Traumatic aortic rupture
|Traumatic aortic rupture|
The aorta, shown in red
|Classification and external resources|
Traumatic aortic rupture, also called traumatic aortic disruption or transection, is a condition in which the aorta, the largest artery in the body, is torn or ruptured. The condition is frequently fatal due to the profuse bleeding that results from the rupture. Since the aorta branches directly from the heart to supply blood to the rest of the body, the pressure within it is very great, and blood may be pumped out of a tear in the blood vessel very rapidly. This can quickly result in shock and death. Thus traumatic aortic rupture is a common killer of victims of automotive accidents and other traumas, with up to 18% of deaths that occur in automobile collisions being related to the injury. In fact, aortic disruption due to blunt chest trauma is the second leading cause of injury death behind traumatic brain injury.
The injury is usually caused by high speed impacts such as those that occur in vehicle collisions and serious falls. It may be due to different rates of deceleration of the heart and the aorta, which is in a fixed position.
Location of rupture
By far the most common site for tearing in traumatic aortic rupture is the proximal descending aorta, near where the left subclavian artery branches off from the aorta. The tethering of the aorta by the ligamentum arteriosum makes the site prone to shearing forces during sudden deceleration. An angiogram will often show an irregular outpouching beyond the takeoff of the left subclavian artery at the aortic isthmus, representing an aortic pseudoaneurysm caused by the trauma.
The condition is difficult to detect and may go unnoticed, because many patients have no specific symptoms. Diagnosis is further complicated by the fact that many patients with the injury experienced multiple other serious injuries as well, so the attention of hospital staff may be distracted from the possibility of aortic rupture.
The preferred method of diagnosis is CT angiogram. Though not completely reliable, chest X-rays are initially used to diagnose this condition when the patient is unstable and cannot be sent to the CT bay.
The classical findings on a chest x ray will be widened mediastinum, apical cap, and displacement of the trachea, left main bronchus, or nasogastric tube. A normal chest x-ray does not exclude transection, but will diagnose conditions such as pneumothorax or hydrothorax. The aorta may also be torn at the point where it is connected to the heart. The aorta may be completely torn away from the heart, but patients with such injuries rarely survive very long after the injury; thus it is much more common for hospital staff to treat patients with partially torn aortas. When the aorta is partially torn, it may form a "pseudoaneurysm". In patients who do live long enough to be seen in a hospital, a majority have only a partially torn blood vessel, with the outermost adventitial layer still intact. In some of these patients, the adventitia and nearby structures within the chest may serve to prevent severe bleeding. After trauma, the aorta can be assessed by a CT angiogram or a direct angiogram, in which contrast is introduced into the aorta via a catheter.
Traumatic aortic rupture is treated with surgery. However, morbidity and mortality rates for surgical repair of the aorta for this condition are among the highest of any cardiovascular surgery. For example, surgery is associated with a high rate of paraplegia, because the spinal cord is very sensitive to ischemia (lack of blood supply), and the nerve tissue can be damaged or killed by the interruption of the blood supply during surgery.
Since high blood pressure could exacerbate the tear in the aorta or even separate it completely from the heart, which would almost inevitably kill the patient, hospital staff take measures to keep the blood pressure low. Such measures include giving pain medication, keeping the patient calm, and avoiding procedures that could cause gagging or vomiting.
Death occurs immediately after traumatic rupture of the thoracic aorta 75%–90% of the time since bleeding is so severe, and 80–85% of patients die before arriving at a hospital. Though there is a concern that a small, stable tear in the aorta could enlarge and cause complete rupture of the aorta and heavy bleeding, this may be less common than previously believed as long as the patient's blood pressure does not get too high.
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