Perspectives in Vascular Surgery and Endovascular Therapy

Endovascular repair has become the primary treatment option for abdominal aortic aneurysms over the past decade. The favorable results as well as technical evolution have led endovascular repair to include fenestrated and branched technology for complex juxtarenal, suprarenal, and thoracoabdominal aneurysms. These grafts are, however, extensively customized and patient tailored at present precluding their use in emergency situations. Certain aspect of aneurysm anatomy also limits them. The chimney technique uses standard, off-the-shelf endovascular devices that extend the use of standard aortic stent grafts for aneurysms without suitable proximal landing zones particularly in acute situations. Early results are promising and warrant a continued development of the technique until such time that dedicated devices are available for the treatment of these complex aneurysms.

Hybrid procedures for the repair of thoracoabdominal aneurysms have become more widely reported in the literature in the past few years. This procedure was developed as an alternative to the traditional method of open thoracoabdominal repair in the absence of a viable total endovascular solution for all cases. The early results of the procedure encouraged more centers to use a hybrid solution in the treatment of complex aortic pathology. This article evaluates the current status of this procedure and future developments.

The management of complex aortic pathologies remains a major challenge particularly in the emergency setting. Bespoke fenestrated and branch stent graft technology has shown encouraging short- and mid-term results in selected patients. Despite tremendous technological advances in this field however, factors such as the inherent delay in device manufacturing, anatomical and technical challenges, high degree of planning, and cost hinder the wider applications of minimally invasive endovascular therapy. In situ fenestration of aortic stent grafts is an attractive alternative that eliminates the need for preoperative custom tailoring with the potential to widen the therapeutic options available and to offer a bailout option after inadvertent side branch occlusion. This article summarizes the principles of this technique and discusses its current applications.

The evolution of endovascular techniques has increased the proportion of patients with abdominal aortic aneurysms suitable for treatment with endovascular aneurysm repair (EVAR). Developments in fenestrated and branched technology provide an endovascular solution to incorporate the visceral branches and iliac arteries into the repair, expanding the indications of EVAR. Iliac branch devices (IBDs) allow preservation of flow into one or both internal iliac arteries in patients with ectatic or aneurysmal iliac arteries. The technique has been performed with high technical success rates and no added morbidity and mortality as compared with standard EVAR, potentially decreasing pelvic ischemic complications associated with hypogastric exclusion. This article summarizes the state of the art on IBD design, procedure planning, implantation, and clinical results.

Treatment of thoracoabdominal aortic aneurysms has traditionally been by means of open surgery, but in recent years endovascular approaches have emerged as a viable and perhaps superior alternative. Some confusion appears to exist in discussions in the literature regarding the exact definition of the various types of thoracoabdominal aneurysm depending on whether open or endovascular repair is undertaken, with some authors comparing the preoperative extent of disease and others comparing the degree of aortic coverage required. Accurate preoperative planning and meticulous implantation technique are critical to successful outcomes with the endovascular approach. This study discusses the anatomical classification of type IV thoracoabdominal aneurysms as applied in open and endovascular surgery and outlines the authors’ approach to the critical preoperative planning of endografts used to treat these aneurysms. The authors describe their techniques used to implant these devices, whether they consist of fenestrated or branched components, and some of the mechanisms by which minimization of complications such as spinal cord ischemia is sought.

Thoracoabdominal aortic aneurysms (TAAA) remain a challenging problem to manage. Operative care for patients afflicted with this devastating problem is associated with significant risks, including renal failure and paraplegia. Several techniques have been developed to help limit the risk for these complications, yet they still remain some of the greatest hurdles associated with these procedures. Endovascular technology is rapidly advancing and may provide an alternate approach to patients with TAAA. Endograft treatment of TAAA is possible with the use of fenestrated and/or branched aortic endografts. Although still early in its evolution, we are beginning to understand some of the risks and benefits of this approach to complex aortic disease. Fenestrated and branched aortic endografting may provide an option that has lower risk to patients. Spinal cord ischemia, however, still remains a critical problem in patients who require treatment of a significant portion of their aorta. In addition, renal failure is also still observed. The mechanisms leading to the development of these complications following endograft repair, however, may not be the same as observed with open TAAA repair. This review will highlight some of our current understandings of endovascular repair of thoracoabdominal aortic aneurysms.

Anatomical constraints limit the utility of endovascular therapy with infrarenal stent grafts in approximately 40% of the patients. Fenestrated and branched stent grafts that incorporate the visceral and renal arteries are currently not approved for commercial use in the United States and require at least 6 to 8 weeks for customization. These devices are not currently available as an “off-the-shelf” option to treat complex aneurysms, although recent publications suggest that standardization will be possible in 70% to 80% of patients. Modification of aortic stent grafts with creation of reinforced fenestrations or side branches has been reported and may have a future role in the compassionate treatment of high-risk patients with complex aneurysms who otherwise would not have access to a manufactured device, or for those in need of urgent or emergent repair as in the case of a patient with an impending or contained ruptured aneurysm. This article summarizes the current principles applied for device design, procedure planning, and potential applications of modified stent grafts for urgent treatment of symptomatic or contained ruptured aortic aneurysms.

Endovascular techniques have been slow to assume a primary role in the management of thoracoabdominal aortic aneurysms (TAAAs) because of the high cost of multiple components, regulatory challenges, manufacturing delays, and the complexity of multibranched stent graft insertion. Standardized off-the-shelf stent grafts have the potential to lower all these barriers to the widespread application of multibranched endovascular technology. Despite the desire for a single design to accommodate all variations of thoracoabdominal aneurysms, different approaches are likely required for patients with extensive aneurysmal disease compared with disease that is more localized to the infradiaphragmatic region or that which does not extend below the renals. This article summarizes the basic concepts and stent graft designs for repair of TAAA using off-the-shelf fenestrated and branched endografts.

Endovascular aortic arch reconstruction provides an attractive alternative to treat aortic arch disease in high-risk patients who would otherwise be unsuitable for open repair. Success with multibranched stent grafts in the thoracoabdominal aorta along with recent advances in design such as the precurved inner nitinol cannula have simplified the endovascular reconstruction of aortic arch aneurysms with multibranched stent grafts. These devices allow for greater flexibility in conforming to difficult anatomy and preserving important side branches. During the first surgical stage, a left carotid -subclavian bypass or left subclavian artery transposition is performed. The second stage is the endovascular procedure. The device is inserted through a transfemoral approach, and crossing of the aortic valve with the device is necessary. The stent graft is deployed during brief periods of rapid pacing. Bridging from the branches to the innominate and left common carotid arteries requires a suitable covered stent. In the case of a large-diameter innominate artery, a custom-made bridging limb has to be used to ensure that adequate length and size are available. Direct flow to the innominate and left common carotid arteries do not cease for any significant time during the procedure. Initial experience with mean follow up more than 6 months is encouraging. The method is not suitable for patients with extensive atheromatous involvement of the aortic arch. Careful preoperative planning (preoperative imaging, device construction, and access issues), high endovascular skills, and appropriate imaging equipment are imperative for a successful result. Long-term follow-up is necessary to evaluate the efficacy and safety of these new devices.

Spinal cord injury (SCI) stands as one of the most dreadful complications of thoracoabdominal aneurysm repair. Despite the less invasive nature and recent technical advancements of endovascular aortic repair, SCI still remains a significant danger in endovascular approaches. However, as our understanding of the collateral network of spinal cord vasculature has grown, it has become evident that the incidence of paraplegia and paraparesis in conjunction with endovascular procedures can be minimized through the use of many of the same strategies that have proven successful in reducing SCI associated with open surgical repair. This article highlights important aspects of spinal cord protection, which have been derived from the authors’ clinical and experimental experience.