Platelet monitoring for dose adjustment of prasugrel is not superior to a conventional fixed dose in elderly patients stented for ACS, according to a Hot Line study yesterday. The results of the ANTARCTIC trial, published simultaneously in The Lancet, urge a review of current guidelines, which recommend platelet function testing in high risk patients. Senior investigator Gilles Montalescot said that the trial, the largest randomised PCI study ever performed in the elderly, does not support testing. He expected guidelines and practice to change as a result.
‘Platelet function testing is still being used in many centres to measure the effect of antiplatelet drugs and adjust the choice of drugs and their doses,’ said Montalescot, from Hopital Pitie-Salpetriere in Paris. ‘Our study does not support this practice or the recommendations.’
ANTARCTIC confirms the results of the ARCTIC trial of 2011, which investigated a different patient population (low risk and elective PCI) and a different antiplatelet therapy (clopidogrel). All 877 patients enrolled in the ANTARCTIC study were aged 75 or more and had coronary stenting for ACS.
All were started on prasugrel (5 mg) with 442 randomised to conventional fixed dose therapy and 435 to monitoring and treatment adjustment.
Patients in the monitoring arm received the daily 5 mg prasugrel dose for 14 days at which point a platelet function test was used.
If the test showed high platelet reactivity, medication dose was increased - or decreased if reactivity was low. Patients within the therapeutic range remained on the same dose.
The primary endpoint over 12 months was bleeding, SV death, MI, urgent revascularisation, stent thrombosis and stroke. This endpoint occurred at a similar rate in both arms of the study, - 27.6% in the monitoring group and 27.8% in the conventional group.
Similarly, no significant difference was found in rates for the main secondary endpoint, a composite of CV death, MI, stent thrombosis or urgent revascularisation - which occurred in 9.9% and 9.3% of each group.
Overall, platelet function monitoring led to a change of treatment in 44.8% of patients, who were identified as being over or under treated. Yet the strategy did not improve ischaemic or safety outcomes. ‘ANTARCTIC after ARCTIC confirms a failure to improve clinical outcomes for patients,’ said Montalescot. ‘In this case, however, the failure is not related to risk level or the type of P2Y12 antagonist. Although measuring the effect of antiplatelet agents makes some sense, this costly and more complex strategy does not appear to benefit patients.’
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