Primary angioplasty and selection bias in patients presenting late (⟩12 h) after onset of chest pain and ST elevation myocardial infarction

OBJECTIVES This study was designed to compare the in-hospital outcome of patients presenting with >12 h from onset of chest pain and acute ST elevation myocardial infarction (AMI) who received either immediate invasive or conservative therapy. BACKGROUND The benefits of fibrinolytic therapy diminish in patients presenting with AMI and onset of chest pain >12 h. Primary angioplasty has been suggested as a possible treatment for such patients, but they have been excluded from most trials of primary angioplasty. It remains unclear if an invasive treatment strategy is beneficial to these patients. METHODS Patients presenting with >12 h of chest pain and AAII were identified from the National Registry of Myocardial Infarction 2 database. Patients receiving invasive therapy <6 h after hospital admission were compared with those receiving conservative therapy. Short-term outcomes were compared on the basis of the initial therapy received. To help control for baseline differences in the groups, patients were matched with controls by propensity score methodology. RESULTS On preliminary analysis, in-hospital outcome was improved in terms of recurrent ischemia, angina, Myocardial infarction and mortality in patient,,, receiving initial invasive therapy (odds ratio [OR] = 0.67; 95% confidence interval [CI] 0.49 to 0.92 for mortality). After matching by propensity score, the mortality benefit persisted on bivariate analysis (3.5% vs. 5.0%, p = 0.036), though on multivariate, analysis. Only a non-significant but strong trend toward decreased mortalin, remained (OR = 0.73; 95% CI 0.53 to 1.01). CONCLUSIONS Patients receiving early invasive therapy had lower risk features on presentation. Selection bias may play an important role in choosing these patients' course of treatment and their subsequent outcomes. Certain patients presenting with AMI and duration of chest pain > 12 h may, benefit from early invasive therapy. These patients could be characterized in a randomized trial. (C) 2002 by the American College of Cardiology Foundation.