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Volume–Outcome Relationships in Lower Extremity Arterial Bypass Surgery

Moxey, Paul W. MD*; Hofman, David BSc; Hinchliffe, Rob J. MD*; Poloniecki, Jan PhD; Loftus, Ian M. MD*; Thompson, Matt M. MD*; Holt, Peter J. PhD*

doi: 10.1097/SLA.0b013e31825f01d1
Original Articles

Objective: We sought to investigate whether a volume–outcome relationship exists for lower extremity arterial bypass (LEAB) surgery.

Methods: All LEAB procedures performed in England between 2002 and 2006 were identified from Hospital Episode Statistics data. A Charlson-type risk profile, including operating hospital annual case volume, was identified per patient. Outcome measures of revision bypass, amputation, death and a composite measure were established during the index admission and at 1 year.

Quintile analysis and multilevel multivariate modeling were used to identify the existence of a volume–outcome relationship and allow adjustment of results for significant determinants of outcome.

Results: A total of 27,660 femoropopliteal bypass and 4161 femorodistal bypass procedures were identified.

As volume increased, in-hospital mortality after popliteal bypass decreased from 6.5% to 4.9% (P = 0.0045), with a corresponding odds ratio of 0.980 [95% confidence interval (CI), 0.929–0.992; P = 0.014] for every increase of 50 patients per year. Major amputation decreased from 4.1% to 3.2% (P = 0.006) in high-volume hospitals, with a reduction in risk of 0.955 (95% CI, 0.928–0.983; P = 0.002) at 1 year.

For distal bypass, in-hospital mortality decreased from 9.8% to 5.5% (P = 0.004) and 1-year major amputation decreased from 25.4% to 18.2% (P < 0.001), with a corresponding odds ratio of 0.658 (95% CI, 0.517–0.838; P < 0.0001) as the volume increased.

An increase in the chance of revision surgery (10.6% vs 8.2%, P < 0.001) was seen with higher volume, with an increased odds ratio of 1.031 (95% CI, 1.005–1.057; P = 0.018).

Conclusions: A positive volume–outcome relationship exists for LEAB procedures even after employing multilevel risk adjustment models. There are benefits in terms of mortality and limb salvage both in the short-term and at 1 year postsurgery.

We have demonstrated a robust volume–outcome relationship in lower extremity arterial bypass procedures. As hospital volume increases, the adjusted in-hospital mortality and major amputation rate falls compared with low-volume centers. This has important implications for vascular surgical service planning and delivery.

*Department of Outcomes Research, St George's Vascular Institute, St George's Healthcare NHS Trust, London, United Kingdom

Department of Outcomes Research, Community Health Sciences, St George's University of London, London, United Kingdom.

Reprints: Paul W. Moxey, MD, St George's Vascular Institute, 4th Floor, St James Wing, St George's Hospital, Tooting, London, SW17 0QT, UK. E-mail

Disclosure: P.W.M. is supported by a joint Dunhill Medical Trust/Royal College of Surgeons of England Surgical Research Fellowship.

© 2012 Lippincott Williams & Wilkins, Inc.