This analysis shows that in the US, endovascular repair for rAAA is associated with a lower mortality compared to open repair. In addition, the rEVAR mortality rate has been decreasing over time, while open repair mortality has remained stable. The use of rEVAR has increased over time in centers that see a high volume of rupture cases, adopting the repair method more rapidly than lower volume centers. These higher volume centers have a significantly improved mortality for all repairs and, notably, half of the rEVAR mortality of low-volume centers. High-volume centers additionally have shown significant decreases in mortality over time from 2000 to 2005 for both methods of repair.
Institutional studies have demonstrated the feasibility of emergent endovascular repair programs for rAAA, with mortality rates ranging from 8% to 40% for rEVAR and 12% to 46% for all rAAA repairs after program initiation (compared to the current study of 33% rEVAR and 41% overall).14–17,19–21
In these programs, the proportion of rEVAR versus open repair range from 27% to 75%, with most around 50%. Success rates for rEVAR completion were all cited as above 90%. Mehta et al.20
treated 85 patients with rAAA after establishment of an emergency protocol in 2002; they successfully performed rEVAR in 40 patients with a mortality of 18%. These excellent results are supported by our finding of a difference in mortality at high- versus low-volume centers and a 22% rEVAR mortality at the high-volume centers in 2005. It is significant to note that mortality with rEVAR showed continued improvement over time only in high-volume centers. Interestingly, open repair mortality is decreasing as well in this group. Development of rEVAR protocols may benefit all types of repairs as awareness and response to the arrival of a ruptured aneurysm patient is streamlined. Although experience of the higher volume hospitals may be increasing, leading to improved outcomes with both procedures, it could be that more regionalization of services would increase transit times, resulting in more deaths prior to operation.
Recent meta-analyses have cited overall lower mortality with rEVAR, but they also point to the pitfalls of publication bias.30–32
Rayt et al.31
reviewed studies with cohorts ranging from 5 to 56, with one study of 290 patients. A 25% overall mortality for rEVAR was found; however, an assessment for publication bias proved that only rEVAR studies with good and exceptionally good outcomes are reported.31
Sadat et al.32
analyzed 730 patients from various studies and showed a decreased odds ratio of 0.6 for mortality after rEVAR, with lower ICU and hospital stays.
Administrative databases have also been used to examine the differences between open and endovascular repair for rAAA.22,25
Greco et al.25
examined the databases of 4 large states from 2000 to 2003 and found, even in those earlier years, that mortality in 290 rEVAR patients was lower than in 5508 open repair patients (39% versus 48%, p<0.005). As rEVAR is more widely utilized, it is likely that more complex aneurysms and hemodynamically unstable patients are being repaired, thus the current finding that mortality is still decreasing for rEVAR is even more notable.
Similar to our data, Greco et al.25
also found a hospital volume trend when both elective and ruptured aneurysm repairs were included in the calculations; they documented a 20% difference in absolute mortality for rEVAR between high- and low-volume hospitals (cutoff >100 elective and ruptured EVARs annually).
Procedural volume has been shown previously to have an impact on outcome for open elective AAA and rAAA repair. Dimick et al.22
found improved mortality in high-volume centers after open intact and ruptured AAA repair in the NIS population from 1996 and 1997, while Dardik et al.33
demonstrated improved open rAAA repair mortality in Maryland for surgeons performing a high volume of rAAA repairs but not elective procedures. The meta-analysis by Holt et al.26
also indicated that patients with both nonruptured and ruptured aneurysms had improved mortality in high-volume centers; however, the studies differed with respect to volume definitions. These findings have been used to argue for the regionalization of AAA repair; the current study lends more evidence in support of this for endovascular as well as open repairs for rAAA.
Differences in hemodynamic stability cannot be assessed using the current dataset, and this is something that must be considered in the decision to transfer to higher volume centers and may limit the ability to perform EVAR in centers with limited experience. In a recent retrospective institutional review, Lee et al.34
identified a selection bias in that hemodynamically unstable patients tended to undergo open repair even when potentially anatomically suitable for rEVAR; however, their use of rEVAR (32%) was lower than in most other reports from programs with emergency protocols. As experience increases, hemodynamic stability may not factor into repair method as much or else may push the choice toward rEVAR for unstable patients as access and balloon occlusion are rapidly attained to stop hemorrhage. Given prior volume-outcome relationships for elective AAA repair, high-volume centers may be the first line for elective and semi-elective (symptomatic) AAAs, which may influence the distribution of rAAA admissions among medical centers as well.
Length of stay, hospital cost, and complications are likely influenced by a greater survival within high-volume centers; therefore, conclusions from these outcomes should be considered within this context.
Other limitations of this study are those inherent to studies using administrative datasets. There could be coding variability among institutions, limiting the ability to accurately identify comorbid conditions and complications. The standardization of the ICD-9 coding system helps to minimize this; however, the dataset represents only what is recorded in discharge information. The ICD-9 coding system does not differentiate between ruptured and symptomatic AAAs. Likewise, the proportions of free versus contained ruptures are unknown. Related to this and mentioned above is the fact that differences in patient hemodynamic stability, as well as any potential differences in anatomical characteristics, are unknown.
We also are limited by the fact that we cannot longitudinally follow the sample and assess longitudinal outcome. As we have learned from the data on intact AAA repairs, the long-term durability of endovascular repairs may be different than open repair and result in more late AAA-related complications, although open repair is associated with more laparotomy-related complications.5,8,9
It will be important to follow patients undergoing rEVAR to assess long-term outcomes as compared to open repair.
This study lends support for the use of EVAR for ruptured aneurysms, showing that in a national population, overall mortality is lower than with open repair. Additionally, because of lower mortality rates in higher volume hospitals for both types of repairs and a very large difference in endovascular outcomes, regionalization of referrals of ruptured AAA patients to high-volume centers preferentially may improve overall national outcomes. Based upon prior institutional studies and further supported by large database analyses such as this, it is reasonable for hospitals with adequate rEVAR experience to adopt a rEVAR-first strategy for ruptured aneurysms when conditions allow.