Inter-regional differences and outcome in unstable angina; analysis of the international ESSENCE trial. Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-wave Coronary Events

Worldwide there is a large variation in outcome (death, myocardial infarction and recurrent myocardial infarction) in patients with unstable angina or non-Q wave myocardial infarction. These variations may be explained by differences in characteristics of the presenting patients. Here we describe differences in patient presentation, treatment protocols and outcome and we investigate their relationship using data from the ESSENCE (Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-wave Coronary Events) trial. A total of 2981 patients from six countries which enrolled more than 100 patients were included in the present analysis: United States, Canada, Argentina, France, the Netherlands and United Kingdom. Logistic regression analysis was performed to determine the effect of baseline characteristics on regional outcome. At day 30, the lowest triple end-point rate, irrespective of study drug treatment, was noted in the Netherlands (18.9%) and the highest in Argentina (30.5%). A model including the variables age > or = 65 years, prior angina, diabetes, prior aspirin use, ECG changes at baseline and diagnosis of non-Q wave myocardial infarction and dummy variables for Argentina and France resulted in concordance of about 60%. Inter-regional differences in outcome in unstable angina and non-Q wave myocardial infarction patients can reasonably well be explained by differences in patient characteristics. However, other so far unidentified variables present in Argentina and France also contributed to differences in outcome and their effect warrants further investigation.