in road traffic accidents, and may be occur in other impacts, such as in fall victims. One of the most hotly debated questions is whether some kind of impact (e.g. of a steering wheel with the chest cavity) is required to cause BTAI, or whether a sharp deceleration will suffice.

During the week of the study group, a number of fluid dynamical and mechanical models, which may lend valuable insight into the causes of BTAI, were considered. Whilst fluid dynamical models of BTAI already exist in the literature, these have incorporated some effects, such as shocks, but have neglected others, such as the curvature of the aorta and swirling effects caused by turbulent fluid flow.

Dimensional analysis involving key parameters associated with the problem, such as blood velocity and the effects of deceleration over a short distance, showed that fluid dynamical effects may not be enough to cause rupturing of the aorta. Indeed, more likely scenarios include the effects of shearing, stretching and bending of the aorta. However, fluid dynamical effects could not be completely discounted.

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