Study Finds Mortality and Rupture Are Uncommon After Elective FB-EVAR of Asymptomatic, Intact Thoracoabdominal Aortic Aneurysms

KEY FINDINGS

• The incidence of early ARM was 2.7%, and the 5-year cumulative incidence was 3.8%.
• Advanced age and extent I-III TAAA were independently associated with late ARM.
• The incidence of early aortic rupture was 0.4%; the 5-year cumulative incidence was 2.7%.
• Extent I-III TAAA was associated with late aortic rupture.
• Five-year all-cause mortality was 45.7%, mostly due to non–aortic-related causes.
• Secondary interventions were required in one of four patients after the first 30 days, and the 5-year cumulative incidence of secondary interventions was 40.3%.

ENDOVASCULAR TODAY ASKS…

We asked study investigators Ying Huang, MD, PhD, and Gustavo Oderich, MD, with University of Texas Health Science Center at Houston–McGovern Medical School in Houston, Texas, to comment on what these results mean for future research and practice.

In the big picture, what do these data tell us about the applicability of FB-EVAR?

The current American College of Cardiology/American Heart Association guidelines for the management of aortic diseases advised FB-EVAR for patients with intact TAAAs with suitable anatomy and no evidence of connective tissue diseases at centers with expertise and access to appropriate stent grafts. Using standardized definitions for variables and outcomes of interest, this multicenter, prospective, nonrandomized investigational clinical trial demonstrates that FB-EVAR can be performed effectively with low ARM and aortic rupture in anatomically eligible patients with asymptomatic intact TAAAs. Although both 5-year cumulative incidences of ARM (3.8%) and aortic rupture (2.7%) were low after FB-EVAR, extent I–III TAAA carried an increased risk of having late ARM and aortic rupture compared with extent IV TAAA. Half of the aortic-related deaths occurred early, and most of the late deaths were not aortic-related. Rigorous surveillance after FB-EVAR is required because the need for secondary interventions was high among patients undergoing FB-EVAR of TAAAs, and identifying the need for secondary interventions will paradoxically be higher with better surveillance. But it is worth noting that our study cohort were well selected—only those who met the inclusion and exclusion criteria of the PS-IDE studies at each center were included; additionally, all the procedures were performed in aortic centers by experienced principal investigators of the PS-IDE studies using customized or off-the-shelf aortic devices from the same industry. Therefore, these data may not reflect the results from real-world practice, which includes FB-EVAR using physician-modified devices or devices from other industries. Unlike conventional EVAR, a randomized controlled trial is impossible for FB-EVAR due to the complexity of the anatomy and the aortic segment involved; these data are likely to be the most reliable and obtainable to validate the role of FB-EVAR for the treatment of TAAA. Overall, our data support the use of FB-EVAR in anatomically eligible patients with intact TAAAs. This data-driven evidence also supports centralizing complex aortic cases to centers with high volumes and expertise and access to the aortic devices to achieve better outcomes for patients who require treatment for complex aortic aneurysm.    

If accepted into wider practice, what can be done to ensure results match those of the centers that have had significant long-term experience with the procedure and its associated technologies?

We need to understand the protocols they use by review of the published results from centers with long-term experience and communications with experts in these centers. We also need to identify the differences in practice that lead to different results, such as patient inclusion and exclusion criteria, aortic devices used, protocol to prevent spinal cord ischemia, and the use of cone-beam CT. In addition to publications, we share our insights, learn from experienced centers, and stay informed about new technologies by attending the conferences, forums, and workshops. We also collaborate with those centers in aortic research. We adopt best practices not only from the participating centers in the US ARC, but also from centers with high volume. For example, cerebrospinal fluid drainage was frequently indicated in extent I to III TAAAs, with decreased utilization since 2018 due to high rate of hemorrhagic complications, and the use of drainage had no effect on outcomes, which has been demonstrated by multiple US ARC investigators in single series. Therefore, it is important to implement standardized procedures that have been confirmed effective by multicenter, prospective studies or single-center studies from experienced centers and regularly assess the outcomes to improve the gaps. Again, we emphasize the importance of centralization of the complex aortic cases to centers of excellence to improve health care.

Given the rate of secondary interventions found in patients undergoing FB-EVAR for TAAAs, what is required in terms of surveillance? Does this differ from your follow-up for standard EVAR/thoracic endovascular aortic repair (TEVAR), and if so, in what ways? What specifically are you looking for?

Given the high rate of reintervention, imaging surveillance is important for patients undergoing FB-EVAR for TAAAs to assess sac morphology, stent graft integrity, and patency of fenestrated or branched stent and detect device-related complications such as endoleaks or stent graft migration. The imaging studies include CTA, contrast-enhanced CT scans, and duplex ultrasound of targert arteries if patients are contraindicated for contrast due to impaired renal function. As FB-EVAR procedure is more complicated than standard EVAR/TEVAR, which involves incorporation of visceral arteries, there is no doubt that FB-EVAR patients require more detailed imaging using advanced imaging modalities and potentially may require more frequent imaging than standard EVAR/TEVAR patients after the procedure. The Society for Vascular Surgery (SVS) guidelines recommend CT scan at 1 month postimplantation and annual duplex ultrasound thereafter. CT imaging should be performed every 5 years after EVAR unless new findings. The SVS guideline also recommends contrast-enhanced CT scan at 1 month and 12 months and then annually after TEVAR, and a repeated CT scan at 6 months if the 1-month CT scan detects an abnormality. However, there is no consensus on the follow-up of FB-EVAR patients.

Currently, in the PS-IDE protocols within the US ARC, follow-up includes clinical examination and abovementioned imaging studies at 6 to 8 weeks, 6 months, 1 year, and annually thereafter. We are conducting a data-driven analysis on the necessity of each follow-up after FB-EVAR. For imaging surveillance, in addition to sac morphology, type II endoleak from lumbar arteries, type I/III endoleak, and main device migration that are investigated in EVAR/TEVAR patients, we also pay special attention to fenestrated or branched stent graft–related AEs such as bridging stent graft thrombosis, kinking, fracture, migration, endoleak, and target artery stenosis or occlusion. A report from the US ARC has demonstrated that more than two-fifths of the reinterventions were target artery related. In addition to imaging follow-up, renal function monitoring is also pivotal for FB-EVAR patients, as the renal arteries are usually stented during the procedure and the risk of renal ischemia due to stent stenosis or occlusion may be higher, and this is not the case for EVAR/TEVAR patients.   

This study found that CAD was protective against early mortality and both CAD and peripheral artery disease (PAD) were protective against late secondary interventions, but you noted that the mechanisms are unclear and warrant further investigation. How would future studies go about further validating this finding?

In our study, the mechanisms of protective effect of CAD on early mortality and the protective effect of CAD and PAD on late reintervention are unclear. As this multicenter, prospective clinical trial is ongoing, we will conduct studies with more patients as well as longitudinal studies to confirm the findings and rule out confounders. In addition, as pointed out in our paper, patients with CAD or PAD may have better adherence to medical therapy including antiplatelet medications and statins, which are recommended for cardiovascular event risk reduction. Although some studies suggested that aspirin significantly reduced aneurysm growth, others reported negative findings. Similar mixed results were also observed for statins. We did not investigate the medications in this study, further studies may focus on the impact of antiplatelet drugs or statins on the aneurysm morphology and outcomes after FB-EVAR. Imaging follow-up frequency between CAD and non-CAD patients or PAD and non-PAD patients might be another research topic. It is important to note that our results are from a well-selected study cohort who received fenestrated-branched devices from the same manufacturer. It would be nice to see the findings from TAAA patients who underwent FB-EVAR using physician-modified endografts or devices from other manufacturers.