With advances in technology, device availability and surgical skill sets we can expect the outcomes from endovascular repair of thoracoabdominal aortic aneurysms to continue to improve and become the treatment of choice for these patients, according to Stéphan Haulon, Lille, France.
Why, in your opinion, are fenestrated and branched grafts, rather than surgery, the optimal way to treat thoracoabdominal aortic aneurysms?
A large number of thoracoabdominal aortic aneurysm patients are unfortunately faced with significant comorbidities that decrease their ability to tolerate an open procedure. Those who survive open repair have their quality of life significantly impacted with most patients being referred to rehab or long-term care facilities. Patients undergoing endovascular procedures experience a far less traumatic procedure. Morbidity and mortality rates at centres of excellence are less than or equal to centres of excellence performing open repair. Greenberg et al (Circulation. 2008 Aug 19;118(8):808-17) showed an overall 30-day mortality rate of 5.7% for patients treated endovascular for thoracoabdominal aneurysms. Finally, the majority of patients treated with EVAR for thoracoabdominal aneurysms are released from the hospital within 10 days. Given future advances in technology, device availability and surgical skill sets we can expect the outcomes from EVAR for thoracoabdominal aneurysms to continue to improve and become the treatment of choice for these patients.
What are the potential issues surrounding endovascular repair?
The potential issues surrounding endovascular repair include:
- Just as with open repair, endovascular repair of thoracoabdominal aortic aneurysms is complex and a high skill level is required to ensure good outcomes. Endovascular repair of thoracoabdominal aneurysms should be restricted to high volume centres where these types of cases are completed routinely.
- Currently, devices to treat thoracoabdominal aneurysms are commercially available in a limited number of countries. Those countries without commercial access rely on physician-sponsored studies to gain access to these technologies or treatment via physician-modified endovascular grafts. In order to ensure long-term success of the endovascular repair, devices to treat a broad range of patients need to be developed and made available on a global scale. To date a majority of the published experience in endovascular repair of thoracoabdominal aneurysms is with devices designed to fit each patient’s individual anatomy. In order to treat patients in a more expedient manner, better off-the-shelf devices should be designed or techniques to reduce time to plan, manufacture and deliver a patient-specific endograft should be employed.
- These complex repairs have many potential failure modes (eg. branch vessel instability) and as with all endovascular repairs require long-term surveillance. The aorta is dynamic during the cardiac cycle; when coupled with the movement of the diaphragm, it presents potential challenges for graft durability. Given these challenges, our results to date have shown excellent long-term durability owing to conservative techniques in selection of seal zones and endograft design.
- Bridging stents used to make the modular connections between the endovascular graft and the branch vessels were not originally designed for that purpose. Currently, covered stents intended for use in peripheral disease are typical used to bridge the endovascular graft to the native branch vessels and some concerns have been raised about the long-term durability of these components. Several devices have proven successful in accomplishing the bridging in the short to medium term. Stents designed specifically to bridge fenestrated and branched grafts to native anatomy have the potential to further improve patient outcomes.
How new technology can improve outcomes in complex TEVAR procedures?
Several areas exist where technological evolution can improve patient outcomes. Continued reduction in delivery system profile can have a big impact. Reductions in delivery system size will reduce the need to perform endovascular conduits and reduce rates of access vessel complications especially in women. Advances in delivery techniques also have the ability to simplify these procedures. New technologies, such as preloaded wires, catheters and sheaths can simplify access of fenestrations, branches and target vessel. The results will be reductions in surgical time, fluoroscopy time, total contrast used, and surgical complications.
What is it known in terms of durability of these endovascular procedures?
Complex endovascular procedures are built on the same design philosophies that have evolved in more than 20 years of experience with standard EVAR devices. Design features such as active fixation, durable graft materials, and durable stents that provide radial force for sealing that have been proven key in the durability of standard devices are even more critical in complex endovascular repairs often cover a larger portion of the aorta. More contemporary studies (Mastracci et al. J Vasc Surg 2013;57:926–33) have systematically evaluated branch vessel durability for complex repairs. We believe these studies provide evidence that branched and fenestrated endografts are a durable alternative to open repair in patients with complex aortic disease if the principles of device design are adhered to and vigilant follow-up can be ensured.
What is the role of off-the-shelf branched devices and who should be treated with these devices?
The immediate role of off-the-shelf branched devices for thoracoabdominal aortic aneurysms should be for those patients that need to be treated under emergent surgery. These devices have limitations in the anatomy that can be treated and unanswered questions as to long-term compromises in branch vessel durability. Devices manufactured to fit an individual patient’s anatomy are a better choice in the thoracoabdominal aneurysm setting if the patient is not considered at high risk of aneurysm rupture. As we continue to learn more about off-the-shelf devices we can begin to better understand the trade-offs in patient-specific and off-the-shelf strategies, and most importantly we can understand what group of patients will benefit most from each technology.
Experience matters when performing complex TEVAR procedures. What operators and centres should be performing this type of procedure?
As with all new surgical procedures, only those operators and centres with the highest skill sets should be performing these procedures in the beginning. These centres see these patients routinely on a referral basis today and have developed the skills and teams required to provide patients the highest standard of care. As confidence builds with these devices, technology improves, and extensive training is established the technology may be disseminated to a larger group of physicians. It is important that both industry and physicians support this strategy from a technology and training standpoint as this will promote long-term success of these complex devices.
A study by Marzelle et al (Annals of Surgery 2014) concluded that although promising, fenestrated and branched EVAR still carries a significant rate of mortality and complications, mostly related to the complexity of the procedure. In your opinion, what needs to be done to improve outcomes?
Most centres enrolling patients had limited experience with FEVAR for juxtarenal aneurysms and performed their first thoracoabdominal aneurysm endovascular repairs during that study. Their learning curve in patient’s selection and branched EVAR implantation was thus included. While mortality and complications are still experienced with FEVAR and branched EVAR, these rates decrease as user experience has increase. A similar trend was seen with standard EVAR for abdominal aortic aneurysms during the infancy of the treatment but as experience increased, training improved and devices improved, morbidity and mortality were reduced to levels lower than open repair and became the gold standard of abdominal aortic aneurysm treatment. This trend will hold with advanced endovascular repair. These devices should be used by high volume centres, those that see these cases routinely and have experience with open surgery and advanced technologies. Those wishing to gain access to such technology will need to go through extensive training to ensure they understand how to properly plan these procedures and to ensure they have the proper surgical skills to have positive patient outcomes. Additionally, our industry partners are working on devices and delivery systems which will significantly reduce the procedure complexity. One example of this is preloaded delivery systems which allow for quick access of the branches and fenestrations on the stent graft. This will significantly reduce surgical time and fluoroscopy and contrast exposure, all of which will improve upon patient outcomes.