Don’t Understand Balloon Pumps – don’t bother

Alas – another intervention bites the dust. For decades the intra-aortic balloon pump has been heralded as the great savior of the patient with cardiogenic shock. If you have always found these devices confusing (when to use, when to wean, what difference 1:1 versus 1:2 augmentation etc), then worry not: they are heading to the Swan Ganz junkyard. In this week’s NEJM the IABP-SHOCK II trial is published (read here). Six hundred patients were recruited in 37 locations in Germany in 3 years – randomized to IAB-counterpulsation at 1:1 or control, essentially catecholamine, therapy. Patients were eligible for the trial if they had had any form of myocardial infarction complicated by cardiogenic shock, or needed an emergency percutaneous coronary intervention. The majority of patients had PCIs and the IABP could be placed before or after.

There is a widespread belief that using IABP improves pump function, restoring cardiovascular health and preventing the development of multi-organ failure. The primary endpoint of the study was 30 day all cause mortality. This is a flawed measure in critical care, as many patients will still be alive at 30 days, awaiting withdrawal of life sustaining therapy. The authors are in the process of collecting 90 day and 6 month data. The authors also looked for evidence of multi-organ failure (using SAPS II), infectious and ischaemic (using lactate) complications.

Previous studies have reported mortality rates of 42-48% in cardiogenic shock. The authors reported 30 day mortality of 39.7% in the IABP group and 41.3% in the control group (not significant). There was no significant difference in any of the other endpoints either..

Criticisms and generalizability? The mortality rate was lower than expected, but this was a heterogenous German population, a single health system, with an average BMI of 27. So maybe the patients were less unhealthy than comparable North American Studies. More likely, the IABP can be added to a long list of devices that receive religious like devotion, but have little clinical benefit. Further data of interest would be whether or not IABP really benefits postoperative cardiac patients. In the meantime, it is likely that we will encounter these devices less frequently in the future.

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