MMCTS
(May 23, 2008). doi:10.1510/mmcts.2007.003095
Copyright © 2008 European Association for Cardio-thoracic Surgery
Procedure
Endovascular grafts for thoracic aortic pathologies
Hani Shenniba,*,
Marko Turinab,
Venkatesh G. Ramaiaha,
Julio Rodriguez-Lopeza,
Grayson Wheatley, IIIa,
Jacques Kpodonuc and
Edward Diethricha
a Arizona Heart Institute, Phoenix, AZ, USA
b University Hospital Zurich, 8091 Zurich, Switzerland
c Northwestern Memorial Hospital, Chicago, IL, USA
* Corresponding author: Cardiovascular Research Center, Mercy Gilbert Medical Center, Catholic Health West, Gilbert, Arizona.hani.shennib{at}mcgill.ca
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Summary
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Endovascular aortic repair (EVAR) is rapidly being adopted to capture a substantial proportion of surgical candidates with aneurysmal disease of the descending thoracic aorta. This new technique requires both special equipment (hybrid operating room, full range of catheterization tools) and additional technical skills, which an average cardiothoracic surgeon usually lacks, not being exposed to this particular training during his formative years. Presently, EVAR is applied to high-risk surgical candidates, its main advantages being the avoidance of cardiopulmonary bypass, minimal invasiveness (no large incisions) and often the ability to perform the procedure under local anesthesia. Early mortality in the author's (H.S.) institution is comparable to the best surgical results published, which is remarkable with respect to the high-risk patients. The techniques are rapidly being developed, with treatment of the aortic arch aneurysm employing transposition of supra-aortic arteries, and of the thoraco-abdominal aneurysms with branched grafts.
Key Words: Aneurysm • Aortic arch • Aortic grafts • Endovascular therapy • Thoracic aneurysm • Thoracic aorta
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Introduction
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An essential condition for performance of endovascular aortic repair is a hybrid operating room with good imaging facilities, preferably with intravascular ultrasound (IVUS) (Video 1 and Photo 1); and necessary ancillary equipment for a successful endovascular aneurysm repair (EVAR).
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Video 1 Intravascular ultrasound together with angiography in a dissecting aortic aneurysm. It is essential to have IVUS to optimize landing zones and to prevent the placement of the endoprosthesis in the wrong lumen.
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Photo 1 Additional information about the exact relation of the subclavian artery to the actual post-traumatic aneurysm can be quickly gained from IVUS images.
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Catheter equipment necessary for performing EVAR
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Full scale of various guidewires and dilators is necessary for successful performance of EVAR. The guide-wires are long stiff wires (260 cm). The softer wires are preferred to initially navigate often diseased, small or tortuous iliac arteries.
The introduction of an EVAR graft is performed through large diameter sheaths which are usually in the size of 22–24 French (6.7–8 mm).
A substantial choice of catheters is necessary for angiography and planning the procedure: Pigtail, Marker pigtail, TR flush. Bentson 2 (JB2); headhunter, IM, Vitek, Glide catheters and others may be used to cannulate arch branches if needed. Furthermore, therapeutic balloons as well as various profiled balloons are essentials in the EVAR armamentarium – MMCTSLink 169 and MMCTSLink 170.
A useful tool is the trilobar balloon – MMCTSLink 171 – which has the advantage of not obstructing the flow in the aorta when an inflation is performed. The residual flow in the aorta is essential to prevent displacement of the graft when implanting the balloon.
EVAR specialists also need additional tools like snares, embolization coils, stents and covered stents which are essential to deal with the diversity of pathologies when performing thoracic and abdominal endoluminal grafts.
The snares are used to deliver a brachiofemoral wire which can be used to facilitate placement of the thoracic endoluminal graft past the excessive angulation along the iliac arteries and proximal descending thoracic aorta (Video 2). The schematic use of a snare is shown in Schematic 1.
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Video 2 The snare is coming from the innominate artery and will grasp the catheter which comes by the transfemoral route to assure the placement of the endovascular graft in the aortic arch.
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Schematic 1 Introduction of right brachiofemoral wire to assure the proper placement of the endovascular graft in the aortic arch covering the origin of the left subclavian artery.
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Endoluminal grafts for use in the thoracic aorta
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A variety of endoluminal grafts were adapted from original abdominal aortic designs and are now currently applied to the thoracic aorta. In Europe, several thoracic endoluminal grafts have been approved for use in selected indications (Talent, Valiant, TAG, Zenith, Endofit). In the USA, TAG was approved two years ago and Talent in the summer of 2008.
Several modifications in the design of Talent led to the Valiant device which is widely used in Europe and in Australia. The construction is shown in Photo 2.
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Photo 2 Talent graft made of polyester with a nitinol wire as a skeleton. At the end of the device there are springs which are used to stabilize the device; these distribute their circumferential force around the proximal end of the device without causing-penetration. (Copyright Medtronic. Courtesy of Medtronics. All rights reserved.)
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The first Talent graft was implanted in 1996 in Australia; presently, approximately 20,000 of these devices have been used clinically and Talent served in the Valor trial which was submitted to the FDA [1].
The actual implantation of the device is shown in a series of schematic representations (Schematics 2, 3, 4).
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Schematic 2 Insertion of the system over the stiff guide wire. The system is advanced to the target landing zone and it is deployed several millimeters proximally. Stamp position is verified by angiography.
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Schematic 3 The endograft is delivered by turning the delivery system several times until the graft cover separates from the tip and the first stents are deployed. At this point angiography is performed to verify the position of the graft.
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Schematic 4 The delivery system is removed by depressing the Quick Disconnect button and the handle is pulled back to retract the tip into the graft cover. After establishing a smooth transition between the tip and graft cover the entire delivery system is removed.
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The Endofit device (Photo 3) has the great advantage of flexibility and tapering. This is particularly useful in dissecting aneurysms where the same lumen throughout the system might result in folding of the dissection, and where the proximal part of the aneurysm, distal to the subclavian artery, usually has the largest diameter.
In the US, the Gore Tag [2] is the only device approved for use in the thoracic aorta (Schematic 5).
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Schematic 5 In order to qualify for the Gore Tag implantation the proximal neck should be at least 20 mm. The length of the device is limited to 40 cm in commercial use and the aortic neck diameters should range between 23 and 37 mm.
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The limitation shown in the illustration basically restricts the use of the device to a less extensive thoracic aortic aneurysm, but the devices are widely used off-label to treat a variety of thoracic aortic pathologies and in different locations beyond its original recommendation.
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Results
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At the Arizona Heart Institute endografting was used in the thoracic aorta in 504 patients [3]. The Gore device was used in the vast majority of them (79.4%).
The overall mortality was 8.3% (42 patients out of 504). Respiratory complications caused death in 8 patients; vascular complication in 7 patients; myocardial infarction in 7; renal failure in 3; cerebrovascular accident in 1; unknown cause of death in 8.
The overall incidence of spinal cord neurologic events was 14 out of 409 patients (3.6%). Out of those, four resolved, three improved significantly and seven remained with significant neurologic deficits (1.8%).
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Future use of thoracic EVAR
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The potential indication for use of thoracic endografts is shown in Schematic 6.
There is a widespread range of indications, atherosclerotic aneurysms being the most common pathology, followed by chronic dissection with expansion. The evolving indications for EVAR are in the area of aortic ulcer and recurring distal embolization from a severely diseased thoracic aorta. Excellent indication is furthermore the acute traumatic transection of the aorta, and the acute aorto-bronchial and aorta-esophageal fistulae. EVAR is also used widely in an adult coarctation, both for primary treatment as well as for the late complications of surgical coarctation repair with development of a pseudoaneurysm, especially after patch repair. In the vast majority of the patients, nowadays a transfemoral approach can be used: it was possible in 87% of procedures in the Arizona Heart Institute. Only in 9.2% of patients the iliac conduit had to be implanted as a means of access for the endograft.
Some examples can be given here: penetrating aorta ulcer can be very efficiently covered with an endograft (Photos 4 and 5).
The use of an endograft in hybrid procedures is shown in a patient with an aortic aneurysm following a previous coarctation repair (Photo 6 and Schematic 7). The aneurysm extends into the subclavian artery which makes a hybrid procedure necessary. In Photo 6 the aneurysm is shown in its entirety.
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Photo 6 Patient with substantial aneurysm of the upper thoracic aorta and of the left subclavian artery following previous coarctation repair.
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Schematic 7 Schematic of the repair done in this case. The subclavian aneurysm was surgically resected and the subclavian artery implanted into the left carotid artery.
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In a second step the endograft was placed (Photo 7).
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Photo 7 Finished repair. The patient had an endograft placed which covered the origin of the left subclavian artery and excluded the thoracic aneurysm.
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The dissecting aneurysms can be difficult to treat with endografting because a distal vascular compromise can occur (Photo 8).
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Photo 8 Distal true lumen compromise after placement of an endograft in the dissecting aneurysm of the descending thoracic aorta.
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This distal compromise can be repaired with an open stent which is used to dilate the true lumen. The final result is shown in Photo 9.
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Photo 9 Distal flow compromise is resolved in a patient with type B dissection after placement of the distal open stent and normalization of the distal blood flow.
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Future development of the thoracic aorta endografting will be found in the area of true thoraco-abdominal aneurysm [4] (Schematic 8).
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Schematic 8 Treatment of the thoraco-abdominal aneurysm encompassing the origin of the vessels involves the use of endografts with prepared side-arms which are used for placing them into the superior mesenteric, celiac and both renal arteries. (Reproduced with permission from David Hartley.)
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Devices which are under development (and almost ready for clinical trial) are those which will be used for treatment of the aortic arch aneurysm. The Talent device is shown in Video 3.
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Video 3 Expansion of the preformed device in the aortic arch with arms of the graft entering the innominate artery, the left carotid and the left subclavian artery.
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References
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- Fattori R, Nienaber CA, Rousseau H, Beregi JP, Heijmen R, Grabenwöger M, Piquet P, Lovato L, Dabbech C, Kische S, Gaxotte V, Schepens M, Ehrlich M, Bartoli JM, Talent Thoracic Retrospective Registry. Results of endovascular repair of the thoracic aorta with Talent thoracic stent graft: the Talent Thoracic Retrospective Registry. J Thorac Cardiovasc Surg 2006;132:332–339.[Abstract/Free Full Text]
- Bavaria JE, Appoo JJ, Makaroun MS, Verter J, Yu ZF, Mitchell RS. Endovascular stent grafting versus open surgical repair of descending thoracic aortic aneurysms in low risk patients: A multicenter comparative trial. J Thorac Cardiovasc Surg 2007;133:369–377.[Abstract/Free Full Text]
- Rodriguez JA, Olsen DM, Shtutman A, Lucas LA, Wheatley G, Alpern J, Ramaiah V, Diethrich EB. Application of endograft to treat thoracic aortic pathologies: a single center experience. J Vasc Surg 2007;46:413–420.[CrossRef][Medline]
- Greenberg RK, West K, Pfaff K, Foster J, Skender D, Haulon S, Sereika J, Geiger L, Lyden SP, Clair D, Svensson L, Lytle B. Beyond the aortic bifurcation: branched endovascular grafts for thoraco-abdominal and aortoiliac aneurysms. J Vasc Surg 2006;43:879–886; discussion 886–887.[CrossRef][Medline]
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Summary
Introduction
