title: Intra-aortic Balloon Pump Therapy for Acute Myocardial Infarction: A Meta-analysis.
abstract: OBJECTIVE
  Intra-aortic balloon pump (IABP) therapy is a widely used intervention for acute myocardial infarction with cardiogenic shock. Guidelines, which previously strongly recommended it, have recently undergone substantial change.
  
  
  OBJECTIVE
  To assess IABP efficacy in acute myocardial infarction.
  
  
  METHODS
  Human studies found in Pubmed, Embase, and Cochrane libraries through December 2014 and in reference lists of selected articles. Search strings were "myocardial infarction" or "acute coronary syndrome" and "intra-aortic balloon pump" or "counterpulsation."
  
  
  METHODS
  Randomized clinical trials (RCTs) and observational studies comparing use of IABP with no IABP in patients with acute myocardial infarction.
  
  
  METHODS
  Two reviewers independently extracted the data, and risk of bias in RCTs was assessed using the Cochrane risk of bias tool. We conducted separate meta-analyses of the RCTs and observational studies. Data were quantitatively synthesized using random-effects meta-analysis.
  
  
  METHODS
  Thirty-day mortality.
  
  
  RESULTS
  There were 12 eligible RCTs randomizing 2123 patients. In the RCTs, IABP use had no statistically significant effect on mortality (odds ratio [OR], 0.96 [95% CI, 0.74-1.24]), with no significant heterogeneity among trials (I2 = 0%; P = .52). This result was consistent when studies were stratified by the presence (OR, 0.94 [95% CI, 0.69-1.28]; P = .69, I2 = 0%) or absence (OR, 0.98 [95% CI, 0.57-1.69]; P = .95, I2 = 17%) of cardiogenic shock. There were 15 eligible observational studies totaling 15 530 patients. Their results were mutually conflicting (heterogeneity I2 = 97%; P < .001), causing wide uncertainty in the summary estimate for the association with mortality (OR, 0.96 [95% CI, 0.54-1.70]). A simple index of baseline risk marker imbalance in the observational studies appeared to explain much of the heterogeneity in the observational data (R2meta = 46.2%; P < .001).
  
  
  CONCLUSIONS
  Use of IABP was not found to improve mortality among patients with acute myocardial infarction in the RCTs, regardless of whether patients had cardiogenic shock. The observational studies showed a variety of mutually contradictory associations between IABP therapy and mortality, much of which was explained by the differences between studies in the balance of risk factors between IABP and non-IABP groups.
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Yousif
authors.initials: Y
authors.lastname: Ahmad
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Sayan
authors.initials: S
authors.lastname: Sen
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Shun-Shin
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Jing
authors.initials: J
authors.lastname: Ouyang
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Judith A
authors.initials: JA
authors.lastname: Finegold
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Rasha K
authors.initials: RK
authors.lastname: Al-Lamee
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Justin E R
authors.initials: JER
authors.lastname: Davies
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Graham D
authors.initials: GD
authors.lastname: Cole
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
mesh_terms: D006801:Humans; D007423:Intra-Aortic Balloon Pumping; D009203:Myocardial Infarction / Q000150:complications / Q000401:mortality / Q000601:surgery*; D064887:Observational Studies as Topic; D016032:Randomized Controlled Trials as Topic