University of Groningen Advances in complex endovascular aortic surgery Dijkstra, Martijn Leander

Advances in complex endovascular aortic surgery

Dijkstra, Martijn Leander

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martijn l. dijkstra

advances in complex

PhD thesis, University Medical Center Groningen, with a summary in Dutch ISBN: 978-94-6361-038-4

Copyright © M.L.Dijkstra, 2017 Groningen

All rights are reserved. No part of this book may be reproduced or transmitted in any form or by any means, without prior written permission of the author.

Cover design: Optima Grafische Communicatie (www.ogc.nl) Lay-out: Optima Grafische Communicatie (www.ogc.nl) Printed by: Optima Grafische Communicatie (www.ogc.nl)

Financial support by the Dutch Heart Foundation for the publication of this thesis is grate-fully acknowledged.

Additional financial support was gratefully provided by: Wetenschapsfonds Martini Ziek-enhuis, Rijnstate onderwijsinstituut, Bayer, Chipsoft, Krijnen Medical Innovations, Exam vision, Noord 90, Pfizer, Sanofi-Aventis, ScoVas Medical, Siemens, Vascutek

Advances in complex endovascular aortic

surgery

PhD thesis

to obtain the degree of PhD at the

University of Groningen

on the authority of the

Rector Magnificus Prof. E. Sterken

and in accordance with

the decision by the College of Deans.

This thesis will be defended in public on

Monday January 22

_{2018 at 16:15 hours}

by

Martijn Leander Dijkstra

born on January 26

₁₉₈₅

Co-supervisors:

Dr. M.M. Reijnen Dr. M.J. van der Laan

Assessment committee:

Prof. M. Mariani Prof. L.J. Schulze Kool Prof. E.L.G. Verhoeven

Chapter 1: General introduction 9

Chapter 2: Intraoperative C-arm cone-beam

computed tomography in fenestrated/branched aortic endografting

23

Chapter 3: Dutch experience with the fenestrated Anaconda endograft for short-neck infrarenal and juxtarenal abdominal aortic aneurysm repair

39

Chapter 4: Midterm results of the fenestrated Anaconda endograft for short-neck infrarenal and juxtarenal abdominal aortic aneurysm repair

55

Chapter 5: Endovascular Aneurysm Sealing for Juxtarenal Aneurysm Using the Nellix Device and Chimney Covered Stents

73

Chapter 6: Initial Experience With Covered Endovascular Reconstruction of the Aortic Bifurcation in Conjunction With Chimney Grafts

87

Chapter 7: One-Year Outcomes of Endovascular Aneurysm Repair in High-Risk Patients Using the Endurant Stent-Graft: Comparison of the ASA Classification and SVS/AAVS Medical Comorbidity Grading System for the Prediction of Mortality and Adverse Events

101

Chapter 8: Spinal cord ischemia in endovascular

thoracic and thoraco-abdominal aortic repair: review of preventive strategies

121

Chapter 9: Summary & future perspectives 149

Chapter 10: Nederlandse samenvatting 157

Chapter 11: Curriculum Vitae 165

chapter 1

General introduction

1

General inTroducTion

advances in complex endovascular aortic surgery

In 1948 Dr Rudolph Nissen performed an exploratory laparotomy on one of the most famous scientists of all time. He found that the patient suffered from an abdominal aortic aneurysm. At the time treatment options were limited and ligating the aorta had already been proven ineffective. He therefore ‘wrapped’ the aneurysm using cellophane hoping this would induce scar tissue formation and reinforce the aneurysm wall. The patient, Dr Albert Einstein, recovered from surgery and lived for several more years until 1955, when he developed severe generalized abdominal pain and died. Autopsy confirmed a ruptured aneurysm.1

Historically, as illustrated by the first paragraph, surgical procedures for aortic pathology were extensive and invasive. Most commonly for the abdominal aorta, a midline incision and trans-peritoneal approach was used. Subsequent dissec-tion of the retro-peritoneal space exposes the abdominal aorta, roughly from the level of the renal arteries to the iliac bifurcation. Alternatively a retroperitoneal approach can be used, which can be combined with a thoracotomy for more proximal disease.2, 3 _{Until recent, this has been the mainstay of treatment for}

both aneurysmal and occlusive aortic vascular disease. Needless to say, these approaches carry considerable peri-operative morbidity and mortality rates.4

The most widely used definition for an abdominal aortic aneurysm is an abdomi-nal aorta of more than 30 mm in diameter, measured perpendicular to the ves-sel. The infra-renal aorta is most commonly affected, but aneurysms can extend to (juxta-renal aneurysms) or beyond the renal arteries (supra-renal aneurysms) in up to 15 % of cases.5, 6 _{Distally, concomitant common iliac aneurysms are}

present in up to 20 % of the patients with an AAA.7

Pathogenesis is believed to be multi-factorial but remains largely unclear.8, 9 _{Several risk factors have been}

identified, including older age, male sex, Caucasian race, a family history of aortic aneurysms, smoking and the presence of other large vessel aneurysms.5

The vast majority of AAA patients is asymptomatic and identified incidentally upon physical examination or imaging studies. Symptomatic patients commonly present with non-specific abdominal, back or flank pain. In case of a ruptured aneurysm the classic presentation of severe abdominal pain radiating to the back, hypotension and a palpable pulsatile abdominal mass is present in about 50 % of cases.5 _{Rupture of an aortic aneurysm is a surgical emergency and is}

associated with very high morbidity and mortality rates.10 _{To prevent rupture}

a certain diameter, elective treatment is the course of action. Current practice guidelines encourage elective treatment for AAAs > 5.5 cm for men and > 5.0 cm for women, and for rapidly growing aneurysms (> 5 mm within 6 months).2, 3

If the indication for operative repair is established and the patient is deemed fit to undergo an intervention, there are now mainly two options: open surgery or endovascular repair. 2, 3 _{In 1952 Dubost et al. were the first to report an open}

AAA repair and the use of a conduit to exclude the aneurysm and restore blood flow. In this case, the thoracic aorta of a 20 year old female donor was used as a bypass, at the time synthetic grafts were not available yet (Figure 1).11 _Advances

1

(includ-ing polyester (eg. Dacron) and polytetrafluoroethylene (PTFE) grafts) led to the current open surgical treatment which has been the gold standard ever since. The only real contra-indication for open surgical repair is extensive co-morbid conditions with an unacceptable peri-operative mortality and morbidity risk. Relative contra-indications include a hostile abdomen, obesity and limited life expectancy.

In order to treat aortic disease without having to undergo major open surgery, endovascular aortic surgery has been developed.12 _{In 1986 the first case of an}

endovascular aneurysm repair was published by the Volodos et al.13 _{In the}

land-mark study by Parodi et al.14 _{the treatment of 5 patients using an intraluminal,}

stent-anchored, Dacron prosthetic graft with retrograde cannulation of the com-mon femoral artery was described (Figures 2 and 3). Initially the technique was utilized to treat patients deemed unfit for open surgery because of the novelty of the procedures, lack of follow up data and unknown durability. However, over the past two decades endovascular techniques and devices have evolved rapidly. This has resulted in a valuable alternative to open surgery, which has

Figure 2. Schematic by Parodi et al. showing intra-luminal exclusion of an aneurysm by means of Dacron tubular grafts delivered through the transfemoral route.

now become the mainstay of treatment for abdominal aortic aneurysms in the United States and other parts of the Western World.15 _{Adverse anatomy is the}

main limitation of EVAR. Ideally there should be adequate proximal and distal landing zones without significant angulation. The exact anatomic criteria depend on specific endograft instructions for use (IFU) as provided by the manufacturer. If however the aneurysm extends up to, or beyond the visceral vessels, EVAR falls short. Several more complex endovascular treatment options have been developed to address this shortcoming, including fenestrated EVAR (FEVAR)16

, branched EVAR (BrEVAR)17_{, chimney EVAR (ChEVAR)}18 _{and thoracic endovascular}

aneurysm repair (TEVAR).19

One of the major issues with EVAR is the post-operative occurrence of endoleaks. This occurs when there is persistent blood flow within the aneurysm sac after endograft deployment. Five different types of endoleaks have been described, depending on the origin of the leak (Table  1). Type II endoleaks are generally considered benign, although rupture does occur in a very small proportion of patients.20 _{Type I and III endoleaks do have a significant risk of aneurysm}

rup-ture if left untreated.21 _{The correct identification of endoleaks is therefore very}

important. Ideally, type I and III endoleaks should be identified peri-operatively and treated where possible. With increasing complexity of endovascular

pro-Figure 3. Aortogram by Parodi et al. showing successful aneurysm exclusion 53 days after endograft implantation.

1

cedures, conventional angiography can fall short and many centers perform a pre-discharge CTA in these cases. The development of flat panel detectors with cone beam CT capabilities have made it possible to obtain peri-operative CT-like images.22 _{It was hypothesized this allows for accurate endoleak identification}

and allow for prompt treatment. In addition, the cone beam CT images in conjunction with a pre-operative CTA can be used for image fusion and supply a roadmap. This in turn can facilitate target vessel cannulation and result in decreased operative time, fluoroscopy and contrast dosage. In chapter 2 the use of this novel technique to detect endoleaks and the possible benefits of a roadmap were investigated.

For conventional EVAR, there are a number of commercially available endografts. Having several device options gives the operator the advantage to choose an en-dograft which best matches the patients’ anatomy. For FEVAR options have been limited. The vast majority of patients have been treated using the Zenith custom-made fenestrated endograft (Cook Medical Australia, Brisbane, Queensland, Australia).23, 24

Alternative endografts have been launched recently, including in 2011 the Fenestrated Anaconda (Vascutek, Renfrewshire, Scotland).25 _This

custom-made endograft, based on the infrarenal Anaconda platform, has potential advantages compared to the Zenith endograft, including the option to reposition the endograft after initial deployment, less constraints in terms of fenestration position and upper access for antegrade cannulation of target vessels. In chapter 3 the initial experiences and short-term results with this new endograft in the Netherlands are presented. In FEVAR, high-technical success and good short-term results do not necessarily amount to a good treatment option. Mid- and long-term complications do arise and re-intervention rates are higher compared to open surgery.26 _{Longer term results will therefore ultimately}

decide the performance and value of a new endograft. A follow up study was

Table 1. Endoleak classification. Type of endoleak Origin

Type I Inadequate seal at graft ends IA Proximal

IB Distal IC Iliac occluder

Type II Branch vessels, e.g. lumbar or inferior mesenteric artery Type III Disconnection of graft components

Type IV Porous graft

undertaken and in chapter 4 the mid-term results of a larger cohort of patients treated with the fenestrated Anaconda in the Netherlands are presented. Both the Zenith and the fenestrated Anaconda endografts have extended the applicability of EVAR. Both endografts are however custom made and typically require 6 to 8 weeks to manufacture, which precludes their use in an acute set-ting. This presents a problem in patients presenting with either a symptomatic or a ruptured aneurysm that are not suitable for both conventional EVAR and open surgery. Off-the-shelf fenestrated endografts are being developed and used in clinical trials, but are still bound to anatomical restrictions. For these patients other ‘bailout’ procedures have been developed. The chimney EVAR (Ch-EVAR) procedure was initially used to treat unintentionally overstented target vessels during FEVAR27, 28

and has successfully been used in patients with juxtarenal aneurysms in urgent and emergency settings.29, 30 _{A caveat of this technique}

is the occurrence of so called ‘gutters’ between the chimney graft, the main graft and the aortic wall, resulting in endoleaks.31, 32 _{Combining the chimney}

technique with another novel technique called endovascular aneurysm sealing (EVAS) might resolve this. EVAS uses dual balloon-expandable stents surrounded by polymer-filled endobags (Nellix endoprosthesis, Endologix, Irvine, California, USA) which fill the aneurysm sac.33, 34 _{In chapter 5 the feasibility of the combined}

use of chimney grafts and EVAS is investigated in two patients deemed unsuit-able for FEVAR and open surgery.

As for aneurysmal disease, the gold standard for treatment of aorto-iliac oc-clusive disease has been open surgery and carries much the same morbidity and mortality risks.35 _{Parallel to the growing experience and evolving endovascular}

techniques in aneurysmal disease, progress has been made for the treatment of occlusive disease as well.36 _{The Inter-society Consensus for the Management}

of Peripheral Arterial Disease (TASC II)37

guideline recommends endovascular treatment for TASC A and B lesions, and open surgery for TASC C and D (if the operative risk is acceptable). Recent studies on endovascular treatment of aorto-iliac occlusive disease have shown high primary and secondary patency rates (87 % and 95 %) in patients with TASC C and D lesions using the covered endovascular repair of the aortic bifurcation (CERAB) technique.38 _{A prerequisite}

for successful treatment is a disease free proximal landing zone. Disease extend-ing up to, or beyond, the visceral vessels precludes endovascular treatment. In chapter 6 the feasibility of the chimney technique combined with the CERAB to extend the proximal landing zone was explored.

Lower morbidity and mortality rates are the main reason for pursuing and pushing the boundaries of endovascular treatment. Overall survival benefits

1

survival seems to be largely dependent on non-aneurysm related events, which might warrant a conservative strategy in high risk patients.39–41 _{This is based on}

fairly dated trials (published in 2005). Current practice has improved in terms of advanced imaging, improved devices, increased operator experience and patient selection, advances in peri-operative cardiopulmonary care and treat-ment of peri-operative adverse events. It was hypothesized this led to a decrease in peri-operative morbidity and mortality, even in high risk patients. Chapter 7 describes the outcomes of a large cohort of real-world high risk patients treated with conventional EVAR, specifically in terms of technical success, morbidity and 30-day and 1-year mortality.

Having the opportunity to treat extensive segments of the aorta by endovascular means does come with specific complications. Spinal cord ischemia (SCI) and concomitant paraplegia after endovascular aneurysm repair is one of the most dreaded complications, which is especially relevant after TEVAR.42–44 _{This has}

been the scope of extensive research and several preventive measures have been explored (spinal fluid drainage, avoidance of hypotension, staged repair, permis-sive endoleak, and hypothermia) but no optimal preventive strategy has been established. Guidelines mention some of these, but are not uniform. Chapter 8 aims to provide an overview of preventive measures used and their effectiveness to prevent spinal cord ischemia after TEVAR and recommend an optimal preven-tive strategy based on the available data.

Finally, the results of the studies are summarized and future perspectives dis-cussed in Chapters 9 and 10, in English and Dutch, respectively.

references

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4. Stather PW, Sidloff D, Dattani N, Choke E, Bown MJ, Sayers RD. Systematic review and meta-analysis of the early and late outcomes of open and endovascular repair of abdominal aortic aneurysm. Br J Surg. 2013; 100(7): 863-72.

5. Sakalihasan N, Limet R, Defawe OD. Abdominal aortic aneurysm. Lancet. 2005; 365(9470): 1577-89.

6. Gillum RF. Epidemiology of aortic aneurysm in the United States. J Clin Epidemiol. 1995; 48(11): 1289-98.

7. Armon MP, Wenham PW, Whitaker SC, Gregson RH, Hopkinson BR. Common iliac artery aneurysms in patients with abdominal aortic aneurysms. Eur J Vasc Endovasc Surg. 1998; 15(3): 255-7.

8. MacSweeney ST, Powell JT, Greenhalgh RM. Pathogenesis of abdominal aortic aneurysm. Br J Surg. 1994; 81(7): 935-41.

9. Nordon IM, Hinchliffe RJ, Loftus IM, Thompson MM. Pathophysiology and epidemi-ology of abdominal aortic aneurysms. Nat Rev Cardiol. 2011; 8(2): 92-102. 10. Reimerink JJ, van der Laan MJ, Koelemay MJ, Balm R, Legemate DA. Systematic

review and meta-analysis of population-based mortality from ruptured abdominal aortic aneurysm. Br J Surg. 2013; 100(11): 1405-13.

11. Dubost C, Allary M, Oeconomos N. Resection of an aneurysm of the abdominal aorta: reestablishment of the continuity by a preserved human arterial graft, with result after five months. AMA Archives of Surgery. 1952; 64(3): 405-8.

12. Criado FJ. EVAR at 20: the unfolding of a revolutionary new technique that changed everything. J Endovasc Ther. 2010; 17(6): 789-96.

13. Volodos NL, Karpovich IP, Troyan VI, Kalashnikova Yu V, Shekhanin VE, Ternyuk NE, et al. Clinical experience of the use of self-fixing synthetic prostheses for remote endoprosthetics of the thoracic and the abdominal aorta and iliac arteries through the femoral artery and as intraoperative endoprosthesis for aorta reconstruction. VASA Supplementum. 1991; 33: 93-5.

14. Parodi JC, Palmaz JC, Barone HD. Transfemoral intraluminal graft implantation for abdominal aortic aneurysms. Ann Vasc Surg. 1991; 5(6): 491-9.

1

15. Schwarze ML, Shen Y, Hemmerich J, Dale W. Age-related trends in utilization and outcome of open and endovascular repair for abdominal aortic aneurysm in the United States, 2001-2006. J Vasc Surg. 2009; 50(4): 722-9.

16. Georgiadis GS, van Herwaarden JA, Antoniou GA, Giannoukas AD, Lazarides MK, Moll FL. Fenestrated stent grafts for the treatment of complex aortic aneurysm disease: A mature treatment paradigm. Vasc Med. 2016; 21(3): 223-38.

17. Greenberg R, Eagleton M, Mastracci T. Branched endografts for thoracoabdominal aneurysms. J Thorac Cardiovasc Surg. 2010; 140(6 Suppl): S171-8.

18. Li Y, Zhang T, Guo W, Duan C, Wei R, Ge Y, et al. Endovascular chimney technique for juxtarenal abdominal aortic aneurysm: a systematic review using pooled analysis and meta-analysis. Ann Vasc Surg. 2015; 29(6): 1141-50.

19. Abraha I, Romagnoli C, Montedori A, Cirocchi R. Thoracic stent graft versus surgery for thoracic aneurysm. The Cochrane database of systematic reviews. 2016; 6: Cd006796.

20. Sidloff DA, Stather PW, Choke E, Bown MJ, Sayers RD. Type II endoleak after endo-vascular aneurysm repair. Br J Surg. 2013; 100(10): 1262-70.

21. Buth J, Harris PL, van Marrewijk C, Fransen G. The significance and management of different types of endoleaks. Semin Vasc Surg. 2003; 16(2): 95-102.

22. Eide KR, Odegard A, Myhre HO, Lydersen S, Hatlinghus S, Haraldseth O. DynaCT during EVAR—a comparison with multidetector CT. Eur J Vasc Endovasc Surg. 2009; 37(1): 23-30.

23. Greenberg RK, Sternbergh WC, 3rd, Makaroun M, Ohki T, Chuter T, Bharadwaj P, et al. Intermediate results of a United States multicenter trial of fenestrated endograft repair for juxtarenal abdominal aortic aneurysms. J Vasc Surg. 2009; 50(4): 730-7. 24. Verhoeven EL, Vourliotakis G, Bos WT, Tielliu IF, Zeebregts CJ, Prins TR, et al.

Fenes-trated stent grafting for short-necked and juxtarenal abdominal aortic aneurysm: an 8-year single-centre experience. Eur J Vasc Endovasc Surg. 2010; 39(5): 529-36. 25. Bungay PM, Burfitt N, Sritharan K, Muir L, Khan SL, De Nunzio MC, et al. Initial

experience with a new fenestrated stent graft. J Vasc Surg. 2011; 54(6): 1832-8. 26. Paravastu SC, Jayarajasingam R, Cottam R, Palfreyman SJ, Michaels JA, Thomas

SM. Endovascular repair of abdominal aortic aneurysm. The Cochrane database of systematic reviews. 2014(1): CD004178.

27. Donas KP, Torsello G, Austermann M, Schwindt A, Troisi N, Pitoulias GA. Use of abdominal chimney grafts is feasible and safe: short-term results. J Endovasc Ther. 2010; 17(5): 589-93.

28. Moulakakis KG, Papapetrou A, Giannakopoulos TG, Avgerinos ED, Kakisis J, Brountzos EN, et al. The chimney graft technique for preserving renal arteries in stent-graft sealing zones. Vasa. 2012; 41(4): 295-300.

29. Tolenaar JL, van Keulen JW, Trimarchi S, Muhs BE, Moll FL, van Herwaarden JA. The chimney graft, a systematic review. Ann Vasc Surg. 2012; 26(7): 1030-8.

30. Katsargyris A, Oikonomou K, Klonaris C, Topel I, Verhoeven EL. Comparison of out-comes with open, fenestrated, and chimney graft repair of juxtarenal aneurysms: are we ready for a paradigm shift? J Endovasc Ther. 2013; 20(2): 159-69.

31. Niepoth WW, de Bruin JL, Yeung KK, Lely RJ, Devrome AN, Wisselink W, et al. A proof-of-concept in vitro study to determine if EndoAnchors can reduce gutter size in chimney graft configurations. J Endovasc Ther. 2013; 20(4): 498-505.

32. De Bruin JL, Yeung KK, Niepoth WW, Lely RJ, Cheung Q, de Vries A, et al. Geomet-ric study of various chimney graft configurations in an in vitro juxtarenal aneurysm model. J Endovasc Ther. 2013; 20(2): 184-90.

33. Donayre CE, Zarins CK, Krievins DK, Holden A, Hill A, Calderas C, et al. Initial clinical experience with a sac-anchoring endoprosthesis for aortic aneurysm repair. J Vasc Surg. 2011; 53(3): 574-82.

34. Krievins DK, Holden A, Savlovskis J, Calderas C, Donayre CE, Moll FL, et al. EVAR using the Nellix Sac-anchoring endoprosthesis: treatment of favourable and adverse anatomy. Eur J Vasc Endovasc Surg. 2011; 42(1): 38-46.

35. Garcia-Fernandez F, Marchena Gomez J, Cabrera Moran V, Hermida M, Sotgiu E, Volo Perez G. Chronic infrarenal aortic occlusion: predictors of surgical outcome in patients undergoing aortobifemoral bypass reconstruction. J Cardiovasc Surg (Torino). 2011; 52(3): 371-80.

36. Goverde PC, Grimme FA, Verbruggen PJ, Reijnen MM. Covered endovascular reconstruction of aortic bifurcation (CERAB) technique: a new approach in treating extensive aortoiliac occlusive disease. J Cardiovasc Surg (Torino). 2013; 54(3): 383-7. 37. Norgren L, Hiatt WR, Dormandy JA, Nehler MR, Harris KA, Fowkes FG, et al. Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II). J Vasc Surg. 2007; 45 Suppl S: S5-67.

38. Grimme FA, Goverde PC, Verbruggen PJ, Zeebregts CJ, Reijnen MM. Editor’s Choice - First Results of the Covered Endovascular Reconstruction of the Aortic Bifurca-tion (CERAB) Technique for Aortoiliac Occlusive Disease. Eur J Vasc Endovasc Surg. 2015; 50(5): 638-47.

39. Greenhalgh RM, Brown LC, Powell JT, Thompson SG, Epstein D, Sculpher MJ. En-dovascular versus open repair of abdominal aortic aneurysm. N Engl J Med. 2010; 362(20): 1863-71.

40. De Bruin JL, Baas AF, Buth J, Prinssen M, Verhoeven EL, Cuypers PW, et al. Long-term outcome of open or endovascular repair of abdominal aortic aneurysm. N Engl J Med. 2010; 362(20): 1881-9.

41. Brown LC, Powell JT, Thompson SG, Epstein DM, Sculpher MJ, Greenhalgh RM. The UK EndoVascular Aneurysm Repair (EVAR) trials: randomised trials of EVAR versus standard therapy. Health Technol Assess. 2012; 16(9): 1-218.

1

42. 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(2): 369-77.

43. Ullery BW, Cheung AT, Fairman RM, Jackson BM, Woo EY, Bavaria J, et al. Risk factors, outcomes, and clinical manifestations of spinal cord ischemia following thoracic endovascular aortic repair. J Vasc Surg. 2011; 54(3): 677-84.

44. DeSart K, Scali ST, Feezor RJ, Hong M, Hess PJ, Jr., Beaver TM, et al. Fate of patients with spinal cord ischemia complicating thoracic endovascular aortic repair. J Vasc Surg. 2013; 58(3): 635-42.

chapter 2

Intraoperative C-arm cone-beam computed tomography

in fenestrated/branched aortic endograft ing

M.L. DIJKSTRA,

_{M.J. EAGLETON,}

_{R.K. GREENBERG,}

T. MASTRACCI,

_{AND A. HERNANDEZ,}

1 _{Department of Vascular Surgery, Cleveland Clinic, Cleveland, Ohio, U.S.} 2 _{Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio, U.S.} 3 _{Department of Quantitative Health Sciences, Cleveland Clinic, Lerner College of Medicine-CWRU.}

absTracT

Objectives: To evaluate the use of intraoperative guidance by means of C-arm

cone-beam computed tomography (CT) (cone-beam computed tomography [CBCT]) and the use of postoperative CBCT to assess for successful aneurysm exclusion in fenestrated branched endovascular aneurysm repair (FEVAR).

Methods: Patients with FEVAR who underwent CBCT were retrospectively

evaluated and categorized into one of two groups. The CBCT-fusion group was comprised of patients who underwent preprocedural CBCT to guide FEVAR using fusion imaging with multidetector computed tomography (MDCT). The postpro-cedure CBCT group consisted of patients undergoing CBCT following deployment of the endograft. Outcomes from the CBCT-fusion group were compared with historical controls. These controls were patients who underwent FEVAR for similar groups of abdominal and thoracoabdominal aortic aneurysms in the 12 months preceding the initiation of a CBCT program. The findings on postprocedural CBCT were compared with those on predischarge MDCT. Results are expressed as mean standard error of the mean, or as median and interquartile range.

Results: Forty patients were included in the “CBCT-fusion” group and compared

with the historical cohort. The use of perioperative guidance of FEVAR by means of CBCT resulted in a significantly lower contrast dose (94 cc [72-131] vs 136 cc [96-199]; P = .001). While there was a trend toward lower operative (330 minutes [273-522] vs 387 minutes [290-477]; P = .651) and fluoroscopy times (81 min [54-118] vs 90 minutes (46-128), P = .932); this difference did not reach statisti-cal significance. Nineteen patients were included in the “postprocedural CBCT” group and compared with predischarge MDCT. Postoperative CBCT identified eight endoleaks. Type I and III (n = 6) endoleaks were identified and treated during the primary procedure. When CBCT did not show an endoleak, this was confirmed by MDCT. The use of CBCT required significantly less contrast compared to MDCT (50 cc [set amount] vs 100 cc [80-125]; P  < .0001).Mean skin dose was 0.27 (0.011) Gy for preoperative CBCT and 0.552 (0.036) Gy for postoperative CBCT.

Conclusions: CBCT is a valuable addition to complicated aortic interventions

such as FEVAR. Intraoperative use utilizing fusion imaging limits contrast dos-age and postdeployment CBCT is of sufficient quality to evaluate successful aneurysm exclusion and for detection of early complications after FEVAR. With the information we are able to obtain from the CBCT at the completion of the FEVAR, we can intervene on problems earlier and potentially decrease the subsequent need for reintervention.

2

inTroducTion

Endovascular technology has evolved at a rapid rate, allowing for the treatment of more complex diseases. The endovascular treatment of complex aortic disease relies heavily on a combination of imaging modalities, but pre and postoperative computed tomography (CT) and intraoperative fluoroscopy remain the two most widely used radiologic tools. CT provides detailed morphologic information about the aorta, which allows for accurate preoperative planning and postoperative surveillance. While the complexity of the procedures increases, such as with the development of fenestrated/branched endovascular aneurysm repair (FEVAR), the ability to more accurately evaluate the three-dimensional (3D) architecture of the aortic tree before, during, and after surgery becomes increasingly important. While the use of multidetector computed tomography (MDCT) has allowed for the 3D imaging of these arterial structures in the pre- and postoperative period, intraoperative arterial assessment has historically been limited to two-dimensional (2D) angiography and fluoroscopy. Flat panel detectors (FPD) have begun to re-place the standard imager intensifiers used on conventional fluoroscopy units. The application of FPD has provided the ability to perform intraoperative 3D imaging using rotational angiography. C-arm cone-beam computed tomography (CBCT) is an advanced imaging capability that uses C-arm flat panel fluoroscopy systems to acquire and display 3D images. The FPD functions much like the multiline detec-tors used in MDCT and provides “CT-like” images in multiple viewing planes. CBCT systems are now commercially available and each manufacturer has its own imaging protocol that is tailored to each system’s different rotation time, number of projections acquired, image quality, and time required for reconstruction. There are at least three potential applications of CBCT in aortic endografting including its use for preprocedure anatomic assessment and stent-graft sizing,1–3

fusion imaging to guide device implantation, and postprocedural assessment of successful aneurysm exclusion. Preliminary experience has demonstrated its potential utility in pre- and postdeployment scenarios.1–5 _{One of the most}

poten-tially useful applications of CBCT is intraoperatively to guide the performance of fluoroscopy-driven procedures using fusion of CT images and fluoroscopy, similar to traditional “roadmapping.” Intraoperative CBCT images can be registered, or fused, with preoperative MDCT allowing the MDCT image to be superimposed on the live fluoroscopic image. The superimposed image will then update in the correct projection depending on the arc angle of the C-arm. There is little informa-tion about the usefulness of this technology in the treatment of aortic aneurysms or complex aortic disease. It has been shown, however, to accurately outline the coronary sinus anatomy and assist in guiding cardiac resynchronization therapy placement, which relies heavily on understanding the 3D structure of the heart.6

The aim of this study is to evaluate our initial experience using CBCT during FEVAR. CBCT is currently not sophisticated enough to allow for preoperative planning and sizing for FEVAR. This study will assess our initial experience with two other applications of CBCT: (1) the intraoperative use of CBCT to direct placement of fenestrated/branched endografts; and (2) the postdeployment use of CBCT to assess for the adequacy of endograft exclusion of the aortic aneurysm.

MeThods

All patients who underwent FEVAR between August 2009 and March 2010 were retrospectively evaluated. FEVAR was performed as part of an investigational device exemption protocol. Written informed consent was obtained from all pa-tients and the study was approved by the Institutional Review Board (IRB # 4281). Patients in whom CBCT was performed were reviewed and categorized into one of two groups. The “CBCT-fusion” group was comprised of patients who under-went predeployment CBCT and fusion of this image with a preoperative MDCT to guide placement of the fenestrated graft. The “postprocedural CBCT” group contained patients in whom CBCT was performed postdeployment to assess the effectiveness of aneurysm exclusion and maintenance of branch patency. CBCT was performed at the Cleveland Clinic since August 2009. Scans were performed on Artis zeego with syngo DynaCT (Siemens Healthcare, Forchheim, Germany) at the discretion of the operating surgeon using standardized proto-cols. The decision to perform CBCT was dependent on multiple factors including total radiation and contrast dose used during the primary procedure and base-line renal function. Excluded from both cohorts were patients who underwent FEVAR for type II thoracoabdominal aneurysms (TAAAs) and those patients undergoing staged endovascular procedures. Predischarge contrast-enhanced MDCT scanning was routinely performed for patients following FEVAR as part of the investigational device exemption study protocol. Patients who did not have a predischarge MDCT scan were excluded from the “postprocedural CBCT” group analysis. Patient demographics, operative data, and follow-up data were extracted from the medical records.

cbcT fusion

This cohort entailed patients who used predeployment CBCT fusion with preop-eratively performed MDCT to direct FEVAR placement. Predeployment CBCT was performed using a 5sDR or an 8sDR protocol. The 5sDR protocol has a 5-second acquisition time capturing 133 frames at 30 frames/second (f/s) where the 8sDR

2

Figure 1. Images depicting the fusion of the cone-beam computed tomography (CBCT) performed prior to stent graft introduction. The colored images represent those of the pre-operative multidetector computed tomography (MDCT), while the gray-scale images are the ones obtained from the CBCT. The images are aligned in multiple planes including (A) axial, (B) anterior, and lateral (not shown). Once the scans are registered, or fused, with each other, the images from the MDCT can be overlaid on the live fluoroscopic image.

Figure 2. Example of an image that has been fused with the live fluoroscopy-obtained im-age. The images obtained on cone-beam computed tomography (CBCT) are fused with those of the preoperative multidetector computed tomography (MDCT). The baseline aortic morphology (A) can then be depicted on the live fluoroscopy. The overlay image can either be the image of the aorta (as seen in Figure 3, panel A) or a computer-generated outline of the aorta (B).Note the location of the branches and the ostia of these branches, which are represented by circles (arrows). The image is fused with a three-dimensional (3D) orientation, and as the C-arm arc rotates, the orientation of the fused image will change accordingly.

takes 8 seconds with 397 frames at 60 f/s. Typically, bony structures and areas of heavy calcification identified on the CBCT were used as landmarks to “fuse” the CBCT image with the MDCT (Figure 1). In case of a heavily calcified aorta, or a stent graft in situ, the 5sDR protocol is sufficient for adequate registration to MDCT. In all other cases, the 8sDR allowed registration by means of soft tissue landmarks. The MDCT image can then be seen overlying the fluoroscopy image (Figure  2). Alternately, after adequate registration, the system automatically graphically outlines the aorta, and the ostia of the target vessels are identified and manually encircled in the MDCT dataset (Figure 3). These graphics are then overlaid and displayed live on the in-suite monitors (Figure 3). The system adjusts the overlay according to C-arm and table positions, making the location of the target vessel ostia and the outline of the aorta visible throughout the procedure. In this setting, predeployment aortography was not performed. FEVAR was performed based on the fusion imaging.

Figure 3. Image obtained from intraoperative fluoroscopy with multidetector computed to-mography (MDCT) images of the aorta (color) overlaid on the fluoroscopy image (A). The yellow circles represent the ostia of the visceral vessels. These are used to direct catheters and wires into the target vessels during the placement of a fenestrated endograft. Note the catheter (arrow) and wire (double arrow) that are within the highlighted left renal artery. B, Alternatively, a computer-generated graphic image of the aorta can be displayed on the live fluoroscopy image. Both the actual image and computer-generated image are linked in a three-dimensional (3D) setting and will rotate with revolution of the C-arm. Again, note the catheters and wires that are present in the visceral vessels. Notice that the catheter and wire in the left renal artery do not follow the exact path of the vessel. This represents one of the potential limitations of this technology in that while it can accommodate for rotation of the C-arm, it cannot account for the in vivo movement of the arterial tree.

2

results from this initial cohort were compared with outcomes from historical controls. The historical cohort was collected from patients undergoing FEVAR at the Cleveland Clinics in the 12 months prior to initiation of CBCT. These included all patients undergoing FEVAR with the exception of patients undergoing treat-ment for a type II TAAA. Demographics, operative details, and outcomes were compared between the two groups.

Postprocedural cbcT

The postprocedural CBCT group included patients in whom a completion CBCT was performed to assess the adequacy of repair. Postprocedural images were acquired using the 8sDSA protocol. Two complete runs are acquired including a native and a contrast run. The contrasted run required an injection rate of 10 cc per second for a total of 10 seconds. Fifty percent dilute contrast (Visipaque; GE Healthcare, Buckinghamshire, UK) was used routinely for a total of 50 cc of contrast per run. After acquisition, the data were automatically sent to the Syngo X-Workplace (Siemens Healthcare) and reconstructed to 3D datasets. CBCT images were reviewed by the operator and the main investigator in 2D side-by-side viewing, native vs contrast-injected images, and dedicated 3D postprocessing recon-structions (Figure  4) were developed and reviewed to optimize sensitivity and specificity. Reviewing was done using the Aquarius Workstation (Tera- Recon, San Mateo, California). CBCT and MDCT were evaluated for endoleaks, stent graft integrity, vessel patency, and aortic diameter measurements. Attenuation (Hounsfield unit [HU]) measurements of the stent graft lumen, aneurysm sac, and contrast extravasation (endoleak) if present were assessed. Results from postprocedural CBCT were compared with those on the predischarge MDCT.

sTaTisTical analysis

Data analysis was performed using SPSS statistics 17.0 (SPSS Inc, Chicago, Ill). Continuous variables are described as mean and standard deviation or median and interquartile range (IQR) in case of skewed data. Differences between con-tinuous variables were tested using independent t test for pre-CBCT vs historical cohort and paired t-test or the Wilcoxon rank-sum test (if n < 30) for post-CBCT vs MDCT. Categorical variables were tested using Pearson χ2 test or the Fisher exact test (if n < 5). Two-sided P values <.05 were considered significant. tion dosage for CBCT is noted as skin-absorbed dose expressed in mGy. Radia-tion dosage for MDCT is noted as dose length product expressed in μGycm.

resulTs

A total of 82 patients who underwent FEVAR were reviewed. In 40 patients, CBCT fusion was performed, 19 patients underwent a postprocedural CBCT, and eight patients underwent both. In the remaining 23 patients, no CBCT was performed, and they were excluded from further analysis.

Figure 4. Demonstration of endoleaks identified on cone-beam computed tomography (CBCT) and follow-up multidetector computed tomography (MDCT). (A) CBCT image idtifying the presence of a type II endoleak immediately following fenestrated/branched en-dovascular aneurysm repair (FEVAR). The arrow demonstrates a patent lumbar branch that provides continued flow into the aortic sac. Images demonstrating CBCT identification of type III endoleaks (B, C, and D). (B) demonstrates type III endoleak arising from the left renal artery (arrows). Axial reconstructions (C) demonstrate continued flow in the aneurysm sac. Note the ability to calculate HU within the aneurysm sac and within the aortic graft itself. Alternate fields of view (D), similar to that obtained with MDCT (E), can demonstrate the origin of an endoleak that is difficult to identify on conventional angiography. Note the ar-row demonstrating the origin of the type III endoleak arising from the superior mesenteric artery (SMA) branch (arrow).(E) For comparison, MDCT axial cross-section image of a type III endoleak arising from a SMA branch following FEVAR. Note that there is better visualization of the soft tissues in the MDCT compared with CBCT.

2

cbcT fusion

Demographics and operations performed were similar between the CBCT fusion group (n = 40) and the historical controls (n = 49) (Table 1). Median follow-up

Table 1. Demographic and operative characteristics of the CBCT fusion group and the his-torical controls.

CBCT fusion Historical control P value

Total 40 49 -Demographics Gender N (%) .628 Male 34 (85.0) 37 (75.5) Female 6 (15.0) 12 (24.5) Age (mean [SD]) 74.1 (9.5) 74.6 (7.0) .508 BMI (mean [SD]) 28.3 (5.1) 28.5 (4.3) .625 Comorbidities N (%) Diabetes 6 (15.0) 8 (16.3) .864 Hypercholesterolaemia 34 (85.0) 46 (93.9) .167 Carotid artery disease 6 (15.0) 7 (16.3) .924 Current Smoker 7 (17.5) 6 (12.2) .485 Family history of aortic aneurysm 3 (7.5) 11 (22.4) .054 Coronary artery disease 24 (60.0) 7 (16.3) .117 Renal insufficiency 10 (25) 11 (22.4) .778 Pulmonary disease 13 (32.5) 20 (40.8) .419 ASA classification N (%) .223 3 22 (55.0) 33 (69.3) 4 18 (45.0) 16 (32.7) Aneurysm anatomy N (%) .779 Juxtarenal 8 (20.0) 11 (22.4) Thoracoabdominal 32 (80.0) 38 (77.6) Number of fenestrations N (%) .683 1 1 (2.5) 0 (0.0) 2 2 (5.0) 4 (8.2) 3 19 (47.5) 25 (51.0) 4 18 (45.0) 20 (40.8) Helical branch N (%) .602 No 33 (82.5) 44 (89.8) Visceral 3 (7.5) 2 (4.1) Hypogastric 4 (10.0) 3 (6.1)

Abbreviations: BMI, Body mass index; ASA, American Society of Anesthesiologists (ASA) Physical Status Classification; CBCT, cone-beam computed tomography.

was 2 (1.3–4.0) months for the CBCT fusion group compared and 10 (8.0–14.5) months for the historical controls. All but one preoperative-acquired CBCT proved of sufficient quality for adequate image overlay (39/40 [98 %]). The 5sDR protocol was used in eight (20 %) cases, and the 8sDR protocol in 32 (80 %) cases. Median radiation dose was 0.18 Gy (0.11–0.25) for the 5sDR protocol and 0.29 Gy (0.27–0.31) for the 8sDR protocol. Median contrast dose was 94 cc for the CBCT fusion group compared to 136 cc in the historical cohort (P = .001) (Table 2). There was a trend toward lower operative times and fluoroscopy times in the CBCT fusion group, but this did not reach statistical significance (Table 2).

Technical success was defined as successful deployment of the endograft with stenting of all the target vessels. The procedure was technically successful in 84.8 % of the cases in the CBCT fusion group, compared with 89.8 % in the historical cohort (P=.98). In the CBCT group, there were four (10 %) cases in which one of the target vessels could not be cannulated (two renal arteries, one celiac artery, and one hypogastric artery) and thus were not stented. All visceral vessels were successfully stented at a follow-up procedure, and the hypogastric artery ultimately occluded and was left untreated. Early endoleak rates, detected on 1-month follow-up MDCT, did not differ in the CBCT fusion group (7 [17.5 %] type II and 1 [2.5 %] type III (endoleaks) compared to the historic control group (3 [6.1 %] type I, 3 [6.1 %] type II, and 4 [8.2 %] type III endoleaks).

Postprocedural cbcT

A total of 19 patients underwent evaluation by postdeployment CBCT. In this series, two infrarenal, four juxtarenal, and eight thoracoabdominal aneurysms

Table 2. Operative data from CBCT fusion and historical control groups

CBCT fusion Historical control P value

Fluoro time (minutes) Median (IQR) 81 (54–118) 90 (46–128) .932 Contrast dose (cc) Median (IQR) 94 (72–131) 136 (96–199) .001 Radiation dose (mGy) Median (IQR) 7 (4–12) 7 (5–10) .782 Operative time (minutes) Median (IQR) 330 (273 – 522) 387 (290–477) .651 Technical succes N (%) 28 (85) 44 (90) .975

Failure to cannulate celiac 1 (2.5) 1 (2.0)

SMA 0 (0.0) 2 (4.1)

Right renal artery 2 (5.0) 2 (4.1) Left renal artery 0 (0.0 0 (0.0) Hypogastric artery 1 (2.5) 0 (0.0)

Abbreviations: IQR, interquartile range; CBCT, Cone-beam computed tomography; SMA, su-perior mesenteric artery.

2

imaging by means of CBCT was performed prior to treatment for a known endoleak after FEVAR.

A total of 8 (36.8 %) endoleaks were found on postprocedural CBCT. Endoleaks were easily discernable. The stent lumen was found to have a mean attenuation value of 583.4  ±  58.6 HU. Contrast extravasation in the aneurysm sac mea-sured a mean attenuation 319 ± 20.8 HU compared with a mean attenuation 72.2  ±  44.5 HU for aneurysm sac without contrast extravasation, making endoleaks clearly visible (Figure  4). CBCT demonstrated two (10.5 %) type I endoleaks. One originated from the right common iliac artery and the second case was a proximal type I endoleak. In both cases, the endoleaks were success-fully treated with a limb extension and a proximal cuff, respectively. Four type III (21.1 %) endoleaks were found (Figure 4). Three originated from a renal artery branch, and one originated from a superior mesenteric artery (SMA) branch. All cases were successfully treated with either reangioplasty (n = 3) or placement of another stent (n = 1). Two (10.5 %) type II endoleaks from single lumbar arteries were diagnosed and left untreated. When there were no endoleaks visible on CBCT, this was confirmed by MDCT. There were no endoleaks found on MDCT that were not visible on CBCT. One type II endoleak found on CBCT was not visualized by the predischarge MDCT. No stent fractures were noted and all incorporated vessels were patent on CBCT, which correlated to MDCT findings. Diameter measurements obtained by CBCT were the same as those obtained on MDCT. All images had metal artifacts from the stent graft and guidewires in situ. These included two (10.5 %) stripe artifacts and two (10.5 %) calibration error artifacts. The latter arose from misalignment of the detector after it was accidentally dislodged. No movement artifacts were observed.

Median radiation dose for the whole procedure was 3.81 Gy (IQR 2.18–5.44). Postoperative CBCT contributed a median radiation dose of 0.55 ± 0.036 Gy. For MDCT, mean radiation dose was 2.56 ± 0.76 μGy/cm2. Contrast dose for CBCT was 50 cc (set amount) compared to median contrast dose of 100 cc (80–125) for MDCT (P < .0001).

discussion

Endovascular technology is rapidly advancing, allowing for the treatment of more complex disease processes such as complex aortic aneurysmal disease. Corresponding with these advancements is the need for improved intraoperative imaging capabilities that will allow the successful execution of these procedures.

The advent of FPDs and development of CBCT is a significant step forward in this process. As imaging systems at many centers are updated, this technology will become increasingly available. Given this, it is imperative that practitioners become familiar with these technologies and their potential applications. To date, little research has been presented regarding the application of CBCT during abdominal aortic interventions. This preliminary evaluation demonstrates that the use of intraoperative CBCT to guide deployment of fenestrated en-dografts results in significantly lower contrast dosage (P = .001), with a trend toward lower fluoroscopy and total operative times. Certainly, based on this data, one could call into question the significance of this technology, as the only significant difference was a 40-cc reduction in contrast use. In the authors’ opinion, however, the findings are extremely important. There is evidence to suggest that repeated doses of contrast agent may contribute to the develop-ment of lifelong nephrotoxicity.7 _{In addition, the application of this technology}

was limited to patients that did not have the need for more complicated fenes-trated/branched endograft placement, and few of the patients had significant renal impairment. This was at the discretion of the operating surgeons and represents self-imposed limitations during the initial application of this technol-ogy. Patients requiring aortic interventions, however, are not without significant contrast-associated risks due to the presence of pre-existing renal insufficiency.8

All efforts to reduce the use of contrast agents to the lowest dose that will allow successful performance of the procedure should be employed. With growing experience with this technology, the authors have found the use of CBCT-guided deployment of fenestrated/branched endografts invaluable, particularly in very complex anatomy and in patients with renal insufficiency. In fact, since the analysis of the analysis of these initial outcomes, the use of CBCT in this manner has been liberalized and the deployment of fenestrated/branched endografts has been performed using as little as 10 cc of contrast in patients with significant renal impairment. We suspect that on later analysis, as the experience grows, we will see an additional reduction in fluoroscopy and operative times as well. Postoperative CBCT provides an image quality sufficient for evaluating success-ful aneurysm exclusion and assessment of complications following endovascular aneurysm repair. One of the difficulties in assessing adequacy of treatment with FEVAR using completion angiography is determining the potential source of en-doleaks. Typically, if the source of an endoleak is not discernable by conventional angiography, it can be identified on follow-up MDCT. This requires, however, return to the operating room for a secondary intervention in the postoperative period.9 _{As described above, and by others,}4,5 _{postdeployment CBCT allows for}

2

In fact, case reports have been published showing CBCT is able to detect an endoleak where angiography fails to do so.4,5 _{We did not perform completion}

angiography in conjunction with completion CBCT to avoid the additional radia-tion and contrast loads. As such, direct comparison of sensitivity and specificity of endoleak identification between angiography and CBCT is not possible. It was noted, however, that when no abnormality was identified on CBCT, none was visualized on MDCT. With increased application of this technology, however, we will be able to more effectively evaluate the rate of subsequent re-interventions to determine whether this is reduced by the use of CBCT. One limitation, however, may be in the identification of type II endoleaks. In one case, CBCT identified a type II endoleak, which was not visible on the pre-discharge MDCT. There are multiple explanations for this finding including resolution of the endoleak prior to follow-up MDCT. Alternatively, MDCT failed to show the endoleak due to the fact that these scans are made on fixed times. CBCT acquisition is done during continuous contrast injection, allowing for uninterrupted evaluation of early arterial to venous phase images, not only demonstrating where the endoleaks might originate, but also when they do.

In addition, post-deployment CBCT proved to be adequate for assessment of in-corporated vessel patency and stent graft integrity. As has been previously dem-onstrated that diameter measurements on CBCT and MDCT showed comparable outcomes,3,10 _{results from this study support these findings. While not applicable}

to current fenestrated endografting, this technology may prove useful in the on-table planning and sizing of patients undergoing endovascular aneurysm repair (EVAR),1,2 _{particularly in the setting of ruptured abdominal aortic}

aneu-rysms. In addition, while this study was limited to the deployment of fenestrated endografts, the technology, both to guide deployment and to assess adequacy of aneurysm exclusion, can easily be applied successfully to the performance of elective EVAR and thoracic aortic endograft placement. In addition to using this imaging modality to plan and size for EVAR or thoracic endovascular aneurysm repair, the fusion technology can be used to more accurately deploy the graft near important branch vessels—without the use of contrast. In addition, it can be used to immediately assess the success of aneurysm exclusion. With increased experience and improvements with this imaging modality, it may be possible to ultimately supplant follow-up MDCT, at least in the short-term period. The use of CBCT, however, is not without its limitations. First, it is limited by the fixed area available for scanning. For instance, DynaCT (Siemens Healthcare) is limited by a maximum of 18-cm scanning distance in the z-axis, thus, in cases in which a long length of aorta is covered with a stent graft, the entire treatment area would not be imaged by CBCT. In addition, imaging artifacts were identified

in 10 % of the CBCT scans performed. Other problems include difficulty with contrast differentiations, particularly in areas of low radiographic contrast.11 _Of

some concern is the additional radiation dose provided by CBCT, particularly if two applications of this technology are performed during one operation. The radiation dose for a 14-second acquisition is similar to that of a biplane digital subtraction acquisition during a routine cerebral angiogram.12 _{Radiation dose,}

however, is higher in CBCT (236 mGy) compared to traditional 3D-DSA with a standard image intensifier (50 mGy).11 _{A comparison between the CBCT and}

MDCT in terms of radiation exposure is complicated by a lack of a universally accepted common dose metric. Previous experiments done using CBCT dem-onstrated a lower radiation dose compared to single helical CT, however in this experiment, contrast and spatial resolution were inferior to MDCT.10 _{Eide et al}

reported radiation doses to be comparable between these modalities, but ef-fective dose was calculated using a conversion factor to overcome some of the differences that cannot be directly measured.13 _{Estimates of radiation dosages in}

this article are derived from unpublished data supplied by Siemens Healthcare. These data suggest CBCT radiation dosage to be comparable or slightly higher compared with MDCT. Internal Alderson phantom measurements by Siemens report an estimated dose of 11 mSv for the 8sDR. The 5sDR protocol was not tested. An estimate derived from the values for the 8sDR would be roughly 11 mSv * (133/397) = 4 mSv. In comparison, literature reports an average estimated dose for completion aortography of 12 mSv (values reported 4.0–48.0) and 8 mSv (values reported 3.5–25) for abdominal MDCT.14

CBCT is a valuable addition to the endovascular suite and the treatment of complex and routine aortic diseases. In the preprocedural setting, it can be used to identify pathology and accurately plan treatment. Its use intraoperatively to guide the accurate placement of endovascular devices results in lower contrast doses and may ultimately reduce operative and fluoroscopy times. This will improve overall safety for both patients and surgeon. Lastly, CBCT appears to identify success of repair as readily as follow-up MDCT. Its use intraoperatively may reduce subsequent rates of reintervention following procedures such as FEVAR, but this has yet to be shown. Further studies evaluating a larger number of patients could potentially demonstrate the valuable nature of this technology in evolution.

Aknowledgements

The authors would like to thank Martin von Roden (Siemens Healthcare) for his technical assistance with regard to the imaging equipment.

2

references

1. Van den Berg J, Overtoom T, de Valois J, Moll F. Using threedimensional rotational angiography for sizing of covered stents. AJR Am J Roentgenology 2002; 178: 149-52. 2. Nordon I, Hinchcliffe R, Malkawi A, Taylor J, Holt P, Morgan R, et al. Validation

of DynaCT in the morphological assessment of abdominal aortic aneurysm for endovascular repair. J Endovasc Ther 2010; 17: 183-9.

3. Eide K, Odegard A, Myhre H, Lydersen S, Hatlinghus S, Haraldseth OD, et al. Com-parison with multidetector CT. Surg Eur J Endovasc 2009; 37: 23-30.

4. Biasi L, Ali T, Hinchcliffe R, Morgan R. Intraoperative DynaCT detection and immedi-ate correction of a type 1a endoleak following endovascular repair of abdominal aortic aneurysm. Cardiovasc Intervent Radiol 2009; 32: 535-8.

5. Biasi L, Ali T, Thompson M. Intra-operative dynaCT in visceral-hybrid repair of an exten-sive thoracoabdominal aortic aneurysm. Eur J Cardiothorac Surg 2008; 34: 1251-2. 6. Auricchio A, Sorgent A, Soubelet E, Regoli F, Spinucci G, Vaillant R, et al. Accuracy

and usefulness of fusion imaging between three-dimensional coronary sinus and coronary veins computed tomographic images with projection images obtained using fluoroscopy. Europace 2009; 11: 1483-90.

7. Solomon R, DuMouchel W. Contrast media and nephropathy: findings from sys-tematic analysis and food and drug administration reports of adverse effects. Invest Radiol 2006; 41: 651-60.

8. Haddad F, Greenberg R, Walker E, Nally J, O’Neill S, Kolin G, et al. Fenestrated endovascular grafting: the renal side of the story. J Vasc Surg 2005; 41: 181-90. 9. Roselli E, Greenberg R, Pfaff K, Francis C, Svensson L, Lytle B. Enodvascular

treat-ment of thoracoabdominal aortic aneurysms. J Thor Cardiovasc Surg 2007; 133: 1474-82.

10. Hirota S, Nakao N, Yamamato S, Kobayashi K, Maeda H, Ishikura R, et al. Cone-beam CT with flat-panel-detector digital angiography system: early experience in abdominal interventional procedures. Cardiovasc Intervent Radiol 2006; 29: 1034-8. 11. Irie K, Murayama Y, Saguchi T, Ishibashi T, Ebara M, Takao H, et al. DynaCT soft-tissue visualization using an angiographic C-arm system: initial clinical experience in the operating room. Neurosurgery 2008; 62(3 Suppl 1): 266-72.

12. Klucznik R. Current technology and clinical applications of threedimensional angi-ography. Radiol Clin North Am 2002; 40: 711-28.

13. Suzuki S, Furui S, Yamaguchi I, Yamagishi M, Watanabe A, Abe T, et al. Effec-tive dose during abdominal three-dimensional imaging with a flat-panel detector angiography system. Radiology 2009; 250: 545-50.

14. Mettler F, Jr, Huda W, Yoshizumi T, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology 2008; 248: 254-63.

chapter 3

Dutch experience with the fenestrated Anaconda

endograft for short-neck infrarenal and juxtarenal

abdominal aortic aneurysm repair

M.L. DIJKSTRA,

_{I.F. TIELLIU,}

_{R. MEERWALDT,}

_{M. PIERIE,}

_{J. VAN}

BRUSSEL,

_{G.W. SCHURINK,}

_{J.W. LARDENOYE,}

_{AND C.J. ZEEBREGTS.}

absTracT

Objective: In the past decennium, the management of short-neck infrarenal

and juxtarenal aortic aneurysms with fenestrated endovascular aneurysm repair (FEVAR) has been shown to be successful, with good early and midterm results. Recently, a new fenestrated device, the fenestrated Anaconda (Vascutek, Ren-frewshire, Scotland), was introduced. The aim of this study was to present the current Dutch experience with this device.

Methods: A prospectively held database of patients treated with the fenestrated

Anaconda endograft was analyzed. Decision to treat was based on current international guidelines. Indications for FEVAR included an abdominal aortic an-eurysm (AAA) with unsuitable neck anatomy for EVAR. Planning was performed on computed tomography angiography images using a three-dimensional workstation.

Results: Between May 2011 and September 2013, 25 patients were treated in

eight institutions for juxtarenal (n = 23) and short-neck AAA (n = 2). Median AAA size was 61 mm (59 - 68.5 mm). All procedures except one were performed with bifurcated devices. A total of 56 fenestrations were incorporated, and 53 (94.6 %) were successfully cannulated and stented. One patient died of bowel ischemia caused by occlusion of the superior mesenteric artery. On completion angiography, three type I endoleaks and seven type II endoleaks were observed. At 1 month of follow-up, all endoleaks had spontaneously resolved. Median fol-low-up was 11 months (range 1-29 months). There were no aneurysm ruptures or aneurysm-related deaths and no reinterventions to date. Primary patency at 1 month of cannulated and stented target vessels was 96 %.

Conclusions: Initial and short-term results of FEVAR using the fenestrated

Ana-conda endograft are promising, with acceptable technical success and short-term complication rates. Growing experience and long-short-term results are needed to support these findings.

3

inTroducTion

In the past two decades, endovascular aneurysm repair (EVAR) has evolved rapidly and has proven to be a good alternative to open repair in the treatment of infrarenal abdominal aortic aneurysms (AAAs). Advantages of EVAR include reduced periprocedural mortality, reduced postoperative complications, less blood transfusion requirement, and shorter hospital stay.1–4_{A variety of standard}

commercial devices are available for infrarenal EVAR. Standard endografts are insufficient in more complex anatomy lacking an adequate sealing zone in the infrarenal aorta (short neck length < 15 mm, angulation > 60°, a reversed coni-cal neck, or aneurysm involvement of important aortic side-branch vessels). Fenestrated and branched endografts have been developed for the treatment of these complex aneurysms. The use of fenestrated endografts was first intro-duced in 1996, and the subsequent evolution in devices and delivery systems has been enormous.5 _{In the past decennium, the management of short-neck}

infrarenal, juxtarenal, and suprarenal aortic aneurysms with fenestrated endo-vascular aneurysm repair (FEVAR) has been shown to be successful, with good early and midterm results.6–8 _{Most of the accumulated experience has involved}

the Zenith (Cook Medical Australia, Brisbane, Queensland, Australia) custom-made fenestrated endograft.

Recently, the new Fenestrated Anaconda Endograft (Vascutek, Renfrewshire, Scotland) was introduced for the treatment of juxtarenal and infrarenal AAAs with a short neck. Potential advantages of the endograft include the ability to reposition the body with a controlled deployment system, the ability to position the superior mesenteric (SMA) or celiac artery (CA) in an anterior augmented scallop, the ability to cannulate target vessels using axillary access, and the lack of stent material compromising the position of the fenestrations. The initial experiences with this new device were published in 2011 by Bungay et al.9 _The

aim of this study was to present the first Dutch experience with the fenestrated Anaconda endograft.

MeThods

design of the study

A prospectively held database was retrospectively analyzed. Research collabo-rators at the respective hospitals prospectively collected the data, which were entered into a centrally kept database. All patients underwent preoperative

assessment using multislice-detector computed tomography angiography (CTA). The decision to treat was according to current international guidelines.10,11

Indi-cations for FEVAR included an AAA with unsuitable neck anatomy for conven-tional EVAR (aortic neck length < 15 mm, neck angulation > 60°, conical neck). Planning was performed from CTA images and multiplanar reconstructions on a three-dimensional (3D) workstation. The procedures took place in a hybrid suite equipped for interventional radiology and open surgical procedures or in a surgical theater using a recent-generation mobile C-arm.

Follow-up consisted of CTA at 1 month and 1 year, and CTA scanning every other year thereafter. Given the data were anonymous and analysis performed retro-spectively, the study was exempted from Institutional Review Board approval.

description of the fenestrated anaconda endograft

The fenestrated Anaconda endograft is a new customizable device for individual patient use and is based on the Anaconda AAA endograft system (Conformité Européene approved).12 _{The device is trimodular and consists of a dual proximal}

ring stent with two or four fixation hooks (depending of the configuration of the fenestrations), an unsupported graft body that facilitates the nitinol-reinforced fenestrations, and a distal ringed stent. A range of endograft configurations is currently available, allowing for one up to four fenestrations. Also, the addition of an augmented valley (comparable to a scallop) and a bifurcated or a tube design add further possibilities to treat AAAs with a various range of anatomy (Figure 1). The instructions for use advise oversizing the main device by 10 % to 20 %. The outer diameter of the main device introducer is 20F or 23F, depending on the size. Construction time for the device is 6 weeks.

The fenestrated Anaconda has several special features that are new. It can be repositioned after full deployment, allowing for accurate deployment and easy repositioning of the endograft body and its fenestrations. The fenestrations are placed in the unsupported region, in this way maximizing the area available and potentially allowing for easier alignment and subsequent cannulation of target vessels. The lack of columnar strength combined with a ringed distal design might also allow for treatment of more angulated and stenotic anatomy. Preoperatively, a 3D model of each patient’s aorta was made and a test run per-formed using an exact copy of the endograft that was planned to be implanted. This allowed for ex vivo visualization of the endograft and fenestration position and also for radiographically controlled cannulation of fenestrations with wires and catheters.

3

stent implantation

Bilateral open femoral access was obtained. All patients received 5000 U of heparin before femoral artery cannulation, with additional boluses of heparin added intraoperatively depending on the length of the procedure. After intro-duction and deployment of the fenestrated main body, the fenestrations and target vessels were cannulated, guided by the four radiopaque markers at each fenestration and by the radiopaque saddle-shaped top stents (Figure 1). At this point, angiography was performed to confirm the position. If not satisfactory, the control and release wires could be used to collapse the top ring stent and the device repositioned to achieve a more satisfactory position. Once the graft was in place, the target vessels were provided with covered stents using standard endovascular techniques, which were flared with a 12-mm x 20-mm balloon. Finally, the limb extensions were placed, and a completion angiogram was performed.

Figure 1. Illustrations of the fenestrated Anaconda show (a) the endograft with the top stents collapsed, (b) the endograft after deployment, and (c) the endograft in situ. In this case, a three-fenestration device with a valley for the celiac artery (CA) was used. (Figure provided by Vascutek, Renfrewshire, Scotland.)