Heart failure (HF) remains a major public health problem in western countries, despite the enormous progress in its diagnosis and treatment. Acute and chronic decompensated HF are leading medical causes of hospitalization among people aged over 65 years in European countries, the USA, Australia and New Zealand. However, there have been few studies on acute and chronic decompensated HF and the European Society of Cardiology (ESC) guidelines on this subject have only just been published. OBJECTIVE To evaluate the overall prevalence of hospitalization due to HF according to its subtypes, comorbidities, and decompensating factors, in the Medical Department of a central teaching hospital in an urban area. METHODS We performed a retrospective observational study of patients admitted consecutively to the Medical Department via the emergency room between January and June 2001. Discharge casenotes on 1038 admissions were reviewed. Those with a diagnosis of HF or cardiovascular conditions associated with or precursors of HF were analyzed. Cases with a final diagnosis of HF according to the criteria of the ESC guidelines were included in the study. We evaluated the overall prevalence of HF and subtypes of cardiac dysfunction, etiological risk factors, patients' demographic characteristics, decompensating factors, comorbidity, mean length of hospital stay, and in-hospital mortality rate. RESULTS We identified 180 patients with HF (17.4%), mean age 74.6 +/- 14; 87 were male (48%), aged 73.7 +/- 14.2, and 93 female (52%), aged 75.6 +/- 14. Left ventricular systolic dysfunction (LVSD) was present in 42.2% of cases, preserved left ventricular systolic function in 32.6%, and valvular heart disease in 10.6%. Hypertension and coronary artery disease were the main etiological risk factors (62.2% and 42.8% respectively). Atrial fibrillation was recorded in 43.4% of the patients, diabetes was diagnosed in 21.6%, and anemia and chronic obstructive pulmonary disease in about one third. Infection, predominantly respiratory, was the main factor triggering decompensation, followed by uncontrolled hypertension and supraventricular tachyarrhythmia. At admission, 42.2% of the patients were in NYHA class III and 44.8% in NYHA class IV. HF patients had a mean hospital stay of 13.8 days, slightly shorter than the mean overall stay of patients admitted to the Medical Department in the same period (14.5 days). In-hospital mortality for HF patients was 7.7%, with HF being the first cause of admission to the Medical Department, followed by stroke (10.6%). CONCLUSIONS This study confirms the high prevalence of acute or chronic decompensated HF in patients hospitalized in the Medical Department of a central teaching hospital in an urban area. The patients were mainly elderly, of both genders, with a slightly higher proportion of HF due to LVSD. Most patients were in NYHA classes III and IV. Mean hospital stay was no longer than that of all patients admitted in the same period. The in-hospital mortality rate was low. The age-group affected and the high prevalence of multiple comorbidities emphasize the need to establish HF clinics with multidisciplinary teams to manage these patients, and health authorities must be made aware of the burden of this syndrome.