Expanding the armamentarium of endovascular thoracoabdominal aneurysm repair—hydrogel-reinforced fenestrations

The surgical treatment of complex thoracoabdominal aortic aneurysms (TAAAs) is performed to protect against aortic rupture and ensure survival in the long term [1]. At the same time, management of TAAAs is complex, challenging and associated with considerable morbidity and mortality rates despite several advances in preoperative patient optimalization, anaesthesia, surgical techniques and postoperative care. Regionalization to high-volume centres of excellence can reduce morbidity and mortality rates associated with open surgical TAAA repair [2, 3]. Over the last decades, several endovascular options to treat complex TAAAs in high risk, and otherwise inoperable patients, have emerged. These options range from hybrid procedures to fenestrated or branched endovascular TAAA repair, with the use of custom-made manufactured devices, off-the-shelf use of existing devices or physician-modified endografts (PMEGs) [4]. Several authors have been reporting high technical success rates and respectable clinical outcomes on a relatively large series of endovascular TAAA repairs, at mid-term follow-up, using different devices [4, 5]. As stated by the authors of the present study, not every high-risk patient in Japan has access to custom-made manufactured devices for the treatment of complex TAAAs [6]. To offer these patients a treatment option, Azuma et al. [6] meticulously devised a novel PMEG with hydrogel-reinforced fenestrations. For this, they cauterized fenestrations in the distal component or distal extension component of the Zenith Alpha™ thoracic endovascular stent graft (Cook Medical, Bloomington, IN, USA) and reinforced those with hydrogel. The hydrogel that is applied to the fenestrations offers a more secure connection between the fenestrations and the bridging grafts, as stated by the authors. Consequently, type IIIc endoleaks and reinterventions are less likely to occur. Here, the rationale lies in the fact that some authors have reported migration of the bridging graft relative to the main stent graft [7]. Some other authors have reported additional modification techniques, next to creating fenestrations with consequent fortification [8, 9]. These consist of diameter reducing ties to facilitate longitudinal and rotational movements of the main stent graft during deployment so that the position of fenestrations can be adjusted to facilitate catheterization of the respective target vessel [8, 9]. Moreover, an additional fenestration was proposed that may ensure temporary aneurysm sac perfusion after main stent graft deployment and branch reconstruction, with the aim of reducing the risk of spinal cord ischaemia [8]. This additional fenestration can be occluded by an additional intervention to fully exclude the TAAA several weeks later. Regarding PMEG deployment, the stepwise technique posed by Azuma et al. [6] has several advantages. It allows for a stepwise revascularization of target vessels from top to bottom and allows for longitudinal and rotational movements during the early stages of main stent graft deployment. This could be compared to the intended effect of diameter reducing ties, when main stent graft devices are completely released after cannulation of a single target vessel [9]. Azuma et al. [6] applied their novel PMEG with hydrogel-reinforced fenestrations to clinical practice and evaluated the technical and clinical success rates in the present retrospective analysis of 40 patients with a median age of 73.6 (range 49–87) years. They were treated for complex TAAAs, regardless of anatomic suitability. The analysis showed a high technical success rate, with 100% of the target vessels revascularized without migration of a single bridging graft. Consequently, type Ic and IIIc endoleaks did not occur while Ib (n = 3, 7.5%) and IIIa (n = 5, 12.5%) endoleaks did. Even more important, clinical success rates were found to be high. The authors report a 30-day mortality of 2.5% due to 1 cerebral haemorrhage at postoperative day 5 and a 3-year mortality of 17.5% due to 2 aorta-related deaths and 4 non aorta-related deaths. Moreover, the associated morbidity was respectable, with 1 (2.5%) perioperative transient paraplegia and 1 (2.5%) late permanent paraplegia at 6 months follow-up. In general, there are few data available on the application of PMEGs to the endovascular treatment of TAAAs in clinical practice. This might raise suspicion towards the technical durability and clinical success of these procedures on the long-term. Involved physicians might feel a great sense of responsibility if treatment failure would occur. On the other hand, physicians can offer to a considerable number of high-risk, and otherwise inoperable patients, an experimental treatment option. Moreover, given the high costs and manufacturing time of up to 12 weeks for custom-made devices, PMEGs could also be useful in a subacute and symptomatic TAAA setting. The management of complex TAAAs remains challenging and a wider application of endovascular TAAA repair to lower-risk groups remains limited. This might be possible if the associated reintervention rates, related to endoleaks and long-term durability, can be improved and secured. Enforcement of fenestrations with hydrogel may help to achieve this goal; however, results from larger series with longer follow-up are needed to confirm these encouraging initial results. Nevertheless, modification of an existing endovascular device requires thorough knowledge and understanding of the device, imaging studies and pathophysiology of aortic disease. This needs to be combined with technical skills and attention to detail, to be able to deliver the best-tailored treatment option for a specific patient.