Rupture rates of untreated large abdominal aortic aneurysms in patients unfit for elective repair

Background: Elective abdominal aortic aneurysm (AAA) surgery relies on balancing the risk of the intervention against the risk of the aneurysm causing death. Although much is known about intervention at 5.5 cm, little is known about the fate of the patient unfit for elective surgery at this threshold. Medical therapy and endovascular surgery have revolutionized management of aortic aneurysms in the last 20 years and are thought to have affected rupture rates. Methods: MEDLINE via PubMed, EMBASE, and the Cochrane Library Database were searched for studies reporting follow-up of untreated large AAA approach from inception to January 2014. Data were pooled using random-effects analysis with standardized mean differences and 95% confidence intervals (CIs) reported. The primary end points were rupture rates and all-cause mortality per year by AAA size. Results: The search strategy identified 1892 citations, of which 11 studies comprising 1514 patients experiencing 347 ruptured AAA were included. The overall incidence of ruptured AAA in patients with AAA >5.5 cm was 5.3% (95% CI, 3.1%-7.5%) per year. This represented cumulative yearly rupture rates of 3.5% (95% CI, -1.6% to 8.7%) in AAAs 5.5 to 6.0 cm, 4.1% (95% CI, -0.7% to 9.0%) in AAAs 6.1 to 7.0 cm, and 6.3% (95% CI, -1.8% to 14.3%) in AAAs >7.0 cm. There was no heterogeneity between studies (I-2 = 0%). Only 32% of these patients were offered repair on rupturing an AAA, with a perioperative mortality of 58% (95% CI, 32%-83%). The risk of death from causes other than AAA was higher than the risk of death from rupture. Conclusions: Rupture rates of untreated AAA were lower than those currently quoted in the literature. Non-AAA-related mortality in this group of patients is high.