Medical Device Daily

Over-anxious physicians are being cited as one reason why Abiomed (Danvers, Massachusetts) is abruptly ending its PROTECT II study of Impella, which was designed to study major adverse events in high-risk percutaneous coronary intervention (PCI) patients who received support with Impella 2.5 vs. intra-aortic balloon (IAB) pumps.

The company said that it appears as if physician behavior was substantially different in each subgroup of the study, likely in part due to perceived superiority of support offered by the Impella device.

Specifically, a small subset of the studied group received atherectomy, or the removal of plaque from the vessel wall, a more risky intervention that appears to be skewing trial data, especially in the Impella subgroup, where that treatment was used more freely.

“Atherectomy was an unanticipated variable which resulted from the operators' decision to 'do more with Impella.' Our investigators had unblinded knowledge of the treatment arm after randomization,“ said William O'Neill, MD, University of Miami and principal investigator of the PROTECT II study. “It is interesting that operators felt that they could do more complex interventions once randomized to Impella and this in and of itself is an important finding.“

But despite ending the trial, the firm was optimistic about some of the data that came from PROTECT II. In fact, during its conference call, company executives touted potential success from the study of the FDA-approved device.

For the entire study population, Impella significantly reduced out-of-hospital major adverse events by 52% compared to IAB for the duration of the monitoring of 90 days, according to Mike Minogue Abiomed's chairman president/CEO.

“This study applies to the 26,000 of the 124,000 IABs utilized in the U.S. and we are excited at the prospect of converting the majority of the prophylactic IAB PCI patients,“ Minogue said. “With PROTECT II interim results, we now have both the clinical and cost effectiveness data to pave the way to change the standard of care for PCI requiring prophylactic hemodynamic support. These data will augment our increasing commercial momentum as we now focus on execution to capture this market opportunity.“

In the 305-patient study, 38% of the subjects treated with the Impella suffered adverse events, compared with 43% of patients treated using an intra-aortic balloon. But only 32% of the Impella cohort (which amounted to 88% of the entire patient base in the study) suffered an adverse event when that device alone was used, compared with 72% of patients treated both with the device and via atherectomy.

The company said that it would release more comprehensive data from PROTECT II at the American College of Cardiology (Washington) conference in April.

The news comes less than a week after the firm reported that it was given FDA approval to start a prospective, randomized, controlled multi-site trial to assess the potential role of Impella 2.5 in reducing infarct size in patients suffering from ST-elevation myocardial infarction (STEMI) (Medical Device Daily, Dec. 3, 2010).

The study is called MINI-AMI and today's news regarding PROTECT II will not affect it, the firm said.

The intent of this newly approved study is to investigate the unloading capabilities of Impella 2.5 and its effect in reducing the oxygen demand on the heart muscle.

The MINI-AMI study will enroll patients with acute anterior STEMI or large inferior STEMI, primary PCI performed within five hours of the onset of symptoms, patients undergoing emergent primary PCI of one culprit lesion in one major coronary vessel, and successful revascularization of the native coronary artery at the end of PCI.

The Impella was initially developed in Aachen, Germany, by Impella CardioSystems (Aachen Germany). Abiomed acquired Impella CardioSystems in the spring of 2005 for $62 million (MDD, April 28, 2005).

“I feel like I'm on third base with two outs in the fifth inning and the umpire called it because it rained,“ O'Neill said during the conference call.

He said that the company could only imagine what would have happened or the data they would be able to get from PROTECT II had it been allowed to run its course.

Omar Ford, 404-262-5546;
omar.ford@ahcmedia.com