While the competing mortalities of observation and open surgical repair for TAA have been investigated for several decades, the effect of TEVAR on survival remains less well studied. Most reports regarding survival after TEVAR are single center series, or the results of highly selected industry-sponsored registries4, 6, 26, 27–29
. Our study examined survival following open repair and TEVAR in national, real-world practice, and found that while peri-operative mortality is lower in TEVAR, patients selected for TEVAR have worse long-term survival than patients selected for open repair. These results suggest that higher risk patients are being offered TEVAR, and that some do not benefit based on long-term survival.
Understanding the effect of a less invasive endovascular option for aneurysm repair on patient selection and survival following aortic aneurysm surgery has been a topic of extensive study, but primarily in patients with infrarenal abdominal aortic aneurysm (AAA)3, 30
. Several randomized trials31–33
have demonstrated lower peri-operative mortality with endovascular techniques. However, in these trials, as well as large observational analyses30
, the survival advantage gained by an endovascular approach consistently disappears within two years after surgery, and little difference in long-term survival is evident thereafter across procedures. Patients who experience late death following infrarenal AAA repair most commonly die from cardiopulmonary comorbidities unrelated to their aneurysm, and relatively few experience aneurysm-related death, in either open or endovascular repair34
. In other words, in both randomized trials and in real-world practice, while EVAR is as effective in preventing aneurysm-related death as open repair, it does not result in prolonged improvement or detriment in survival. Rather, it has decreased peri-operative morbidity and mortality, and expanded the pool of patients undergoing elective repair35
Our results demonstrate that the treatment of TAA follows a similar course to infrarenal AAA, with one important exception. As with infrarenal AAA, we found a survival advantage in short-term mortality for patients who undergo TEVAR as compared to open repair, especially in patients presenting with ruptured TAA, and this finding has been reported in similar analyses in other national datasets36
. Further, as with infrarenal AAA, any survival advantage gained in the peri-operative period following endovascular repair was lost within two years after surgery. However, unlike infrarenal AAA, wherein long-term survival is similar across procedure type, adjusted survival at five years was significantly worse for patients selected for TEVAR as compared to open repair. Therefore, the widespread application of TEVAR has resulted in a cohort of patients who may have previously not undergone surgery, but now undergo TEVAR. Patients selected for TEVAR achieve worse survival than patients undergoing open repair, and many of these deaths occur within the first two years after TEVAR. These deaths could be due to the selection of “sicker” patients for TEVAR, although our finding of poorer survival following TEVAR persists, even in propensity-matched analyses that account for differences in patient risk measurable using administrative claims. Alternatively, these differences in survival could be explained by device-related complications occurring within the first five years following surgery.
As with patients with infrarenal AAA, we suspect that the loss of survival advantage is secondary to patient-level comorbidities. For example, in the EVAR-2 trial37
, survival was similar among patients treated with endovascular repair and patients who did not undergo repair. All patients in EVAR-2 were deemed “unacceptable for open repair”, as they often had comorbidities that limited their survival, but not their ability to undergo endovascular repair. The data available from our study supports this presumption, as TEVAR patients tend to be older and have higher comorbidity scores than the patients selected for open repair. However, it is important to acknowledge that our findings are based solely on administrative claims, and our analysis is therefore limited in terms of clinical detail.
Given the lack of anatomic and procedural detail in our dataset, it remains uncertain if the lack of survival advantage seen in patients selected for TEVAR could be related to late-occurring, device-related complications. To best determine whether or not late device-related complications are contributing to the poorer “real-world” survival in patients undergoing TEVAR, post-implantation follow-up using device-specific registries will be necessary. Efforts in this regard have already been discussed and implemented by specialty societies interested in outcomes of endovascular procedures, and these registries will also provide more robust clinical detail for risk adjustment as compared to the administrative data used in our current work38
Finally, following FDA approval and widespread implementation of TEVAR, the peri-operative mortality associated with open repair declined significantly, and a small but significant survival benefit was evident 3 years following surgery. While indirect, this evidence suggests that after FDA approval, higher risk patients were being offered TEVAR rather than open repair, and patients selected for open repair were lower risk than those selected for TEVAR. However, more definitive characterization of these changes is necessary, and will require registry-based data with more detailed covariates for risk adjustment than currently available from administrative data.
Our findings add important context to the studies used to demonstrate the efficacy of endovascular repair of TAA12, 13, 39–41
. First, when compared to data from TEVAR clinical trials (), it is evident that peri-operative mortality is higher in “real-world” practice than in the centers of excellence where the clinical trials were performed. Second, when examining the relative effectiveness of TEVAR in comparison to open surgical repair at five years, we see that it is important where the “bar” is set, in terms of open surgical repair. In real-world practice, patients selected for open repair had better survival the surgical controls used in clinical trials (72% five-year survival in Medicare, 67% five-year survival in the single trial that reported this measure). Further, patients selected for TEVAR in real-world practice performed slightly worse than patients studied in the clinical trial (62% five-year survival in Medicare versus 68% five-year survival in the clinical trial). Collectively, these two differences resulted in the disparity in conclusions between our study, wherein TEVAR patients fared significantly worse at five years, and the clinical trial, wherein outcomes were similar at five years. Which rate is right? Certainly, future trials and analyses will address this question. While a formal meta-analysis comparing these results is beyond the scope of this manuscript, a recent meta-analysis addressed this question, and included the clinical trials shown in , as well as several single-center studies reporting 2 and 3-year outcomes. These investigators found little long-term survival benefit for patients undergoing TEVAR compared to open surgical repair 42
. Therefore, given the findings in our study and others, there is little evidence to suggest that long-term survival is better in patients selected for TEVAR as compared to open surgical repair. Further, dependent upon the surgical controls selected for comparison, survival after TEVAR may be worse. 13, 39–41
Outcomes at 30 days, 1 year, and 5 years, by repair type and study
Our study has several limitations. First, as mentioned previously, the limitations of administrative data in describing clinical details of aortic aneurysm repair and providing clinical-level covariates for risk-adjustment have been well described43
. Therefore, we sought to be highly specific in our attempt to create a cohort of descending thoracic aneurysms, and searched for both procedural and diagnostic codes commonly used for branched, fenestrated, ascending, and transverse arch thoracic aortic repair, and eliminated these patients from our cohort of isolated descending TAA to ensure uniformity in our cohort. Second, our comparison of patients undergoing open repair and TEVAR procedures is risk-adjusted using demographic data, ICD-9 derived diagnoses, and a propensity-matched model studying low-risk patients undergoing TEVAR and open surgical repair. Further attempts to develop comparative populations, either via instrumental variable analysis44
or other statistical techniques designed to account for selection bias in observational studies, would be limited by the absence of important clinical variables such as aneurysm extent, size, and prior aneurysm surgery. Third, FDA approval was granted in 2005, and our dataset extends to 2007, limiting our insight into patients who underwent surgery in the post-FDA approval era. However, because patients with TAA experience limited survival regardless of procedure type, the overall size of our cohort combined with the frequency of these events allowed insight into significant survival differences even in this limited time period. And lastly, our dataset does not allow us to discern causes of death34
. It is possible that differences in aneurysm-related deaths might better inform decision-making about which patients should undergo open repair or TEVAR, but these data would be unlikely to alter the primary conclusion of our study.
In summary, our study demonstrates that short and long-term survival following surgery for TAA varies by presentation and repair type. The consistent short-term survival advantage offered by TEVAR disappears within the first two years after surgery, and patients currently selected for TEVAR have worse long-term survival than patients selected for open repair. These results suggest that higher risk patients are being offered TEVAR, and that some do not benefit based on long-term survival. Future work is needed to identify TEVAR candidates unlikely to benefit from repair.