Preoperative intra aortic balloon pumps in patients undergoing coronary artery bypass grafting

The intra aortic balloon pump (IABP) is a mechanical assist device which improves cardiac function. The device has a well-established place in algorithms for managing low cardiac output following cardiac surgery. There is increasing evidence that certain cardiac surgery patients benefit from a period of preoperative augmentation with the intra aortic balloon pump.

To determine the effect of the preoperative intra aortic balloon pump on mortality and morbidity in a number of different patients groups undergoing coronary artery bypass grafting.

Searches were performed of the following databases: Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library (Issue 1 2005), MEDLINE (2000-2005) and EMBASE (1998-2005). No language restrictions were applied.

Randomised or controlled trials of any size or length were included.

Papers were assessed for inclusion by two reviewers independently. Differences were settled by consensus with a third reviewer. Data were extracted and entered into RevMan 4.1, through which a meta-analysis of the data was performed.

Five randomised controlled trials were identified from a total of 765 studies (4 on-pump and 1 off-pump). Data from a total of 193 patients were included in the meta-analysis; all on-pump. Generally, the patients were designated as "high risk" . 105 patients were treated preoperatively with IABP and 88 patients served as controls. There were three hospital deaths in the intervention arm and 18 in the non-intervention arm (odds ratio (OR) 0.16; 95% confidence intervals (CI): 0.06 to 0.4; P<0.0001). Low cardiac index (<2.0 L/min/m2) was noted in 21 out of 105 patients in the treatment arm and 59 patients out of 88 in the non-treatment arm (OR 0.14; 95% CI: 0.08 to 0.25; P<0.00001). A large proportion of the control group had an IABP inserted postoperatively for low cardiac index (52 out of 88). An off-pump versus on-pump analysis was not possible due to the limited number of off-pump studies. However a single well-conducted randomised controlled trial suggested favourable effect of the preoperative IABP in off-pump patients.

Available evidence suggests the preoperative intra aortic balloon pump may have a beneficial effect on mortality and morbidity in specific high risk patient groups undergoing coronary artery bypass grafting, however, the randomised evidence is from a number of small trials, with a high proportion of unstable patients, recruited at a single institution.