Abstract: Eight RCTs with a total of 8915 participants (4545 invasive strategies, 4370 conservative strategies) were eligible for inclusion. We included three new studies and 1099 additional participants in this review update. In the all-study analysis, evidence did not show appreciable risk reductions in all-cause mortality (RR 0.87, 95% CI 0.64 to 1.18; eight studies, 8915 participants; low quality evidence) and death or non-fatal MI (RR 0.93, 95% CI 0.71 to 1.2; seven studies, 7715 participants; low quality evidence) with invasive strategies compared to conservative (selective invasive) strategies at six to 12 months follow-up. There was appreciable risk reduction in MI (RR 0.79, 95% CI 0.63 to 1.00; eight studies, 8915 participants; moderate quality evidence), refractory angina (RR 0.64, 95% CI 0.52 to 0.79; five studies, 8287 participants; moderate quality evidence) and re-hospitalisation (RR 0.77, 95% CI 0.63 to 0.94; six studies, 6921 participants; moderate quality evidence) with routine invasive strategies compared to conservative (selective invasive) strategies also at six to 12 months follow-up. Evidence also showed increased risks in bleeding (RR 1.73, 95% CI 1.30 to 2.31; six studies, 7584 participants; moderate quality evidence) and procedure-related MI (RR 1.87, 95% CI 1.47 to 2.37; five studies, 6380 participants; moderate quality evidence) with routine invasive strategies compared to conservative (selective invasive) strategies. The low quality evidence were as a result of serious risk of bias and imprecision in the estimate of effect while moderate quality evidence was only due to serious risk of bias. In the all-study analysis, the evidence failed to show appreciable benefit with routine invasive strategies for unstable angina and non-ST elevation MI compared to conservative strategies in all-cause mortality and death or non-fatal MI at six to 12 months. There was evidence of risk reduction in MI, refractory angina and re-hospitalisation with routine invasive strategies compared to conservative (selective invasive) strategies at six to 12 months follow-up. However, routine invasive strategies were associated with a relatively high risk (almost double the risk) of procedure-related MI, and increased risk of bleeding complications. This systematic analysis of published RCTs supports the conclusion that, in patients with UA/NSTEMI, a selectively invasive (conservative) strategy based on clinical risk for recurrent events is the preferred management strategy.

Plain-language summary: We included randomised controlled trials that compared routine invasive strategies to conservative strategies in patients with UA and NSTEMI in the stent era. We searched the available literature up to 25 August 2015. We included eight studies with 8915 participants: five trials were in the review version published in 2010, and three were new trials. Of the included participants with UA and NSTEMI, there were 4545 in the invasive strategy arm and 4370 in the conservative strategy arm. Evidence failed to show appreciable risk reduction in all-cause mortality and death or non-fatal myocardial infarction (MI) with routine invasive management strategy compared to conservative strategies. There was appreciable risk reduction in MI, refractory angina and re-hospitalisation with routine invasive strategies compared to conservative strategies, but this was associated with an increased risk of procedure-related MI and bleeding complications. The quality of the evidence in this review update ranged from low quality to moderate quality. Low quality evidence was as a result of serious risk of bias and uncertainty surrounding the effect, while moderate quality evidence was only due to serious risk of bias. The debate continues as to which strategy is better. The invasive strategy reduces the incidence of further chest pain or re-hospitalisation. Also, long-term follow-up from three studies suggests that it lowers the risk of a heart attack over the next three to five years. However, the invasive strategy also is associated with double the risk of heart attack during or soon after initial treatment, as well as an increased risk of bleeding. In summary, the published scientific research suggests that the invasive strategy may have particular benefit in those patients who are at high risk for recurrent events, and that patients at low risk for a recurrent event may even suffer harm from such an approach.