Background In the setting of percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS), bivalirudin has been shown to be superior to unfractionated heparin (UFH) in reducing major adverse cardiac events, driven by a reduction in major bleeding. With increasing use of radial access and potent anti-platelet therapy, recent trials suggest that the previous benefit observed with bivalirudin may now be substantially reduced. ACS encompasses both ST-elevation ACS (STE-ACS), with generally high thrombus burden and non-ST-elevation ACS (NSTE-ACS), with lower thrombus burden. Whether bivalirudin offers differential clinical benefit in these two groups, is unknown.

Methods We conducted a meta-analysis of randomised trials comparing bivalirudin and UFH in patients receiving PCI for ACS divided into STE-ACS and NSTE-ACS groups. Overall estimates of effect were calculated with a fixed-effects model or random-effects model.

Results In STE-ACS, 6 trials (10,368 patients) were identified. Compared to UFH, bivalirudin increased the risk of myocardial infarction (MI) (OR 1.41; CI 1.02–1.95; p = 0.04) and acute stent thrombosis (ST) (OR 3.81; CI 2.15–6.74; p < 0.00001), and reduced the risk of major bleeding when comparing bivalirudin combined with provisional glycoprotein IIb/IIIa inhibitor (GPI) use versus UFH with planned GPI use (OR 0.51; CI 0.41–0.64; p < 0.00001). We identified 15 NSTE-ACS trials (25,250 patients). There was no difference between bivalirudin and UFH in the occurrence of death (OR 0.98; CI 0.71–1.33; p = 0.88), MI (OR 1.09; CI 0.98–1.21; p = 0.12), or ST (OR 1.20; CI 0.85–1.70; p = 0.31). However, bivalirudin significantly reduced the risk of major bleeding compared to UFH, either with provisional use of GPI in both arms (OR 0.62; CI 0.48–0.81; p = 0.0005), or in the bivalirudin arm only (OR 0.53; CI 0.44–0.63; p < 0.00001).

Conclusions Although in STE-ACS, bivalirudin is associated with an increased risk of ischaemic events, it may confer an advantage over UFH in NSTE-ACS patients undergoing PCI, with a reduction in major bleeding and without an increase in ischaemic events. Large scale multi-centre randomised trials are needed to elucidate the optimal anti-thrombotic regimen in patients presenting with STE-ACS undergoing PCI in the contemporary era.