MUNICH – Although it is routinely used in clinical practice, the intra-aortic balloon pump provided no early mortality benefit in patients with myocardial infarction complicated by cardiogenic shock in the randomized IABP-SHOCK II study.
The primary end point of 30-day all-cause mortality was 41.3% in controls and 39.7% in patients receiving intra-aortic balloon pump (IABP) support, a difference that was not significant. None of the subgroups that were analyzed derived benefit.
Use of an IABP also failed to improve any of the secondary outcomes of the trial, the largest to date in patients with cardiogenic shock, Dr. Holger Thiele reported at the annual congress of the European Society of Cardiology (ESC).
However, "it’s too early to say that it’s the end of the pump," Dr. Thiele said in an interview. "Before we close this chapter, I think we have to wait for long-term follow-up data."
While awaiting 6- and 12-month mortality data, which could be reported by the end of 2013, use of IABPs is likely to go down because of the negative results of IABP-SHOCK II (Intraaortic Balloon Pump in Cardiogenic Shock II), he said.
Discussant Dr. Uta Hoppe, of the Paracelsus Medical University of Salzburg, Austria, agreed that it’s unlikely clinicians can improve the outcome of patients by implanting more IABPs.
"These data rather show that IABPs are not useful for most of these patients, and we still have to define the individuals that might derive benefit," she said. "Particularly, if the long-term data would support and confirm this neutral effect of IABP, I think that our guidelines have to be reconsidered."
Before the trial, IABP results were available from registries and only one randomized controlled trial of just 57 patients. Results were mixed, possibly explaining why the IABP is currently used in only about 35% of cardiogenic shock patients in Europe and 39% in the United States, said Dr. Thiele, professor of medicine at the University of Leipzig (Germany) Heart Center.
Despite the limited data, IABPs became part of contemporary practice and were carried forward through various iterations of the ESC guidelines and American College of Cardiology/American Heart Association guidelines with a class I recommendation.
The lack of solid data, however, was likely behind the decision to downgrade the IABP recommendation to IIb in the new ESC guidelines for ST-segment elevation acute MI, presented just 24 hours earlier at the meeting, Dr. Thiele said. It was also the impetus for IABP-SHOCK II.
In the trial, investigators at 37 German sites randomized 600 acute MI patients in cardiogenic shock to either percutaneous coronary intervention plus IABP insertion and optimal medical therapy or PCI plus medical therapy only.
Nearly 50% of patients underwent resuscitation before randomization, 80% had mild vessel disease that was the cause of the shock, and 96% underwent primary PCI. Notably, the timing of pump insertion was left up to the investigators, with 87% of IABPs inserted after the procedure.
There were no significant differences between groups in the secondary outcomes of renal function, serum lactate, and inflammatory reaction, Dr. Thiele said. There was a significant benefit on the Simplified Acute Physiology Score-II intensive care instrument, favoring the balloon pump on day 2 and day 3 post procedure, but this was attenuated and no longer significant on day 4.
Dr. Thiele said in an interview that he will likely stop using IABPs in cardiogenic shock patients because the trial has shown that 60% of patients will not need anything else, if treated according to guidelines with early revascularization and optimal management.
He went on to say that, although some may be tempted to turn to left ventricular assist devices in high-risk patients, data are almost nonexistent comparing assist devices with the balloon pump. Only 5.5% of patients received LVADs in IABP-SHOCK II, and mortality was high at 67%. "Nevertheless, if you have a young patient who is not responding to the standard therapy, then I would always put in such a percutaneous left ventricular assist device," he added.
The study was simultaneously published in the New England Journal of Medicine (2012 Aug. 27 [doi: 10.1056/NEJMoa1208410]).
In an accompanying editorial (2012 Aug. 27 [doi: 10.1056/NEJMe1209601]), Dr. Christopher M. O’Connor and Dr. Joseph G. Rogers, both of Duke University in Durham, N.C., called the results surprising, and said that "on the basis of the findings of the IABP-SHOCK II trial, we must move forward with the understanding that a cardiovascular condition with 40% mortality at 30 days remains unacceptable."