Background Elective intra-aortic balloon pump (IABP) support may reduce acute complications occurring during percutaneous coronary interventions (PCI) in patients with severe depression of the left ventricular ejection fraction (EF ≤ 30%). Methods Since February 1998, 133 consecutive patients with EF ≤30% underwent elective PCI in our institution; 61 had elective preprocedural IABP support (group A) and 72 patients had conventional PCI (group B). Jeopardy score was calculated in each patient from the coronary angiograms to quantify the myocardium at risk. Results EF was similar in the 2 groups. Jeopardy score was higher in group A (8.0 ± 2.8 vs 6.7 ± 2.4, P = .008). The other principal clinical and angiographic characteristics were similar in the 2 groups. Severe hypotension and/or shock occurred in 11 patients, all in group B (P = .001). All required urgent IABP support, and 3 eventually died. Intraprocedural major adverse cardiac and cerebral events (eg, myocardial infarction, severe hypotension and/or shock, urgent bypass surgery, stroke, and death) were higher in group B (17% vs 0%, P = .001). By stepwise logistic regression analysis, elective IABP support (odds ration [OR] 0.11 [95% CI 0.21-0.60], P = .011), jeopardy score (OR 5.37 [95% CI 1.10-8.70], P = .040), and female sex (OR 2.72 [95% CI 1.85-3.10], P = .015), were the correlates of intraprocedural events. Conclusions This study supports the potential usefulness of elective versus provisional IABP to prevent intraprocedural major adverse cardiac and cerebral events in high-risk PCI. (Am Heart J 2003;145:700-7.)