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MUNICH -- Intraaortic balloon counterpulsation failed to improve outcomes in patients with acute MI complicated by cardiogenic shock, most of whom underwent percutaneous coronary intervention (PCI), challenging both European and U.S. guidelines.

At 30 days, the rate of all-cause mortality was 39.7% in the balloon group and 41.3% in the control group (RR 0.96, 95% CI 0.79 to 1.17, P=0.69), according to Holger Thiele, MD, of the University of Leipzig-Heart Center in Germany.

In addition, there were no differences for any of the secondary efficacy outcomes or in safety, he reported at the European Society of Cardiology meeting here. The findings were published simultaneously online in the New England Journal of Medicine.

"We could not show that the intraaortic balloon pump, which has been highly recommended in guidelines, can improve mortality," Thiele said at a press briefing.

Intraaortic balloon counterpulsation for mechanical hemodynamic support is considered a class IB treatment for patients with acute MI complicated by cardiogenic shock. Just recently, the ESC guidelines downgraded its use from a class IC to a class IIb (evidence level C) recommendation.

The evidence supporting those recommendations, however, is conflicting and largely based on registries, Thiele said, potentially explaining why the intraaortic balloon pump is used in only 25% of eligible patients in Europe and 39% in the U.S.

Clinicians generally agreed that the findings of the current trial would result in a reconsideration of the routine use of the technology.

"This will definitely impact our practice," said Helmut Schühlen, MD, of Vivantes Auguste-Viktoria-Klinikum in Berlin, a spokesman for the ESC

Elliott Antman, MD, a cardiologist at Brigham and Women's Hospital in Boston and a spokesman for the American Heart Association, said that "the routine use of a balloon pump probably needs to be revisited," but added that all of the information from the trial should be digested before considering reworking the guidelines.

The open-label IABP-SHOCK II trial, conducted at 37 sites in Germany, was designed to help fill the void of supporting evidence for the guidelines. The researchers randomized 600 patients with an acute MI complicated by cardiogenic shock to intraaortic balloon counterpulsation or no balloon. All patients were expected to undergo early revascularization and receive optimal medical therapy.

In the group that received the balloon pump, the device was inserted either before or immediately after PCI at the discretion of the interventionalist. The median duration of balloon pump support was 3.0 days.

The primary efficacy endpoint of 30-day all-cause mortality occurred at a rate of about 40% in each group, consistent with the high mortality in patients with cardiogenic shock, Thiele said. The rate was, however, somewhat lower than that seen in other studies of cardiogenic shock (42% to 48%), perhaps indicating a patient population with more mild or moderate cardiogenic shock.

It is logical, Antman noted, that it would be harder to show a benefit for an intervention in a lower-risk population.

There were no significant differences in mortality among any of the prespecified subgroups, and no significant differences in secondary endpoints or in rates of major bleeding, peripheral ischemic complications, sepsis, stroke, reinfarction, and stent thrombosis, indicating that use of the intraaortic balloon pump was safe, Thiele said.

The safety was noteworthy, said Uta Hoppe, MD, of Paracelsus Medical University in Salzburg, Austria, who added in comments following Thiele's presentation that findings from the planned assessments at 6 and 12 months would be of interest.

"Particularly," she said, "if … the long-term data would support and confirm this neutral effect of [intraaortic balloon pumps] I think that our guidelines have to be reconsidered."

Spencer King III, MD, professor emeritus at Emory University in Atlanta and a past president of the American College of Cardiology, told On The Scene that the findings call into question whether patients should routinely receive an intraaortic balloon pump, but said that there may be some patients who would still benefit.

"When I reflect on how I'm going to use the balloon pump in the future, certainly for patients who are hemodynamically severely compromised I think the balloon pump is still a worthwhile approach," he said.

Antman agreed that a wholesale abandonment of the technology is not supported by the results, pointing to nonsignificant trends for benefit among patients younger than 50 and those who had an anterior ST-segment elevation MI.

"It's conceivable that one might conclude that the routine use of an intraaortic balloon pump should be revisited and should not be recommended," he said, "but it may be worth still considering use of a balloon pump, even on a routine basis, in individuals who appeared to have the greatest likelihood of benefiting."