Endovascular management of complex thoracoabdominal aortic aneurysms (TAAA) is currently considered the first option in many tertiary centres, while open surgery is reserved for young and fit patients and for patients with connective tissue disease. Although the prevalence of TAAA is only around 10% of aortic aneurysms [1], it represents a significant challenge to the medical community. Despite several developments in surgical techniques and anaesthetic management, morbidity and mortality post open repair remain high. The in-hospital mortality ranges from 4 to 15% [1,2], renal failure ranges from 2-14% [3], spinal injury occurs in up to 16% [1], the stroke rate is 3.9% [4] and open reinterventions are necessary in 2-25% of cases [3].
Over the last couple of decades, endovascular techniques have evolved, and technology has undergone several iterations. Currently, a few designs are available from various manufacturers including Cook Medical Inc., Denmark, GORE® EXCLUDER® Thoracoabdominal Branch Endoprosthesis (TAMBE Device), and E-Nside (Jotec GmbH, Hechingen, Germany) with the custom-made Extra-Design (Artivion, Kennesaw, GA).
However, a large registry or head-to-head comparison is not available. Industry sponsored pivotal single arm trials and single centre series reported promising technical and clinical outcomes of f/BEVAR in complex TAAA. The technical success is reported as high as 98% [5] for elective cases and 90% for acute emergent cases [6]. The in-hospital mortality is relatively low at 2.8- 8% [5,7]. The rate of spinal cord injury, however, can be high, reported around 50% in some series [8]. Improved experience, early diagnosis and treatment as well implementing a staging approach have shown improved results. The more recent experience reports a 3.8% rate of spinal cord injury [5].
Despite the use of nephrotoxic contrast in complex cases and the potential impact of occluded renal arteries, permanent dialysis was reported to be as low as 1% [5]. On the other hand, Cucuruz et al [9] have shown a relatively high incidence (37%) of acute kidney injury in the perioperative period, but permanent dialysis was needed in 6.7% of patients. In their experience of 113 patients, non-staged procedure and renal artery reinterventions were risk factors for poor renal function.
Reintervention is the Achilles heel of all endovascular interventions, and F/BEAVR for such a complex pathology is not an exception. The reported aortic stent graft and branches reintervention varies widely and ranges from 11-40% over two to five years [5,10,11]. Most reinterventions are related to endoleak and component separation.
The published data show good side branch patency over 2 and 5 years’ time at around 93% [5,6]. Bridging stent technology has improved over 2 and 5 years’ time. The balloon expandable stent grafts (BESG) outperform self-expandable or hybrid stents with a higher patency rate, a lower risk of endoleak, and better stability [12]. There is, however, a lack of strong evidence on direct comparison between various types of BESGs.
Stroke, especially in patients with type II TAAA, is relatively low (2.7%) but can be devastating [4].
The successful experience of F/BEVAR in degenerative TAAA has stimulated operators to extend their experience to post-dissection TAAA (PD-TAAA) [14,15]. The low in-hospital mortality and high technical success of F/BEVAR are comparable between degenerative and PD-TAAA (3% vs. 2-3.6% respectively). However, the risk of endoleaks and need for reinterventions are significantly higher in post dissection cases (73% vs. 43% respectively). Beside a centre’s experience, patient selection is critically important in treating PD-TAAA to ensure satisfactory and durable results.
It is conceivable that dealing with complex TAAA using sophisticated technology mandate a high level of training and adequate infrastructure support, both clinical and radiological. The learning curve in specialised high-volume centres has shown significant improvement in clinical outcomes. In a series of 157 patients with TAAA, the reinterventions were improved by almost 50% after 3 years down the line and after doing around 50% of the studied cohort [13]. Team work which involves interventional radiologists, vascular surgeons, and anaesthetists is the best way to provide the highest standards of care.
Radiological advances continue to feed into this field. Image fusion, fiber optic image guidance and advanced software for planning/follow-up have shown to result in improved technical outcomes [16]. There is, however, the need for more scientific data to establish the real benefits and identify areas for further development. Anatomical adverse features continue to be one of the main sources of early and or late failures. Severe and multiple angulations, ostial stenosis, a hostile take off angle of the side branch, short landing zones, the length of the bridging stent and a relatively large device profile are potential causes for limiting technical success and or could lead to durability issues.
Long term surveillance is mandatory to diagnose and treat endoleaks, stent occlusion, and component separation. Long term durability data should be monitored in the coming years to assess cost effectiveness and to refine technology.
