Translation of clinical trials into practice: a European population-based study of the use of thrombolysis for acute myocardial infarction. European Secondary Prevention Study Group

Abstract

Background: There is conclusive evidence from clinical trials that thrombolytic therapy reduces mortality in acute myocardial infarction (AMI). But still only a minority of patients admitted with AMI receive a thrombolytic drug. We have looked at a sample of AMI patients from several centres to study which factors limit the widespread use of thrombolytic therapy.

Methods: From eleven European countries, we drew a sample of 4035 patients who were discharged or died in hospital with a diagnosis of AMI between January, 1993, and June, 1994. From the medical records, we obtained the observed rate of thrombolytic use, and we defined the shortfall as the proportion of patients with no contraindication but who did not receive a thrombolytic.

Findings: Thrombolytic treatment had been used in 13-52% (median 36%) of the patients. Among untreated patients, we identified three groups of similar size: those whose symptom onset was more than 12 h (or unknown) before presentation; those causing diagnostic difficulty at presentation and/or lacking ECG criteria for treatment; and those with no apparent reason for withholding thrombolytic treatment (ie, the shortfall, which was 20%). Logistic regression analysis in all patients without contraindications showed that older patients and women were less likely to receive thrombolytic treatment. The adjusted odds ratio for female sex was 0.69 (95% CI 0.53-0.89), and that for age 65-74, for instance (versus 0-44), was 0.55 (0.34-0.89). These factors of age and sex were independent, and we noted that older patients and women were under-represented in the clinical trials of thrombolytic therapy for AMI.

Interpretation: We confirmed that only about one-third of patients admitted to European hospitals with AMI receive a thrombolytic drug. Allowing for delays to presentation and difficulty of early diagnosis, the maximum rate of thrombolysis is about 55%. The lower use of thrombolysis in the elderly may be due to their under-representation in the clinical trials; the sex difference is unexplained.