Changes in Open Surgery for Abdominal Aortic Aneurysms in the Endovascular Era

VASCULAR DISEASE MANAGEMENT 2012;9(4):E57-E63

Abstract

In less than 3 decades, endovascular abdominal aneurysm repair (EVAR) has been converted from an escape procedure exclusively confined to high-risk patients to a primary choice procedure and preferred method for most patients with infrarenal abdominal aortic aneurysm (AAA). Open surgery has increased in technical complexity in the new endovascular era. Open aneurysm repairs are currently performed primarily in patients who are not anatomically suitable for EVAR with the main limitation being an anatomically unfit proximal neck, requiring suprarenal clamping or in patients with EVAR failure (eg, conversion after stent-graft migration, persisting endoleak with aneurysm growth, stent-graft rupture, etc.). This new high-complexity open surgery for AAA exposes to higher surgical risks and raises new challenges regarding surgical training, surgical indications, and perioperative management.

Open surgical repair has been considered the gold standard for treatment of abdominal aortic aneurysms (AAA) for a long time. Nevertheless, with the significant advances in the management of AAA in the last decades, and particularly after the introduction of endovascular treatment modalities, the impact of open AAA surgical repair on national practices and the utilization of services for AAA repair have changed. Since its first approval in the nineties and U.S. Food and Drug Administration endorsement in 1999, endovascular aortic aneurysm repair (EVAR) has rapidly expanded and considerably modified its position with respect to traditional open surgery for AAA repair. In less than 3 decades, EVAR went from being an escape procedure exclusively confined to high-risk patients to a primary choice procedure and a preferred method for most patients with AAA. The scenery of open surgery has been correspondingly narrowed and limited to non-suitable EVAR cases or to management of post-EVAR complications. It has been estimated that currently 55% or more AAA are treatable with endovascular grafts approved by the FDA,¹ the most common cause of unsuitable EVAR being related to inadequate and short aortic neck.^2,3 Thus, the application of EVAR resulted in a proportionate decrease in overall volume of elective open AAA repairs with a concomitant increase in open juxtarenal aortic aneurysm (JAA) repairs with related higher technical complexity and surgical risks, while straightforward infrarenal aneurysm anatomies are now being routinely performed by endovascular route. 

The noteworthy shift in trends and complexity of AAA repair for open surgery in this new EVAR era is supported by a number of studies and may raise issues of concern.^2,4-8

Trends and Characteristics of Open AAA Surgery in the EVAR Era

The decrease in open surgery volume for AAA repair in the last decades after the introduction of EVAR is mainly justified by well-demonstrated, consistently lower perioperative risks with new mini-invasive techniques despite the more uncertain durability often requiring reinterventions.^9,10 Development of more advanced technologies and devices (fenestrated, branched stent-graft, etc.) progressively expanded the range of suitability for endovascular approaches also in the presence of more challenging and adverse AAA anatomies, such as large and angulated necks, small iliac arteries, and extensive aneurysms. Nevertheless, morphology is still the main and probably irreversible reason of concern for EVAR. Forced application of EVAR when not suited for AAA morphology (Figures 1-4) produces increased failure and complication rates. Schanzer et al reviewed outcomes of 10,228 EVAR performed in a 5-year period in the U.S. and found that only 42% of patients had an anatomy that met the most conservative definition of device instructions for use. The 5-year post-EVAR rate of AAA sac enlargement was exceptionally high at 41%. Notably, the rate of AAA sac enlargement was significantly higher in patients who underwent EVAR outside the instructions for use.¹¹ Therefore, despite the feasibility in deployment, long-term efficacy of EVAR in forced AAA anatomies remains a main drawback allowing these cases to be better pursued by an open surgical approach.

A number of either supportive or conflicting experiences have been published regarding changes in trends and types of aneurysms treated today by open surgery.^5-8 In addition to agreeing on a decline in trend rates for open AAA repairs, many studies confirmed an increased complexity of the fewer AAAs assigned to open repair in the new EVAR era. ^5-7

Dillavou et al analyzed trends in AAA repair over the last 10 years in a large sample of Medicare patients from 1994 to 2003 and found no increased mortality for open repairs in the first years of the EVAR era. Authors concluded that improvements in AAA management allowed low perioperative mortality risks, especially in males, with an elective perioperative mortality rate of 5.57% in 1994 and 4.75% in 2003.⁸

Landry et al showed how after EVAR introduction there has been an inevitable higher technical complexity in open repairs supported by occurrences of suprarenal cross-clamping in nearly half the patients and higher blood loss (2586 mL vs 1638 mL, P=0.006) and operative time (391 min vs 355 min, P=0.005). Specifically, over a total of 185 AAA open repairs performed from 2000 to 2007 by the authors during the endovascular era, 44.3% required suprarenal cross clamp and 44% required additional visceral or renal grafts.²

Costin et al published their open AAA practice following the institution of an EVAR program in 2006.⁵ Authors compared 301 patients (group 1), who underwent open repair before, with 305 patients (group 2) who underwent open repair after the beginning of the stent-graft program experience.  They found a significant increase in number of repairs requiring suprarenal clamping, from 6% in the pre-EVAR period to 20% in the initial post-EVAR period. Furthermore, there was higher iliac complexity in the second period: iliac aneurysms were present in 25% of group 1 patients and 42% of group 2 patients (P<.05). The incidence of associated iliac occlusive disease was 12% in group 1 and 20% in group 2 (P<.05). 

In a large Medicare experience from Boston, data based on administrative codes on AAA repair in the era of endovascular repairs confirmed the trend for decreased open AAA surgery volume for elective repairs over time.¹² In an overall number greater than a half million aneurysms (n=555,577) repaired between 1993 and 2005, it was found that the number of endovascular repairs eclipsed that of open repair for elective surgery in 2004. In 2005, EVAR accounted for 56% of intact repairs and 27% of perioperative deaths. However, in 2005, only 17% of ruptured AAAs were treated by EVAR.¹²

More recently, Hiromatsu et al compared their perioperative data with open AAA surgery before (n=99) and after (n=125) the EVAR era.¹³ In the post-EVAR period, the authors found greater need for suprarenal clamping (11.2% vs 3%), a higher proportion of octogenarians (23.2% vs 11.1%), and extensive iliac involvement (35.2% vs 22.2%).¹³

Thereby, open aneurysm repairs are currently performed primarily in patients with more extensive aneurysms or who are not anatomically suitable for EVAR with the main limitation being an anatomically unfit proximal neck (short, large, thrombosed, angulated) or in patients with EVAR failure (eg, conversion after stent-graft migration, persisting endoleak with aneurysm growth, stent-graft rupture, etc.). Severe vessel calcification, iliac access obstruction, extensive iliac aneurysm extension, and previous aortic graft infection are other common findings in AAAs mainly reserved today for open surgery. These anatomical changes may also pose higher technical challenges for open surgery, such as raised frequency of suprarenal clamping or visceral revascularization and increases in operative duration, use of blood products, intensive care unit stay, hospital length stay, and overall complication rates when compared to repairs in more straightforward and infrarenal AAA, now routinely treated by EVAR.

Perioperative Mortality and Morbidity of Open AAA Surgery in the EVAR Era

The true results of the more infrequent but also more technically challenging open surgery for AAA are not straightforward. However, there is a tendency to support efficacy and safety of open surgery in the current EVAR era.

In a study by Landry et al, the 30-day mortality was not significantly higher after suprarenal cross-clamping more frequently required for open AAA surgery in the EVAR era (6.1% for suprarenal vs 2.9% for infrarenal repairs; P=0.18). However, postoperative renal insufficiency (29.3% vs 7.8%, P<0.001) and pulmonary complications (25.65% vs 12.6%, P=0.03) occurred more frequently in the suprarenal group. Furthermore, suprarenal cross-clamping (OR 2.42, 95% CI, 1.29-4.57, P=0.006) was a significant independent predictor of postoperative complications after open surgery for AAA.²

Giles et al analyzed aneurysm-related deaths in the era of endovascular repairs according to the Nationwide Inpatient Sample from 1993 to 2005. Authors confirmed the trend for decreased open AAA surgery volume for elective repairs but suggested stability or even decreases in aneurysm-related death rates for both elective and urgent open AAA repairs over the years.¹² Perioperative elective mortality associated with open repair was similar before and after the introduction of EVAR: 4.7% vs 4.5%; P=0.31. The authors also noted that the mean annual number of deaths associated with ruptured AAA repair was lower in the post-EVAR period with open repair; mortality rates were 40.8% vs 44.3% in the post- and pre- EVAR years, respectively.¹²

The study by Costin et al compared 301 patients (group 1) who underwent open AAA repair before and 305 patients (group 2) receiving open surgery after the beginning of the stent-graft program experience. Despite the higher anatomical complexity in the last group, the overall perioperative mortality rate was 2.0% for group 1 and 3.8% for group 2 without statistically significant differences. All major sources of morbidity, including renal insufficiency, myocardial infarction, stroke, and intubation times, were similar in the 2 groups. The length of stay was 9.2 days in both groups; 11.3% of group 1 patients and 26% of group 2 patients were discharged to an extended-care facility rather than directly home.⁵

Similarly, Knott et al from the Mayo Clinic in 2008 analyzed 126 open JAA repairs performed after the introduction of EVAR programs.⁶ Despite the juxtarenal anatomical position of aneurysms, 30-day mortality was as low as 0.8% and relatively few patients required adjunctive renal and visceral grafts (12%). Although 18% of patients had renal complications, only one patient had permanent renal failure. Authors concluded that open surgical repair of JAA is currently associated with low mortality.⁶

Comparable conclusions regarding low operative risk in high-complex open surgery for AAA were supported more recently by Hiromatsu et al who showed zero perioperative mortality with open AAA repair in both pre- and post-EVAR periods while the morbidity rates were similar (22.3% vs 24.8%) despite the higher overall complexity of AAA treated in the most recent cases.¹³

In a group of 171 patients requiring suprarenal clamping during elective open AAA repair in the EVAR era, Chong et al found perioperative mortality rates similar to those of 849 patients with infrarenal clamping (1.8% vs 1.2%, P=0.44). Postoperative decrease in renal function occurred in 17% of patients with suprarenal clamping vs 9.5% of those without (P=0.003). However, new onset dialysis was rare (0.6%).¹⁴

Open Questions and Points of Concern Regarding Open Surgery in the EVAR Era

Assessment of mortality risk

Despite these excellent results, consistent concerns remain regarding outcomes of contemporary open repair for AAA due to its highly complex nature. Most of the authors examined small samples of patients leading to the possibility of type II errors but more relevantly, only very early time points were used to analyze data (perioperative or 30 days from surgery). Increasing evidence outlines how the mortality impact of AAA repair is not realized until 3 months after treatment.¹⁵ This is especially true for AAA open repairs where the duration of the highest perioperative mortality risk extends longer than for EVAR. Assessment of mortality rates at 30 days or during hospitalization can overestimate the benefit of treatment since a large number of postoperative deaths can be missed. Accurate estimates of aneurysm-related deaths due to aneurysm repair should be provided at 3 months or 1 year. Schermerhorn et al used a propensity score model to create matched cohorts of U.S. Medicare beneficiaries undergoing AAA endovascular (n=22,830) and open (n=22,830) repair from 2001 to 2004 and calculated perioperative mortality using different definitions including in-hospital, 30-day, and combined 30-day and in-hospital mortality.¹⁵ Absolute differences in mortality rates between open and endovascular repair were similarly higher for open surgery regardless of the definition of mortality: 3.5% in-hospital, 3.2% 30-day, and 3.7% combined in-hospital and 30-day mortality. Nevertheless, the total period of elevated mortality risks extended beyond 30 days and persisted for approximately 3 months after repairs. The highest risk of death due to AAA repair was about 2 times longer after open surgery and indeed persisted for about 1.5 months after EVAR and 2.5 months after open repair. At 90 days, mortality rates were still significantly higher after open repair (7% for open repair vs 3.2% for EVAR). The authors concluded that mortality risks assessed in the perioperative period could be underestimated using the conventional definitions of most current reports.¹⁵

Indication for treatment and prognostic indicators of increased risk

One of the most dreadful risks of the current safety of both EVAR and open surgery for high-complexity AAA cases is to alter the recommended indications for treatment. This is particularly true for EVAR due to the very low periprocedural risks, short hospital stay, and quick recovery. Nevertheless, similar concerns might also apply to current open surgery for AAA. The potential risk to lower the threshold for AAA repair in the endovascular era was recently well addressed by Schanzer et al, who re-measured aneurysmal morphology on preoperative and postoperative computed tomography scans in 10,228 patients who underwent EVAR in the U.S.  They found that as high as 59% treated aneurysms had a maximum AAA diameter below the 55 mm threshold at which intervention is recommended over surveillance.¹¹ The mean AAA diameter for open aneurysm treated in the post-EVAR era according to Hiromatsu et al was 55.2±11.8 mm suggesting a non-excessive risk of impending rupture in most of the patients receiving open treatment for more complex AAA.¹³

Risk and complications of surgical AAA repair in the EVAR era might be increased in the presence of one or more adverse prognostic factors, one of the most important being the age of the patients. Old age is a risk factor for any surgery and indication to perform invasive treatment in the elderly is challenging because of the limited life expectancy and the higher operative risk.

In Hiromatsu et al’s study, there was an increasing prevalence of highly-complex elective AAA surgery performed in octogenarians in the post-EVAR period accounting for about one third of the overall population (23.2% vs 11.1% in the pre EVAR period; P=0.0391) even though this did not alter morbidity rates; mortality rate was 0%.¹³ Less positive findings of current open AAA surgery for old patients were found in other studies. In their large cohorts of U.S. Medicare beneficiaries undergoing AAA endovascular (n=22,830) and open (n=22,830) repair, Schermerhorn et al showed how the mortality risk of both groups increased significantly with age and was particularly high in patients over 80 years of age.¹⁵ In-hospital and 30-day mortality rates in this age subgroup were 12.7% for open vs 4.2% for EVAR; 90-day mortality rate was 16.8% for open and 7.6% for EVAR.¹⁵

Similarly, in 14,517 patients receiving elective or urgent repair for AAA in the state of Illinois, Leon et al found that patients >80 years of age had a higher mortality after open repair for both elective and ruptured AAA.16 Independent predictors of higher in-hospital mortality were age >80 years, female gender, rupture, and open procedure vs EVAR.¹⁶

In a propensity score-matched Medicare cohort of patients with AAA treated by open surgical (n=11,415) or endovascular repair (n=11,415), Giles et al found that old age (OR 3.1, 95% CI 2.4-4.2), as well as open repair, female gender, renal disease, peripheral disease, and congestive heart failure were independent predictors of perioperative mortality.¹⁷ Using a simple scoring system developed from the logistic regression model to predict mortality risks (and therefore to help guide clinical decisions in AAA treatment), the absolute predicted mortality ranged from 0.7% for an EVAR patient with no comorbidities to 38% for an open patient with all comorbidities. The absolute difference was greater for older patients confirming old age as a main concern in indication for treatment of AAA.¹⁷

Dillavou et al reviewed the Medicare national database on trends for AAA repairs from 1994 to 2003, outlining how average mortality rates in either elective or emergent AAA repairs were significantly higher for females. For males, elective perioperative mortality rate decreased from 5.57% in 1994 to 4.75% in 2003; for females, despite a similar decreasing trend, the rates were higher at both time points: 7.48% in 1994 and 5.45% in 2003.⁸ For ruptured aneurysm average mortality did not significantly change over time and was substantially higher: in females (52.8%) vs males (44.2%, P<0.001). The authors raised concerns regarding the persisting high mortality risks for females with current open AAA surgery especially in emergency.⁸

Fast Track Recovery

Advanced protocols and optimal care management could optimize outcomes of patients receiving open surgery for AAA despite the high complexity. In the last decades, fast-track recovery programs have been increasingly applied to reduce patient morbidity/mortality and costs and to improve outcomes in different types of open surgery. Similar protocols have been seldom applied in AAA open repairs.^18-19 Muehling et al randomized 101 patients undergoing elective AAA open repair to receive a traditional or a fast-track treatment. The basic fast-track issues were no bowel preparation, reduced postoperative fasting, patient-controlled epidural analgesia, enhanced postoperative feeding, and postoperative early mobilization.¹⁹ In the fast-track group the need for postoperative ventilation (6% vs 32%, P=0.002) and the rate of postoperative complications (gastrointestinal, cardiac, pulmonary, renal, and infective; 16% vs 36%, P=0.039) were significantly less frequent with respect to traditional management. Postoperative mortality rate was also significantly shorter with the fast-track protocol and mortality rate was 0% in both treatment groups. Larger implementation of fast-track protocols for open AAA surgery in the EVAR era should definitively support the benefit of such management.

Training

Landry et al recently raised concerns regarding the likelihood of a regionalization of certain complex procedures (such as juxtarenal and suprarenal AAA repairs) in high-volume selected centers due to difficulties in the maintenance of high surgical skills for open AAA surgery in the endovascular era.² As the numbers of open aneurysm repairs continue to decline and the complexity of AAA treated with open surgery increases in complexity, there will likely be fewer trained vascular surgeons who will obtain suitable experience to be independent in these procedures at the completion of their residency. The need for practice pattern shifts in vascular training programs to accommodate the new highly complex open surgery was emphasized by the authors reversing the concerns towards stent-graft use raised at the beginning of the endovascular era. During the evolution phase of the endovascular mini-invasive approach, the ability for classical vascular surgeons, who were unfamiliar with guidewires, interventional maneuvers, and endovascular devices, to perform new procedures was the object of long debate and a major issue of concern. With the widespread diffusion of EVAR, availability of training for specific endovascular aortic procedures has been proportionately applied. In the current endovascular era, training programs for new vascular surgeon trainees have been refined and appropriately changed to better suit mini-invasive new techniques. At the same time the ongoing new occurrence of fewer but more complex open AAA repairs (suprarenal clamping, visceral revascularization, extensive iliac involvement, conversion from EVAR failure, etc.) may present a challenge for the new generation of vascular surgeons. Since the overall open AAA have decreased in volume and increased in complexity this will allow few numbers with really challenging techniques to practice on for the next generation of vascular surgeon trainees. There is the concern that only few fellows/residents will obtain suitable experience to be independent in such complex procedures after the completion of traditional training. Training programs focused on high-complexity open AAA repair are lacking while the acquisition and maintenance of the required surgical skills can become increasingly difficult to achieve and open AAA repairs could be allowed only in selective highly experienced centers with vascular surgeons practiced in highly complex open AAA surgery.²

Conclusion

Despite the advantages of mini-invasive EVAR, open surgical repair remains a valuable choice for AAA treatment also in the post-EVAR era. Nevertheless, the role of open surgery for treatment of AAA has changed with advancement in technical complexity and reduction in volume. In many trained and experienced centers this shift toward high-complexity AAA did not translate in substantial increase of operative risks.

One of the main advantages of current safety in performance of both EVAR and open surgery for AAA is to allow the use of one or the other technique as alternative (but not competitive) options according to different best suitability settings for each of these approaches. On the other side, one potential risk of the high safety of both procedures might be to alter the recommended indications for treatment. There are standardized and updated guidelines with established criteria to treat or not-to-treat AAA, also related to the specific EVAR or open technique. Any forceful indication will inevitably increase the complications and risks of the treatment without benefit for patients.

Optimized patient care programs, as well as appropriate surgical training fully respecting the recommended standards should decrease concerns toward the new highly complex open surgery for AAA.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted September 1, 2011, provisional acceptance given October 28, 2011, final version accepted December 9, 2011.

Address for correspondence: Dr. Paola De Rango, Division of Vascular and Endovascular Surgery, Hospital S.M. Misericordia, Piazza Menghini 1, Perugia, 06134, Italy. Email: plderango@gmail.com

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