PARIS (FRONTLINE MEDICAL NEWS) – Patients undergoing complex percutaneous intervention for acute coronary syndrome fared significantly better with prasugrel than clopidogrel as antiplatelet therapy in the large, real-world PROMETHEUS registry, Dr. Jaya Chandrasekhar reported at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.

Cumulative 1-year all-cause mortality was 8% with clopidogrel (Plavix), compared with 2% with prasugrel (Effient), for an adjusted 42% relative risk reduction favoring the more potent oral thienopyridine.

Moreover, the 1-year composite MACE (major adverse cardiac events) outcome comprising death, MI, stroke, or unplanned revascularization occurred in 24.3% of the clopidogrel group, compared with 13.3% of the prasugrel group. That translates to an adjusted 22% relative risk reduction, noted Dr. Chandrasekhar of Mount Sinai Medical Center in New York.

Bleeding rates were similar in the prasugrel and clopidogrel groups, she added.

She stressed that these findings must be viewed as hypothesis-generating rather than definitive, since PROMETHEUS was not a randomized clinical trial. Rather, it was a retrospective observational study of 19,914 patients who underwent PCI for ACS at eight major U.S. medical centers, 20% of whom got prasugrel, 80% clopidogrel. Half of the patients had a complex PCI, defined by Dr. Chandrasekhar and coinvestigators as one targeting the left main coronary artery, any bifurcation lesion, any moderate or severely calcified lesion, or an intervention resulting in a total stent length of 30 mm or longer.

The complex PCI patients were significantly older, by just under 2 years. They had higher rates of diabetes, unstable angina, and multivessel disease, and were more likely to receive at least one second-generation drug-eluting stent.

In a multivariate analysis adjusted for these potential confounders as well as race, body mass index, kidney function, hypertension, hemoglobin, previous PCI, and concomitant use of bivalirudin, the benefits of prasugrel over clopidogrel at 1 year remained significant in patients who underwent complex PCI. In contrast, among the 10,179 ACS patients who underwent noncomplex PCI, the trends favoring lower mortality and MACE in the prasugrel group no longer attained statistical significance upon multivariate adjustment, she said.

Discussant Dr. Pascal Meier said that registry data on prasugrel are inevitably biased because physicians don’t give the drug to patients older than 75 or patients who have had a prior stroke, are low weight, or low risk.

“Do you think there’s any way we can adjust for this bias?” asked Dr. Meier of University Hospital, Geneva.

Dr. Chandrasekhar conceded the possibility of unrecognized confounders.

“I think no matter what statistical methods you use, there will be that potential for bias. This is a real-world study. We understand that physicians and operators select their patients very carefully and the healthier ones get prasugrel rather than clopidogrel.”

She reported having no financial conflicts regarding this study. PROMETHEUS was sponsored and funded by Daiichi Sankyo and Eli Lilly.