IABP SHOCK II: No Survival Benefit of Balloon Pump in AMI With Shock

Shelley Wood and Reed Miller

August 27, 2012

August 27, 2012 (Munich, Germany) — Use of an intra-aortic balloon pump (IABP) offered no mortality benefits at 30 days in the 600-patient IABP SHOCK II trial, according to Dr Holger Thiele (University of Leipzig, Germany), who presented the trial results in a hot-line session here at the European Society of Cardiology (ESC) 2012 Congress.

While use of the pump may make PCI safer by improving left ventricular unloading, this did not translate into any survival benefit or give a boost to any of the secondary end points in the study, Thiele and colleagues observe.

"We were really surprised by the results," Thiele told heartwire . "We thought we'd at least find something positive in the secondary end points. Our assumption was that the trial would be positive, but we have to live with the results. That's why we need randomized trials."

The results were published simultaneously in the New England Journal of Medicine [1].

In an accompanying editorial [2], Drs Christopher O'Connor and Joseph G Rogers (Duke University, Durham, NC) called the results "disappointing," given the long-time use of balloon pumps.

"The IABP-SHOCK II trial could have affirmed contemporary clinical practice and guidelines," they write. "Instead, it revealed surprising results. . . . We must now move forward with the understanding that a cardiovascular condition with 40% mortality at 30 days remains unacceptable."

Decades of Use Called Into Question

The trial randomized 600 AMI patients with cardiogenic shock to IABP or no IABP; all were scheduled for early PCI and optimal medical therapy.

At 30 days, 39.7% of the IABP patients and 41.3% of controls had died (p=0.69), with no significant differences in process-of-care measures, length of stay, dose and duration of catecholamines, or renal function. Importantly, no safety differences were seen either, in terms of bleeding, peripheral ischemic complications, sepsis, or stroke.

Asked whether he believed the guidelines should change, Thiele told heartwire he'd always believed the class I recommendation "was too optimistic, because no evidence from randomized trials showed that IABP can improve outcomes." With only registry results to rely on, the German/Austrian S3-guidelines, first published in 2011, "took this into account and recommended only that the IABP may be used," he said.

Of note, in new STEMI guidelines released during the ESC 2012 meeting, IABP use in STEMI patients was downgraded from 1C to 2B.

Dr Uta Hoppe (University of Salzburg, Austria), the discussant for the trial after its ESC presentation, agreed. "These data rather show that IABPs are not useful for most of these patients, and we still have to define individuals that might yet derive benefit. Particularly, if the long-term data will support and confirm this neutral effect of IABP, then I think our guidelines have to be reconsidered."

Hoppe, as well as Dr Simon Redwood (King's College, London, UK), who commented on the study for heartwire , pointed out that one important consideration in IABP-SHOCK is the timing of pump use.

"It was left to the investigators when the balloon pump was inserted," Redwood observed, adding, "It would be unlikely to have a benefit after PCI." In all, he pointed out, "86.6% of IABPs went in postprocedure, and this may have had a bearing on the negative results."

Both Hoppe and REdwood also pointed to the fact that 10% of control patients crossed over to IABP treatment, which may have had a "minor" impact on the results.

Thiele, however, predicts IABP use will decline as a result of the trial results.

"What we have learned from IABP-SHOCK II is that approximately 60% of the patients will survive if we treat them according to guidelines--namely, early revascularization in all and dedicated intensive care."

Another positive effect of the trial may be a rethinking of when to provide left ventricular support more generally, he added. "Many will now reflexively assume that we will need more and earlier left ventricular assist devices [LVADs]. I believe that this is not the way to go. We will have to identify patients who might benefit from LVADs, those who might be harmed by these devices, and those who don’t need one at all. We will need good risk scores to predict outcomes for cardiogenic-shock patients. This is one of the many areas in which we must move forward."

Another trial of intra-aortic balloon counterpulsation, BCIS-1--in this case, used electively, in patients with low ejection fraction undergoing high-risk angioplasty--also failed to find a benefit within the first 28 days, but in a curious finding presented earlier this year, mortality curves appeared to diverge, favoring the IABP group, after a median of 51 months.

For IABP-SHOCK, Thiele said: "I do not believe that at longer follow-up the results of the 30-day outcome will change; nevertheless, we are very interested in the long-term results."

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