Which Endograft Is Best?

Personal recommendations for achieving the best AAA outcome.

By DIETER RAITHEL, MD
 

To view the tables that correspond to this article, please refer to the print version of our November/December issue, page 40.

The high expectations seen during the initial phase of abdominal aortic aneurysm (AAA) endografting have been somewhat dampened by the close follow-up of the devices used in the minimally invasive procedure. In 1999, 70% of the infrarenal AAAs treated in my clinic were managed endovascularly. By 2001, the percentage of endovascular AAA procedures (EVAR) dropped to 45%. In 2002, we have seen a slight increase in the number of EVAR procedures, attributable to the fact that some endografts now show positive long-term results and others have been refined considerably. I expect that on the basis of careful patient selection and consideration of the initial failures, the rate of EVAR will probably stabilize between 50% and 60%. These rates however, may only occur in clinics with high expertise in endovascular techniques.

In the Department of Vascular Surgery at Nuremberg Hospital in Nuremberg, Germany, my colleagues and I began performing EVAR in August 1994. As of August 2002, we had treated 748 infrarenal aortic aneurysms and 72 thoracic aneurysms endovascularly. Median follow-up was 30 months.

Out of the 748 patients, we performed EVAR on 681 men and 67 women with a mean age of 70.1 years. The mean diameter of the aneurysms treated was 50.1 mm. We used 154 tubes, 591 bifurcated grafts, and three monoiliac systems. Between 1994 and 1997, we still implanted a relatively large number of tubes; we now apply tube devices in a few exceptional cases. Table 1 shows the different types of devices we used.

This series of repairs included ten ruptured aneurysms, which were treated three times with a tube graft: one MinTec (later Vanguard) and two Vanguard (Boston Scientific Corporation, Natick, MA). In seven cases we used a bifurcated graft: three Ancure (Guidant, Indianapolis, IN), one Endologix (Endologix, Irvine, CA), one Vanguard, and two Zenith (Cook, Bloomington, IN).

ANALYZING THE RESULTS
For results analysis, we have to compare the modular systems (AneuRx [Medtronic AVE, Santa Rosa, CA]; Excluder [W.L. Gore, Flagstaff, AZ]; Lifepath [Edwards Lifesciences, Irvine, CA]; Quantum [Cordis Corporation, a Johnson & Johnson Company, Miami, FL]; Talent [Medtronic AVE]; Vanguard; and Zenith) with the unibody systems (Ancure, Chuter [Boston Scientific], and Endologix). It is also important to compare grafts with suprarenal fixation to those with infrarenal fixation. The Endologix and Vanguard grafts offer the possibility of both suprarenal and infrarenal fixation.

Endoleak Rates
The endoleak rate in 280 unibody bifurcated grafts was 18.9% (Table 2). In this series, the endoleak rate for 180 Ancure devices was 15% and the 98 Endologix devices had a 25% rate of endoleak.

The modular systems (n=311) had an endoleak rate of 28.5% (Table 3). The highest endoleak rate of 49% was seen with the MinTec/Vanguard system. The AneuRx system had an endoleak rate of 28.1%, the Lifepath rate was 5.4%, and the Zenith graft had a leak rate of 29.7%. The tube graft endoleak rate was very high at over 36%. Most of these leaks were distal type I endoleaks.

The 748 grafts had a 4.9% rate of proximal type I endoleaks. Comparing the 220 grafts that had suprarenal or transrenal fixation to the 528 grafts with infrarenal fixation, we found endoleak rates of 5% and 7%, respectively.

Limb Occlusions
We found an occlusion rate of 14.4% rate in the 97 MinTec/Vanguard grafts; a rate of 7.2% in the 180 Ancure bifurcated grafts; a 5.3% rate of occlusion in the 57 AneuRx grafts; a 5.0% rate in 101 Zenith grafts; an occlusion rate of 3.1% in the 98 Endologix devices; and in the 37 Lifepath grafts we found an occlusion rate of 0% (the numbers were too low).

These occlusions were treated with PTA (with or without lysis) and Wallstent (Boston Scientific) implantation, if necessary. In some patients, the iliac occlusion was reconstructed by means of a crossover femoro-femoral graft.

Stent Fractures and Conversions
The first series of MinTec/Vanguard devices had a relatively high rate of stent fractures or suture breaks. These problems led to a high rate of re-do surgery and conversion rate with those endografts: The primary conversion rate was 2.9% and there was a 5.5% rate of secondary conversions, for a total conversion rate of 8.4%.

Out of 63 conversions, 52% were due to tube graft failures. As mentioned, the conversion rate was highest with the MinTec/Vanguard devices. Furthermore, the modular systems had a higher conversion rate than the unibody systems (7.4% vs 2.5%). Fortunately, my colleagues and I lost no patients with elective conversions, however, we had a 27% mortality rate in emergency conversions.

Renal Infarctions
In 11.1% of cases, we had a relatively high renal infarction rate (n=82). We anticipated infarction in 3.1% of cases (covering the pole artery); 8% (n=59) were unexpected renal infarcts. The renal infarction rate was highest (22%) in patients treated with the Zenith graft.

Fifteen patients had a total unilateral renal infarction (four AneuRx, four Vanguard, seven Zenith). In 23.2% of cases, devices with suprarenal fixation had a higher renal infarction rate than those using infrarenal fixation (6.6%).

COMPLICATIONS
Most complications (including endoleaks, limb occlusions, or conversions) could be attributed to poor patient selection for EVAR or to technical failures. In addition to problems related to the general learning curve, the first-series grafts showed mechanical failures, such as stent fractures, suture breaks, and other problems, that resulted in higher endoleak and conversion rates.1 Furthermore, in the beginning we implanted too many tube grafts. Many of these grafts failed (mostly due to distal type I endoleaks) and either required a secondary repair or were finally explanted.2

Analyzing our results, my colleagues and I found that in most cases a reconstruction using grafts with suprarenal fixation is not mandatory. Especially after implantation of grafts with suprarenal fixation, a higher rate of renal infarctions is likely (which was observed in our patient population at least) compared to patients treated with devices with infrarenal fixation.

Problems With Modular Systems
Modular systems seem to be associated with a higher endoleak rate than unibody devices. The higher rate may have to do with the fact that in this series of patients we used many MinTec/Vanguard devices. As mentioned earlier, these first-generation systems had a significantly higher complication rate.

The new generation of modular systems has substantially profited from the experience gained with the initial systems. The problems interventionalists faced then are no longer observed; it seems prudent to expect that leakage and conversion rates will drop dramatically.

Fixation Issues
When comparing the results from devices with suprarenal or infrarenal fixation, we found no difference in proximal type I endoleak rates. In the long run, grafts with infrarenal fixation may even show a lower endoleak rate, due to the fact that our patient population received a large number of first-generation devices (which have been improved considerably since that time).

In our clinic, optimal infrarenal fixation with hooks, as provided by the Ancure device, seems to produce the best late results. The Ancure system provides active fixation to the aorta, even in short and angulated necks. To date, no hook fractures have been observed with the new generation of the Ancure device in more than 8,000 implants worldwide. In addition, Makaroun et al have not seen any significant difference comparing the Ancure device with the Excluder.3 Furthermore, these researchers showed that the bifurcated grafts had a lower endoleak rate than tube or aorto-monoiliac grafts.

Tube Graft Ruptures
Analyzing the literature regarding ruptured AAA after EVAR, Bernhard et al found seven ruptures with the Ancure device (five of these were first-generation). All ruptures occurred in tube grafts; no ruptures were found in patients with bifurcated or unilateral Ancure iliac implants. A literature search identified 40 additional ruptures related to other devices.4 These data indicate optimal long-term results especially with the Ancure bifurcated device.

Endoleaks
The MinTec/Vanguard prosthesis is no longer on the market; this graft’s high endoleak rate is probably attributable to first-generation device failure issues.5 A markedly high endoleak rate has been found among our patient population after implantation of the Zenith prosthesis, regardless of the high rate of renal infarctions. The Endologix prosthesis also produced a relatively high endoleak rate (25.5%), due to the fact that the prosthesis tends to migrate distally during implantation. We now try to safely deposit the prosthesis on the aortic bifurcation, and we prolong it by adding a proximal cuff. This action has resulted in a clearly better outcome.

SPECIFIC DEVICES
Since autumn of 1999, my colleagues and I have become familiar with the Lifepath system. This graft features ?fixation crimps? that allow a reliable infrarenal fixation. The sheaths allow the ipsilateral limb to be stabilized optimally during the infrarenal balloon fixation; this is particularly important in cases of short or angulated necks (Figures 1 and 2). Long-term results gathered from our use of the Lifepath system in our patient population cannot yet be presented, however; the period of implantation is still too short.

In three cases, we have implanted an Ancure prosthesis for ruptured aortic aneurysm (Figure 3). This prosthesis offers the advantage of blocking the infrarenal aorta with a balloon after deployment of the main body. We were able to reduce the incidence of limb occlusions when using the Ancure prosthesis in our patient population by employing intraprocedural balloon dilatation of both iliac limbs using the “kissing balloon” technique. This step resulted in a dramatic reduction of the limb occlusion rate.

My colleagues and I rely on the Ancure or Lifepath prosthesis for endovascular management of infrarenal AAAs in our patient population. Generally, however, the operative proceeding is determined by the vascular situation; that is, the more prostheses are offered, the more patients can be successfully treated endovascularly. For example, larger infrarenal aortic diameters (those exceeding 28 mm) in high-risk patients will probably be managed using the Zenith graft; in patients with a narrow iliac artery, an Endologix prosthesis may be preferred.

An enlargement of the spectrum of operations seems to be possible in the long run. For example, we are now using the Ancure prosthesis with large iliac limbs (16 or 18 mm). Additional devices with a central diameter of 28 and 30 mm have already been introduced. Furthermore, the new Quantum endograft offers the possibility of treating additional iliac aneurysms with side branches in the future (the Tributary system). Due to the small number of implantations of the Quantum endografts, however, no statement regarding potential late results is possible.

COOPERATION AND CONSIDERATION
In conclusion, mortality rate and adverse events can be reduced significantly if the AAA patient is treated in a department with a team of highly experienced vascular surgeons cooperating with interventional radiologists.6 Outcomes can be further improved by well-considered use of the variety of devices on the market.

Dieter Raithel, MD, is Professor of Surgery at the Klinik fuer Gefaesschirurgie in Vasculare und Endovasculaere Chirurgie, Klinikum Nuernberg in Nuernberg, Germany, and is an advisor to Boston Scientific, Edwards, Gore, Guidant, and Medtronic. Dr. Raithel may be reached at +49 911 398-2651; dieter.raithel@rzmail.uni-erlangen.de.

1. Raithel D. Which industry-made endovascular grafts are best for abdominal aortic aneurysm repair and why? In: Gloviczki P, ed. Perspectives in Vascular Surgery. Vol 12. No. 1. Thieme, NY: Stuttgart; 1999:1-10.
2. Faries PL, Vania I, Briggs BA, et al. Failure of endovascular aortoaortic tube grafts: A plea for preferential use of bifurcated grafts. J Vasc Surg. 2002;35:868-873.
3. Makaroun M, Zaiko A. Endoleaks following endovascular aortic aneurysm repair: Clinical significance and treatment modalities. In: Gloviczki P, ed. Perspectives in Vascular Surgery. Vol 13. No. 1. Thieme, NY: Stuttgart; 2000:1-14.
4. Bernhard VM, Mitchell RS, Matsumura JS, et al. Ruptured abdominal aortic aneurysm after endovascular repair. J Vasc Surg. 2002;35:1157-1162.
5. Beebe HG. Late failures of devices used for endovascular treatment of abdominal aortic aneurysm: What have we learned and what is the task for the future? In: Gloviczki P, ed. Perspectives in Vascular Surgery and Endovascular Therapy. Vol. 14. No. 1. Thieme, NY: Stuttgart; 2001;29-46.
6. Laheij RJF, Van Marrewijk CJ, Buth J, et al. The influence of team experience on outcomes of endovascular stenting of abdominal aortic aneurysms. Eur J Vasc Endovasc Surg. 2002;24:128-133.

 

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