Over-ambitious doctors seem to have prompted Abiomed Inc. (NASDAQ:ABMD) to close down a clinical trial of its flagship cardiac assist device.
The Danvers, Massachusetts-based company pulled the plug on the Protect II trial of its Impella 2.5 heart pump “based on a futility determination at the planned interim analysis regarding the primary end-point, which the company views as likely to be due to unanticipated confounding variables related to the use of rotational atherectomy,” according to a press release.
That’s because surgeons, perhaps emboldened by their patients’ being stabilized by the device, sometimes opted to add atherectomies — which uses a high-speed rotating metallic burr to abrade hardened plaque blockages at speeds of up to 200,000 RPM — to the angioplasty procedures the study called for.
“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,” noted principal study investigator Dr. William O’Neill in prepared remarks. “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.”
In the 305-patient study, 38 percent of the subjects treated with the Impella suffered adverse events, compared with 43 percent of patients treated using an intra-aortic balloon. But only 32 percent of the Impella cohort (which amounted to 88 percent of the entire patient base in the study) suffered an adverse event when that device alone was used, compared with 72 percent of patients treated both with the device and via atherectomy.
“Impella significantly reduced major adverse events as compared to IAB in the majority of patients in Protect II and the Impella arm had 52 percent lower out of hospital major adverse events as well. This study applies to the 26,000 of the 124,000 IABs utilized in the U.S. annually and we are excited at the prospect of converting the majority of the prophylactic IAB PCI patients,” Abiomed chairman, president and CEO Michael Minogue said.