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

Patients with acute myocardial infarction complicated by cardiogenic shock still have a poor prognosis after primary revascularization procedures such as coronary artery bypass grafting or primary percutaneous coronary intervention. Under patho-physiological considerations, the failing heart due to impaired left ventricular function following acute myocardial infarction is the main cause for the development of cardiogenic shock characterized by instable haemodynamics with reduced systolic and mean arterial pressures. The reduced blood pressure leads to hypoperfusion with reduced oxygen supply to vital organs. Following these pathophysiological considerations it seemed to be a consequent therapeutic concept to give haemodynamic support to these haemodynamically instable patients by a mechanical assist device, called intra-aortic balloon pump (IABP). While the balloon becomes in- and deflated synchronal with the beats of the heart, it acts to increase blood flow to the heart as well as reduce the amount of work the heart is doing. This support can be provided for a few hours and up to several days. Recent evidence suggests that certain patients with acute myocardial infarction complicated by cardiogenic shock and treated by thrombolysis may have a benefit from a period of support with the IABP after revascularization by thrombolysis. Nowadays the most preferred revascularization procedure is primary percutaneous coronary intervention. For these patients a few number of heterogeneous randomised trials with only small patient numbers were not able to show convincing evidence, for either benefit or harm, supporting the use of the intra-aortic counterpulsation beyond initial haemodynamic improvements. This present lack of evidence due to a small number of randomised controlled trials with small numbers of patients does not exclude, that there might be clinically significant effects, which only can be proven by larger randomised controlled trials. For this reason a larger multicenter trial (IABP-SHOCK II) has been started in 2009, to clarify the use of the IABP in infarct related cardiogenic shock and its results will  provide better evidence at the beginning of 2013.