According to the US Centers for Disease Control and Prevention, abdominal aortic aneurysms (AAAs) accounted for over 9,000 deaths in 2019. AAAs are a disease that preferentially affects men and smokers. While open surgery still has its place in the treatment of AAAs, the introduction of endovascular techniques in the 1980s has redefined the landscape of treating this potentially deadly disease.
Related: Advances in Abdominal Aortic Aneurysm Management: From Diagnosis to Treatment
Risk factors for abdominal aortic aneurysm
The development and causes of AAAs are still not fully understood. However, researchers have identified several factors that contribute to their formation. The main risk factors for developing AAAs include age, being male, and smoking. Family history and genetics also influence the likelihood of developing AAAs, as recent studies have linked specific gene variations to the development of AAAs. Additionally, people with genetic connective tissue disorders, like Ehlers-Danlos syndrome, are at higher risk.
The rate of enlargement of these aneurysms can vary significantly between individuals. However, experts observed that larger AAAs tend to expand at a faster pace. An expansion of more than 1 cm per year is often a warning sign. It may prompt medical professionals to consider elective repair for aneurysms smaller than 5.5 cm. Using growth as an indicator of rupture risk remains somewhat ambiguous.
Similarly, the risk of an aneurysm rupturing can differ dramatically from one individual to another. A recent meta-analysis identified that for every 0.5 cm increase in aneurysm diameter, the growth rate jumps by 0.5 mm per year. Likewise, the risk of rupture doubles.
Rupture risk for men and women
If an aneurysm is not monitored or treated, the risk of rupture becomes a serious concern. Factors such as older age, female sex, smoking, and elevated blood pressure have all been associated with a heightened risk of rupture in those with small AAAs. Women, in particular, face nearly four times the rupture risk compared to men. Current smokers are at double the risk of rupture compared to former smokers or non-smokers. Other factors that may contribute to rupture risk include peak stress on the AAA wall and rapid increases in the aneurysm’s size.
While there’s still much to uncover about AAAs, understanding these risk factors can empower individuals to take action and potentially reduce their risks.
Screening recommendations for abdominal aortic aneurysm
Guidelines advocate for one-time ultrasound screening for men aged 65 to 75 who have a history of smoking. Additionally, there are recommendations for earlier screenings in men with a family history of AAAs (starting as early as age 55). Screenings are recommended for women over 65 with a similar background or a history of tobacco use.
Once a provider identifies an AAA, the course of action hinges on its size as well as the risks of rupture and surgical mortality. Most detected aneurysms fall below the threshold warranting immediate surgery, 5.5 cm for men and 5.0 cm for women. For these smaller AAAs, accepted protocol includes regular ultrasound surveillance, as the risk of rupture remains negligible. However, reports show that compliance with surveillance recommendations is suboptimal, with adherence averaging only about 65%.
For those with AAAs measuring 5.5 cm or larger, refer to a vascular surgeon for surgical repair. This may be through open surgery or endovascular aneurysm repair (EVAR).
Screening tests for abdominal aortic aneurysm
When it comes to AAAs, early detection is essential. Since most AAAs develop without any obvious symptoms, they pose a significant risk of fatal rupture. Identifying effective screening strategies is essential for reducing mortality and negative health outcomes. A few key methods can detect these silent threats. These include:
- Ultrasound
- Computed tomography (CT)
- Magnetic resonance imaging (MRI)
Ultrasonography is a non-invasive and highly efficient way to detect AAAs. With sensitivity rates between 94% and 100% and specificity ranging from 98% to 100%, it has become the preferred method for many healthcare providers.
CT scans are another valuable tool. They are known for their accuracy and reproducibility with the ability to produce accurate measurements that are within 2 mm of the actual size. However, due to concerns about radiation exposure, CT scans are usually reserved for planning surgical interventions rather than as a first-line screening method.
MRI is becoming an important complement to traditional imaging methods for assessing AAAs. Advanced MRI techniques provide valuable insights into the pathophysiology of AAAs. Techniques may include:
- Superparamagnetic particles of iron oxide (SPIO) for contrast enhancement
- High-resolution black blood sequences
These techniques allow for precise measurement of AAA dimensions and detailed characterization of intraluminal thrombus composition. This information is crucial for effective risk stratification and ongoing disease monitoring.
Treatment approaches for AAA
Providers consider surgical repair for any aneurysm larger than 5.5 cm in men and 5.0 cm in women. Even aneurysms larger than 4.0 cm that show rapid growth can warrant immediate attention.
Open surgery has long been the traditional treatment, but since its introduction, EVAR has become increasingly utilized. Nowadays, 80% of intact AAA repairs and 52% of repairs for ruptured AAAs in the United States utilize this innovative technique.
In recent years, a trio of major randomized controlled trials has changed the conversation around elective abdominal aortic aneurysm repair. It compares the outcomes of traditional open surgical techniques with the less invasive endovascular aneurysm repair (EVAR). The findings are compelling and consistent. Patients undergoing EVAR experience significantly lower morbidity and mortality rates—ranging from 0.5% to 1.7%, compared to the 3.0% to 4.7% seen with open surgery. What’s more, recovery time is notably quicker. Medicare beneficiaries spending a median of just 2 days in the hospital after EVAR versus 7 days for open surgery.
However, this initial advantage tends to fade over time. For patients who survive beyond the first 2 to 3 years, the long-term survival rates between the two procedures appear strikingly similar. This trend continues even through 8 to 10 years of follow-up. While reintervention rates are higher for EVAR, largely owing to catheter-based follow-up procedures, the overall costs tend to be steeper compared to traditional surgery.
Choosing the right strategy
Choosing the right repair strategy for an abdominal aortic aneurysm comes down to shared decision-making between patient and physician. Factors like the patient’s anatomical suitability, operative risks, and commitment to lifelong follow-up imaging are pivotal in this choice. Each EVAR device has specific anatomical requirements for its use. Failure to follow these guidelines can lead to poorer outcomes. To catch potential complications—like endoleaks or the expansion of the aortic sac—lifelong follow-up imaging is typically recommended.
In summary, AAAs are a complex area within vascular medicine that continues to evolve. This is due to:
- Changes in patient demographics
- Advancements in understanding its underlying mechanisms
- Development of new diagnostic and treatment approaches
To effectively address the challenges associated with AAA management, healthcare providers are encouraged to adopt a comprehensive approach and keep up to date with the latest research. This proactive stance can lead to better patient outcomes and a decrease in the morbidity and mortality linked to this serious condition.
