title: Intra-Aortic Balloon Pump Counterpulsation during Primary Percutaneous Coronary Intervention for ST-Elevation Myocardial Infarction and Cardiogenic Shock: Insights from the British Columbia Cardiac Registry.
abstract: BACKGROUND
  Cardiogenic shock complicating ST-elevation myocardial infarction (STEMI) is associated with significant morbidity and mortality. In the primary percutaneous coronary intervention (PPCI) era, randomized trials have not shown a survival benefit with intra-aortic balloon pump (IABP) therapy. This differs to observational data which show a detrimental effect, potentially reflecting bias and confounding. Without robust and valid risk adjustment, findings from non-randomized studies may remain biased.
  
  
  METHODS
  We compared long-term mortality following IABP therapy in patients with cardiogenic shock undergoing PPCI during 2008-2013 from the British Columbia Cardiac Registry. We addressed measured and unmeasured confounding using propensity score and instrumental variable methods.
  
  
  RESULTS
  A total of 12,105 patients with STEMI were treated with PPCI during the study period. Of these, 700 patients (5.8%) had cardiogenic shock. Of the patients with cardiogenic shock, 255 patients (36%) received IABP therapy. Multivariable analyses identified IABP therapy to be associated with increased mortality up to 3 years (HR = 1.67, 95% CI:1.20-2.67, p<0.001). This association was lost in propensity-matched analyses (HR = 1.23, 95% CI: 0.84-1.80, p = 0.288). When addressing measured and unmeasured confounders, instrumental variable analyses demonstrated that IABP therapy was not associated with mortality at 3 years (Δ = 16.7%, 95% CI: -12.7%, 46.1%, p = 0.281). Subgroup analyses demonstrated IABP was associated with increased mortality in non-diabetics; patients not undergoing multivessel intervention; patients without renal disease and patients not having received prior thrombolysis.
  
  
  CONCLUSIONS
  In this observational analysis of patients with STEMI and cardiogenic shock, when adjusting for confounding, IABP therapy had a neutral effect with no association with long-term mortality. These findings differ to previously reported observational studies, but are in keeping with randomized trial data.
authors: Department of Cardiology, Victoria Heart Institute Foundation, Victoria, BC, Canada.|Department of Cardiology, Royal Jubilee Hospital, Victoria, BC, Canada.
authors: M Bilal
authors: MB
authors: Iqbal
authors: Department of Cardiology, Victoria Heart Institute Foundation, Victoria, BC, Canada.|Department of Cardiology, Royal Jubilee Hospital, Victoria, BC, Canada.
authors: Simon D
authors: SD
authors: Robinson
authors: Cardiac Services BC, Provincial Health Services Authority, Vancouver, BC, Canada.
authors: Lillian
authors: L
authors: Ding
authors: Department of Cardiology, Vancouver General Hospital, Vancouver, BC, Canada.
authors: Anthony
authors: A
authors: Fung
authors: Department of Cardiology, St. Paul's Hospital, Vancouver, BC, Canada.
authors: Eve
authors: E
authors: Aymong
authors: Department of Cardiology, Royal Columbian Hospital, Vancouver, BC, Canada.
authors: Albert W
authors: AW
authors: Chan
authors: Department of Cardiology, Kelowna General Hospital, Kelowna, BC, Canada.
authors: Steven
authors: S
authors: Hodge
authors: Department of Cardiology, Victoria Heart Institute Foundation, Victoria, BC, Canada.|Department of Cardiology, Royal Jubilee Hospital, Victoria, BC, Canada.
authors: Anthony
authors: A
authors: Della Siega
authors: Department of Cardiology, Victoria Heart Institute Foundation, Victoria, BC, Canada.|Department of Cardiology, Royal Jubilee Hospital, Victoria, BC, Canada.
authors: Imad J
authors: IJ
authors: Nadra
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D007423:Intra-Aortic Balloon Pumping; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000401:mortality / Q000628:therapy*; D062645:Percutaneous Coronary Intervention; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012770:Shock, Cardiogenic / Q000209:etiology / Q000401:mortality / Q000628:therapy*