Editorial | A brief history of EVAR and current devices | Which Medical Device

1994 saw the introduction of commercially produced bifurcated devices which enabled many more endovascular centres to get involved in the procedure and a shift towards the use of bifurcated devices worldwide. The early single component devices soon gave way to modular component systems, many of which have evolved through a number of iterations to become the devices of choice today.

Over the years the importance of a number of concepts relating to device design has become apparent. Broadly speaking these involve either the delivery system or the stent itself.  Delivery systems, once rather cumbersome and rigid have become more flexible, allowing access in extremely tortuous vessels, better proximal alignment and improved accuracy of stent deployment. In addition, re-deployment of the proximal fixation system is now possible. Regarding the proximal stent, supra- and infra-renal fixation systems have evolved, reducing stent-graft migration rates. Evolution of nitinol based systems has produced more conformable devices and will probably result in a reduction in long term stent fractures.

Main Bifurcated Devices in Commercial Use

The way device use is regulated varies worldwide. In the USA this is controlled by the Food and Drugs Administration (FDA); within the European Economic Area (EAA) devices must bear the ‘CE’ conformance mark for consumer safety, health and environmental requirements.

Talent – (Medtronic Vascular, USA)

The Talent is a modular (2 piece) stent-graft that has been used worldwide for over 10 years. The introduction system has a hydrophilic coating to reduce friction in tortuous iliac vessels and has stood the test of time with regard to ease of use and accuracy.  The graft is a nitinol and polyester fabric graft construction with a non-barbed suprarenal fixation stent. There has been a reduction in popularity in Europe since the Endurant became available.  

FDA approved & CE marked.

Endurant – (Medtronic Vascular, USA)

This is currently the most widely used device in Europe. Modular 2-piece design, nitinol based with similar polyester graft to the Talent device. Large proximal uncovered nitinol stent; stent configuration in body and limbs designed to increase flexibility and conformability. Small caliber introduction system (18F) facilitates percutaneous EVAR. Unique proximal cap so that the covered body can be deployed prior to releasing the proximal uncovered fixation stent.

CE marked and now also FDA approved since Dec 2010.  

AneuRx AAAdvantage – (Medtronic Vascular, USA)

This device has been around since the early days of EVAR, with over 15 years of use and the design now in its 7th generation. Modular two piece device with infra-renal fixation. No longer in common use in Europe but popular in the USA.

FDA approved & CE marked.

Zenith Flex - (Cook, Denmark)

Until the release of the Endurant this modular (3 piece) stent-graft was the most widely used stent-graft in Europe and there is a large world-wide experience over 15 years. Large proximal uncovered Gianturco stainless-steel stent; long body design with Z-stent configuration in body and limbs. Flexible 20-24Fr introduction system with a long tapered proximal cap; the covered body can be deployed prior to releasing the proximal fixation stent. Safety wires prevent inadvertent early release of the top cap. Robust device with good long term safety profile.

FDA approved & CE marked

Zenith Low Profile (LP) - (Cook, Denmark)  

New modular (3 piece) device, launched in 2010 as an addition to the Zenith series. The delivery system is an 18F hydrophilic, braided sheath. Like the Endurant this system facilitates the minimally invasive pure percutaneous approach. The new graft remains Dacron but is held on a nitinol frame with stent shapes that encourage conformability. There is a small top cap above the long suprarenal bare stent which is held in check by a very robust safety wire prior to satisfactory release of the main body.  

CE marked. 

Gore Excluder (WL Gore, USA)

Available world-wide since the early days of EVAR with continuous design improvements and good long-term follow up data. Modular two piece nitinol based device with infrarenal fixation. Longer body, 20Fr profile and larger contralateral limbs available. Recent introduction of a new ‘C3’ delivery system allows repositioning of the proximal sealing stent after initial deployment. This can be a real life saver in the short or difficult proximal aortic necks.

FDA approved & CE marked.

Powerlink (Endologix, USA)

Employed in Europe since 1999, the Powerlink device is a unibody bifurcated device.  A self-expanding single wire nitinol endoskeleton is covered with ePTFE fabric. The Powerlink is implanted through one surgically exposed femoral artery and a contralateral 9 Fr puncture. 

FDA approved & CE marked.

Aorfix (Lombard Medical, UK)

Two piece modular infrarenal device, which can be very useful in angulated proximal necks and tortuous iliac anatomy. A proximal (robust and barbed) fixation stent forms a fish mouth when compressed. The unique stent design uses encircling nitinol rings to provide maximum flexibility of the entire stent-graft. Excellent conformability to angulated anatomy.

CE marked.

Anaconda (Vascutek Terumo, UK)

The proximal orifice of this 3 piece modular infrarenal device can also form a fish mouth configuration. But in this case proximal fixation is with a double-stent ring which is uniquely leashed to the central introduction cannula. This particular mechanism allows for repositioning of the proximal device in difficult anatomy. The body of the device is largely unstented but nitinol rings in the limbs allow for excellent conformability to angulated anatomy.

CE marked.

Ovation (Trivascular, USA) 

This is a very new 3 piece device, with the first investigational clinical case implantations in September 2010. The stent graft body (with suprarenal stent) is delivered in a 14F (outer diameter) system, designed to expand the patient population suitable for EVAR by addressing a wider range of diseased anatomies. The proximal seal is provided by hollow rings in the fabric which are expanded by polymer injection after deployment. The stent-graft limbs are inserted separately.

CE marked.

Incraft (Cordis, USA)

This stent-graft is undergoing a preliminary trial in Europe. No available images or information regarding design other than the fact that the introduction system is 14F.

Final Thoughts

Over the last 20 years the volume of patients treatable via an endovascular approach has grown consistently, mainly due to advancements in device design.  Classically this revolved around new generations of existing devices, with a move towards lower profile delivery systems.  Importantly this has enabled EVAR in increasingly tortuous iliac anatomy and also allowed an entirely percutaneous procedure, shown to reduce wound complications compared to surgical cut-downs (1).  With increased market place competition,  greater number of manufacturers and dedicated research teams, increasingly novel design concepts are being seen; including a yet to be launched polymer fillable EVAR system developed by Nellix Endovascular (USA).  No doubt this technology will continue to evolve for the next 20 years and more.

Compare the range of EVAR devices mentioned above on Which Medical Device here.

References