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When myocardial infarction (MI) is complicated by cardiogenic shock, use of intraaortic balloon counterpulsation (IABP) did not reduce mortality among patients scheduled for revascularization -- a finding that calls into question current guidelines for treating cardiogenic shock in this population.

At 30 days, only 60% of the patients treated with IABP were still alive, a mortality that was no different from the rate in the control group (39.7% versus 41.3% relative risk 0.96, 95% CI 0.79-1.17, P=0.69), according to findings from the IABP-SHOCK II trial reported online by the New England Journal of Medicine.

The findings were simultaneously reported as a Hot Line presentation at the European Society of Cardiology meeting in Munich.

Holger Thiele, MD, from University of Leipzig-Heart Center, Leipzig, Germany, and colleagues recruited 600 patients for a randomized, prospective, open-label, multicenter trial and assigned 300 to IABP.

While there was no mortality benefit for IABP, there also was no apparent harm:

• Rates of major bleeding: 3.3% versus 4.4% in controls (P=0.53)
• Rates of sepsis: 15.7% versus 20.5% (P=0.15)
• Rates of stroke: 0.7% versus 1.7% (P=0.28)
• Rates of peripheral ischemic complications: 4.3% versus 3.4% (P=0.53)

Current American College of Cardiology/American Heart Association guidelines for treatment of STEMI support use of IABP in this population, but that recommendation comes from a trial "that did not address this question, it really looked at the question of revascularization of these patients," said Mariell Jessup, MD, of the University of Pennsylvania Perelman School of Medicine in Philadelphia.

The , called SHOCK (Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock), "was really about bypass surgery in these patients," she said.

Jessup, who is president-elect of the American Heart Association, told 木瓜直播 that the results of the IABP-SHOCK II trial "may very well be the most important finding to be reported at this meeting."

She said the current Class I recommendation is for use of IABP when the patient is not stable. "It is possible that this [IABP-SHOCK II] could completely change this guideline."

Jessup noted that use of IABP has become the norm for treating these patients and she suggested that physicians will find it hard to resist using IABP because "it is hard for physicians to not do something for these patients."

Christopher O'Connor, MD, and Joseph Rogers, MD, echoed Jessup's view in an NEJM editorial. They are from Duke University.

Under the title, "Evidence for Overturning the Guidelines in Cardiogenic Shock" O'Connor and Rogers wrote that data from IABP-SHOCK II, and a number of recent meta-analyses, "do not support the routine use of IABP in patients with acute myocardial infarction complicated by cardiogenic shock, and the level I guideline recommendation is now strongly challenged. Members of guideline committees and clinicians should take note of another example of a recommendation that is based on insufficient data."

Patients in the IAPB-SHOCK trial were recruited from June 16, 2009 through March 3, 2012 at 37 centers in Germany.

Thirty of the 299 patients assigned to the control group did eventually undergo IABP, usually within 24 hours of randomization, and 26 of those patients were classified as protocol violations. Likewise, 13 patients assigned to IABP did not undergo the treatment, with death being the most common reason.

The authors noted a number of limitations, starting with lack of blinding, and the failure to obtain "hemodynamic measurements or assess laboratory inflammatory markers other than blood pressure, heart rate, and C-reactive protein levels."

Also, the mortality rate in both arms was lower than anticipated -- 40% versus a range of 42% to 48% in other studies -- suggesting that most patients in this study had mild or moderate cardiogenic shock, which could limit the generalizability of these results, they cautioned.

"Finally, we do not yet have any information about longer-term outcomes. Since a balloon intraaortic counterpulsation was used for a median of only 3 days, it seems unlikely that any beneficial effect will become evident later than 30 days," they wrote.

From the American Heart Association:

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