Intraaortic balloon pump does not show 30-day mortality benefit for MI complicated by cardiogenic shock

Image: CC/IABP (rotated)

Key Study Points:

1.  The use of intraaortic balloon counterpulsion (IABP) in patients with MI complicated by cardiogenic shock did not decrease 30-day mortality in comparison to control group without IABP.

 Primer: Intraaortic balloon pump counterpulsation (IABP) is the most commonly employed circulatory assist device in hemodynamically compromised patients. The purpose of this device is to improve cardiovascular function by increasing mean arterial pressure, coronary perfusion pressures, cardiac output, and decreasing heart rate. This device is frequently inserted through the common femoral artery under fluoroscopy and placed just distal to the left subclavian artery. Using advanced software algorithms synced to the aortic pressure and electrocardiogram, the balloon is deployed during diastole and deflated just before the aortic valve opens in systole. Conventional uses of this device include cardiogenic shock, intractable myocardial ischemia, and refractory heart failure while patients await further therapy. Contraindications to using this device include moderate to severe aortic regurgitation, hemorrhage, and severe peripheral arterial disease.

Cardiogenic shock post-myocardial infarction is a devastating outcome associated with a high mortality rate. At time of publication, international guidelines widely recommended the use of intraaortic balloon counterpulsion (IABP) for patients with MI complicated by cardiogenic shock. Given inconclusive survival benefits of using these intraaortic balloon pumps, this study focused on the use of IABP in the setting of cardiogenic shock secondary to myocardial infarction in assessing 30-day all-cause mortality.

 Background reading:

 1. Sjauw KD, Engstrom AE, Vis MM, et al. A systematic review and meta-analysis of intra-aortic balloon pump therapy in ST-elevation myocardial infarction: should we change the guidelines? Eur Heart J 2009; 30:459-68.

2. Prondzinsky R, Unverzagt S, Russ M, et al. Hemodynamic effects of intra-aortic balloon counterpulsation in patients with acute myocardial infarction complicated by cardiogenic shock: the prospective, randomized IABP SHOCK trial. Shock 2012; 37:378-84.

3. Goldberg RJ, Spencer FA, Gore JM, et al. Thirty-year trends (1975 to 2005) in the magnitude of, management of, and hospital death rates associated with cardiogenic shock in patients with acute myocardial infarction: a population-based perspective. Circulation 2009; 119:1211-9.

This [prospective open-label, randomized] study: The study included 598 patients who had myocardial infarctions complicated by cardiogenic shock between June 16, 2009 and March 3, 2012. Patients were randomized into two treatment groups consisting of those who received intraaortic balloon counterpulsation (300 patients) and those who did not (298 patients). Results showed no statistically significant difference in 30-day all-cause mortality between the treatment groups, 39.7% vs. 41.3% respectively. Subgroup analysis of the primary end-point showed a mortality benefit of IABP in patients who were younger (19.4% vs. 44.1%), had no previous infarctions (37.3% vs. 43.3%), and did not have hypertension (28.9% vs. 43.0%). They demonstrated that there was no improvement in secondary end-points such as serum lactate, renal function, or C-reactive protein between the two treatment groups.

In sum: This study showed that in patients who suffered cardiogenic shock secondary to myocardial infarction that underwent early revascularization, the use of IABP when compared to standard therapy, did not demonstrate improved survival. Intraaortic balloon pumps have, for nearly 5 years, been considered a Class I treatment recommendation per numerous international guidelines for post-myocardial cardiogenic shock, though this study questions the validity of this recommendation. The study also concurs with recent prior studies and meta-analyses that also indicate a lack of survival benefit in using IABP in patients post-MI. Subgroup analyses did indicate possible benefit for younger patients and patients without prior MI, and further study will be required to delineate this further. Similarly, the relatively small sample size and short time of follow-up (re-assessment are planned at 6- and 12- months) must be kept in mind when interpreting this otherwise well-designed study.

In the bigger picture, the study serves as another reminder that many of the guidelines followed in everyday patient management do not always have strong evidence to support them. Randomized, controlled trials in seriously ill patients (e.g. post-MI cardiogenic shock) are difficult to conduct, but this study illustrates their value in providing a means to evaluate both novel interventions and existing guideline recommendations.

 Click to read the study in NEJM

 Click here to read the accompanying editorial

Written by [BH] and [RR]

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