A ruptured abdominal aortic aneurysm (rAAA) is a life-threatening complication of an abdominal aortic aneurysm (AAA).
It's caused by the an inability of the abdominal aorta's already weakened and thinned wall to handle the stress incoming blood flow puts in under, causing the aortic wall to burst. Following aneurysm rupture, blood will leak outside of the aorta, into the abdominal cavity.
What are the risk factors for AAA rupture?
When the abdominal aorta, the largest blood vessel in the human body, develops a bulge or swelling due to a weakening of the wall, this is called an aneurysm. An abdominal aortic aneurysm often has no symptoms, and its rupture is a very serious complication.
Aside from the risk factors that cause AAA in the first place, the risk of a ruptured abdominal aortic aneurysm depends on several factors:
- The size of the aneurysm: An abdominal aortic aneurysm with a diameter measuring more than 4 cm is more likely to rupture.
- Aneurysm diameter growth rate: Faster than 0,5 cm in six months.
- Sex – women are three times more likely to have an abdominal aortic aneurysm rupture than men.
- High blood pressure.
- Continued smoking.
The numbers we’ve mentioned here are used as a threshold in aortic surgery. For example, although aneurysms smaller than 5.5 cm are statistically less likely to rupture, due to these differences, it is up to the surgeon to ultimately evaluate the risk of aneurysm rupture in each patient. The surgeon can then decide if surgical treatment is in order, by calculating the benefit vs risk ratio. It’s also important to mention that even small aneurysms in women are more likely to burst than in men.
Similarly, more collagen in the aortic wall leads to the aorta being less elastic, therefore further increasing the risk of rupture. Furthermore, the risk of abdominal aortic aneurysm rupture increases with the existence of inflammation and the presence of blood clots in the aorta. Therefore, it is very hard to predict the moment when the aortic wall is about to rupture.
What are the symptoms of an AAA rupture?
Abdominal aortic aneurysm rupture is most commonly presented in a classic triad of symptoms, seen in about one half of patients:
- Abdominal or back pain, which is sudden, sharp and severe.
- Hypotension (low blood pressure).
- Pulsatile mass in the abdomen.
Abdominal aortic aneurysm rupture is a medical emergency, in which the increasing loss of blood causes blood pressure to drop dramatically as a part of a reaction called a circulatory shock, or to be more precise – hypovolemic, or hemorrhagic shock.
During hypovolemic shock, your body first tries to compensate for blood loss by increasing your heart rate (manifested by a faster pulse), and divert circulation to your more important organs, such as the heart and the brain. This diversion causes the skin to be pale, cold and sweaty. As the blood loss continues, less blood will be reaching the lungs, therefore causing oxygen levels to drop in the remaining circulating blood. This reduced oxygen circulation also affects the brain, therefore causing confusion and disorientation, or even loss of conscience.
However, it’s important to mention that aortic aneurysm rupture can also exist in a chronic form, which happens if the rupture itself is small enough that a blood clot can seal it spontaneously.
How is a ruptured abdominal aorta diagnosed?
When talking about a patient in an unstable condition, the symptoms alone are enough to send the patient to surgery. Additionally, an ultrasound examination may confirm any doubts that the patient is facing an abdominal aortic aneurysm rupture.
Usually, a simple ultrasound exam, along with color duplex sonography methods, is enough to diagnose a ruptured aortic aneurysm. However, if the patient’s condition allows for a CT exam, it is a preferable method of choice, because the CT can visualize the aneurysm in more detail, allowing the medical team to see its exact shape, relation to other arteries, or other possible complications.
How is a ruptured abdominal aorta treated?
Due to the rapidly worsening of the patient’s state, when talking about treatment of a ruptured AAA, time is of the essence.
In patients with hemorrhagic shock, in order to normalize blood pressure, fresh-frozen plasma, along with platelets and erythrocyte concentration are administered, before sending the patient to the operating room. Just like in aortic repair surgery, two types of procedures are available – open surgery and endovascular aortic repair (EVAR).
Open surgery is done under general anesthesia, where after the incision, the surgeon cross-clamps the aorta in order to stop the blood flow, and finally inserting a prosthetic graft in place of the ruptured part of the aorta.
The Endovascular aortic repair (EVAR) procedure is a minimally invasive procedure, which involves inserting a stent-graft into the aorta in order to seal the ruptured part of the aorta.
The choice of treatment depends on the state of the patient, the availability of equipment (EVAR is an expensive procedure), and the preference of the surgeon. Because EVAR is a relatively new procedure, its superiority remains controversial, but according to available data, it seems to show a better overall survival in patients. Nevertheless, the survival rate of treated patients is still not optimistically high, due to complications such as bleeding and vascular complications.
Abdominal aortic aneurysm rupture is a catastrophic complication of AAA, with almost half of patients dying before reaching the hospital. Of those patients who are hospitalized, roughly one quarter doesn’t live long enough to undergo surgery, and almost 40 percent of people who are operated on don’t survive.