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Ann Thorac Surg 2001;72:54-57
© 2001 The Society of Thoracic Surgeons

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Original article: cardiovascular

Preoperative intraaortic balloon pumps in high-risk patients undergoing open heart surgery

Accepted for publication March 30, 2001.

Address reprint requests to Dr Kang, 3/25-27 Darcy Rd, Westmead NSW 2145, Australia
e-mail: nicholak{at}bigpond.com

	Abstract

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Background. The use of the preoperative intraaortic balloon pump (IABP) in patients with severe left ventricular dysfunction or unstable angina with critical coronary anatomy is becoming more frequent as surgical casemix changes. The aim of this study was to determine the impact of preoperative IABP use on survival in high-risk patients having open heart surgery.

Methods. Prospectively collected data for 645 consecutive patients were reviewed. Patients receiving an IABP were identified and grouped as follows: group A (preoperative IABP for high-risk nonemergent cases), group B (preoperative IABP for emergent cases), and group C (intra/postoperative IABP). Risk-adjusted hospital mortality rates in these three groups was compared using the modified Parsonnet score for preoperative risk stratification.

Results. IABPs were used in 101 cases (16%). The predicted versus actual hospital mortality rate was 20% versus 5.7% in group A, 32.1% versus 47.6% in group B, and 12.6% versus 22.2% in group C (group A vs group B, p = 0.0014; group A vs group C, p = 0.012). IABP-related morbidity occurred in 3% of cases (all in group C).

Conclusions. Risk-adjusted mortality was significantly lower in high-risk cases with preoperative IABPs compared with emergent cases and intraoperative/postoperative IABPs. We encourage the use of preoperative IABPs in selected high-risk patients.

	Introduction

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
With the enormous growth of interventional cardiology in recent years, patients coming to surgery for coronary artery bypass grafting are often at the end-stage of their disease, with more ischemic myocardium and energy-depleted hearts compared with the surgical population seen before the era of coronary angioplasty and stenting. Patients referred for cardiac surgery are now older, sicker, have poorer left ventricular function, and more extensive disease, often after previous failed revascularization, than those of 10 years ago [1].

As a result, short-term circulatory support with the intraaortic balloon pump (IABP) during the perioperative period may be required. There is growing evidence to support the use of preoperative IABPs in those patients having open heart surgery who are thought to be "high risk," on the basis of poor left ventricular function or critically ischemic hearts such as left main lesions or reoperative cases [2–5].

The aim of this study was to compare the outcome of preoperative IABP use in high-risk patients with patients receiving intraoperative or postoperative IABPs, to determine whether the timing of insertion of the IABP had an impact on postoperative survival.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Patients
Data for 645 consecutive patients having open heart surgery from January 1998 to October 1999 were prospectively collected and entered into the hospital cardiac surgery database. Patients having an IABP were identified retrospectively and grouped into one of three groups as follows. Group A: preoperative IABP for high-risk urgent or elective cases. High risk was defined as severe left ventricular dysfunction (as reported on ventriculography or echocardiography) or unstable angina with critical coronary anatomy (defined as left main stenosis > 50% and right coronary stenosis > 70%, or redo case with graft-dependent circulation). Group B: preoperative IABP for emergency cases (defined as operation within 12 hours of referral to avoid death from cardiogenic shock). Group C: unplanned intraoperative or postoperative IABP.

Parsonnet scores
Parsonnet scores [6] based on patient and procedural risk factors were calculated for all patients, using the modification reported by St. George Hospital, London [7] (see Table 1). The predicted mortality for an individual patient was derived from the total Parsonnet score for that patient, as previously published [6, 7].

Intraaortic balloon pumps
The IABP catheter used was an 8F 40-mL sheathed Profile IABP catheter (Datascope, Oakland, NJ) connected to a Datascope portable computerized console (Datascope). Percutaneous femoral artery insertion was employed in all cases, except for 4 patients in group C who required surgical cutdown to cannulate the femoral artery. Preoperative IABP insertion was performed under radiological control using an image intensifier (without intravascular contrast material) in all cases.

Statistical analysis
Using the normal approximations for the decline in mortality between predicted and observed mortality, the likelihood ratio test was performed to test if the decline for group A versus group B was the same against the hypothesis that the decline for group A was higher than group B. The same test was applied to compare group A with group C. Fisher’s exact probability test was used to compare IABP-related complication rates between group A and group C.

	Results

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Operations performed and indications for IABP
One hundred one patients had an IABP (16% of total) (Fig 1). In group A, there were 35 patients (25 coronary artery bypass graft [CABG], 5 CABG and valve replacement, 3 valve replacement, 2 implantation of LVAD as bridge to transplantation). In group B, there were 21 patients (12 CABG, 3 valve replacement, 2 implantation of LVAD for cardiac arrest, 2 repair of postinfarction ventricular septal defect, 1 CABG and valve replacement, 1 repair of acute type A aortic dissection with left coronary occlusion). In group C, there were 45 patients (24 CABG, 8 CABG and valve replacement, 6 valve replacement, 6 cardiac transplantation, 1 aortic root replacement). Six cases in group A were reoperations, one case in group B was a reoperation, and 10 cases in group C were reoperations. One-quarter of these reoperations were second- or third-time reoperations. Other demographic data are shown in Table 2. The primary indication for insertion of an IABP in patients in the third group is shown in Figure 2.

View larger version (38K): [in this window] [in a new window]   Fig 1. Hospital mortality in 101 patients receiving IABPs.

View larger version (40K): [in this window] [in a new window]   Fig 2. Primary reason to insert IABP intra/postoperatively (group C).

IABP-related morbidity
Vascular complications occurred in 3 patients (all in group C). There were two retroperitoneal haematomas and one distal limb ischemia (which resolved with removal of the IABP catheter sheath). There was no IABP-related morbidity in group A or group B (group A vs group C, p = 0.17).

	Comment

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
This study compares outcome in three groups of patients receiving IABPs. Because the three groups differ in their characteristics, comparison must take into account these differences, and therefore, the differing predicted risks for each group. It is probably not surprising that mortality is higher for emergency cases than for high-risk nonemergent cases, but when the difference in predicted risk is accounted for by the Parsonnet score, the improved outcome in the latter group remains significantly better (p = 0.0014).

Similarly, risk-adjusted mortality was significantly higher in the group receiving an IABP intraoperative/postoperatively compared with the preoperative nonemergent high-risk group (p = 0.012). Forty-four percent of patients in the former group had either poor left ventricular function or were redo CABG cases. In retrospect, this subset of patients may have fared better with a planned preoperative IABP, rather than one inserted urgently once their hemodynamic condition had deteriorated. Of note, all the IABP-related vascular complications in this series (3%) occurred in the intraoperative/postoperative unplanned IABP group. This provides further evidence to support preoperative over urgent intraoperative/postoperative IABP insertion, although this difference does not reach statistical significance because of the low overall complication rate (p = 0.17).

In a recent randomized controlled trial [2] of 52 high-risk patients having CABG, patients randomized to receive preoperative IABPs had a significantly lower postoperative mortality than patients randomized not to receive an IABP (6% vs 25%). Furthermore, 55% of the latter group subsequently required an IABP intraoperatively. The definition of "high risk" in this study was two of the following criteria: left ventricular ejection fraction (LVEF) less than 30%, left main stenosis greater than 70%, unstable angina, or reoperative case. We have used similar criteria for selecting patients for a preoperative IABP, although we have only accepted patients with unstable angina who have both significant left main and right coronary artery lesions. Our operative mortality rate of 5.7% in the preoperative high-risk group compares with these results.

In a larger retrospective study [3] of 163 patients with LVEF less than 0.25 having CABG, patients who had received preoperative IABPs again did better than those who had not (2.7% operative mortality vs 11.9%). A 27-year review of IABP use at Massachusetts General Hospital [4] also demonstrated lower mortality in 2,038 patients having preoperative IABPs compared with 771 intraoperative and 276 postoperative IABPs (13.6% vs 35.7% vs 35.9%, respectively).

These studies highlight the benefits of preoperative balloon counterpulsation in terms of improved myocardial oxygen supply/demand ratio, redistribution of blood flow toward areas of ischemic myocardium, hemodynamic stability during induction and prebypass, pulsatile flow during bypass, and less inotrope requirement and improved graft flow postbypass.

Another important issue about preoperative IABP use is the timing of preoperative insertion. We have done this 12 hours before operation in nearly all cases. This is mainly for logistic reasons, so that the IABP can be inserted in the intensive care unit the evening before surgery, with operation the next morning. Other investigators have found no difference in outcome whether the IABP is inserted 2, 12, or 24 hours preoperatively [2, 8].

The Benchmark Registry [9] is a prospectively collected database that has recently reported the results of over 5,000 patients receiving IABPs at 132 US and European centers. Preoperative IABP insertion in high-risk patients accounted for 11% of patients. In our practice, this indication accounted for 35% of cases. This higher rate may reflect both a difference in casemix seen at our institution as well as a lower threshold for preoperative IABP use on the basis of our encouraging results to date.

The Benchmark Registry reports an overall IABP-related morbidity rate of 3.2% and IABP-related mortality rate of 0.1%. Our morbidity rate is comparable with this. As noted, we have not had any morbidity in the preoperative nonemergent or emergent groups, which may be due in part to the use of radiological control (image intensifier) in all these cases, which is usually not practical in the urgent intraoperative setting.

Limitations of the study
A number of limitations are inherent to this study design. The Parsonnet scoring system, although still a widely used and validated risk stratification tool, is now more than 10 years old. Thus, surgical results in the current era might be expected to outperform those of a decade ago. Furthermore, in the higher risk groups (Parsonnet score > 20), the system starts to lose accuracy. This problem is most relevant to patients in group B of this study who had the highest scores (mean score 32.1).

Another limitation of this study is the heterogeneity of operative procedures represented. Although most of the group A patients were CABG operations, we have also included valve replacements and bridge-to-transplant patients. While the modified Parsonnet score is able to account for different operative procedures as well as different patient-related variables, inferences about the merits of preoperative IABP in patients having the same operation (such as CABG) cannot necessarily be drawn.

Conclusions
In our current practice, we have used the preoperative IABP liberally. While the current trend in surgical casemix continues, we believe that an increasing number of selected patients are likely to benefit from preoperative IABP use. Our favorable recent experience has encouraged us to continue to adopt this approach.

	Acknowledgments

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
The authors wish to kindly acknowledge Dr Rita Gupta, Department of Mathematics and Statistics, University of Western Australia, for the statistical analysis presented in this paper.

	References

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 

1. STS National Database. 1998 Cardiac Surgery Data Summary.
2. Christenson JT, Simonet F, Badel P, et al. Evaluation of preoperative intraaortic balloon pump support in high risk coronary patients. Eur J Cardio-thorac Surg 1997;11:1097–3.
3. Dietl C.A., Berkheimer M.D., Woods E.L., et al. Efficacy and cost-effectiveness of preoperative IABP in patients with ejection fraction of 0.25 or less. Ann Thorac Surg 1996;62:401-409.[Abstract/Free Full Text]
4. Torchiana D.F., Hirsch G., Buckley M.J., et al. Intraaortic balloon pumping for cardiac support: trends in practice and outcome, 1968 to 1995. J Thorac Cardiovasc Surg 1997;113:758-764.[Abstract/Free Full Text]
5. Davidson J., Baumgariner F., Omari B., et al. Intra-aortic balloon pump: indications and complications. J Nat Med Assoc 1998;90:137-140.[Medline]
6. Parsonnet V., Dean D., Bernstein A.D. A method of uniform stratification of risk for evaluating the results of surgery in acquired adult heart disease. Circulation 1989;79(6 Suppl):I3-I12.
7. Poloniecki J., Valencia O., Littlejohns P. Cumulative risk adjusted mortality chart for detecting changes in death rate: observational study of heart surgery. Br Med J 1998;316:1697-1700.[Abstract/Free Full Text]
8. Christenson J.T., Simonet F., Badel P., et al. Optimal timing of preoperative intraaortic balloon pump support in high-risk coronary patients. Ann Thorac Surg 1999;68:934-939.[Abstract/Free Full Text]
9. Ferguson J.J., Cohen M., Freedman R., et al. The Benchmark Counterpulsation Outcomes Registry: initial results in 5335 patients. J Am Coll Cardiol 1999;33:203A.

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Mark Edwards Robert Larbalestier Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kang, N. Articles by Larbalestier, R. Search for Related Content PubMed PubMed Citation Articles by Kang, N. Articles by Larbalestier, R. Related Collections Mechanical Circulatory Assistance