November 10, 2011

November 9, 2011 (San Francisco, California) — Early data from an observational study analyzing the discontinuation of dual antiplatelet therapy has shown that 98% of patients were taking aspirin and clopidogrel (Plavix, Bristol-Myers Squibb/Sanofi-Aventis), prasugrel (Efient, Lilly), or ticlopidine at 30 days, but that nonadherence to dual antiplatelet therapy was associated with significantly higher risk of ischemic events, including a higher risk of stent thrombosis.

Dr Roxana Mehran

"I was impressed to see such a low rate of nonadherence, which really speaks for, I think, the increased education we're doing in letting patients know that they really need to remain compliant with the medication," lead investigator Dr Roxana Mehran (Mount Sinai School of Medicine, New York) told heartwire . "Having said that, of those patients who did not adhere to the medications, there was a sixfold increase in the risk of stent thrombosis in the patients who were noncompliant or who disrupted their dual antiplatelet agents."

The study, known as Patterns of Nonadherence to Antiplatelet Regimens in Stented Patients (PARIS), was presented this week here at TCT 2011 and included data on 5033 individuals enrolled in 15 clinical centers in five countries. The purpose of the registry is to assess whether discontinuation, interruption due to the need for surgery, or disruption of dual antiplatelet therapy due to bleeding or noncompliance leads to subsequent ischemic events.

Of the 5033 patients, 92% were prescribed clopidogrel, 6% were prescribed prasugrel, and 2% were prescribed ticlopidine on top of aspirin therapy. Of the 2% of patients who stopped dual antiplatelet therapy, 72 patients disrupted therapy due to bleeding or noncompliance, 20 interrupted medical therapy because of a scheduled surgery, and 12 discontinued therapy at the direction of their physician.

The study was not powered for clinical events, but investigators report a higher rate of major adverse cardiac events at 30 days among the 104 patients no longer taking both antiplatelet medications. There was a higher rate of ischemic events, including MI and stent thrombosis, as well as an increase in bleeding events, among the patients nonadherent to dual antiplatelet therapy. Of the 17 patients with definite stent thrombosis, 14 were adherent to dual antiplatelet therapy, while two patients had stopped aspirin and one patient stopped clopidogrel.

To heartwire , Mehran noted that this was a contemporary registry, with 80% of patients receiving second-generation drug-eluting stents, such as the everolimus-eluting and zotarolimus-eluting stents. During the press conference, Mehran said the timing of bleeding events were variable, with most patients bleeding first and then stopping the medication. She added that all three patients who were nonadherent and had a stent thrombosis were nonadherent before the clinical event. The group plans to report two-year data next year at TCT 2012 in Miami, FL.