In the per-protocol analysis, at 30 days the Impella patients had a major adverse event rate of 35%, compared with 43% in the IABP patients, which was not a statistically significant difference. At 90 days, the rates reached 41% and 51% respectively, a difference that was statistically significant.
Dr. O’Neill addressed concerns that the major adverse event measure included many elements of sharply differing clinical importance. "What drove the difference [between the two study arms] was death, myocardial infarction, and need for urgent revascularization – not the small stuff. The real major adverse cardiac events were significantly better" when the Impella device was used, he said in an interview.
An analysis of several prespecified subgroups also highlighted certain types of patients who had significant benefit from the Impella device for the study’s primary end point. Among the 88% of patients in the study who were not treated with rotational atherectomy, the 30-day major adverse event rate reached 30%, compared with 42% in the IABP patients, a statistically significant difference. A significant difference in the primary outcome in favor of the Impella patients also occurred in the subgroup that had an STS mortality score lower than 10.
The results also showed a strong trend toward a better primary outcome in the Impella-treated patients when the analysis excluded the first Impella-treated patient for each operator, a finding that highlighted an important learning curve in using the device, Dr. O’Neill said.
Analysis also showed that the 90-day rate of major adverse events in the Impella patients fell from 48% in 2008 to 39% in 2009 and to 37% in 2010. In contrast, the rate in the IABP patients stayed fairly constant (at 47%-52%) in all 3 years, again highlighting the role of experience with the Impella device in achieving better patient outcomes, he said.
"I think many clinicians will see [from these data] that Impella provides a lot of safety," Dr. O’Neill said.
PROTECT II was sponsored by Abiomed, the company marketing the Impella 2.5 assist device. Dr. O’Neill said that he has been a consultant to Medtronic. Dr. Waksman said that he has been a consultant to or received honoraria from Medtronic Vascular, Abbott Vascular, Biotronik, Merck, and Boston Scientific.