Abstract
BACKGROUND: The efficacy of reperfusion therapy after acute myocardial infarction is time dependent. The risk profile of every patient should be available as soon as possible. Our aim was to determine whether collection of simple clinical markers at hospital admission might allow reliable risk stratification for in-hospital mortality. METHODS: The subjects were 11,483 patients with acute myocardial infarction from the GISSI-2 cohort. The GISSI-1 and GISSI-3 populations were selected to validate the classification. To stratify patients, the tree-growing method called recursive partitioning and amalgamation (RECPAM) was used. This method is used to identify homogeneous and distinct subgroups with respect to outcome. RESULTS: The RECPAM algorithm provided 6 classes. RECPAM class I included Killip class 3 to class 4 patients (516 deaths/1000). RECPAM class II included Killip 2 patients older than 66 years and with anterior infarction or sites of infarction that could not be evaluated (314 deaths/1000). Killip 1 patients older than 75 years and with anterior or multiple sites or sites that could not be evaluated were included in RECPAM class III with Killip class 2 patients younger than 66 years and with systolic blood pressure less than 120 mm Hg or older than 66 years and with any other infarction site (207 deaths/1000). The other classes showed lower mortality rates (91, 32, and 12 deaths/1000 for RECPAM classes IV, V, and VI). In the GISSI 1 and GISSI 3 samples the 6 classes ranked in the same order in terms of mortality rate. With respect to low-risk strata, patients belonging to RECPAM class VI without serious clinical events in the first 4 days had a very low incidence of in-hospital death (0.9%) or morbidity. Cumulative 6-month mortality for the 6 RECPAM classes was 59.6%, 41.2%, 26.4%, 12.9%, 4. 8%, and 2.2%. CONCLUSIONS: Four simple clinical markers readily available at admission of patients with myocardial infarction allow a quick, reliable, and inexpensive prediction of risk for in-hospital and 6-month mortality. The RECPAM classification also helped identify a large subgroup of patients fit for early hospital discharge.