ESC: Guideline change for IABP in acute MI with shock?
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The use of intra-aortic balloon pump (IABP) counterpulsation did not significantly reduce 30-day mortality in patients with cardiogenic shock complicating acute MI for whom an early revascularization strategy was planned, according to the IABP-SHOCK II trial, presented Aug. 27 at the European Society of Cardiology (ESC) 2012 Congress in Munich. Based on these “surprising results” along with other outcomes data, editorialists questioned its use in routine practice and recommended a guideline change.

The study and editorial were published simultaneous to the trial’s presentation in the New England Journal of Medicine.

In current international guidelines, IABP counterpulsation is considered to be a Class I treatment for cardiogenic shock complicating acute MI. However, evidence is based mainly on registry data, and there is a paucity of randomized clinical trials, according to the study authors.

In this prospective, open-label, multicenter trial, Holger Thiele, MD, of the department of internal medicine/cardiology at University of Leipzig-Heart Center in Leipzig, Germany, and colleagues randomly assigned 600 patients with cardiogenic shock complicating acute MI to IABP counterpulsation (300 patients) or no IABP (298 patients, control group). All patients were expected to undergo revascularization either through PCI or CABG, as well as guideline-recommended medical therapy.

The primary efficacy endpoint was 30-day all-cause mortality. Safety assessments included major bleeding, peripheral ischemic complications, sepsis and stroke.

At 30 days, 119 patients in the IABP group (39.7 percent) and 123 patients in the control group (41.3 percent) had died, reported the researchers. Also, there were “no significant differences” in the secondary endpoints or in process-of-care measures, according to the authors, including the time to hemodynamic stabilization, the length of stay in the ICU, serum lactate levels, the dose and duration of catecholamine therapy and renal function.

Death in patients with cardiogenic shock can result from one or more of three factors: hemodynamic deterioration, occurrence of multi-organ dysfunction and development of the systemic inflammatory response syndrome. The researchers said their trial provides “some information” regarding the effect of IABP counterpulsation on these causes of death. For instance, there was no immediate improvement in blood pressure or heart rate among patients in whom an IABP was inserted, compared with the control group.

Thiele et al also reported that IABP group and the control groups did not differ significantly with respect to the rates of major bleeding (3.3 percent and 4.4 percent, respectively), peripheral ischemic complications (4.3 percent and 3.4 percent, respectively), sepsis (15.7 percent and 20.5 percent) and stroke (0.7 percent and 1.7 percent).

While the use of IABP counterpulsation before coronary revascularization may make revascularization safer by improving left ventricular unloading (Am J Cardiol 2010;105:967-971), the study authors said the current trial demonstrated no mortality benefit in the subgroup of patients in the IABP group.

Introduced nearly five decades ago, IABP is now “routinely used as an adjuvant treatment for MI complicated by cardiogenic shock, on the basis of evidence that it is associated with hemodynamic improvements accompanied by enhanced coronary blood flow, increased perfusion of vital organs, maintenance of infarctartery patency and decreased systemic inflammation,” wrote Christopher M. O’Connor, MD, and Joseph G. Rogers, MD, of Duke University Medical Center in Durham, N.C., in the accompanying editorial in the New England Journal of Medicine.

They added that despite a lack of data from outcomes trials and meta-analyses, international guidelines endorse IABP use for treating post-MI shock, with a Class I recommendation.

“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 percent mortality at 30 days remains unacceptable, “ wrote O’Connor and Rogers. “Most important, we hope that the results of the trial will galvanize a broadly based mandate to address the devastating clinical problem by re-establishing equipoise and international engagement in research on novel devices and pharmacologic therapies.”