Posts Tagged ‘IABP-SHOCK II’

Evidence for Overturning the Guidelines in Cardiogenic Shock

Reporter: Aviva Lev-Ari, PhD, RN


Christopher M. O’Connor, M.D., and Joseph G. Rogers, M.D.

August 27, 2012 (10.1056/NEJMe1209601)

Cardiogenic shock complicating acute myocardial infarction continues to be a devastating event associated with extremely high mortality. The results of the Intraaortic Balloon Pump in Cardiogenic Shock II (IABP-SHOCK II) trial,1 now reported in the Journal, show that in patients with acute myocardial infarction and hemodynamic compromise who undergo revascularization, the routine use of an intraaortic balloon pump (IABP), as compared with standard therapy, does not improve survival.1

Introduced nearly five decades ago,2 IABP is now routinely used as an adjuvant treatment for myocardial infarction 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 infarct-artery patency, and decreased systemic inflammation.3 Until recently, few alternatives have been available to support patients with severely compromised hemodynamics. Despite a lack of robust data from outcomes trials and meta-analyses4,5 that have shown limited efficacy, international guidelines endorse the use of IABP for treating post-myocardial infarction shock, with a class I recommendation.6,7

The IABP-SHOCK II trial could have affirmed contemporary clinical practice and guidelines. Instead, it revealed surprising results. In a comparison of IABP with standard therapy, the investigators found no difference in 30-day mortality or in any key secondary end points. Although IABP was safe, there was no evidence that it was associated with hemodynamic improvement — a mechanistic effect of IABP that has long been considered to be critical for its clinical application. Moreover, there were no benefits with respect to renal function or attenuation in lactate or C-reactive protein levels.

Conducting a randomized clinical trial in the emergency setting of acute myocardial infarction with shock is exceptionally difficult. In an era of rapid intervention in the catheterization laboratory and a pervasive perception of lack of equipoise, the IABP-SHOCK II investigators should be commended for completing a moderate-sized trial in 3 years at 37 sites. The results of the trial have important clinical implications, but several issues must be addressed. First, this 600-patient study could be considered too small to be definitive. However, the conclusions are bolstered by more than 240 primary end-point events, making them far more robust than might be surmised from the sample size alone. Second, the patients represented a moderate-risk cohort, with a 30-day mortality of 40%. This rate is lower than that reported in other trials involving patients with cardiogenic shock, so the results may not be applicable to the highest-risk patients. In the decade since the original Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock (SHOCK) trial was reported,8 emphasis on early revascularization and increased use of background medical therapies would be anticipated to have favorably altered the natural history of cardiogenic shock occurring after myocardial infarction, leading to lower 30-day mortality. Third, asymmetry in the number of crossovers may have influenced the final results analyzed according to the intention-to-treat principle. However, a per-protocol analysis (which included all the patients who had confirmed acute myocardial infarction, with the exclusion of those who crossed over) and an adjusted multivariate model showed similar nonsignificant results. Finally, favorable trends with IABP were observed in younger patients and in those with a first myocardial infarction, although these findings can be considered only as hypothesis-generating. Given the concordance of data from the meta-analyses and the current trial, the data 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.

The results of the IABP-SHOCK II trial parallel those from many recent outcome trials that have challenged our understanding of the management of acute and chronic heart failure, including those regarding the use of pulmonary artery catheters9 and the role of revascularization in ischemic cardiomyopathy.10

Therapeutic strategies for patients with cardiogenic shock have changed abruptly and are ready for renewed growth and development. Although many will find the results of the IABP-SHOCK II trial disappointing, we must recognize the opportunity to develop novel and innovative strategies to treat this condition. Integrated systems to ensure rapid reperfusion may reduce the incidence of shock among patients who have had an acute myocardial infarction.11 Secondary analyses of data from the IABP-SHOCK II trial may help us understand the mechanisms of the failed response. Comparing the patient populations and outcomes of the IABP-SHOCK II study groups and the concurrent registry cohort may yield important insights, with therapeutic implications for the use of other mechanical devices for circulatory support. 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. Most important, we hope that the results of this trial will galvanize a broadly based mandate to address this devastating clinical problem by reestablishing equipoise and international engagement in research on novel devices and pharmacologic therapies.

This article was published on August 27, 2012, at NEJM.org.

Source Information

From Duke University, Durham, NC.



Intraaortic Balloon in Cardiogenic Shock 

Original Article

Intraaortic Balloon Support for Myocardial Infarction with Cardiogenic Shock

H. Thiele and Others

In current international guidelines, intraaortic balloon counterpulsation (IABP) is considered to be a class I treatment for cardiogenic shock complicating acute myocardial infarction. However, evidence is based mainly on registry data, and there is a paucity of randomized clinical trials.

Clinical Pearls

  What were the results of this study, which compared intraaortic balloon counterpulsation or no intraaortic balloon counterpulsation in patients with cardiogenic shock complicating acute myocardial infarction?

At 30 days, mortality was similar among patients in the IABP group and those in the control group (39.7% and 41.3%, respectively; relative risk with IABP, 0.96; 95% confidence interval, 0.79 to 1.17; P=0.69).

Table 3.Clinical Outcomes.

Figure 1. Time-to-Event Curves for the Primary End Point.

  Among patients who received IABP, did results differ between those who had the IABP inserted before versus after revascularization?

Among patients in the IABP group, there was no significant difference in mortality between the patients (13.4%) in whom the balloon pump was inserted before revascularization and the patients (86.6%) in whom the balloon pump was inserted after revascularization (mortality, 36.4% and 36.8%, respectively; P=0.96).

Morning Report Questions

Q. Did safety end points differ between the two groups? 

A. There were no significant differences between the IABP group and the control group with respect to the rates of stroke, bleeding, sepsis, or peripheral ischemic complications requiring intervention in the hospital. There were also no significant differences in the rates of reinfarction or stent thrombosis.

Q. How do the authors explain the effect of intraaortic balloon counterpulsation in this trial on the factors that are known to cause death in patients with cardiogenic shock? 

A. Death in patients with cardiogenic shock can result from one or more of three factors: hemodynamic deterioration, occurrence of multiorgan dysfunction, and development of the systemic inflammatory response syndrome. There was no immediate improvement in blood pressure or heart rate among patients in whom an intraaortic balloon pump was inserted, as compared with those who did not have a balloon pump inserted. Although there was a positive effect of intraaortic balloon counterpulsation on multiorgan dysfunction at day 2 and day 3, this effect was not evident at day 4. There were also no significant effects on C-reactive protein level or serum lactate level, which were assessed as measures of inflammation and tissue oxygenation. Experimental and clinical studies have indicated that intraaortic balloon counterpulsation results in a hemodynamic benefit as a result of afterload reduction and diastolic augmentation with improvement in coronary perfusion. The authors postulate that the effects on cardiac output are modest and might not be sufficient to reduce mortality.


NEJM Resident E-Bulletin <resebulletin@nejm.org> on 10/3/2012


    1. 1Thiele H, Zeymer U, Neumann F-J, et al. Intraaortic balloon support for myocardial infarction with cardiogenic shock. N Engl J Med 2012. DOI: 10.1056/NEJMoa1208410.

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