Is There a Selection Bias in Applying Endovascular Aneurysm Repair for Rupture?

Accumulating data suggest that endovascular repair (EVAR) of ruptured abdominal aortic aneurysms (RAAAs) leads to reduced mortality, but concern exists that this may reflect selection bias. We reviewed our overall rupture experience early after our protocol was instituted to explore this question. We instituted a defined protocol for RAAA with emphasis on EVAR in July 2002, which included device availability (consignment), preoperative training, 24-hr access to our surgical endosuite and ability to operate imaging in an emergency, and immediate availability of a transbrachial balloon cutdown cart for all cases. Charts of all RAAA patients who arrived in the operating room alive since institution of our protocol were reviewed. Computed tomographic (CT) scans were re-reviewed to assess potentially suitable anatomic candidates. From July 2002 to May 2006, a total of 52 RAAAs were treated at our institution: 15 pararenal RAAAs, all treated by open repair (PR-OPEN), and 37 infrarenal RAAAs, 20 treated by open repair (IR-OPEN) and 17 treated by EVAR (IR-EVAR, 32% of all ruptures). Mortality rates in the three groups were 47%, 75%, and 35% (p < 0.02 vs. IR-OPEN), respectively. Although mortality was significantly lower in the EVAR group, overall mortality was 53% (28/52). On re-review of the operative notes and CT scans, it is estimated that more than half of those cases repaired using open techniques could have been repaired using EVAR based on anatomic criteria alone. The most common reason for open repair was hemodynamic instability preoperatively; only a minority of cases were excluded from EVAR based on unfavorable anatomy after CT scan review in the emergency room. In conclusion, during our early experience EVAR for rupture was associated with significantly reduced mortality. However, our overall mortality was no different from historical values, and this fact along with the extremely high mortality seen in the IR-OPEN group suggest that we are simply selecting patients with the greatest chance of survival to undergo EVAR. It also appears that many patients who are anatomically suitable for EVAR are undergoing open operation because of hemodynamic instability. If EVAR for rupture truly decreases mortality in all patients, a much more aggressive attitude toward EVAR may be required to lower the overall mortality rate.