Defining Perioperative Mortality after Open and Endovascular Aortic Aneurysm Repair in the US Medicare Population

BACKGROUND: Perioperative mortality is reported after abdominal aortic aneurysm (AAA) repair, but there is no agreed upon standard definition. Often, 30-day mortality is reported because in-hospital mortality may be biased in favor of endovascular repair given the shorter length of stay. However, the duration of increased risk of death after aneurysm repair is unknown. STUDY DESIGN: We used propensity score modeling to create matched cohorts of US Medicare beneficiaries undergoing endovascular (n = 22,830) and open (n = 22,830) AAA repair from 2001 to 2004. We calculated perioperative mortality using several definitions including in-hospital, 30-day, and combined 30-day and in-hospital mortality. We determined the relative risk (RR) of death after open compared with endovascular repair as well as the absolute mortality difference. To define the duration of increased risk we calculated biweekly interval death rates for 12 months. RESULTS: In-hospital, 30-day, and combined 30-day and in-hospital mortality for open and endovascular repair were 4.6% versus 1.1%, 4.8% versus 1.6%, and 5.3% versus 1.7%, respectively. The absolute differences in mortality were similar, at 3.5%, 3.2%, and 3.7%. The RRs of death (95% confidence interval) were 4.2 (3.6 to 4.8), 3.1 (2.7 to 3.4), and 3.2 (2.8 to 3.5). Biweekly interval death rates were highest during the first month after endovascular repair (0.6%) and during the first 2.5 months (0.5% to 2.1%) after open repair. After 2.5 months, rates were similar for both repairs (<0.5%) and stabilized after 3 months. The 90-day mortality rates for open and endovascular repair were 7.0% and 3.2%, respectively. CONCLUSIONS: In-hospital mortality comparisons overestimate the benefit of endovascular repair compared with 30-day or combined 30-day and in-hospital mortality. The total mortality impact of AAA repair is not realized until 3 months after repair and the duration of highest mortality risk extends longer for open repair.