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Three Part Question

In [high risk patients undergoing coronary arterial surgery] does [prophylactic IABP insertion] improve [in-patient survival, or time to discharge]?

Clinical Scenario

You are about to perform a coronary arterial bypass graft on a 70 year old lady who has left main stem disease and an ejection fraction of 30% on echocardiography. She was an urgent referral from the cardiologists after being admitted 3 weeks ago with unstable angina, but has been stable since admission. You realise that she is a high risk case and you wonder whether preoperatively inserting an intra-aortic ballon pump would be of benefit to her?

Search Strategy

Medline 1966-07/03 using the OVID interface.
[exp Coronary Artery Bypass OR CABG.mp OR exp Thoracic surgery OR Coronary art$ bypass.mp OR cardiopulmonary bypass.mp OR exp Cardiovascular surgical procedures OR exp Thoracic surgical procedures] AND [exp Intra-aortic balloon pumping OR intra-aortic balloon pump.mp OR IABP.mp] AND [exp pre-operative care OR pre-operative.mp OR preoperative.mp]

Search Outcome

110 papers were found of which 7 were deemed to be relevant.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Dietl et al 1996 USA	37 high risk patients received 9.5F IABP 126 high risk patients were used as controls Definition of High Risk: Left ventricular ejection fraction of <25%	Retrospective cohort study (2b)	Mortality	IABP group, 1 death (2.7%). Control group 15 deaths (12%) p<0.005	28 control patients went on to need IABP (with 4 complications) IABP group had significantly higher incidence of recent MI, emergency priority, left main stem disease, NYHA IV and iv nitrate use
			Hospital Stay	IABP group 9.9 day. Control group 12.0 days p=NS
			Complications	3 IABP patients had complications, 1 vascular haemorrhage, 1 vascular reconstruction, 1 leg ischaemia
Christenson et al, 1997, Switzerland	52 high risk patients undergoing CABG (different cohort to 1999 patients) 13 patients had 9F IABP 24hrs prior to surgery, 19 had IABP 1-2hrs pre-op, 20 Controls Definition of high risk: 2 or more of left ventricular ejection fraction <40%, left main stem stenosis >70%, Redo-CABG, unstable angina 29 patients were redo-CABG	RCT single blind (2b)	Mortality	IABP 24hrs 1 death. IABP 2 hrs 1 death. Controls 5 deaths (25%) P<0.05	Our calculation of IABP mortality vs contol gives Fishers 1 sided P value of 0.0925, in contrast to their figures 45/52 were men (87%) only 9 patients had LIMA used No sample size estimates
			ICU stay IABP vs control, C.I. 30 mins post CPB	2.39+/-0.9 days vs 3.59 +/-1.1 days P<0.004. 4.17 +/-0.64 vs 2.01 +/-0.61 P<0.001
			Complications	No IABP related mortality or complications
Christenson et al, 1997, Switzerland	24 high risk redo-CABG patients received 9F St. Jude IABP 2 hrs pre-op. 24 high risk redo-CABG patients randomised as controls Definition of high risk: Any two of; LVEF <40%, unstable angina or Left main stem disease >70%	RCT single blind	Mortality	IABP group, no deaths. Control group 4 deaths, P=0.049	5 women in this study in total No sample size estimates Supported by Grant from St. Jude Our calculation of their Fishers two-sided test is that the P-value is 0.1092 for mortality
			CPB time	IABP group 88mins. Control group 110mins, P=0.006
			Complications	2 patients had leg ischaemia , one required thrombectomy
Gutfinger et al, 1999, USA	Cohort of 206 patients undergoing CABG by a single surgeon aged over 70 years, if operation performed within 24 hrs of catheterisation. 97 had IABP. Decision to insert IABP, after angiography: Patients who required an urgent operation because of failed PTCA, critical left main stenosis >70%, significant left ven-tricular ejection fraction <40%, unstable angina or who required an emer-gency cardiac reoperation	Retrospective Cohort Study (2b)	In hospital mortality	IABP group 6/97 deaths no IABP group 3/109 deaths	IABP patients had a significanty higher Parsonnet score, lower LVEF, CCF and rate of Acute MIs No attempt to allow for group differences by multivariate analysis
			Hospital stay	IABP group 6.0 +/- 3.7 days control group 9.0 +/- 10.5 days p, 0.01
			Complications	Two incidences of leg ischaemia requiring thrombectomy (2%)
Christenson et al, 1999, USA	60 consecutive high risk patients undergoing CABG 30 patients had a 9.5F IABP placed at 2, 12 or 24 hours preoperatively 30 controls who did not have preoperative IAPB Definition of high risk: The presence of 2 or more of the following; LVEF of <30%, Left main stem disease >70%, unstable angina, reoperation	RCT single blind (2b)	In hospital mortality	IABP group 1 death. Control group 6 deaths. Two-sided Fisher's test p=0.1028	Study sponsored by Datascope The significance test for mortality was not reported by this paper. Therefore we calculated this p-value 53/60 patients were male (88%) 23/30 control patients ended up having an IABP postoperatively due to poor C.I. Mortality of controls is high (20%) No sample size estimates
			CPB time	IABP group 83.6 +/- 21.7 minutes. Control 127.3 +/- 45.6 minutes p = 0.001
			Complications	5 patients (5/53=9.4%). 2 removals of IABP, 1 thrombectomy, 1 thrombectomy and fasciotomy and 1 interposition graft
Holman et al, 2000, USA	7581 high-risk but haemodynamically stable patients of which 592 patients received an IABP prophylactically prior to CABG. These patients were matched using a propensity score and final groups were 550 patients with IABP and 550 controls Patient group: Excluded if pt in shock, ventilated, emergency CABG, PTCA 6 hrs previously, or MI 3 days ago or less, or if it was decided that the IABP was inserted for treatment rather than prophylaxis. Surgeons tended to include patients with: LVEF <30%, left main stem disease >70%, diabetics, comorbidity, renal failure, elderly	Retrospective cohort study (2b)	In hospital mortality	IABP group 30/550 Control group 28/550	Of 8972 all CABG patients on their database, 15% had an IABP Matching was performed using an 8 factor propensity score, but 4 of these factors had a non-significant association with IABP placement.
			Long term mortality (5 year F/u)	Hazard ratio for mortality 0.90 (CI 0.72 – 1.13)
			Hospital stay	IABP group 9 ± 7.8 days, Control group 11 ± 7.3 days P < 0.005
			Complications	Not reported in this paper
Fasseas et al, 2001, USA	457 stable patients with severe left main stem disease. 170 patients had prophylactic IABP Definition of patients: Left main stem disease >50%, and multivessel coronary disease, but no angina or haemodynamic compromise, heart failure, shock or previous CABG	Retrospective cohort study (2b)	Mortality	IABP group 6 deaths. Control group 2 deaths P=0.02. This became p=0.1 after multivariate analysis allowed for confounding variables	Higher PVD, ejection fraction and less diabetes in non IABP group No sample size estimate
			Hospital stay	No difference in hospital stay or bypass time

Comment(s)

The 3 papers by Christenson et al provide evidence for the placement of an IABP in patients with two of the following: LVEF <30% or 40%, left main stem disease, unstable angina or redo-operation. Although their individual papers are on the margins of significance, if all patients in these papers are different then taken together there is a significant mortality reduction. The IABP mortality in these three papers was 3.4% and in the control group it was 14 % thus giving a number needed to treat in this group of patients of 10. The remaining papers are cohort studies. Dietl shows a mortality reduction in patients with LVEF <25%, but the remaining studies show no mortality benefit in cohorts of patients that are lower risk than the groups studied by Christenson. There is some evidence provided in these papers that in the highest risk patients the prophylactic placement of an IABP may be of benefit in terms of survival. However the exact groups that may benefit have not been established. Further randomised studies in this area are needed to establish the benefit of pre-operative IABP use. If a reduction in mortality from 10% to 3% were desired a PRCT of 440 patients would be needed to have an 80% chance of uncovering this difference.

Clinical Bottom Line

There is evidence to support preoperative IABP insertion in patients with two of LVEF <30% or 40%, left main stem disease, unstable angina or redo-operation.

References

1. Dietl CA, Berkheimer MD, Woods EL, et al. Efficacy and cost-effectiveness of preoperative IABP in patients with ejection fraction of 0.25 or less. Ann Thorac Surg 1996;62(2):401-8.
2. Christenson JT, Simonet F, Badel P, et al. Evaluation of preoperative intra-aortic balloon pump support in high risk coronary patients. Eur J Cardiothorac Surg 1997;11(6):1097-103.
3. Christenson JT, Badel P, Simonet F, et al. Preoperative intraaortic balloon pump enhances cardiac performance and improves the outcome of redo CABG. Ann Thorac Surg 1997;64(5):1237-44.
4. Gutfinger DE, Ott RA, Miller M, et al. Aggressive preoperative use of intraaortic balloon pump in elderly patients undergoing coronary artery bypass grafting. Ann Thorac Surg 1999;67(3):610-3.
5. Christenson JT, Simonet F, Badel P et al. Optimal timing of preoperative intraaortic balloon pump support in high-risk coronary patients. Ann Thorac Surg 1999;68(3):934-9.
6. Holman WL, Li Q, Kiefe CI, McGiffin DC, et al. Prophylactic value of preincision intra-aortic balloon pump: analysis of a statewide experience. J Thorac Cardiovasc Surg 2000;120(6):1112-9.
7. Fasseas P, Cohen M, Kopistansky C, et al. Pre-operative intra-aortic balloon counterpulsation in stable patients with left main stem coronary disease. J Invasive Cardiol 2001;13(10):679-83.