Konstantinos P Donas (Münster, Germany) claims that the “widespread scepticism” over the safety and efficacy of endovascular aortic aneurysm repair (EVAR) procedures using the chimney technique is probably not justified after the largest collection of data for the strategy indicated that it was a safe and effective alternative endovascular approach for pararenal aortic pathologies.
Speaking at the annual meeting of German Society of Vascular Surgery (DGG; 16–19 September, Münster, Germany), Donas (Department of Vascular Surgery, St Franziskus Hospital, Münster, Germany) said that, at present, the current evidence base for chimney EVAR is limited because data for the strategy is only available for a limited number of patients, covers a wide variety of treated pathologies, and concerns “several combinations of the off-the-shelf devices”.
Therefore, as Donas and colleagues note in Annals of Surgery, critics of the chimney technique as a mainstream approach claim that, because of the limited data, “it remains difficult to obtain a clear picture of chimney EVAR outcomes and its potential applications”.
The aim of the PERICLES (Performance of the chimney technique for the treatment of complex aortic pathologies) registry was to provide the latest pooled evidence base about chimney grafts in pararenal aortic pathologies. The goal was also to “resolve the controversy and to see if the scepticism about them [chimney grafts] was justified,” Donas said.
Donas and colleagues performed a retrospective review of outcomes of patients who had undergone chimney EVAR at centres in Europe and the USA, with the investigators commenting in the Annals of Surgery paper that centres could only participate in the registry if they had “treated at least 10 patients with complex aortic pathologies by the snorkel/chimney technique”. The primary endpoints included aneurysm sac diameter regression, chimney graft patency, and freedom from endoleak, and secondary endpoints included all-cause mortality, aneurysm-related mortality, chimney graft-related reinterventions and renal function.
Overall, data for 517 patients (398 of whom were treated at European centres and 119 were treated at US centres) who underwent chimney EVAR between 2008 and 2014 were reviewed. Donas et al comment: “In all, 898 target aortic branch vessels were revascularised using chimney grafts. The mean number of chimney grafts placed was 1.73 per patient, with 692 renal chimneys, 156 superior mesenteric artery chimneys and 50 coeliac chimneys inserted.” They add 49.2% of the chimney grafts were with balloon-expandable covered stents (Advanta, Maquet) and 39.6% were with self-expanding covered stents (Viabahn, Gore Medical) and that bare metal nitinol stents were used reline to the inside of a covered stent—“most often the Viabahn”—in 25.4% of cases. The mean preoperative diameter of the juxtarenal aneurysms treated was 65.9±16.5mm with a mean preoperative proximal neck length of 4.8±7.4mm, characteristics which—Donas et al note—are “unsuitable for traditional EVAR”. However, they comment: “The snorkel/chimney strategy increased the theoretical neck/seal length to 21.1±12.7mm.”
Technical success was achieved in 97.1% of cases and the 30-day mortality rate was 4.9%, with the authors stating: “Of note, 29 patients had chimney EVAR for ruptures, with a 30-day mortality rate of 24.1%, making the elective mortality rate 3.7%.” They add that estimated patient survival was 91.3% at six months, 84.9% at one year, 77.2% at two years, and 74.9% at three years. At the 17.1±8.2 month follow-up point, mean aortic aneurysm diameter was significantly decreased to 61.2±19.7mm (p<0.001) compared with preoperative levels with a mean sac regression of 4.4±13.1m. “Overall, all primary chimney graft patency was 94.1%,” Donas et al report and they add that the incidence of postoperative type Ia endoleaks that required reintervention was relatively low.
According to the authors, the results seen in the PERICLES registry are comparable “with published results from series of fenestrated grafts” and, therefore, chimney EVAR “should be in the armamentarium of surgeon treating complex aortic lesions because it provides an immediate off-the-shelf solution that is safe, effective, and durable in the midterm.” They add that they see the strategy as “complementary” to fenestrated and branched devices “with numerous advantages and disadvantages depending on the anatomy and presentation of the patient with a complex aneurysm.” They conclude: “Although close attention to technical details, device selection, and careful planning to create a sufficient sealing zone of at least 20mm is necessary to achieve good outcomes, the present results indicate that snorkel/chimney EVAR and other parallel graft techniques are a viable treatment method that deserves further study and wider usage.”
At DGG, Donas said that the widespread scepticism that has existed about chimney EVAR is “probably not justified” and that the results of the registry would help to bring the strategy “out of the shadows”.
Donas spoke to Vascular News about the study results and conclusions.
Why do you think, up until now, chimney EVAR “has been in the shadows”?
The option to treat pathologies with off-the-shelf devices (with currently available abdominal stent grafts) as in the chimney technique is very comfortable for physicians. On the other hand, the use of several combinations in a limited number of patients treated, and reported in a plethora of single-centre studies, underlined the lack of standardisation for the appropriate combinations between abdominal stent grafts and chimney covered stents. Correct combinations are needed to minimise the risk of gutters which can be persistent and finally lead to type Ia endoleaks requiring reintervention. The lack of standardisation made difficult to obtain a clear picture of the chimney technique creating enthusiastic reports on the one side and criticisms on the other. Therefore, until the publication of the PERICLES Registry in Annals of Surgery, chimney EVAR “had been in the shadows”.
Compared with branched and fenestrated devices, what do you think the potential advantages and disadvantages of chimney EVAR are?
There is no doubt that use of off-the-shelf devices allows treatment of symptomatic or ruptured pathologies without delay. Additionally, the use of flexible and low profile abdominal devices expands the application of total endovascular means in hostile iliac arteries with severe tortuosity and calcification or hostile neck with high-grade angulation. These conditions are not friendly for fenestrated devices which need straighter aortic neck and absence of severe angulation and stenosis of the iliac arteries. Moreover, the chimney technique is cost-effective. Another indication which demonstrates clear superiority of the chimney technique is the treatment of type Ia endoleaks after failed EVAR and migration of stent grafts. The cannulation of the renal arteries from the upper extremity is beneficial mainly due to downward orientation of the renal arteries and flexible abdominal tubes perform very well in angulated necks. On the contrary, cannulation of the renal arteries through the fenestrations in case of fenestrated endografting, having often the suprarenal stent struts of the migrated endograft between the renal origin and the fenestrations, can be very tedious and technically challenging.
On the other hand, the absence of a clear recommendation for the needed new neck length after placement of chimney grafts to achieve durable results makes the option to perform single or multiple chimneys free for the physicians. This is a potential disadvantage for the chimney technique. Involvement of more target vessels and chimney graft placement in more than one aortic branches create a longer new neck which is crucial in order to avoid late endoleaks. On the other hand, single chimneys may be technically easier but the new neck length is shorter and this can lead to late type Ia endoleaks with need for reintervention. This liberal decision about the number of the chimney graft placement and finally the determination of the length of the created neck is one of the major limitations of the chimney technique. Therefore, the PERICLES Registry presented for first time in the literature that the needed new length to achieve durable mid-term results has to be at least 20mm.
In your opinion, will off-the-shelf fenestrated and branched devices replace parallel graft in the future?
There is no doubt that use of off-the-shelf fenestrated devices will be another good option in our armamentarium to treat pathologies in the urgent setting. However, we have to wait and evaluate the applicability of these devices in urgent cases because they have also some remarkable anatomical limitations which may be a drawback to use them in urgent cases. Finally, planning and sizing of these devices requires advanced skills.
What further data for chimney EVAR are required?
The next step will be the evalutation of long-term results after chimney-EVAR and the detection of the most appropriate combinations in order to minimise the risk for gutters and potentially clinically relevant type Ia endoleaks.