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Intraaortic balloon pump placement in various patient populations

St. Elisabeth Department of Heart and Lung Surg, St. Olavs University Hospital, Trondheim 7018, Norway

EuroSCORE directed intraaortic balloon pump placement in high-risk patients undergoing cardiac surgery – retrospective analysis of 267 patients

Diez et al. [1] cover a very interesting subject, namely finding the correct indication for inserting an intraaortic balloon pump (IABP). This is important, because IABP may cause complications [2] but it may also have a significant impact on reducing mortality in certain groups of patients [3]. The authors have to be commended on collecting and analyzing large clinical material. Diez et al. draw conclusions from a comparison of predicted mortality by logistic EuroSCORE with actual observed mortality. It appears uncertain whether the results and conclusions presented by the authors contribute to a clarification of the issue.

The material was divided into 3 groups: patients who received an IABP prior to surgery, those who received it during surgery or following surgery and a third group who was not treated with IABP. It appears that these three groups represent different clinical entities and a direct statistical comparison seems unsound.

Moreover, a statistical comparison of predicted and actual mortality in each of the subgroups is problematic for several reasons:

In the group of patients who received an IABP prior to surgery, the actual mortality was in accordance with predicted mortality. However, it is unclear why the use of IABP was not included in the EuroSCORE count. In the methods section it is stated that preoperative insertion was done on the basis of specific indications which obviously are markers of operative risk and should be included in the EuroSCORE.

An IABP was inserted intraoperatively or postoperatively in 113 patients. This group had the highest number of non-CABG-procedures, highest ejection fraction (EF) and the lowest number of emergency procedures (24%). According to the methods section all patients were high risk with an EF below 40%. Thus, it is surprising that the mean EF in this group was 50%. Patients who received an IABP during or after surgery (because they needed mechanical support) represent a negative selection, i.e. those who developed problems during the course of surgery. It is not surprising that the preoperative EuroSCORE doesn't reflect actual mortality in this situation.

Patients who did not receive an IABP, but were included on the basis of their high-risk status were emergencies in 70% of cases and developed low cardiac output in 60% of cases. It is surprising that these patients did not receive an IABP. Maybe that had an impact on mortality.

It would have been interesting to compare patients with and without IABP on the basis of a matched pair comparison. This might help to find out whether IABP represents a survival advantage in this material.

	References

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1. Diez C, Silber RE, Wachner M, Stiller M, Hofmann HS. EuroSCORE directed intraaortic balloon pump placement in high-risk patients undergoing cardiac surgery – retrospective analysis of 267 patients. Interact CardioVasc Thorac Surg 2008;7:389–397.[Abstract/Free Full Text]
2. Trost JC, Hillis LD. Intra-aortic balloon counterpulsation. Am J Cardiol 2006;97:1391–1398; Epub 2006 Mar 20.[CrossRef][Medline]
3. Christenson JT, Schmuziger M, Simonet F. Effective surgical management of high-risk coronary patients using preoperative intra-aortic balloon counterpulsation therapy. Cardiovasc Surg 2001;9:383–390.[CrossRef][Medline]

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