Previous Myocardial Infarction as a Risk Factor for In-Hospital Cardiovascular Outcomes (from the National Registry of Myocardial Infarction 4 and 5)

Patients with acute coronary syndromes have a substantial disease burden and are at continued risk of future cardiovascular events. In this setting, the relation between previous myocardial infarction (MI) and the risk of subsequent in-hospital adverse cardiovascular outcomes has not been definitively established. The data were analyzed from 427,778 hospitalized patients presenting with acute MI from July 2002 to December 2006, who were enrolled in the National Registry of Myocardial Infarction 4-5 study. Multivariate logistic regression models were developed to examine the association between a history of MI and in-hospital all-cause mortality, recurrent MI, and congestive heart failure/pulmonary edema. Covariate adjustments were made for demographic characteristics, co-morbidities, prearrival medications, and health status at presentation. Similarly, multivariate linear regression models were used to evaluate the length of stay. Of the 232,927 patients with acute MI included in the present study after exclusions, 24.7% reported a history of MI. In-hospital mortality was not significantly different between the patients with and without a history of MI (adjusted odds ratio 0.99, 95% confidence interval 0.95 to 1.04, p = 0.75). However, patients with a previous MI had a small increased risk of in-hospital recurrent MI (adjusted odds ratio 1.18, 95% confidence interval 1.08 to 1.29, p <0.001) and congestive heart failure/pulmonary edema (adjusted odds ratio 1.23, 95% confidence interval1.19 to 1.28, p <0.001) compared with patients with no history of MI. In conclusion, a history of MI did not significantly affect in-hospital mortality after admission for an acute MI.