Author + information
- Graham R. McClure, MD, MSc∗ (, )
- Fadi Elias, MD, MSc and
- Emilie P. Belley-Cote, MD
- ↵∗David Braley Cardiac, Vascular and Stroke Research Institute, 237 Barton Street E., Hamilton, Ontario L8L 2X2, Canada
Chiu et al. (1) present a compelling analysis of thoracic endovascular aneurysm repair (TEVAR) versus open surgical repair in the management of intact descending thoracic aortic aneurysms. Using a large prospective database, their results suggest significant benefit to perioperative as well as 9-year survival with TEVAR. Although their findings are exciting, limitations in novel methods used warrant discussion when interpreting their findings. We believe that residual confounding likely biases the benefit of TEVAR.
The investigators used an innovative approach to generate a “pseudorandomized” cohort, by taking advantage of drastic practice pattern changes when the U.S. Food and Drug Administration approved TEVAR. They stratified patients to an “encouraged to open” (before TEVAR approval) or “encouraged to endovascular” (after TEVAR approval) analysis arm and analyzed using an intention-to-treat design. This solution relies on 2 assumptions: 1) most patients consented for intervention after U.S. Food and Drug Administration approval would have been candidates for open therapy in the pre-TEVAR era; and 2) the proportion of patients whose anatomy was not amenable to TEVAR and underwent open repair was balanced before and after TEVAR introduction.
We argue that the first assumption is not valid. Interventions for descending thoracic aneurysms more than quadrupled after TEVAR introduction, implying that many previously inoperable or conservatively managed patients began undergoing intervention when TEVAR was approved (1). Chiu et al. (1) attempted to mitigate this with propensity matching; however, even after matching, TEVAR volumes are significantly higher than earlier open operative volumes. As such, we doubt that these populations have comparable anatomic characteristics. The essential component missing in these analyses in the “encouraged to open” group is outcomes from conservatively managed patients in the pre-TEVAR era. Many of these patients may have “crossed over” after 2005 and should be statistically accounted for as such.
We also question the second assumption. In the TEVAR era, open repair became concentrated at centers of excellence, increasing surgeon expertise and improving outcomes. This may have caused outcomes to systematically differ after the widespread introduction of TEVAR (2). Given that open operations represented 7.4% of patients included in the “encouraged to endovascular” arm, these systematic differences may have affected study results.
The Chiu et al. (1) results are similar to those from previous smaller cohorts (3) and represent some of the most rigorous data in the field. Their methods are novel and attempt to account for undocumented anatomic factors from population-level data. However, their data are not a substitute for high-quality randomized evidence, which the surgical community must prioritize.
Please note: The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2019 American College of Cardiology Foundation