Aortic aneurysm

An aneurysm is a balloon-like bulge in the wall of a blood vessel, usually in arteries. Aneurysms develop at weak points in the vessel wall and may be congenital or develop during life. They develop slowly usually without symptoms and grow about 4 mm per year.

Aneurysms are also hereditary. However, only a small proportion of aneurysms show a genetic predisposition and thus a familial clustering.

While the incidence of an aneurysm in the general population is about 2%, the risk of an aneurysm increases to 4% if a first-degree family member (father, mother, children, siblings) already has an aneurysm, and to 8% if two first-degree relatives have aneurysms.

When does an aneurysm rupture? How dangerous is an abdominal aortic aneurysm?

How do you know when the aorta bursts?

Aneurysms most commonly occur in the abdomen. An abdominal aortic aneurysm is a pathological irreversible dilatation of the abdominal aorta caused by destabilization of the artery wall. Dilations greater than 30 mm are considered pathologic. Usually, aortic aneurysms do not show any symptoms or discomfort. However, the abdominal aorta may burst at the site of the aneurysm if the dilation of the vessel wall exceeds a critical value. Once an aortic aneurysm has ruptured, internal hemorrhage and thus little chance of survival can be expected. Due to the massive blood loss, blood pressure drops rapidly. The patient suffers circulatory shock. The first sign of rupture is the onset of pain in the lower abdomen and back.

The abdominal aortic aneurysms can occur at any age, but they are rather rare. However, in the age group over 65 years, abdominal aortic aneurysm rupture is commonly listed as the tenth leading cause of death, and the incidence of abdominal aortic aneurysms is much higher in men than in women. Due to increasing life expectancy as well as statistical aging of the population, the number of cases is expected to increase.

The causes of abdominal aortic aneurysm are multifaceted. In addition to age and gender, these include smoking, high blood pressure, elevated blood lipids and genetic predisposition.

When does an abdominal aortic aneurysm require surgery?
Is it possible to live with an aneurysm?

First, there are different aortic aneurysm classifications:

• Aneurysm verum:True aneurysm, all three wall layers are dilated.
• Aneurysm spurium: False aneurysm, hemorrhage into surrounding tissue, merely feigns dilatation of the blood vessel.
• Aneurysm dissecans:Here, blood enters between the layers of the vessel and splits it open (dissects). If the aorta is affected, it is called aortic dissection.

Not all dilations of the abdominal aorta are dangerous. However, the risk of rupture increases exponentially as the diameter of the abdominal aortic aneurysm increases. If a large dilatation of the abdominal aorta is discovered, surgery is strongly recommended. According to current guidelines, elective surgical therapy is performed when the aneurysm is 50-55 mm in diameter in men and 45-50 mm in women. For the smaller abdominal aortic aneurysms, experts recommend regular check-ups to assess the growth rate of the aneurysm. Ruptured abdominal aortic aneurysms require immediate emergency care.

Can an aortic aneurysm regress?
What can be done about an aneurysm?

Once the aneurysm has formed, it cannot shrink on its own. Affected patients can try to prevent further growth: For the small aneurysms with a diameter of less than 45-50 mm, aortic aneurysm treatment is done with medication to lower blood pressure and cholesterol levels, as well as with lifestyle changes – for example, stopping smoking.

Diagnosis and therapy of aneurysms

How to detect an abdominal aortic aneurysm?
How can an aneurysm be prevented?

Most aneurysms are discovered by chance during an examination performed for another reason. A quick and inexpensive way to screen for abdominal aortic aneurysms is with an ultrasound examination. Since the beginning of 2018, it has been possible in Germany for men aged 65 and older with statutory health insurance to take advantage of a one-time ultrasound examination for the early detection of abdominal aortic aneurysm.

The diameter criterion provides only a rough estimate and is not very patient-specific. Therefore, other factors should additionally be included in the decision to intervene, such as the growth and morphology of the aortic aneurysm, lifestyle, and existing concomitant diseases. Furthermore, the indication for preventive aortic aneurysm surgery must take into account the patient’s life expectancy, desire for treatment, and risk of surgery. In addition, it must be noted that many large untreated abdominal aortic aneurysms often remain stable throughout life; however, in rare cases, smaller aneurysms may rupture unexpectedly.

Aortic aneurysm surgery risks and prognosis
How dangerous is surgery on the aorta?

If a decision is made in favor of surgical therapy for a diagnosed abdominal aortic aneurysm, the two options are conventional open surgery with a sutured prosthesis or endovascular aneurysm repair, in which a stent graft is inserted into the aneurysm. Both surgical procedures are complex, expensive, and can lead to serious complications, although minimally invasive endovascular treatment is now much more common.

Although endovascular interventions are very gentle for patients compared with conventional surgery, they have quite high complication rates. In the event of a complication, reintervention is usually necessary.

For these reasons, the approach of personalized medicine also plays a central role here. An individualized indication and the most reliable prognosis possible actually rupture of abdominal aortic aneurysms at risk is of paramount importance.

Outlook: Aortic aneurysm treatment with preoperative planning

The potentially highly relevant patient-specific variables influencing the risk of rupture, such as the morphology of the aneurysm and the properties of the arterial wall and intraluminal thrombus, can be taken into account with the help of mathematical modeling in medical simulation. Physics-based simulation models using patient-specific data enable a much more sophisticated approach to predicting individual aortic aneurysm rupture risk. The simulation environment can be integrated into an expert analysis system for clinical use, allowing predictive assessment and classification of abdominal aortic aneurysms with respect to patient-specific rupture risk, as well as supporting preoperative planning by patient-specific simulation of a procedure.

Together with the Technical University of Munich, Simq has started an R&D project to develop a medical software (Simq AAA) for risk assessment of abdominal aortic aneurysms.

Summary