Single centre experience with Excluder^® stent graft; 17-year outcome

Endovascular management of the aorta with stent grafts (SG) was introduced in the late 1980 and early 1990’s^{1, 2, 3} with the intention of reducing mortality originating from aortic rupture by using a less invasive method as open surgery repair (OSR). In the last decades, endovascular abdominal aortic aneurysm repair (EVAR) has been expanding, surpassing OSR in the USA by 2003.⁴

Large series have already reported good short-and mid-term results after EVAR with a decreased 30-day mortality compared to OSR^{4, 5, 6}, while longterm studies revealed no difference in long-term survival and reported a higher reintervention rate in the EVAR as opposed to the OSR group.^{7, 8, 9}

While large series studies provide a great overview on success and outcome, they provide little data and outcomes on specific SG. Such information plays a crucial role in the modification and evolution of SGs.¹⁰ Thus, information on specific SG should be gathered to contribute to the ongoing evolution of SGs. Several SGs are used in Europe, and some were modified throughout the years, while others were newly designed.^9,11,12 So far, SGs show excellent medium-term results, whereas their long-term efficacy and durability have not yet been proven.⁹ Excluder^® SG (W.L. Gore & Associates, Flagstaff, AZ, USA) was introduced in 1997 and remains one of the most used devices for abdominal aortic aneurysm (AAA) management. Regular modifications and improvements help to maintain Gore Excluder as a safe and durable treatment choice.¹³ Only a handful of studies reported outcomes on the first two generations of Excluder^® SG.^{13, 14, 15} The longest follow-up reported for Excluder^® SG is ten years.¹³ With the increasing life span of the general population, many patients live as far as decades after aneurysmal management. Detailed evaluation of long-term results, even beyond ten years, should therefore be conducted.

The aim of our study was to present a long-term single centre experience with Excluder^® SG. In detail, all-cause mortality, aneurysm-related mortality, incidence of complications and re-interventions have been reported.

The National Medical Ethics Committee approved the study (number 0120-120/2015-2). Between October 2002 and June 2008, 130 consecutive patients with AAA were treated with Excluder^® (W.L. Gore & Associates, Flagstaff, AZ, USA). As seven patients were lost to follow-up, our study included 123 patients (104 men; mean age 73.0 years, range 51–89).

The median follow-up was 9.7 years (interquartile range, 4.6 - 13.8). Patients were followed-up for up to seventeen years.

The comorbidities of this cohort are shown in Table 2. The emergency repair was performed in five (4.1%) patients. One of them later died due to a recurrent AAA rupture, while the other causes of death were trauma and Alzheimer disease. Two of these patients are still alive more than twelve years after the aneurysmal rupture.

30-day mortality and long-term survival

The 30-day mortality was 0.8% due to AAA rupture in one patient on the second day. The average length of hospital stay was 4.3 days (range 2–45 days). Long-term survival is shown in Figure 1. Younger patients (≤ 69 years old) lived longer than older patients (≥ 70 years old) (Hazard Ratio = 1.34; 95% confidence interval: 1.14–2.23; P = 0.02). However, when a division in the same age groups was performed for aneurysm-related survival, no such difference was observed (P > 0.05). Gender did not affect any cause of survival or aneurysm rupture related survival (both P > 0.05).

Figure 1

The one-, five-, ten-, fifteen- and seventeen-year overall survival was 94.3%, 74.0%, 47.2%, 35.8% and 35.8%, while aneurysm-related survival was 98.4%, 96.3%, 92.6%, 92.6%, 92.6% (Figure 1).

Our cross-sectional study presents a cohort of patients with long-term follow-up, up to 17 years, after EVAR treatment with Excluder^® SG.

More than three quarters of our patients were successfully treated completely percutaneously, confirming the minimal invasiveness of EVAR, which is one of the key benefits of endovascular management. Still, surgical backup is essential in centres using percutaneous sutures, since the conversion rate in the previous series was nearly 10%.²⁰ A good primary technical success rate was achieved and is comparable to the previously published paper on Excluder^® SG.¹³ In the first twenty-four hours after EVAR, one in ten patients showed signs of inflammatory reaction. These features of systemic inflammatory response are known as post-implantation syndrome, which is reportedly associated with prolonged hospitalization.¹⁸ However, our data did not confirm this, since the average length of hospital stay in our patients was 4.3 days.

In the EUROSTAR registry (one of the first large series dated in 1996), the reported 30-day mortality was 3.4%.²¹ In more recent large series of studies, the reported 30-day mortality ranges from 1.2% to 2.6%.^{7,22, 23, 24} These rates are even lower in studies reporting outcomes on Excluder^® SG.^{13, 14, 15} The excellent results were confirmed by our data, observing less than 1% 30-day mortality. The decreasing number of deaths in the first thirty days can probably be attributed to technical improvements, as first-generation devices were more robust, as well as to superior operators’ experience.²⁵

The most common secondary procedures were interventions treating endoleaks, namely SG extensions and translumbar sac embolizations.²⁶ This is consistent with the previously published data, since endoleak is common and EVAR-specific complication that occurs in up to 30% of cases using early-generation SG.^{27, 28} Newer studies report a 19–33% reintervention rate in the follow-ups for up to fifteen years after EVAR.^{29, 30, 31, 32} The results of our study are within the reported range with nearly a quarter of patients needing a secondary procedure. A study on Excluder^® SG with a ten-year follow-up period reported 85% secondary procedure free survival, a result that exceeds ours.¹³ The recently published multicenter study by Geraedts et al.³³ reported a mean time of twenty-eight months before a secondary procedure, a time frame that is 8 months shorter than ours. The differences in secondary procedure free survival and mean time to secondary procedure can be attributed to indications which may vary between institutions as the rates of endoleaks are comparable in the studies, while the rates of secondary procedures differ.^{13, 14, 15,33} Overall, relatively high reintervention rates persist despite the surgeon’s experience, graft technology and imaging improvements³⁴, emphasizing the importance of lifelong imaging surveillance in correlation with clinical examinations.³⁵

Since the life expectancy of the general population has been increasing, the optimal treatment choice of AAA is essential for long-term survival. A recent systematic review⁷ confirmed the superiority of the 30-day survival rate after EVAR as opposed to OSR and indicated a similar long-term survival after ten years. The study with the longest follow-up on Excluder^® to our knowledge followed patients for up to ten years.¹³ The results of the overall survival reported in our study coincide with the previously published time points in research on Excluder^®.^{13, 14, 15} Our study, on the other hand, also provides an insight into the outcome even beyond a time point of ten years. Long-term survival is also affected by the patients’ age at the time of the procedure, since the life expectancy of older patients is shorter than that of younger ones. In accordance with the findings of several studies, our results confirmed that patients’ age significantly influenced overall survival.^{36, 37, 38} However, in cases of unfavorable anatomy, OSR has been proven superior to EVAR regarding the long-term survival.³⁹ Additional caution should therefore be taken when considering the standard EVAR procedure for patients with anatomy outside the instructions.³⁹ Within our institution, each patient was examined by a multidisciplinary board to ensure the optimal treatment regime. Patients who were unfit for OSR were sometimes treated outside the instructions for use, since EVAR was the only treatment option for them. The risk of an aneurysmal rupture in these patients was equivalent to the possibility of a suboptimal procedure.

Similar results to ours on aneurysm rupture related survival after EVAR were published by Verzini et al., however Zenith SG was used.⁹ Studies on Excluder^® SG even reported zero aneurysm-related deaths up to ten years^{13, 14}, while one study stressed a potential bias on aneurysm-related deaths due to retrospective data collection.¹³ Based on our results as well as those previously published, patients’ surveillance is most important in the first ten years after EVAR, although opposing conclusions have been drawn in some other studies where secondary aneurysm rupture occurred at any period beyond ten years after EVAR.^{40, 41} This is probably caused by the progression of the disease as well as by material failure due to constant forces present in the aorta, distortion of anatomy due to new hemodynamics, dilatation of the common iliac arteries or progress of previous iliac arteries ectasia.^{42, 43, 44} The follow-up protocol should be carefully adjusted since higher post-EVAR imaging frequency has been associated with a lower risk of death but attributed to higher cost and irradiation dose.^4,24,45 The current recommendations propose imaging at 30 days after the procedure and yearly thereafter if no complications are detected.⁴⁶ The imaging modalities used for surveillance include CT angiography considered as the gold standard modality, duplex ultrasonography and magnetic resonance angiography. A large-scale study based on the nationwide English Hospital Episode Statistics database showed an increased risk of postoperative abdominal and all cancers in patients after EVAR in comparison to OSR.⁴⁷ However, the meta-analysis dating from the same year⁴⁸ reported no significant difference in the risk of death due to cancer between the EVAR and the OSR group. This report draws similar conclusions to our findings, as cancer-related mortality in Slovenia accounts for approximately 30%^49,50, and as a similar rate of cancer-related deaths has also been observed in our study.

The most important limitation of our study is the retrospectivity and, consequently, the limitation in data acquisition. No aneurysm specific parameters could therefore be determined, and a potential sac growth could not be evaluated. The biases may be anticipated in retrospective research and should be carefully interpreted as noted in previous studies on Excluder^® SG.^13,14 However, our results were acquired by real-life data in consecutive patients. Additionally, the research thoroughly examined aneurysm-related deaths to maximize the accuracy of data in our study. To reduce follow-up biases and to be able to process reliable data, we included only patients with obtainable data in the follow-up period. Since only a handful of emergency EVAR repairs were performed in the cohort, only descriptive information is provided.

Our data proved that EVAR with Excluder^® offers good long-term results. More than 75% of patients can be treated completely percutaneously. No late ruptures occur within the first ten years, raising awareness of the importance of regular medical controls.