title: Stentless versus stented bioprosthetic aortic valves: a systematic review and meta-analysis of controlled trials.
abstract: OBJECTIVE
  : This meta-analysis sought to determine whether stentless bioprosthetic valves improve clinical and resource outcomes compared with stented valves in patients undergoing aortic valve replacement.
  
  
  METHODS
  : A comprehensive search was undertaken to identify all randomized and nonrandomized controlled trials comparing stentless to stented bioprosthetic valves in patients undergoing aortic valve replacement available up to March 2008. The primary outcomes were clinical and resource outcomes in randomized controlled trial (RCT). Secondary outcomes clinical and resource outcomes in nonrandomized controlled trial (non-RCT). Odds ratios (OR), weighted mean differences (WMD), or standardized mean differences and their 95% confidence intervals (CI) were analyzed as appropriate.
  
  
  RESULTS
  : Seventeen RCTs published in 23 articles involving 1317 patients, and 14 non-RCTs published in 18 articles involving 2485 patients were included in the meta-analysis. For the primary analysis of randomized trials, mortality for stentless versus stented valve groups did not differ at 30 days (OR 1.36, 95% CI 0.68-2.72), 1 year (OR 1.01, 95% CI 0.55-1.85), or 2 to 10 years follow-up (OR 0.82, 95% CI 0.50-1.33). Aggregate event rates for all-cause mortality at 30 days were 3.7% versus 2.9%, at 1 year were 5.5% versus 5.9% and at 2 to 10 years were 17% versus 19% for stentless versus stented valve groups, respectively. Stroke or neurologic complications did not differ between stentless (3.6%) and stented (4.0%) valve groups. Risk of prosthesis-patient mismatch was numerically lower in the stentless group (11.0% vs. 31.3%, OR 0.30, 95% CI 0.05-1.66), but this parameter was reported in few trials and did not reach statistical significance. Effective orifice area index was significantly greater for stentless aortic valve compared with stented valves at 30 days (WMD 0.12 cm/m), at 2 to 6 months (WMD 0.15 cm/m), and at 1 year (WMD 0.26 cm/m). Mean gradient at 1 month was significantly lower in the stentless valve group (WMD -6 mm Hg), at 2 to 6 month follow-up (WMD -4 mm Hg,), at 1 year follow-up (WMD -3 mm Hg) and up to 3 year follow-up (WMD -3 mm Hg) compared with the stented valve group. Although the left ventricular mass index was generally lower in the stentless group versus the stented valve group, the aggregate estimates of mean difference did not reach significance during any time period of follow-up (1 month, 2-6 months, 1 year, and 8 years).
  
  
  CONCLUSIONS
  : Evidence from randomized trials shows that subcoronary stentless aortic valves improve hemodynamic parameters of effective orifice area index, mean gradient, and peak gradient over the short and long term. These improvements have not led to proven impact on patient morbidity, mortality, and resource-related outcomes; however, few trials reported on clinical outcomes beyond 1 year and definitive conclusions are not possible until sufficient evidence addresses longer-term effects.
authors.affiliation: From the *Department of Anesthesia and Perioperative Medicine, Evidence-Based Perioperative Clinical Outcomes Research Group (EPiCOR), London Health Sciences Centre, The University of Western Ontario, London, ON, Canada; †Department of Cardiothoracic Surgery, Imperial College, Royal Brompton Hospital, London, UK; ‡High Impact Technology Evaluation Centre, London Health Sciences Centre, London, ON, Canada; §Department of Cardiothoracic Surgery, St. Mary's Hospital, London, UK; ¶Division of Thoracic and Cardiovascular Surgery, The Lankenau Hospital, Wynnewood, PA USA; ∥Division of Cardiovascular Surgery, St. Paul's Hospital, University of British Columbia, Vancouver, Canada; **Department of Cardiothoracic Surgery, Mount Sinai Medical Center/Mount Sinai School of Medicine, NY USA; and ††Golden Jubilee National Hospital, Clydebank, UK; and ‡‡Department of Surgery, Siena University School of Medicine, Siena, Italy.
authors.forename: Davy
authors.initials: D
authors.lastname: Cheng
authors.forename: John
authors.initials: J
authors.lastname: Pepper
authors.forename: Janet
authors.initials: J
authors.lastname: Martin
authors.forename: Rex
authors.initials: R
authors.lastname: Stanbridge
authors.forename: Francis D
authors.initials: FD
authors.lastname: Ferdinand
authors.forename: W R Eric
authors.initials: WR
authors.lastname: Jamieson
authors.forename: Paul
authors.initials: P
authors.lastname: Stelzer
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Berg
authors.forename: Guido
authors.initials: G
authors.lastname: Sani