Endovascular elective treatment of the abdominal aortic aneurysm versus conventional open repair: a comparative study

Abstracts

O tratamento eletivo do aneurisma de aorta abdominal é recomendado pela alta morbiletalidade decorrente da eventual ruptura. O objetivo deste trabalho foi comparar o reparo endovascular eletivo com a cirurgia aberta e avaliar as mortalidades hospitalar e perioperatória, em 1 ano, por todas as causas e relacionadas ao aneurisma, a permanência hospitalar, as complicações, as taxas de sobrevida, conversão e reintervenção, a durabilidade do enxerto, o custo-benefício e a relação desses dados com o treinamento da equipe médica responsável pelo tratamento. Realizou-se uma revisão da literatura sobre reparo endovascular versus cirurgia convencional. Foram observados vantagem na sobrevivência perioperatória e menor estresse pós-cirúrgico; no entanto, os benefícios iniciais são perdidos por complicações e reintervenções tardias. Trabalhos baseados nas primeiras gerações de endopróteses superestimam as taxas de mortalidade em curto prazo, complicações e reintervenções. A durabilidade do enxerto, a real vantagem na sobrevida e o custo-benefício são incertos, e outros estudos são necessários para o seguimento em longo prazo.

Tratamento endovascular; aneurisma de aorta abdominal; cirurgia; prótese endovascular

REVIEW ARTICLE

Endovascular elective treatment of the abdominal aortic aneurysm versus conventional open repair: a comparative study

Ana Carolina P. Simão^I; Ana Carolina de Alencar Gonçalves^I; Milena Miguita Paulino^I; Renata Barbosa de Oliveira^I; Camila Aparecida Polli^I; Ayrton Cássio Fratezi^II

^IAcadêmica de Medicina (5º ano), Faculdade de Medicina de Jundiaí (FMJ), Jundiaí, SP

^IIProfessor adjunto, Disciplina de Cirurgia Vascular, Departamento de Cirurgia Geral, FMJ, Jundiaí, SP

Correspondence

Abstract

The elective treatment of the abdominal aortic aneurysm is recommended due to the high morbidity and mortality of a possible rupture. The objective of this study was to compare the elective endovascular aneurysm repair with open repair and to analyze the in-hospital and perioperative mortality rate during 1 year related to all causes and to the aneurysm, as well as the postoperative length of hospital stay, complications, survival rates, conversion and reintervention, graft durability, cost-benefit ratio, and relation with the medical team’s experience. A review of the scientific literature about endovascular versus open repair was carried out. We found a higher rate of perioperative survival and less postoperative stress; nevertheless, the initial benefits were lost due to late complications and reinterventions. First-generation endografts overestimated the early results of mortality rates, complications, and reinterventions. Endograft durability, real advantage of survival rates, and cost-benefits are uncertain and further long-term follow-up studies are necessary.

Keywords: Endovascular treatment, abdominal aortic aneurysm, surgery, endograft.

Introduction

An abdominal aortic aneurysm (AAA) can be defined as an aortic dilatation of at least 50 percent of the arterial diameter, with elective treatment recommended when it reaches at least 5.5 cm due to the risk of the aneurysm rupturing¹ and potentially killing the patient.² In general, diagnosis is either incidental or occurs during screening programs². To cut down on the morbidity of potential ruptures and the deaths they cause, ranging from 65 to 85 percent of cases,³ elective treatment is recommended when AAA size reaches 5.5 cm in diameter¹ or when the transverse diameter dilates more than 5 mm in the space of 1 year.⁴

Four percent of men and 1 percent of women suffer from AAA, most frequently between the ages of 60 and 70.⁴ In a study performed at Hospital das Clínicas de São Paulo, São Paulo, Brazil, Puech-Leão et al. found 2.32 percent rates of incidental aneurysm in the sample surveyed.⁵ A British study found 0.3 percent rates of AAA among males aged 50 to 64, 2.5 percent in males aged 65 to 79, and 4.1 percent rates in those over 80 years old.⁶

For over 50 years, AAA was treated with elective open surgery, a major surgery which required general anesthesia, at least 30 minutes of aortic clamping,⁷ and deep hypothermia. Due to the high mortality rates associated with ruptures, intraoperative death, patient morbidity and comorbidities, researchers looked for alternatives to the classic open procedure. In 1991, Parodi & Palmaz were the first to report the use of the endovascular technique^1,7-9. The procedure is based on two small incisions exposing the femoral artery, through which a prosthesis is introduced, using catheters and guide-wire, into the aneurysmal segment of the aorta.^7,10 Since then, this treatment alternative has become widely accepted due to its less invasive nature^7,8,10 and potential for cutting perioperative morbidity, mortality and recovery times, especially among high-surgical-risk patients who were not good candidates for the traditional surgery.^11,12 Before endovascular surgery, perioperative mortality rates hovered around 8 percent, but they were cut to 4 percent with the advent of EVAR.¹⁰

Various studies have tried to assess the benefits and complications of endovascular aneurysm repair (EVAR) in the medium and long term as compared to open surgery.

The objective of this study was to compare endovascular repair with conventional surgery for AAA patients. The specific goals were to assess hospital mortality, perioperative mortality, one-year mortality, mortality from all causes, mortality from aneurysm, hospital stay, complications, survival rate, conversion rate, reintervention rate, durability of graft and cost-benefit, as well as the relationship between those variables and the training of the medical staff responsible for the treatment.

Materials and methods

The literature review consisted of a survey of electronic databases SciELO, MEDLINE, and PubMed, looking for articles published between 1995 and 2008, with descriptors "endovascular treatment", "abdominal aortic aneurysm (surgery)", "endovascular prosthesis", and the corresponding terms in Portuguese. Thirty two articles were selected and read in full. Of those, 14 were selected for this review based on year of publication, quality of article, and sample size.

Results

Description of studies

Table 1 shows the characteristics of the studies used in this review.

Hospital mortality

Hospital mortality rates were 2.1 and 6.2 percent, respectively, for the EVAR and open surgery groups, meaning the first group had one third as many deaths as the first.⁷

Hospital stay

In all articles comparing treatment alternatives, hospital stays were shorter^{1,3,7,10,11,15} for EVAR, with mean length of hospitalization of 8.9 days.¹³ In terms of ICU stays, EVAR had better results,¹⁰ with rates of 4 percent, versus 7 percent for open surgery. As for length of stay at the ICU, on average, EVAR patients stayed 2.8 days, versus 6.5 days for patients who underwent conventional surgery.^1,11 For patients who died within thirty days of hospital discharge, mean length of hospitalization was 47 days.¹³

Perioperative mortality

In the studies used in this review, perioperative mortality (deaths within 30 postoperative days) was lower for the EVAR group than the conventional surgery one, with values ranging from 1.2 to 14.9 percent.^{1,3,7,10,11,13,15} EVAR Trial 1 had 1.7 percent perioperative mortality for EVAR and 4.7 percent for conventional surgery.⁷ Another study found similar values, with a 1.2 percent rate for EVAR and 4.6 percent for open surgery.¹⁰

One-year mortality

Data from Bush et al. show one-year mortality rates of 8.7% for EVAR and 1211% for open surgery.¹¹

Mortality from all causes

The global mortality rate (causes related or unrelated to the aneurysm) in the Brewster et al. study was 28.2 percent, 11 percent of which can be attributed to the aneurysm or the treatment. Most deaths were caused by heart disease or cancer.⁸ In the study by Koning et al., the total mortality rate was 13 percent, 2.5 percent of which were related to the procedure, while the other 10.5 percent had other causes.¹³ Blankensteijn et al. found higher rates of mortality related to cardiovascular causes in the EVAR group than in the conventional surgery group, though the difference is not statistically significant.¹⁴ For patients with major aneurysms, EVAR treatment led to a statistically significant two thirds decrease in mortality 30 days after the procedure compared to open surgery.³ The 4-year global mortality rate was 28 percent for both groups in EVAR Trial 1³.

Mortality from aneurysm

The cumulative mortality rate for aneurysm-related deaths (deaths caused by rupture, graft infection, thrombosis or reintervention within or after 30 days of the original procedure) was 5.7 percent for traditional surgery and 2.1 percent for EVAR.¹⁴ EVAR Trial 2 found no difference in mortality from aneurysms and other causes, since there were 23 deaths from aneurysm rupture in the clinical follow-up group and 13 postoperative deaths and nine late deaths from ruptures in the EVAR group³. According to Koning et al., mortality related to the procedure was 1.6 percent per year.¹³

Complications

The studies by Bush et al., Aarts et al., and Prinssen et al. found lower rates of complications in the EVAR group.^1,10-12 The primary cause of the difference was the higher rate of pulmonary complications in open surgery.¹⁰ However, EVAR Trial 1 found higher rates of complications for EVAR compared to open surgery, with 41 versus 9 percent, respectively.³ Lee suggests the higher rate of postoperative complications in open surgery is offset by the greater number of local or vascular complications in EVAR.¹⁵

The primary complications caused by the prostheses available in the market have to do with endoleak, migration and thrombosis secondary to high rates of reintervention and failure to prevent aneurysm ruptures.¹¹ After EVAR, the annual risk of aneurysm rupture ranges from 1 to 1.5 percent, and is more likely to occur in patients who suffer endoleak.^7,8 The rate of endoleak, around 24 percent, is significantly associated with reintervention rates.¹ Aarts et al. and Prinssen et al. showed there is a significant difference in intraoperative blood loss^1,10 (150 mL for EVAR versus 1,300 mL for open surgery).¹

Durability of graft

According to EVAR Trial 1, durability of graft ranges from 20 to 30 years.⁷

Cost-benefit

In EVAR Trial 1, cost per patient was circa USD 23,500 for EVAR and USD 17,500 for traditional surgery, while 4-year cost per patient in EVAR Trial 2 was approximately USD 24,000 for EVAR and USD 8,800 for the clinical follow-up group.³ Lee et al. report costs of USD 50,346 for EVAR and USD 47,009 for open surgery.¹⁵

Considering rates of readmission within 30 days and 1 year, EVAR achieved higher levels, with 12.4 and 38.8 percent, respectively, versus 9.4 and 28.1 percent for conventional surgery.¹¹

Reintervention rates

Reinterventions may be needed for at least 25 percent of EVAR patients,⁷ due to persistent primary endoleak, delayed endoleak, migration, thrombosis, progressive AAA increase, and obstructions. In 12 years, 10 percent of patients required reintervention, with time free of reintervention reaching 78 percent in 5 years.⁸ Secondary interventions after EVAR were needed for almost one fifth of all patients.⁸

Reintervention rates over 30 days were 9.8 percent for EVAR and 5.8 percent for open surgery,⁷ with EVAR continuing with higher reintervention rates in the first nine months.¹⁴ EVAR Trials 1 and 2 found that respectively 20 and 26 percent of patients require at least one reintervention within 4 years, while only 6 percent of the open surgery group in EVAR Trial 1³ required it. However, Aarts's study found no statistically significant difference in reintervention between the two groups.¹

Survival rate

The global 2-year survival rate was 89.6 percent for conventional surgery and 89.7 percent for EVAR. Survival without moderate or severe complications was similar for both groups within two years of follow-up.¹⁴ EVAR has been shown to improve 3-year survival from 79 to 86 percent, a clear short term survival benefit.⁷ Five-year survival reached 52 percent for EVAR, but EVAR Trial 1 and Blankensteijn show that survival advantages disappeared, while aneurysm-related mortality remained significantly low within 2 years.⁸ EVAR patients have an 8-year survival rate of 70 percent.¹³

Compared to conventional surgery, EVAR led to a 3 percent higher survival rate for aneurysm-related causes³. The five-year survival rate for aneurysms after EVAR was 96 percent, while the rate for all causes was 52 percent.⁸

Medical staff and hospital volume

There is a direct correlation between greater hospital flow and achievement of better results in following up on patients submitted to open surgery.¹¹

Patients who underwent procedures in low flow hospitals, regardless of surgery type, were under higher risk of perioperative and one-year mortality. There was no significant difference in complication rates between high and low flow hospitals.¹¹

The initial studies (RETA and EUROSTAR) reported higher rates of early death than EVAR Trial 1 and 2. An observational study showed acceptable results when EVAR spreads from the university training center to community practice.³

Conversion rate

The literature reports a conversion rate of approximately 2 percent,¹ with 2.3 percent acute conversion and 1.7 percent late conversion, secondary to ruptures, migration, infection or AAA growth.⁸. Prinssen et al. reports intraoperative conversion rates of 1.7 percent for open surgery.¹⁰

Discussion

Compared to open surgery, EVAR has a clear advantage in terms of perioperative survival.¹⁴ This might be due to the less invasive nature of endovascular treatment, which leads to lower hypermetabolic response after stress. During open surgery, aortic clamping means significant changes to cardiovascular parameters such as cardiac output, mean blood pressure, and systemic vascular resistance, potentially causing hemodynamic instability in patients with previous cardiopathies or at high risk of cardiovascular disease.¹¹ Convergence in global survival rates in the second year after aneurysm repair may be related to the fact that patients who survive the stress of open surgery are less likely to die in the first few postoperative months than who underwent EVAR.¹⁴

Most studies find similar rates of perioperative mortality, except Koning, which found higher values¹³ for the endovascular technique, possibly influenced by high rates of associated cardiovascular comorbidities.

Since groups submitted to EVAR had more comorbidities, compared to open surgery, short term mortality, complications and reintervention rates may be biased towards poorer outcomes.¹⁴ Also, several studies were based on first generation endoprostheses, which might also explain higher rates of mortality, failure, durability issues and complications.^8,14 These factors may justify the similar mortality rates for the two techniques.

Also, the perioperative mortality rate of conventional surgery patients is greater than for EVAR. However, lower mortality in the EVAR group is limited to the first postoperative year;¹⁴ consequently, long term survival is greater for the conventional surgery group. Notice that the studies performed thus far do not have long term follow-up data for EVAR patients, so there are still no data supporting the advantage of that method over open surgery in terms of patient survival. Also, the EVAR group mortality may be undercounted due to shorter hospital stays and underreporting of deaths outside hospitals.¹⁵

For patients who could have been submitted to both techniques and were treated with EVAR, initial mortality gains are lost due to the large number of late complications and reinterventions². However, Prinssen says that EVAR is the best option for this group because it has lower rates of complications and perioperative mortality.¹⁰ For patients who could not undergo open surgery, however, initial complications mask long term decreases in mortality. Therefore, initial results might not offer evidence for the actual benefits from the endovascular procedure, requiring us to always follow patient outcomes over time to acquire more accurate results.²

There is no consensus in the literature regarding the benefits of EVAR for high risk patients who cannot undergo conventional surgery. A retrospective study suggests EVAR is good option for patients with precarious clinical conditions (ASA 3 or 4), making them ineligible for the surgical procedure.^8,13 For patients who could undergo conventional surgery and were submitted to EVAR, there is a small additional benefit in exchange for higher cost, but the cost-benefit ratio was high for patients who could not undergo conventional surgery. A randomized study, however, shows that for patients who could undergo open surgery, EVAR was neither safe nor effective, providing no gains in 2-year survival for high risk patients.³

The literature suggests conversion mostly occurs within the first few years after EVAR, and is associated with greater diameters and lower prosthesis flexibility, inappropriate patient selection, and poor judgment and lack of experience on the part of surgeons. However, because of the use of latest generation prostheses and the adoption of improved selection criteria, the last 4 years have seen lower conversion rates.⁸

Despite improvements in endoprostheses, issues such as delayed endoleaks, migration or increased AAA may occur and are clearly related to the failure of EVAR in resolving the AAA and preventing ruptures.^8,14 However, the natural history and behavior of AAA indicate that, if it remains untreated, the aneurysm has an 11 percent chance of rupture per year and a 10 percent annual growth rate, compared to a 1 percent chance of rupture after EVAR.⁸

Studies show high rates of intervention as compared to open surgery, but secondary procedures, when successful, do not compromise mortality from aneurysm or later follow-up.⁸ Added to the high cost of prostheses, the need for reintervention increases the financial cost of EVAR,³ making it more expensive than traditional surgery, even though the latter requires longer hospital stays.^1,15

In a retrospective nonrandomized study, EVAR proved to have various short term advantages over surgical repair, but there are still questions about the durability of grafts,¹³ despite technological improvements. Also, mortality rates associated with aneurysm repair could decrease further as the method becomes more widespread, causing the technique to improve.¹⁰

Benefits from EVAR include less blood loss and less need for transfusions, procedure times, shorter ICU and ward stays, lower rates of immediate postoperative adverse events, and faster recovery.⁸ Also, patients submitted to EVAR had significantly better statistical follow-up, with lower short term mortality rates.¹¹ However, those benefits might not stand over the long term, since reinterventions may be required for at least 25 percent of EVAR patients.⁷

As discussed above, EVAR requires training programs still unavailable in many vascular surgery centers. With proper patient selection and use of latest generation prostheses, EVAR can effectively reach AAA repair goals such as less morbidity and both short and long term perioperative mortality rates, despite its use in a relatively high risk population.

Training and improvement of the medical staff is key, as well as careful and detailed analysis of patients. One should not underestimate their preference after providing a clear explanation of the technique and its potential advantages and disadvantages.

Conclusion

Compared to conventional surgery, EVAR has some short term benefits, but the advantage disappears after the first year.

EVAR has lower rates of hospital mortality, hospital stay, mortality from all causes, mortality from aneurysm, perioperative mortality, and one-year mortality. However, it has higher rates of complications and reintervention. Durability of graft and clear advantages in terms of survival rates and cost-benefit analysis are uncertain, and further studies are required for long term follow-up. Training and improvement of the medical staff influence outcomes following EVAR.

References

• 1. Aarts F, Sterkenburg SV, Blankensteijn JD. Endovascular aneurysm repair versus open aneurysm repair: comparison of treatment outcome and procedure-related reintervention rate. Ann Vasc Surg. 2005;19:699-704.
• 2. Michaels JA, Drury D, Thomas SM. Cost-effectiveness of endovascular abdominal aortic aneurysm repair. Br J Surg. 2005;92:960-7.
• 3. Brooks MJ, Brown LC, Greenhalgh RM. Defining the role of endovascular therapy in the treatment of abdominal aortic aneurysm: results of a prospective randomized trial. Adv Surg. 2006;40:191-204.
• 4. Carvalho FC, Brito VP, Tribulatto EC, van Bellen B. Estudo prospectivo da morbi-mortalidade precoce e tardia da cirurgia do aneurisma da aorta abdominal. Arq Bras Cardiol. 2005;84:292-6.
• 5. Puech-Leão P, Molnar LJ, Oliveira IR, Cerri GG. Prevalence of abdominal aortic aneurysms: a screening program in São Paulo, Brazil. Sao Paulo Med J. 2004;122:158-60.
• 6. Morris GE, Hubbard CS, Quick CR. An abdominal aortic aneurysm screening programme for all males over the age of 50 years. Eur J Vasc Surg. 1994;8:156-60.
• 7. Greenhalgh RM, Brown LC, Kwong GP, Powell JT, Thompson SG, EVAR Trial Participants. Comparison of endovascular aneurysm repair with open repair in patients with abdominal aortic aneurysm (EVAR trial 1), 30-day operative mortality results: randomised controlled trial. Lancet. 2004;364:843-8.
• 8. Brewster DC, Jones JE, Chung TK, et al. Long-term outcomes after endovascular abdominal aortic aneurysm repair: the first decade. Ann Surg. 2006;244:426-38.
• 9. Parodi JC, Palmaz IC. Transfemural intraluminal graft implantation for abdominal aortic aneurysms. Ann Vasc Surg. 1991;5:491-9.
• 10. Prinssen M, Verhoeven EL, Buth J, et al. A randomized trial comparing conventional and endovascular repair of abdominal aortic aneurysms. N Engl J Med. 2004;351:1607-18.
• 11. Bush RL, Johnson ML, Collins TC, et al. Open versus endovascular abdominal aortic aneurysm repair in VA hospitals. J Am Coll Surg. 2006;202:577-87.
• 12. Alves CM, Souza JA. Estado da arte em stents de aorta. Rev Soc Cardiol Estado Sao Paulo. 2005;15:362-8.
• 13. Koning GG, Vallabhaneni SR, van Marrewijk CJ, Leurs LJ, Laheij RJ, Buth J. Mortalidade relacionada ao tratamento endovascular do aneurisma da aorta abdominal com o uso dos modelos revisados. Rev Bras Cir Cardiovasc. 2007;22:7-14.
• 14. Blankensteijn JD, de Jong SE, Prinssen M, et al. Two-year outcomes after conventional or endovascular repair of abdominal aortic aneurysms. N Engl J Med. 2005;352:2398-405.
• 15. Lee WA, Carter JW, Upchurch G, Seeger JM, Huber TS. Perioperative outcomes after open and endovascular repair of intact abdominal aortic aneurysms in the United States during 2001. J Vasc Surg. 2004;39:491-6.

Publication Dates

• Publication in this collection
  26 Mar 2010
• Date of issue
  Dec 2009

History

• Accepted
  11 Aug 2009
• Received
  10 Sept 2008