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Three Part Question

In [adult patients with cardiogenic shock following myocardial infarction ] [what is the usefulness] of [intra-aortic balloon support]?

Clinical Scenario

A 67-year-old man is brought to the emergency department. He is cold, clammy and confused. He is also hypotensive and an ECG shows that he has had an AMI with ST elevation. While your colleagues prepare some vasopressors you speak to the cardiologist on call. He suggests getting the patient to the cardiac cath lab to put in an IABP. You wonder whether there is any evidence to support this course of action?

Search Strategy

Medline 1946-05/13 using OVID interface, Cochrane Library (2013), PubMed clinical queries
[(myocardial infarction.mp. or exp Myocardial Infarction/) AND (cardiogenic shock.mp. or exp Shock, Cardiogenic/) AND (exp Intra-Aortic Balloon Pumping/ or intra -aortic balloon pump.mp.)] Limit to English language and randomized controlled trial.

Search Outcome

65 papers were identified; of which two recent RCTs answered the clinical question. A systematic review was also identified, which incorporated the RCT data. Two other RCTs were also identified. Only the most recent RCTs and the systematic review are presented.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Thiele H, et al. 2012 Germany	All patients were adults who had acute myocardial infarction complicated by cardiogenic shock and were expecting to undergo early revascularization either by percutaneous coronary intervention or bypass grafting.	Randomized Clinical Trial	30 day all-cause mortality	119 Patients in the IABP group (39.7%) and 123 patients in the control group (41.3%) died (relative risk with IABP, 0.96; 95% CI 0.79 to 1.17, p=0.69)	The timing of intra-aortic balloon insertion was not controlled for. There was also 10% crossover of the control group to the intra-aortic balloon group.
Prondzinsky R, et al. 2012 Germany	Adult patients with acute myocardial infarction complicated by cardiogenic shock who were treated with PCI, and required vasopressor/inotropic support after adequate volume filling.	Randomized controlled trial.	Primary: Change in APACHE II Score 4 days from enrollment	No differences among both groups for disease improvement(18.2 +/- 3.7 vs. 20.2 +/- 2.3 APACHE II score)	Low patient enrollment, only 40 patients in total, making the power of the study sufficiently low.
			Secondary: Hemodynamic parameters (HR, SVR, MAP, CO)	No significant difference between IABP and medical treatment group.
			Secondary: Invasive hemodynamic parameters (cardiac power, LVSWI, PCWP)	No significant difference between IABP and medical treatment group.
Romeo et al. 2013 Italy	14, 186 patients from 17 studies of IABP therapy for cardiogenic shock. 13 of the studies were observational, only 4 were RCTs	Systematic review and meta-analysis	Overall in-hospital mortality with IABP	RR 0.95 (95% CI 0.83-1.10) p=0.52.	Analysis is dominated by the observational studies. The mortality rates for the three subgroups are very different: 83.9% for the no reperfusion subgroup, 66.9% for the thrombolysis subgroup, and 38.4% for the PCI subgroup.
			No reperfusion subgroup, mortality with IABP	RR 0.83 (95% CI 0.65-1.05) p=0.13.
			Thrombolysis subgroup, mortality with IABP	RR 0.77 (95% CI 0.68-0.87) p<0.0001.
			PCI subgroup, mortality with IABP	RR 1.18 (95% CI 1.04-1.34) p=0.01.
			Longterm survival with IABP	RR 0.88 (95% CI 0.65-1.20) p=0.43

Comment(s)

Two recent RCT have been performed to evaluate the clinical utility of intra-aortic balloon support for those patients with AMI complicated by cardiogenic shock. The IABP-Shock trial demonstrated no clinically significant benefit in a small, single-centre study addressing a change in APACHE II score. The IABP-Shock II trial was a much larger, multicentre RCT with a primary endpoint of mortality that still showed no significant clinical difference. The most recent meta-analysis (Romeo et al, 2013) suggests that the IABP may have a role when primary coronary intervention (PCI) will not be possible or as a bridge to delayed PCI or some other mechanical intervention.

Editor Comment

The mortality from cardiogenic shock after AMI remains very high (>80% if no reperfusion therapy) and there is no ideal vasopressor or inotropic drug to restore haemodynamics. A mechanical solution to the problem has always appeared attractive. Intra-aortic ballon pumps have been available since the 1970s and their use was promoted in AMI guidelines with a Class I grading (for example ESC 2008), although the level of evidence was recognized as only being level C. The latest AAHA guideline has downgraded the use of IABPs to Class IIa with an evidence level B.

AMI, acute myocardial infarction; APACHE II, acute physiology and chronic health evaluation score version 2; CO, cardiac output; HR, heart rate; IABP, intra-aortic balloon pump; LVSWI, left ventricular stroke work index; MAP, mean arterial pressure; PCI, primary coronary intervention; PCWP, pulmonary capillary wedge pressure; RCT, randomised controlled trial; RR, risk ratio; SVR, systemic vascular resistance.

Clinical Bottom Line

The role of IABP support in patients with cardiogenic shock from myocardial infarction remains unclear, without evidence of clear confirmed benefit compared to conventional therapy, especially when PCI is available.

References

1. Thiele H, Zeymer U, Neumann FJ, et al. Intraaortic balloon support for myocardial infarction with cardiogenic shock. New England Journal of Medicine 2012;367:1287–96.
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. Romeo F, Acconia MC, Sergi D, et al. The outcome of intra-aortic balloon pump support in acute myocardial infarction complicated by cardiogenic shock according to the type of revascularisation: A comprehensive meta-analysis. American Heart Journal 2013; 165: 679-692.
4. O'Gara PT, Kushner FG, Ascheim DD, et al. 2013 ACCF/AHA Guideline for the management of ST-elevation myocardial infarction: A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines Circulation 2013; 127: e362-425.
5. Van de Werf F, Bax J, Betriu A, et al. Management of acute myocardial infarction in patients presenting with persistent ST-segment elevation. European Heart Journal 2008; 29: 2909-2945.