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

 

Abstract

Background

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.

Objectives

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.

Search strategy

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.

Selection criteria

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

Data collection and analysis

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.

Main results

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.

Authors' conclusions

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.

 

Plain language summary

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

Patients undergoing coronary artery bypass grafting may suffer from heart failure in the immediate hours following surgery due to stunning of the heart muscle. Drugs may be required to support the heart if this happens. Increasingly, a device called an intra-aortic balloon pump is used as a mechanical assist device to help such patients. The device is a balloon which is positioned close to the heart in the main blood vessel from it called the aorta. By inflating and deflating with 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 is a temporary device which supports the heart during the immediate post operative period. Recent evidence suggests that certain patients may benefit from a period of support with the balloon pump before their operation in order to try and optimise heart function before the stress of surgery. This work suggests the intra aortic balloon pump may be beneficial in terms of survival from the operation however there are many problems with the validity of the trials used in this review and a categorical answer to this question requires further randomised controlled trials.