Who Should We Operate On and How Do We Decide: Predicting Rupture and Survival in Patients with Aortic Aneurysm

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The decision to operate on a patient with an aortic aneurysm is based on the risk of aneurysm rupture versus the risk of aneurysm repair, within the context of the patient’s overall life expectancy. Risk of rupture is still primarily based on the maximum aneurysm diameter, with some allowances made for factors that modify rupture risk, such as gender and current smoking. Newer methods for determining rupture risk, such as aneurysm-wall stress analysis, appear promising, but are not yet broadly available. Until then, diameter-based prediction rules for rupture risk will “fail” 10% to 25% of patients with both small and large abdominal aortic aneurysms. With regard to predicting operative mortality and life expectancy after open or endovascular aneurysm repair, multiple risk-stratification algorithms have been created. The best of these algorithms are accurate in 75% to 80% of patients, meaning that they fail in 20% to 25% of cases. Prediction algorithms provide significant guidance, but cannot take the place of an experienced clinician at this point. Somehow, experienced surgeons are able to sift through a massive amount of information and properly select patients who are appropriate for surgery, with quite reasonable perioperative and long-term mortality rates.

Section snippets

Rupture Risk

For the past five decades, the primary determinant of rupture risk has been maximum aneurysm diameter, based on the work of Szilagyi et al in the 1960s.1 These authors compared the outcomes of small-diameter and large-diameter aneurysms, and found that patients with larger aneurysms (>6 cm) were much more likely to die of a ruptured aneurysm. In that era, the diameter had to be determined by physical exam and abdominal x-ray, which are both now known to overestimate the actual diameter, such

Operative Risk

Operative mortality is the most widely reported of all aneurysm-related variables. A literature review by Blankensteijn et al21 found that population-based studies reported mortality rates as high as 8% (prospective), and as a whole are significantly higher than single-center reports averaging 3.8%. A review by Hallin et al22 found a weighted operative mortality for elective open AAA repair of 5%, which is consistent with the UK SAT of 5.6%,23 US hospital discharge data (5.6% for a review of

Life Expectancy

Of the three factors determining who should have an aneurysm repair, life expectancy is perhaps the most difficult to have a “feel” for, but nonetheless critical to determining whether the patient will benefit from repair. One of the difficulties of determining life expectancy is that it is not a simple linear function. A typical 60-year-old surviving AAA repair has a 13-year life expectancy, but a 70-year-old surviving a AAA repair has a 10-year life expectancy, and an 80-year-old has a 6-year

Putting the Factors Together: Simple, Right?

So how do we “operationalize” the concept that intervention for an AAA is appropriate when the cumulative risk of rupture exceeds the risk of repair, within the context of patient life expectancy? Of course, this is often not a simple matter, but it is not always difficult, either. For a young, healthy patient with a large aneurysm, the recommendation for intervention is a relatively easy decision. In healthy patients with aneurysms <5.5 cm in diameter, and in high surgical risk patients with

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