EnChEVAR: A Force for Standardization

The use of EnChEVAR could change the view of physicians regarding the chimney technique, says Konstantinos Donas, Professor of Vascular Surgery and Director of the Vascular Centre at Rhein Main. Professor Donas offers vascular and endovascular services in 3 clinics (Asklepios Clinic Langen, Wiesbaden, and Seligenstadt) in the south area of the federal state of Hesse, in the middle of Germany, and specializes in the evaluation and evolution of the chimney/snorkel endovascular technique in the treatment of complex aortic aneurysms – the topic of his talk Thursday at LINC. 

EnChEVAR is a novel acronym using two Medtronic devices, explained Professor Donas. The standard use of the Endurant II stent-graft is ChEVAR, but used in combination with the Radiant chimney graft, it is marketed as EnChEVAR. “It is a CE-mark approved combination of parallel grafts, allowing an on-label therapeutic option for complex aortic aneurysms, complementary to fenestrated endografting,” he told LINC Today. “EnChEVAR aims to standardize the device combinations for parallel grafts based on profound in vivo and in vitro research and clinical evidence in the European Society for Vascular Surgery guidelines.” 

The combination fills a gap, said Professor Donas. “Lack of standardization, due to the plethora of the available off-the-shelf devices in the stock of each center, has been the main criticism of the parallel grafts technique, and has led to divergent experiences and outcomes,” he explained. 

But standardization is not the only crucial factor in the selection of suitable devices. “Very important also is the preoperative planning and sizing,” said Professor Donas. “Diameter in the planned seal zones of the aortic endografts of more than 30 mm represents a risk for persistent gutter endoleak.”

Additionally, the length of the new landing zone should be more than 20 mm based on the PROTAGORAS and PROTAGORAS 2.0 published experience, said Professor Donas. The PROTAGORAS study evaluated the performance of the Endurant II/IIS stent-graft for patients with pararenal pathologic processes that were treated by the chimney/snorkel endovascular technique. The PROTAGORAS 2.0 Study has been conducted to identify sizing and planning predictors for optimal outcomes in abdominal chimney endovascular procedures. 

As regards the EnChEVAR procedure, there are many parameters that play a crucial role in the final outcome, noted Professor Donas, one being education. “Participation at different workshops and creation of a dedicated endovascular nurse team are tips to achieve good perioperative and durable results,” he advised.

Important trials have been conducted around this combination of grafts, he went on: “I am more than glad to participate in different research groups to contribute to the evidence around the parallel grafts, for example in the Endurant CHevAr New Indication Trial: ENCHANT trial and the PROTAGORAS 2.0 study.” During the same session on Thursday at LINC, Giovanni Torsello, principal investigator of the ENCHANT trial, presented the findings of this unique exploration of the chimney technique, and Stefano Fazzini presented which parameters play a crucial role in the preoperative planning in order to have durable results. “Reproducible outcomes from other centers following EnChEVAR standardization rules are necessary and will improve the credibility of the technique,” added Professor Donas.

Other trials informing EnChEVAR include that of Professor Donas’ colleague, Gergana Taneva, the scientific leader of his research group and an assistant professor at his institution. She published last month in the European Journal of Vascular and Endovascular Surgery on a unique in-vitro evaluation of the EnChEVAR technique.¹ The study showed the variability of performance with each theoretically possible chimney device and explained the divergent outcomes in the published literature. “Balloon-expandable covered stents in combination with the Endurant abdominal device confirms superiority vs bare-metal stents,” relayed Professor Donas. 

“The presence of stent-graft infolding in each test underlines the need for prolonged perioperative kissing ballooning between the aortic stent-graft and the chimneys. Angulation evaluation demands the need for further investigation in transversely or upward-oriented target vessels.” 

EnChEVAR may therefore change the skepticism around the procedure, hopes Professor Donas. “Rather than a ‘bailout’ procedure for the chimney technique, it could become a standardized, therapeutic, complementary option,” he said in closing. 

REFERENCES

1. Taneva GT, Usai MV, Pitoulias GA, Donas KP. In vitro radiological evaluation of different types of chimney stents using a silicon flow model with adjustable physiological simulating conditions. Eur J Vasc Endovasc Surg. 2023;S1078-5884(23)00366-0.