Intra-aortic balloon counterpulsation in patients with acute myocardial infarction and cardiogenic shock

Cardiogenic shock is a severe condition in which a suddenly weakened heart is not able to pump enough blood to meet the body's energy needs, so not enough oxygen will reach the body’s organs. Cardiogenic shock is a life-threatening medical emergency and needs to be treated quickly to avoid organ damage or even death of the affected patient. Most often cardiogenic shock is caused by a severe heart attack and the induced damage to the heart muscle. Despite more than 50 years of effort, patients with cardiogenic shock still have a poor prognosis after primary revascularization procedures such as coronary artery bypass grafting or primary percutaneous coronary intervention. The main cause for the development of cardiogenic shock is the loss of myocardial function due to myocardial infarction leading to impaired left ventricular function with unstable haemodynamics and reduced systolic and mean arterial pressures. The reduced blood pressure leads to hypoperfusion and so reduced oxygen supply to vital organs and the corresponding clinical signs. These include cold and pale skin, reduced or a lack of urine output and signs of impaired cerebral function like dizziness or even unconsciousness.

On this basis, it was reasoned that the use of mechanical means of augmenting pressure and flow would prove effective. The very first mechanical means of assisting the circulation in such a manner was by a counter pulsation strategy using a device called the intra-aortic balloon pump (IABP). Through balloon inflations and deflations synchronized with the natural heartbeat the IABP increases diastolic aortic pressure, which enhances diastolic blood flow to the coronary arteries and vital organs, as well as reduces systolic aortic pressure, which reduces afterload and oxygen consumption of the myocardium and increases cardiac output. This support can be provided for a few hours and, in extreme cases, for several weeks. Evidence from earlier published studies suggested that certain patients with acute myocardial infarction complicated by cardiogenic shock and treated by thrombolysis may derive benefit from a period of support with the IABP. However, nowadays the most widely recommended and preferred revascularization procedure is primary percutaneous coronary intervention.

In contrast to the previous version of this review, this update now includes data from one large and six small randomised controlled trials. It allows more definitive conclusions about the potential beneficial or harmful clinical effects of IABP support beyond its immediate haemodynamic effects. Complications such as moderate and severe bleeding were more frequently observed in patients treated with more invasive devices than IABP. Small randomised trials suffered from inadequate power to address deaths and harmful effects of IABP and were biased by frequent cross-over to the more aggressive strategy, early stopping of the trial, or the inclusion of patients with IABP at randomisation. It is most noteworthy that a recently conducted and published large randomised trial showed no evidence for survival benefits of IABP support in patients with infarct-related cardiogenic shock treated by percutaneous coronary intervention (PCI). On the basis of these data, IABP support is no longer strongly recommended by the European Society of Cardiology (ESC) guidelines for treatment of patients with infarct-related cardiogenic shock. Rather, IABP use is based on the personal experience and decision of the physician and the particular circumstances of individual patients.

Authors' conclusions: 

Available evidence suggests that IABP may have a beneficial effect on some haemodynamic parameters. However, this did not result in survival benefits so there is no convincing randomised data to support the use of IABP in infarct-related cardiogenic shock.

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Background: 

Intra-aortic balloon pump counterpulsation (IABP) is currently the most commonly used mechanical assist device for patients with cardiogenic shock due to acute myocardial infarction. Although there has been only limited evidence from randomised controlled trials, the previous guidelines of the American Heart Association/American College of Cardiology (AHA/ACC) and the European Society of Cardiology (ESC) strongly recommended the use of the IABP in patients with infarction-related cardiogenic shock on the basis of pathophysiological considerations, non-randomised trials and registry data. The recent guidelines downgraded the recommendation based on a meta-analysis which could only include non-randomised trials showing conflicting results. Up to now, there have been no guideline recommendations and no actual meta-analysis including the results of the large randomised multicentre IABP-SHOCK II Trial which showed no survival benefit with IABP support. This systematic review is an update of the review published in 2011.

Objectives: 

To evaluate, in terms of efficacy and safety, the effect of IABP versus non-IABP or other assist devices guideline compliant standard therapy on mortality and morbidity in patients with acute myocardial infarction complicated by cardiogenic shock.

Search strategy: 

Searches of CENTRAL, MEDLINE (Ovid) and EMBASE (Ovid), LILACS, IndMed and KoreaMed, registers of ongoing trials and proceedings of conferences were updated in October 2013. Reference lists were scanned and experts in the field contacted to obtain further information. No language restrictions were applied.

Selection criteria: 

Randomised controlled trials on patients with acute myocardial infarction complicated by cardiogenic shock.

Data collection and analysis: 

Data collection and analysis were performed according to the published protocol. Individual patient data were provided for six trials and merged with aggregate data. Summary statistics for the primary endpoints were hazard ratios (HRs) and odds ratios (ORs) with 95% confidence intervals (CIs).

Main results: 

Seven eligible studies were identified from a total of 2314 references. One new study with 600 patients was added to the original review. Four trials compared IABP to standard treatment and three to other percutaneous left assist devices (LVAD). Data from a total of 790 patients with acute myocardial infarction and cardiogenic shock were included in the updated meta-analysis: 406 patients were treated with IABP and 384 patients served as controls; 339 patients were treated without assisting devices and 45 patients with other LVAD. The HR for all-cause 30-day mortality of 0.95 (95% CI 0.76 to 1.19) provided no evidence for a survival benefit. Different non-fatal cardiovascular events were reported in five trials. During hospitalisation, 11 and 4 out of 364 patients from the intervention groups suffered from reinfarction or stroke, respectively. Altogether 5 out of 363 patients from the control group suffered from reinfarction or stroke. Reocclusion was treated with subsequent re-revascularization in 6 out of 352 patients from the intervention group and 13 out of 353 patients of the control group. The high incidence of complications such as moderate and severe bleeding or infection in the control groups has to be attributed to interventions with other LVAD. Possible reasons for bias were more frequent in small studies with high cross-over rates, early stopping and the inclusion of patients with IABP at randomisation.

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