Intra-aortic balloon pump

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Exiting, expensive. Alas, it comes as a shock 2 find that it is not shown to help

The intra-aortic balloon pump (IABP) is the most widely used form of mechanical circulatory support. The pump itself is a gas filled balloon (usually helium) which is inserted percutaneously via the femoral artery into the aorta. It inflates in ventricular diastole and deflates in ventricular systole. This has 2 main effects on the circulation. Firstly it reduces afterload, so reducing the work of the heart to eject. Secondly it increases coronary perfusion in diastole and hence increase oxygen supply to the myocardium. This technique is known as counterpulsation, and it alters the balance of myocardial supply and demand away from demand and towards supply. Its main uses are in patients with heart failure and in those with myocardial ischaemia or critical coronary anatomy.


Helium is a good choice here because its viscosity is strikingly low compared to other gases which might be used, permitting the significant volumes which have to be moved in and out of the balloon in short periods of time to do so through a manageable diameter of tube. Helium diffuses rapidly and would therefore be removed from bubbles in the circulation faster than some gases, but in the event of a rupture of the balloon there may be major troubles besides the gas embolism.

Myocardial infarction-related cardiogenic shock

Despite no good evidence from randomised controlled trials, guidelines from the American Heart Association/American College of Cardiology and the European Society of Cardiology strongly recommended until 2012 the use of IABP in patients with myocardial infarction related cardiogenic shock[1]. This must change with the publication of the shock II trial, which demonstrated no net outcome advantage in this indication for this expensive technology[2]. A major portion of a global market worth perhaps £200 million is threatened by this new evidence[3].


Arterial waveform during IABP counterpulsation


References

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