Eligible studies were randomised controlled trials (RCTs) that compared adenosine with placebo in patients with acute coronary syndromes undergoing percutaneous coronary intervention or thrombolysis. Trials had to report clinical outcomes. Trials of elective percutaneous coronary intervention, trials in a bypass surgery setting and trials that compared use of a compound similar to adenosine but with different chemical properties were excluded.
The primary outcome was all-cause mortality. Secondary outcomes included incidence of no-reflow (defined as thrombolysis in myocardial infarction zero flow), reinfarction, heart failure symptoms (New York Heart Association class III/IV) and ST-resolution (defined as post-procedural resolution ≥50%).
Most trials investigated patients with ST-elevation myocardial infarction; one trial included a mixed patient population. Intracoronary adenosine was administered during percutaneous coronary intervention in most trials; intravenous adenosine was given after thrombolysis in three trials. Doses varied (up to 70 μg/kg/min). Where reported, ischaemic time before treatment ranged from 106 to 270 minutes. Follow-up ranged from one to 12 months (median six).
It was not clear how many reviewers were involved in study selection.