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Ann Thorac Surg 2001;71:1400
© 2001 The Society of Thoracic Surgeons
a Cardiovascular Surgery, Queen Elizabeth II Health Sciences Centre, 1796 Summer St, Room 2269 NHI, Halifax, Nova Scotia B3H 3AZ, Canada
To the Editor
We read with interest the recent article by Christenson and associates [1] from Geneva. This article assesses the cost-effectiveness of preoperative intraaortic balloon pump (IABP) insertion in high-risk patients, using pooled data from two previous trials [2, 3]. We note in reviewing their references that this group has published four previous papers on prospective trials involving preoperative IABP use [2–5]. Three of these appear to be from a concurrent prospective randomized trial starting in June 1994 [2, 4, 5]. In one of the studies (used for the pooled data in the current publication) 52 patients presenting for coronary artery bypass grafting (CABG) with at least two of the following criteria: ejection fraction 
40%, left main stem stenosis 
70%, redo CABG, and unstable angina, were randomized to receive an IABP 24 hours or 1 to 2 hours preoperatively, or no preoperative IABP. There were 5 of 20 deaths in the control group versus 2 of 32 in the two treatment groups combined, p < 0.05 [2].
The other data used in the current publication is from a prospective randomized controlled trial subsequently undertaken by this same group starting in July 1997 [3]. This essentially repeated the trial published in 1997 [2], except with a potentially higher-risk group of patients (the criteria for entry were the same except that the ejection fraction cut-off was reduced to < 30%). This study was apparently designed to determine the optimal timing of preoperative IABP use. It confirmed their own finding that there was no difference in clinical outcomes between preoperative insertion 24 or 2 hours preoperatively [2], and added the observation that insertion 12 hours preoperatively also had the same results [3]. Six of 30 patients in the control group died compared to 1 of 30 in the three treatment groups (p value not reported) [3].
In the last publication with pooled data from these two trials, the criteria from the later trial (with ejection fraction < 30%) were used [1]. This yielded a total of 112 patients (the exact sum of the two trials); presumably all patients in the first trial meet the more rigorous criteria for the second trial [1–3]. Thus the combined results gave a mortality of 3 of 62 (5%) in the group receiving preoperative IABPs versus 11 of 50 (22%) in the control group (p = 0.007) [1].
Of concern is that a control group (with no preoperative IABP) of these high-risk patients was used in the later trial [3]. Why was a control group used in this trial, if it was already demonstrated that in this group of patients there is an increased mortality associated with nonuse of a preoperative IABP? Perhaps there is some substantial difference between the cohorts in these two trials that is not immediately apparent from the two publications, in which case the two groups should likely not be combined in the current analysis [2, 3].
References
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  R. J.F. Baskett, W. A. Ghali, A. Maitland, and G. M. Hirsch The intraaortic balloon pump in cardiac surgery Ann. Thorac. Surg., October 1, 2002; 74(4): 1276 - 1287. [Abstract] [Full Text] [PDF]
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