Intra-aortic balloon pumps do not improve mortality after severe acute myocardial infarctions

1. Based on a meta-analysis of randomized controlled trials examining the effect of intra-aortic balloon pumps (IABPs) in patients after acute myocardial infarctions, there was no mortality benefit achieved from this circulatory support, regardless of whether the patients were in cardiogenic shock.

2. Similarly, the meta-analysis of observational studies on the same subject did not show improved outcomes amongst patients who received IABPs, though there was a trend towards decreased mortality amongst patients in cardiogenic shock who received the circulatory support. There was, however, significant heterogeneity amongst the observational studies.

Evidence Rating Level: 1 (Excellent) 

Study Rundown: Cardiogenic shock as a result of acute myocardial infarction (MI) leads to a greater than 50% mortality rate. In half of patients who develop shock, they are treated with circulatory support with intra-aortic balloon pumps (IABPs). This study, which was a meta-analysis of randomized and observational studies, sought to determine the outcomes for patients with IABPs versus those without. Amongst the randomized controlled trials, there was no mortality benefit amongst patients who received IABPs compared to those who did not, regardless of whether they were in cardiogenic shock. Similarly, amongst the group of observational studies, there were no improved outcomes amongst patients who received IABPs, though there was a trend towards decreased mortality amongst patients in cardiogenic shock who received the circulatory support. There was, however, significant heterogeneity amongst the observational studies.

The strength of the study was the in depth literature review, which yielded a large number of studies. The investigators also separated the analysis by type of study (i.e., RCTs and observational studies), so comparisons are more legitimate. However, in spite of this, there was significant variation in the study design of the different RCTs and observational studies. There was also significant heterogeneity amongst the observational studies, which makes it more difficult to draw specific conclusions.

Click to read the study, published today in JAMA Internal Medicine

Relevant Reading: Intraaortic balloon counterpulsation and microcirculation in cardiogenic shock complicating myocardial infarction: an IABP-SHOCK II substudy

In-Depth [meta-analysis]: Large databases were used to gather the studies that were included in this meta-analysis, from years 1950 to 2014. Observational and randomized trials were both included, but analyzed separately. Inclusion criteria were usage of IABPs in patients with MIs, along with a control group. In the final analysis, there were 12 randomized controlled trials, and 15 observational studies.

Amongst the RCTs, there was no effect on mortality with the use of IABPs (OR 0.96; 95%CI 0.74-1.24; p = 0.74). Results were similar even when evaluating only those with cardiogenic shock after an MI (OR 0.94; 95%CI 0.69-1.28; p = 0.69). There was no heterogeneity amongst these studies. In the group of observational studies, which did have significant heterogeneity, there was again no mortality benefit identified with the use of IABPs (OR 0.96; 95%CI, 0.54-1.7; p = 0.89). There were also no significant differences in outcomes amongst those with cardiogenic shock after the MI (OR 0.70; 95%CI 0.47-1.05; p = 0.09).

Image: PD

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