Background:
Cardiogenic shock (CS) due to acute coronary syndrome (ACS) is associated with high mortality. The use of intraaortic balloon pump (IABP) for hemodynamic support in CS has significantly decreased after being downgraded in guideline recommendation. Newer percutaneous assist devices such as the Impella centrifugal pump have entered the market, however, available data from studies comparing Impella with IABP in this setting are limited. Therefore, the aim of the present study was to compare the effects of Impella versus IABP in patients with CS due to ACS in terms of benefit of all-cause mortality at 30 days.

Methods:
Between 2011 and 2017, consecutive patients presenting to two tertiary cardiac care centers in CS due to ACS, and treated with either IABP or Impella, were retrospectively analyzed. Primary outcome was all-cause mortality at 30 days. Secondary outcomes were causes of death and surrogate parameters of shock severity (i.e., cardiac power index [CPI], inotropic score, serum lactate, SAPS II score).

Results:
Of a total of 116 patients included, 54 underwent circulatory support with IABP and 62 with Impella. Severity of disease at baseline, assessed by the IABP-SHOCK II Score, was similar between the groups. Although the improvement of the CPI did not differ among the two treatment groups, weaning from catecholamines was faster and improvement of LVEF higher in patients treated with Impella as compared to those treated with IABP (Figure 1A-C). Consequently, a significant reduction of lactate levels and SAPS II score was observed in these patients (Figure 2A-B).
At 30 days, all-cause mortality was 52% (n=32) the Impella group and 67% (n=36) in the IABP group. At Kaplan Meier analysis, estimated all-cause mortality was not significantly different between the two treatment groups (log rank p=0.17).
After stratifying according to the IABP-SHOCK II score, in the low-intermediate risk group, multivariate analysis of all-cause mortality at 30 days showed a trend to lower risk in Impella-treated patients (HR 0.59, CI 0.34 to 1.04, p=0.07) as compared to those treated with IAPB, whereas in the high risk group the mortality risk was similar. 

Conclusion:
In patients with CS due to ACS treatment with Impella is not superior to IABP in reducing all-cause mortality at 30 days. The subgroup of patients with low-intermediate mortality risk might benefit from Impella, but this effect needs to be tested in randomized trials with bigger patient cohorts.

Figure 1.

Figure 2.