Methods: We used data from the Swedish Coronary Angiography and Angioplasty Registry (SCAAR), which contains information about all PCI procedures performed in Sweden (31 hospitals). We included all procedures from 2005 to 2018 in patients with CS due to MI and divided the patients according to whether or not they were treated with IABP. We used instrumental variable analysis to adjust for differences in patient characteristics and hidden bias. Treating hospital was used as a treatment-preference instrumental variable using two-stage least squares regression. Multilevel modeling was used to adjust for clustering of observations in a hierarchical database. In-hospital complication was defined as the occurrence of any of the following events: major bleeding, minor bleeding, extended compression of the access artery, blood transfusion, surgical revision of the access artery, neurologic complication.
Results: In total, 2,991 patients with CS were included in the study. Of these, 737 (25%) were treated with IABP. In the combined cohort, there were 1,554 (52%) deaths 30 days after PCI and 1,239 (41%) cases of in-hospital complications. IABP was not associated with death at 30 days (risk reduction [RR] -1.1 %; 95% confidence interval [CI] -15.7;13.5; P= 0.881). However, IABP was associated with a higher risk of in-hospital complications (RR 35.4%; 95% CI 17.7-53.1; P<0.001). Conclusion: In this observational study, treatment with IABP, was not associated with 30-days mortality in patients with CS. However, the risk of in-hospital complications was substantially higher in patients with CS who were treated with IABP. Our observational study supports class III recommendation by the current ESC guidelines for the use of IABP in CS.