While a ruptured AAA is potentially catastrophic with extremely high mortality and morbidity, the natural history of AAA is fairly well understood.  As a result we know the optimal timing for watching vs. repairing AAA. Timing of surgery is based on the maximum diameter of the aneurysm. Based on several large randomized control trials (RCTs), surgery for AAA did not confer a benefit for patients with 4.5 cm (neither survival benefit nor reduced risk from rupture). Those studies did show a definite statistical benefit from surgical repair of AAA greater than 5.5 cm.

We counsel our patients that timing of AAA surgery is based on optimal risk. While we can’t guarantee that a patient will not have a rupture when their aneurysm is less than 5 cm, we can say that the risk of a rupture at that size is statistically low enough that it does not outweigh the risk of surgery. Conversely, if one thinks of elective AAA repair as an operation to prevent a possible rupture, then there must be a high enough possibility of such a rupture to justify the surgery. The RCT’s mentioned above confirmed that the diameter at which the possibility of rupture was high enough to justify surgery and thus confer a survival benefit was 5.5 cm.

Most surgeons now agree that 5 cm AAA in a relatively young active patient will likely reach the 5.5 cm threshold and therefore is a candidate for repair. Conversely a large aneurysm in an elderly patient with poor functional status may not be a candidate for repair because of the patient’s overall survivability: whether he or she is more likely to die from comorbidities or the chance of a ruptured AAA.