In patients with an acute coronary syndrome (ACS), the rates of major adverse cardiovascular events and net adverse clinical events were not significantly lower with bivalirudin than with unfractionated heparin, according to results from the MATRIX trial presented Sept. 1 during ESC Congress 2015 in London and simultaneously published in the New England Journal of Medicine (NEJM). Additionally, the rate of urgent target-vessel revascularization, definite stent thrombosis or net adverse clinical events, was not significantly lower in patients receiving a bivalirudin infusion following percutaneous coronary intervention (PCI), compared to those who did not receive a post-PCI infusion.

MATRIX randomly assigned 7,213 ACS patients for whom PCI was anticipated to receive bivalirudin or unfractionated heparin. Those patients in the bivalirudin group were also randomly assigned to receive or not to receive a post-PCI bivalirudin infusion. Follow up was conducted after 30 days. The primary outcome was the occurrence of major adverse cardiovascular events and net adverse clinical events. The primary outcome for the bivalirudin subgroup was a composite of urgent target-vessel revascularization, definite stent thrombosis, or net adverse clinical events.

Results found the rate of major adverse cardiovascular events was not significantly lower with bivalirudin (10.3 percent) than with heparin (10.9 percent). There was also no significant difference in the rate of net adverse clinical events between the bivalirudin (11.2 percent) and heparin (12.4 percent) groups. In the post-PCI bivalirudin subgroup, there was no significant decrease in the rate of urgent target-vessel revascularization, definite stent thrombosis or net adverse clinical events among between those patients receiving an infusion and those who did not (11.0 percent and 11.9 percent, respectively).

Investigators did note a lower rate of major bleeding in the bivalirudin group (1.4 percent) than the heparin group (2.5 percent). They also said the results of the study "do not support the concern that the bleeding benefit in the bivalirudin group is attributable to routine use of femoral access or a high heparin dose in control patients." Not only did the use of radial or femoral access, which was randomly assigned, prove not to be an effective modifier in the bivalirudin group for any of the major outcomes, unfractionated heparin was administered according to the guideline-recommended mean dose of 78 units per kilogram.

"Our results reinforce the concept that reducing the rate of major bleeding events among patients with ACS who are treated with PCI does not necessarily affect the risk of major ischemic adverse cardiovascular events," the authors conclude.

In an accompanying NEJM editorial, Peter B. Berger, MD, FACC, from the North Shore-Long Island Jewish Health System in New York, notes that MATRIX "provides the best evidence to date on the question of whether prolonging the infusion of bivalirudin after the end of the PCI procedure is beneficial." "However," he writes, "neither the primary end point, nor any component of it, was reduced in the group receiving the prolonged infusion of bivalirudin." As such, he adds that "the investigators properly conclude that the trial did not produce a clear winner – neither in the comparison of the two regimens … nor in the comparison of in-laboratory vs. prolonged bivalirudin infusion."

Keywords: Acute Coronary Syndrome, ESC Congress, Heparin, Hirudins, Myocardial Infarction, Percutaneous Coronary Intervention, Stents, Stroke, Thrombin, Thrombosis

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