Patients with acute coronary syndromes (ACSs) may develop serious multiorgan complications and require prolonged intensive care. Our aim was to characterize and identify factors that are associated with outcomes in these patients. We retrospectively identified 267 consecutive patients admitted to the coronary care unit for an ACS who required >3 days of mechanical ventilation. Multiple clinical and laboratory variables were correlated with mortality. Patients' ages were 68.3 +/- 10.9 years (mean +/- SD) and 165 (62%) were men. Seventy-six patients (29%) died within 30 days of admission, and the 1 year mortality was 46%. Moderate or severe left ventricular systolic dysfunction was found in 72% of the patients. Eighty-nine patients (33.3%) required vasopressors, of whom 64 (72%) did not survive 30 days. Among 127 patients who required antibiotics (48.3%), 30-day mortality was 53% compared with 4% among patients who did not require antibiotics (p <0.001). The 30-day mortality among patients who received both antibiotics and vasopressors was 64 of 87 patients (74%), and the 1-year mortality in this subgroup was 86.2%. Parameters found to be independent predictors of 30-day mortality were (in descending order): vasopressor requirement, use of antibiotics, peripheral vascular disease, ST-elevation myocardial infarction, renal failure, obesity and Killip class on admission. In conclusion, mortality among patients who require prolonged mechanical ventilation after an ACS is substantial. The main independent predictors of with mortality are the severity of heart failure and the presence of co-morbidities.