We limited our analysis to patients who , in 2005 - 6 , presented to a participating centre within 12 hours of symptom onset with laboratory and electrocardiographic evidence of ST elevation myocardial infarction and subsequently underwent primary percutaneous coronary intervention ( n=64 676 ) . We excluded patients who were transferred from other hospitals ( n=17 992 ) because we could not evaluate their status on admission . We also excluded patients who first received fibrinolytic therapy and were subsequently referred for primary percutaneous coronary intervention ( n=3313 ) . Patients under 18 years or over 99 years ( n=9 ) were excluded to focus analysis on adult   patients suitable for primary percutaneous coronary intervention . Finally , to minimise data coding errors , we excluded patients treated at hospitals that reported fewer than five primary percutaneous coronary interventions ( n=29 ) . A total of 18 989 patients met one or more of the above exclusion criteria , leaving 45 687 patients eligible for analysis .