December 8th, 2010
The Spin on the Impella Device: PROTECTing Whom?
The PROTECT II study — a prospective, multicenter, randomized, controlled comparison of the Impella cardiac assist device (produced by Abiomed) and the intra-aortic balloon pump (IABP) in patients requiring hemodynamic support during nonemergent, high risk PCI — was stopped early based on a futility determination regarding the primary endpoint at the time of planned interim analysis.
What’s the spin?
The results leading to the futility determination are attributed to “unanticipated confounding variables related to the use of rotational atherectomy in the study.” Since the investigators had unblinded knowledge of which device was in place in each subject, they allegedly decided to perform atherectomy more often in patients with the Impella device than in those with IABPs. Yet the company claims that the results of the study were encouraging, with a “positive trend in the majority of patients“ and a “47% reduction in major adverse events over IABP in a subgroup that represents 70% of the protocol study population.”
Huh? The trial was stopped early because of a futility determination (i.e., the groups were not treated similarly because of operator bias), yet trends in favor of the device are touted in an unidentified (and possibly cherry-picked) subgroup of patients.
Perhaps it’s not the spin of the device that’s futile, but the spin of the results by Abiomed.
Given that the Impella device allegedly caused no harm in this study, should Abiomed have been compelled to allow the trial to continue?