In this article, Konstantinos P Donas and Frank J Criado review the evidence for endovascular aneurysm repair using the chimney technique, and consider where current guidelines and research are leading the vascular community when it comes to endovascular strategies for complex anatomy aneurysms.
HISTORICALLY, THE CHIMNEY technique for endovascular aneurysm repair (ChEVAR) emerged as a rescue technique to revascularise or preserve covered critical branches during aortic endografting. Next in its evolutionary path was the observation that ChEVAR offered a viable treatment option for complex aortic repair involving one or more branches, and particularly so in situations where fenestrated repair was not an option due to anatomical constraints or other fenestrated endovascular aneurysm repair (FEVAR) shortcomings. In this context, it was appreciated early on that ChEVAR offered two distinct advantages: off-the-shelf availability, and lower resource-intensity that enabled performance by a larger number of operators managing patients in many centres around the world.
ChEVAR adoption grew steadily over the years, but suffered a notorious absence of strong scientific evidence to underpin the technique. This all changed in 2015 with the publication of clinical results in the landmark PERICLES Registry, demonstrating excellent outcomes in a wide range of complex-anatomy aneurysm patients treated by parallel-graft experts at key medical centres in Europe and the USA.
The next evolutionary milestone focused on specific device combinations (aortic stent-graft and chimney stent), how they influenced results, and, more pointedly, the formation of gutters and related endoleaks. The PERICLES Registry collaborators identified two key factors in the causation of persistent gutters. One was the degree of aortic stent-graft oversizing, and the other related to the length of the new seal zone. The investigators suggested treatment by Onyx and Coils embolisation in the sizing cases and by extension and lengthening of the landing zones in case of primary short new neck creation.
Critically important—and often overlooked—is the observation that the majority of ChEVAR gutter endoleaks detected on completion angiography have resolved spontaneously by the time the first postoperative computed tomography angiography (CTA) is performed. Furthermore, it is not unusual to hear during presentations and discussions at various meetings that ChEVAR gutter endoleaks tend to be lumped together as the sum-total of those detected on completion angiography, first CTA—and even late-onset endoleaks. The impact on the inexperienced can be significant, as it may create the misconception or bias against ChEVAR as a largely ineffective and flawed technique.
But on the positive upside, it is encouraging to see that ChEVAR has been included (for the first time) in the latest 2019 Abdominal Aortic Aneurysm Treatment Guidelines from the European Society for Vascular Surgery (ESVS), where the technique is recommended in urgent cases and when fenestrated repair is unfeasible or contraindicated.
Here is a case example that illustrates powerfully the significant and increasing role of ChEVAR in the management of complex aortic pathologies:
An 88-year-old patient presented with a huge type IA/IB endoleak after an endovascular aneurysm repair performed in 2007. The resultant pressure in the aneurysm sac was causing severe abdominal pain. The angulated neck (Figure 1) and acute symptoms precluded treatment with FEVAR, and her advanced age at almost 90 years old, as well as severe comorbidities, excluded the feasibility of open surgical conversion. Consequently, ChEVAR emerged as the only truly viable technical option for creation of a new proximal neck.
To avoid traversing the heavily calcified supraaortic vessels and minimise stroke risk, we elected to use retrograde transfemoral access with implantation of the chimney graft in the periscope configuration (reversed chimney), and extension of the landing zone with placement of an Endurant cuff (Medtronic; Figure 2). The patient did well and recovered uneventfully.
Worth noting is that the just published ESVS Guidelines assign the same level of evidence (C) to both ChEVAR and FEVAR. In this context, the ongoing multicentre and absolute prospective trial of ChEVAR (ENCHANT) with prearranged endpoints will bring the technique to a higher level (B) of evidence.
In the end, there is little doubt the controversy surrounding ChEVAR will live on in the foreseeable future, at least to some extent. However, we feel confident that dissemination of the ENCHANT study results and, notably, ChEVAR inclusion as an important treatment option in the 2019 AAA Guidelines by the ESVS will go a long way to propel ChEVAR to its next level in the armamentarium of surgeons managing complex aneurysms. In so doing, the rise of ChEVAR will result in an improved perception of the technique in the vascular community regarding its utility and efficacy.
Konstantinos P Donas is a vascular surgeon at St Franziskus Hospital in Münster, Germany.
Frank J Criado is a vascular surgeon at MedStar Union Memorial Hospital in Baltimore, USA.