Randomised and quasi-randomised controlled trials, before-after studies, and controlled cohort studies were eligible for the review. Eligible studies had to involve adults diagnosed with acute ST-elevation myocardial infarction (STEMI) who had experienced chest pain for less than 12 hours and were identified by emergency medical services staff outside hospital. Studies had to compare direct transport to an interventional centre for primary percutaneous coronary intervention with transport to the nearest available emergency department, with or without administration of a fibrinolytic drug. STEMI had to be diagnosed using 12-lead pre-hospital electrocardiography.
Studies had to report at least one outcome related to mortality, treatment time intervals, reinfarction, stroke or cardiogenic shock. The pre-specified primary outcome was 30-day all-cause mortality. Because of the limited evidence found, a post-hoc combination of in-hospital and 30-day mortality (short-term mortality) was used as the primary outcome.
Participants in included studies were mainly male, with a mean or median age in the 60s. Emergency medicine personnel were ambulance medical doctors or paramedics (where reported).
Study selection involved two independent reviewers who were blinded to author, institutional affiliation, journal and year of publication; disagreements were resolved by consensus.