Endovascular repair for abdominal aortic aneurysms: initial experience of an endograft programme

Epidemiology of abdominal aortic aneurysms in a Chinese population during introduction of endovascular repair, 1994 to 2013: A retrospective observational study

The aim of this study was to examine changes in abdominal aortic aneurysm repair and mortality during a period when endovascular aneurysm repair (EVAR) was introduced.Open repair surgery was the mainstay of treatment for abdominal aortic aneurysm (AAA), but EVAR is increasingly utilized. Studies in the Western population have reported improved short-term or postoperative mortality and shorter length of hospital stay with EVAR. However, scant data are available in the Chinese population.We conducted a retrospective observational study using the database of the Hospital Authority, which provides public health care to most of the Hong Kong population. AAA patients admitted to public hospitals for intact repair or rupture from 1994 to 2013 were included in this study. We calculated the incidence of ruptured AAA, annual repair rates according to type of AAA and surgery, as well as death rates (operative and overall short-term). We calculated whether there were significant changes over time and compared short-term mortality between open surgery and EVAR.One thousand eight hundred eighty-five patients were admitted for intact repair and 1306 patients were admitted for AAA rupture, of whom 795 underwent rupture repair. Intact repair rates significantly increased in all age groups (7.3-37.8%, P < .001) over the study period.The incidence of ruptured AAA increased, in all age groups, except in < 64 years old. By 2013, 85% of intact repairs and 55.4% of rupture repair were done by EVAR. Over time, there was a significant decrease in operative mortality for intact repair (16.5 in 1994 to 7.1 in 2013, P = .01) and rupture repair (59.7 in 1994 to 30.8 in 2013, P = .003). Over the same time period, short-term AAA-related deaths decreased by more than half (73% in 1994 to 24% in 2013, P < .001), with a significant decline in all age groups, except < 64 years old. Short-term mortality was significantly lower for EVAR than for open repair (17.2% vs 40.3%, P < .01).Short-term AAA-related deaths have declined likely due to decreased operative mortality and rupture deaths during the period of EVAR introduction and expansion.

The impact of using informative priors in a Bayesian cost-effectiveness analysis: an application of endovascular versus open surgical repair for abdominal aortic aneurysms in high-risk patients

BACKGROUND

Bayesian methods have been proposed as a way of synthesizing all available evidence to inform decision making. However, few practical applications of the use of Bayesian methods for combining patient-level data (i.e., trial) with additional evidence (e.g., literature) exist in the cost-effectiveness literature. The objective of this study was to compare a Bayesian cost-effectiveness analysis using informative priors to a standard non-Bayesian nonparametric method to assess the impact of incorporating additional information into a cost-effectiveness analysis.

METHODS

Patient-level data from a previously published nonrandomized study were analyzed using traditional nonparametric bootstrap techniques and bivariate normal Bayesian models with vague and informative priors. Two different types of informative priors were considered to reflect different valuations of the additional evidence relative to the patient-level data (i.e., "face value" and "skeptical"). The impact of using different distributions and valuations was assessed in a sensitivity analysis. Models were compared in terms of incremental net monetary benefit (INMB) and cost-effectiveness acceptability frontiers (CEAFs).

RESULTS

The bootstrapping and Bayesian analyses using vague priors provided similar results. The most pronounced impact of incorporating the informative priors was the increase in estimated life years in the control arm relative to what was observed in the patient-level data alone. Consequently, the incremental difference in life years originally observed in the patient-level data was reduced, and the INMB and CEAF changed accordingly.

CONCLUSIONS

The results of this study demonstrate the potential impact and importance of incorporating additional information into an analysis of patient-level data, suggesting this could alter decisions as to whether a treatment should be adopted and whether more information should be acquired.

Effects of study design and trends for EVAR versus OSR

Purpose:

To investigate if study design factors such as randomization, multi-center versus single center evidence, institutional surgical volume, and patient selection affect the outcomes for endovascular repair (EVAR) versus open surgical repair (OSR). Finally, we investigate trends over time in EVAR versus OSR outcomes.

Methods:

Search strategies for comparative studies were performed individually for: OVID’s MEDLINE, EMBASE, CINAHL, HAPI, and Evidence Based Medicine (EBM) Reviews (including Cochrane DSR, ACP Journal Club, DARE and CCTR), limited to 1990 and November 2006.

Results:

Identified literature: 84 comparative studies pertaining to 57,645 patients. These include 4 randomized controlled trials (RCTs), plus 2 RCTs with long-term follow-up. The other 78 comparative studies were nonrandomized with 75 reporting perioperative outcomes, of which 16 were multi-center, and 59 single-center studies. Of the single-center studies 31 were low-volume and 28 were high-volume centers. In addition, 5 studies had all patients anatomically eligible for EVAR, and 8 studies included high-risk patients only. Finally, 25 long term observational studies reported outcomes up to 3 years.

Outcomes:

Lower perioperative mortality and rates of complications for EVAR versus OSR varied across study designs and patient populations. EVAR adverse outcomes have decreased in recent times.

Conclusion:

EVAR highlights the problem of performing meta-analysis when the experience evolves over time.