Aims To define the clinical characteristics, co-morbidities, treatment, and clinical outcomes of patients with varying degrees of heart failure (HF) complicating ST-elevation myocardial infarction (STEMI), and to identify patients at high risk for HF following fibrinolysis. Methods and results 15,078 STEMI patients enrolled in a worldwide fibrinolytic trial (InTIME-II) were categorised into one of four hierarchical, mutually exclusive groups of HF: shock (n = 719, 5%); severe HF (n = 1082, 7%); mild HF (n = 1619, 11 %); no HF (n = 11, 658, 77%). In a multivariable model, anterior MI (OR 1.8, 95% Cl [1.6; 1.9]), age greater than or equal to65 (OR 1.8 [1.6; 2.0]), prior HF (OR 3.3 [2.6; 4.2]), and creatinine clearance <60 mL/min (OR 1.8 [1.6; 2.1]) were the four most powerful correlates of HF. Although 30-day mortality was sixfold higher for patients with HF (18.9% vs. 3.1% p < 0.0001), these patients were less likely to undergo angiography (30% vs. 40%, p < 0.0001) and revascularisation (19% vs. 25%, p < 0.0001), than patients without HF. Likewise, angiotensin-inhibitors and beta-blockers were not optimally utilised in patients with HF following MI. Conclusions During the index admission following fibrinolysis 23% of patients had HF. Despite a higher risk profile, patients with more severe HF were treated less aggressively than patients without HF. (C) 2004 The European Society of Cardiology. Published by Elsevier Ltd. All rights reserved.