Invited commentary
Article Outline
The Swedish Vascular Registry (Swedvasc) is a long standing national project used for auditing outcome of a variety of vascular procedures.1 The authors for the Swedish Vascular Registry (Swedvasc) have assessed the outcome of endovascular repair in patients at high-risk for surgical treatment of their abdominal aortic aneurysm in comparison to open surgery. A comparison of this type from registry data carries the risk of unequal distribution of co-morbid factors between treatment groups. The authors selected two studies with a similar design for comparison with their own series. The first study, a Veterans Administration study, was reported by Bush et al and the second by Sicard et al.2, 3 These US studies both concluded from their operative and late mortality data that patients with infrarenal abdominal aortic aneurysm with considerable medical co-morbidities benefit from and should be considered for primary endovascular aneurysm repair (EVAR). The authors of the Swedvasc study came to an opposite conclusion in that they could “not confirm the benefit of EVAR from these previous registry studies with a similar high-risk definition”, and “in clinical practice, open repair may be at least as good as EVAR in high-risk patients fit for surgery”. The conclusion was based on a relatively high all-cause mortality in EVAR patients during follow-up. However, a clear explanation for the striking difference of their results with the two US studies was not provided. Causes of death were not available in their database and “aneurysm-related death” was disposed as an unreliable variable.
Despite a common definition for “high risk” there is considerable leeway for selection bias to lead to noncomparability of subgroups. Two-thirds of the Swedvasc patients had only one of a range of possible conditions indicating unfitness. In their system, the severity, for example, of cardiac problems ranged from a successful aorto-coronary bypass graft (CABG) to manifest unstable angina or congestive heart failure. Most other co-morbid conditions demonstrated a similar variation in severity. This system indeed is imperfect. There is currently no better way to document differences in risk profiles of subgroups than a posthoc comparison of all-cause mortality rates after a follow-up period of 1 or more years. After all, the majority of late deaths come from co-morbidities, rather than from aneurysms or treatment-related causes.4 The EVAR group in the Swedvasc study had a substantially worse general health profile than patients treated by operative repair (OR), considering all-cause mortality rates varying from 41% to 26% after 4 years, respectively. Similarly, fitness in EVAR patients in Swedvasc was inferior compared to those in the VA-study (1-year mortality rates of 15.9% and 9.5%, respectively). The opposite was true for patients with surgical treatment of their aneurysm. Differences in midterm all-cause mortality rates strongly suggested Swedvasc OR-patients to be in far better health at baseline than patients studied by Bush and Sicard (8.5% vs 12.4%-14% mortality at 1 year, 26% vs 34% mortality at 5 years). A more favorable medical risk profile in the Swedvasc patients with OR may be associated with smaller, anatomically less complex aneurysms.4 These factors combined may explain the low 30-day mortality of 3.3%.
The authors had better concluded that differences in outcome between treatment groups in their own study as well as compared to other studies were primarily caused by factors related to patient selection for each treatment.
References
- . Auditing surgical outcome: ten years with the Swedish Vascular Registry – Swedvasc (The Steering Committee of Swedvasc). Eur J Surg Suppl. 1998;581:3–8
- . Performance of endovascular aortic aneurysm repair in high-risk patients: results from the Veterans Affairs National Surgical Quality Improvement Program. J Vasc Surg. 2007;45:227–233
- . Endovascular abdominal aortic aneurysm repair: long-term outcome measures in patients at high-risk for open surgery. J Vasc Surg. 2006;44:229–236
- . Outcome of endovascular abdominal aortic aneurysm repair in patients with conditions considered unfit for an open procedure (A report on the EUROSTAR experience). J Vasc Surg. 2002;35:211–221
PII: S0741-5214(08)01238-X
doi:10.1016/j.jvs.2008.07.068
© 2008 Published by Elsevier Inc.
Refers to article:
- Outcomes of endovascular abdominal aortic aneurysm repair compared with open surgical repair in high-risk patients: Results from the Swedish Vascular Registry , 02 October 2008
