Optimal timing of preoperative intraaortic balloon pump support in high-risk coronary patients

Optimal Timing of Preoperative Intraaortic Balloon Pump Support in High-Risk Coronary Patients Jan T. Christenson, MD, PhD, Franc¸ois Simonet, MD, Pierre Badel, MD, and Martin Schmuziger, MD Departments of Cardiovascular Surgery and Anesthesiology, Hoˆpital de la Tour, Meyrin-Geneva, Switzerland

Background. Beneficial effects of preoperative intraaortic balloon pump (IABP) treatment, on outcome and cost, in high-risk patients who have coronary artery bypass grafting have been demonstrated. We conducted a prospective, randomized study to determine the optimal timing for preoperative IABP support in a cohort of high-risk patients. Methods. Sixty consecutive high-risk patients who had coronary artery bypass grafting (presenting with two or more of the following criteria: left ventricular ejection fraction less than 0.30, unstable angina, reoperation, or left main stenosis greater than 70%) entered the study. Thirty patients did not receive preoperative IABP (controls), 30 patients had preoperative IABP therapy starting 2 hours (T2), 12 hours (T12), or 24 hours (T24), by random assignment, before the operation. Fifty patients had preoperative left ventricular ejection fraction mean, less than 0.30 (less than 0.26 ⴞ 0.08), (n ⴝ 40) unstable angina, 28% (n ⴝ 17) left main stenosis, and 32% (n ⴝ 19) were reoperations. Results. Cardiopulmonary bypass was shorter in the

IABP groups. There was one death in the IABP group and six in the control group. The complication rate for IABP was 8.3% (n ⴝ 5) without group differences. Cardiac index was significantly higher postoperatively (p < 0.001) in patients with preoperative IABP treatment compared with controls. There were no significant differences between the three IABP subgroups at any time. The incidence of postoperative low cardiac output was significantly lower in the IABP groups (p < 0.001). Intubation time, length of stay in the intensive care unit and the hospital was shorter in the IABP groups (p ⴝ 0.211, p < 0.001, and p ⴝ 0.002, respectively). There were no differences between the IABP subgroups in any of the studied variables. Conclusions. The beneficial effect of preoperative IABP in high-risk patients who have coronary artery bypass grafting was confirmed. There were no differences in outcome between the subgroups; therefore, at 2 hours preoperatively, IABP therapy can be started. (Ann Thorac Surg 1999;68:934 –9) © 1999 by The Society of Thoracic Surgeons

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and cost-benefit of preoperative IABP treatment in highrisk patients who had redo CABG was reported [14]. The optimal timing for preoperative IABP treatment has not yet been firmly established. Because of its impact on cost, this prospective randomized study was designed to determine the optimal timing for preoperative IABP treatment on preoperative and postoperative cardiac performance (cardiac index measurements), hospital mortality rate, and postoperative morbidity rate in high-risk patients who had CABG.

he intraaortic balloon pump (IABP) is wellestablished as additional support to pharmacologic treatment of the failing heart, eg, after myocardial revascularization [1–3]. Treatment with intraaortic balloon pump results in a more favorable myocardial blood supply through augmentation of the diastolic pressure, which leads to redistribution of coronary blood flow toward ischemic areas of the myocardium [4, 5]. Christenson and associates [6] reconfirmed earlier findings by others [7, 8] that use of preoperative IABP could lead to preoperative reduction of myocardial ischemia and thus improve outcome in high-risk coronary patients. Well-established high-risk factors for mortality and major postoperative morbidity are poor left ventricular function (left ventricular ejection fraction less than 0.40), diffuse coronary artery disease, left main stem stenosis greater than 70%, and unstable angina at time of operation despite optimal medical treatment [1, 9 –11]. An additional risk factor is reoperative coronary artery bypass grafting (CABG) [12, 13]. In a recent prospective, randomized study, the efficacy

Patients and Methods Between July 1997 and June 1998, 60 consecutive highrisk patients who had CABG at our institution were included in this study, and all gave informed consent. No patient declined participation in the study. High risk was defined as having presented with at least two of the following inclusion criteria: left ventricular dysfunction (preoperative left ventricular ejection fraction less than 0.30, calculated from preoperative ventriculography), unstable angina at the time of operation (angina severity

Accepted for publication March 20, 1999. Address reprint requests to Dr Christenson, Department of Cardiovascular Surgery, Hoˆpital de la Tour, 1 av J.-D. Maillard, CH-1217 MeyrinGeneva, Switzerland; e-mail: [email protected].

© 1999 by The Society of Thoracic Surgeons Published by Elsevier Science Inc

This study was supported by a grant from Datascope Corp, Fairfield, New Jersey.

0003-4975/99/$20.00 PII S0003-4975(99)00687-6

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Table 1. Classic Risk Factors for Coronary Artery Disease From High-Risk Patients Who Had Coronary Artery Bypass Grafting Group 2 Group 2 T2

Group 2 T12

Group 2 T24

Variable

Group 1 (controls) n

%

n

%

n

%

n

%

n

%

Male gender CCS angina class 3 or 4 Hypertension Hyperlipidemia Diabetes mellitus Current smoker Multifocal vascular disease Previous myocardial infarction ⬎ 6 weeks preoperatively ⱕ 6 weeks preoperatively

26 28 12 21 7 13 6

87 93 40 70 23 43 20

27 29 15 21 8 16 5

90 97 50 70 27 53 17

9 10 6 7 2 5 3

90 100 60 70 20 50 30

10 9 5 7 3 4 0

100 90 50 70 30 40 0

8 10 4 7 3 7 2

80 100 40 70 30 70 20

13 7

43 23

15 13

50 43

7 2

70 20

5 5

50 50

3 6

30 60

CCS ⫽ Canadian Cardiovascular Society

fluctuating between Canadian Cardiovascular Society’s classifications of angina or angina at rest despite nitroglycerine infusion and calcium-channel inhibitors), left main stem stenosis at least 70%, or reoperative CABG. The criteria indicating high risk were strict, and the study population would be regarded by some as salvage operations. In our practice these patients represent 18.4% of the total CABG population. Patients who had CABG but did not fulfill these high-risk criteria were not included in this study.

Study Design On admission to the hospital, the patients were randomly assigned to groups by lottery principle, drawing prepared sealed envelopes containing the group assignment. There were two principle groups of 30 patients in each as follows: in group 1 (controls) the patients did not receive preoperative treatment with IABP, and in group 2 (preoperative IABP) patients received preoperative IABP treatment before aortic cross-clamping. Furthermore, group 2 was divided by random assignment, into three subgroups of 10 patients in each, according to the time when preoperative IABP treatment was started. Group 2 (T2) received IABP counterpulsations during the 2 hours before aortic cross-clamping, group 2 (T12) during 12 hours, and group 2 (T24) during 24 hours before aortic cross-clamping. All other interventions and procedures were standardized and remained the same for all patients. They all received a Swan-Ganz catheter preoperatively and cardiac performance was evaluated by cardiac index (L/m2 per minute), calculated from cardiac output data measured repeatedly preoperatively and after weaning from cardiopulmonary bypass (CPB) until at least 72 hours postoperatively. All measurements except values before CPB in group 2 were done without ongoing IABP. Postoperative hospital mortality and morbidity rates, including all balloon-related complications, as well as required stay in intensive care unit, intubation time, and total hospital stay, were registered. Hospital stay was

defined as total hospitalization time in any hospital in conjunction with the CABG operation, except rehabilitation hospitals or cardiovascular readaptation clinics. All preoperative clinical and catheterization data, as well as operative data, were entered into a computer database at the time of hospitalization. Definitions were made before the start of the study and were not changed during the study period.

Patient Characteristics The mean age was 63.0 ⫾ 9.8 years, and 88% of the patients (53 of 60) were men. There were no differences between groups. The classic risk factors for coronary artery disease were similar in all groups (Table 1). Preoperative risk factors and combinations thereof (inclusion criteria) in the two main groups as well as in the subgroups of group 2 are given in Table 2. Twenty-nine patients in group 1 and 27 patients in group 2 had triple coronary vessel disease.

Surgical and Cardiopulmonary Bypass Techniques Anesthesia, CPB, and surgical techniques were standardized and did not change during the study period. Myocardial revascularization was done during normothermic CPB (35° to 37°C). For myocardial protection, intermittent crystalloid cardioplegia (St Thomas’ II, with addition of 100 mg allopurinol) along with topical hypothermia with iced slush was used. Initially 1,000 mL of cardioplegia solution was infused into the aortic root under low pressure. Cardioplegia (500 mL, with 20 mmol/L potassium chloride at 4° to 8°C) was repeated every 30 minutes or whenever electrical activity resumed. Just before aortic declamping, an infusion of 1,000 mL of warm blood cardioplegia (50% venous blood) was given into the aortic root. All operations were done through a median sternotomy. A cell-saving device was used routinely. The internal thoracic artery was harvested as a pediculated graft whenever used as a conduit. No other arterial conduits were used in this series. The sequential bypass grafting technique was used routinely, as described previously [15].

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Table 2. Preoperative Risk Factors in High-Risk Patients Who Had Coronary Artery Bypass Grafting Risk Factor(s)

Group 1

Group 2 T2

Group 2 T12

Group 2 T24

A. Preoperative left ventricular ejection fraction ⱕ 0.30 B. Unstable angina C. Left main coronary artery stenosis ⱖ 70% D. Diffuse coronary artery disease E. Reoperative coronary artery bypass grafting Combination of two factors A⫹B A⫹C A⫹D A⫹E B⫹D Combination of three factors A⫹B⫹C A⫹B⫹D A⫹B⫹E A⫹C⫹D A⫹C⫹E A⫹D⫹E B⫹C⫹D B⫹D⫹E Combination of four factors A⫹B⫹D⫹E A⫹B⫹C⫹D A⫹C⫹D⫹E B⫹C⫹D⫹E

22 18 10 20 10 11 (37%) 3 0 4 2 2 18 (60%) 4 3 0 2 1 3 2 3 1 (3%) 0 0 0 1

8 9 1 10 3 2 (20%) 0 0 0 0 2 5 (50%) 0 5 0 0 0 0 0 0 3 (30%) 2 0 1 0

10 6 4 6 5 2 (20%) 1 1 0 0 0 5 (50%) 1 2 2 0 0 0 0 0 3 (30%) 0 0 3 0

10 8 2 8 1 2 (20%) 2 0 0 0 0 6 (60%) 0 5 0 0 0 1 0 0 2 (20%) 0 2 0 0

Intraaortic Balloon Pump The intraaortic balloon used was a 9.5-F, 40-mL balloon Percor STAT-DL catheter (Datascope Corp, Fairfield, NJ) connected to a Datascope pump (Datascope, Fairfield, NJ). In group 2 (preoperative IABP), a percutaneous route (common femoral artery) was used for 29 of 30 (97%) IABP catheters. Only 1 patient in this group required a surgical cut-down for placement of the IABP catheter. Patients in group 2 (T24) and group 2 (T12) had an IABP catheter inserted in the intensive care unit, using local analgesia, 24 and 12 hours preoperatively, respectively. Patients in group 2 (T2) received an IABP catheter in the operating room just before induction of anesthesia, using local analgesia. In group 1 and IABP was inserted in the operating room in cases (23 of 30, 77%) in which a cardiac index more than 2.0 L/m2 per minute could not be maintained despite pharmacologic support (dopamine at 15 ␮g/kg per minute, dobutamine at 5 to 10 ␮g/kg per minute, amrinone 0.5 mg/kg bolus dose, or a combination thereof). In group 1, percutaneous insertion of the IABP catheter was done in 20 patients, 3 patients required surgical placement (one surgical cut-down of the common femoral artery and two catheters placed through the thoracic aorta). When an IABP catheter was indicated, there were no failures in either group in placing the catheter while using a guide wire. In patients with peripheral vascular disease the percutaneous insertion technique was used initially in all cases; only if that failed was surgical cut down used. All patients received

prophylactic antibiotics and cephalosporins (cephalozolinum 1 g three times intravenously). We did not give thyroid hormones to any patients before beginning postoperative IABP. Patients who had preoperative catheter insertion received anticoagulation with intravenous heparin after IABP placement, with a target partial thromboplastin time greater than 40 seconds. Patients returning from the operating room with an IABP catheter in place were anticoagulated with calciparine after the mediastinal drainage subsided (usually within 24 hours). The IABP support was terminated once hemodynamic stability was restored (ie, a cardiac index greater than or equal to 2.0 L/m2 per minute with only minimal pharmacologic inotropic support, dopamine at 5 ␮g/kg per minute). Preoperative unstable angina in group 2 patients stabilized after preoperative IABP support and was stable at the time of operation, whereas in group 1 all patients except 2 with unstable angina (16 patients) remained unstable at the time of the operation.

Statistical Analyses The ␹2 test (Fisher’s exact test) for nominal measurements, median test and Mann-Whitney test for ordinal measurements, Student’s t test (independent) for metric measurements, and one-way analysis of variance were used to assess differences between groups and subgroups for statistical significance, where appropriate. A probability level of p less than 0.05 was required for a

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Table 3. Cardiac Index Data From High-Risk Patients Who Had Coronary Artery Bypass Graftinga Cardiac Index Before IABP Before cardiopulmonary bypass Weaning ⫹30 minutes ⫹12 hours ⫹24 hours ⫹48 hours ⫹72 hours ⫹96 hours

Group 1

p Value

Group 2

1.82 ⫾ 0.16 (30) ⬍ 0.0001 1.52 ⫾ 0.22 (30) p ⬍ 0.0001 2.69 ⫾ 0.66 1.99 ⫾ 0.54 (30) ⬍ 0.0001 3.20 ⫾ 0.70 (30) 2.58 ⫾ 0.86 (30) ⬍ 0.0001 3.52 ⫾ 0.71 (30) 2.67 ⫾ 0.76 (27) 0.0046 3.45 ⫾ 0.65 (30) 2.80 ⫾ 0.64 (27) 0.0020 3.36 ⫾ 0.58 (29) 2.67 ⫾ 0.52 (24) 0.0008 3.38 ⫾ 0.56 (29) 2.75 ⫾ 0.39 (24) ⬍ 0.0001 3.37 ⫾ 0.53 (29) 2.82 ⫾ 0.92 (21) 0.0521 3.23 ⫾ 0.73 (13)

a

Group 1 did not receive preoperative IABP treatment, and group 2 received preoperative counterpulsations. All measurements except values before CPB in group 2 patients were performed without ongoing IABP. Values are mean ⫾ standard deviation. The number of observations is given in parentheses. CPB ⫽ cardiopulmonary bypass;

IABP ⫽ intraaortic balloon pump.

result to be statistically significant. All data, whenever possible, are presented as mean ⫾ standard deviation.

Results Operative Data The average number of distal anastomoses was 4.4 ⫾ 1.3 per patient in group 1 and 4.1 ⫾ 1.4 per patient in group 2 ( p ⫽ 0.4). The average number of distal anastomoses per patient in the subgroups of group 2 was similar and did not differ statistically from those of the main groups. The internal thoracic artery was used as conduit in 70% in group 1 (21 of 30) and in 67% (20 of 30) in group 2 patients ( p ⫽ 0.39), with an even distribution between the subgroups. Coronary thrombendarterectomy was required in 15 (25%) cases, without group differences. The mean ischemia time did not differ significantly between the groups (65.5 ⫾ 22.4 [group 1], 62.9 ⫾ 22.3 [group 2],

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62.8 ⫾ 21.7 [group 2 T2], 60.0 ⫾ 23.5 [group 2 T12], and 57.8 ⫾ 13.9 minutes [group 2 T24]). In contrast the mean CPB time was significantly shorter in group 2 (83.6 ⫾ 21.7 minutes [group 2] compared with 127.3 ⫾ 45.6 minutes in group 1 patients, p ⫽ 0.001). The average CPB in the subgroups of group 2 did not differ statistically but showed a tendency toward reduced CPB time in subgroup 2 T24 (85.7 ⫾ 21.4 minutes [group 2 T2], 82.2 ⫾ 25.9 minutes [group 2 T12], and 75.9 ⫾ 15.4 minutes [group 2 T24]).

Cardiac Performance Cardiac index data are presented in Table 3 (groups 1 and 2 overall) and Table 4 (group 2 subgroups T2, T12, and T24). The average initial cardiac index values in group 2 before preoperative IABP were significantly lower compared with group 1 values (before CPB), ( p ⬍ 0.0001). In group 2, the cardiac index increased significantly after preoperative IABP treatment was started ( p ⬍ 0.0001). As expected, the cardiac index was higher after myocardial revascularization compared with the preoperative values in both groups. After weaning from CPB and until 72 hours postoperatively the average cardiac index was significantly higher in group 2 compared with group 1 (Table 3). No statistically significant differences were observed between cardiac index values of the group 2 subgroups. An initial tendency at 30 minutes and 12 hours after weaning from CPB to better cardiac indices was observed in groups 2 T12 and 2 T24 compared with group 2 T2 (Table 4). Twenty-five patients (83%) in group 1 (controls) had postoperative low cardiac output (cardiac index at least 2.0 L/m2 per minute) in contrast to only 11 patients (37%) in group 2 ( p ⬍ 0.0001). There were no differences between the subgroups T2, T12, and T24. Twenty-three (92%) of the 25 patients with low cardiac output in group 1 required postoperative IABP support in addition to maximal pharmacologic support for an average duration of 55.3 ⫾ 32.1 hours (23 to 123 hours). All patients in group 2 who had postoperative low cardiac output received immediate continuation of their IABP support

Table 4. Cardiac Index Data From High-Risk Patients Who Had Coronary Artery Bypass Grafting and Received Preoperative Intraaortic Balloon Pump Treatment of Different Duration Before Aortic Cross-Clampinga Cardiac Index Before IABP Before cardiopulmonary bypass ⫹30 minutes ⫹12 hours ⫹24 hours ⫹48 hours ⫹ 72 hours ⫹96 hours a

Group 2 T2

Group 2 T12

Group 2 T24

1.53 ⫾ 0.27 (10) p ⬍ 0.001 2.65 ⫾ 0.75 (10) 3.49 ⫾ 0.75 (10) 3.37 ⫾ 0.51 (10) 3.52 ⫾ 0.52 (10) 3.48 ⫾ 0.76 (10) 3.56 ⫾ 0.79 (10) 3.19 ⫾ 0.77 (5)

1.50 ⫾ 0.21 (10) p ⬍ 0.001 2.70 ⫾ 0.645 (10) 3.40 ⫾ 0.81 (10) 3.57 ⫾ 0.56 (10) 3.42 ⫾ 0.50 (10) 3.43 ⫾ 0.43 (20) 3.35 ⫾ 0.29 (10) 3.28 ⫾ 0.30 (6)

1.53 ⫾ 0.20 (10) p ⬍ 0.001 2.72 ⫾ 0.63 (10) 3.59 ⫾ 0.63 (10) 3.42 ⫾ 0.89 (10) 3.11 ⫾ 0.48 (9) 3.20 ⫾ 0.40 (9) 3.18 ⫾ 0.37 (9) 3.29 ⫾ 0.42 (2)

Group 2 T2 received IABP counterpulsations during 2 hours before aortic cross-clamping, group 2 T12 during 12 hours, and group 2 T24 during 24 hours before aortic cross-clamping. All measurements except values before cardiopulmonary bypass in group 2 patients were done without ongoing IABP. Values are mean ⫾ standard deviation. The number of observations is given in parentheses. No differences between groups were significant, except as noted. IABP ⫽ intraaortic balloon pump.

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Table 5. Intubation Time, Stay in Intensive Care Unit, and Total Hospital Stay for High-Risk Patients Who Had Coronary Artery Bypass Graftinga

Group Group 1 (controls) Range p Value Group 2 (preoperative IABP) Range Group 2 T2 Group 2 T12 Group 2 T24

Intubation Time (h)

Intensive Care Stay (h)

Total Hospital Stay (days)

70.1 ⫾ 64.3 32–338 0.0211 25.0 ⫾ 12.0

116.4 ⫾ 67.8 44 – 696 ⬍ 0.0001 48.4 ⫾ 29.3

17.1 ⫾ 5.7 8 –33 0.002 12.2 ⫾ 2.9

11– 49 26.8 ⫾ 13.1 26.0 ⫾ 13.3 22.7 ⫾ 10.8

24 –141 55.9 ⫾ 40.9 51.0 ⫾ 37.5 46.6 ⫾ 10.5

8 –21 11.6 ⫾ 2.6 13.6 ⫾ 3.7 12.3 ⫾ 2.9

a

There were no statistically significant differences between groups 2 T2, T12, and T24. Group 1 did not receive preoperative IABP treatment, but group 2 received preoperative counterpulsations. Group 2 T2 received IABP counterpulsations during 2 hours before aortic cross-clamping, group 2 T12 during 12 hours, and group 2 T24 during 24 hours before aortic cross-clamping. Values are mean ⫾ standard deviation. IABP ⫽ intraaortic balloon pump.

postoperatively. In contrast to group 1, patients in group 2 could have their IABP successfully removed after 19.7 ⫾ 12.3 hours postoperatively (range, 4 to 42 hours, p ⫽ 0.0002). There were no subgroup differences in group 2.

Hospital Mortality and Morbidity In the control group (group 1), six deaths occurred (20%). All 6 patients had received maximal pharmacologic support and postoperative IABP. The cause of death was low cardiac output due to global ventricular dysfunction in 4 patients, right ventricular dysfunction in 1, and left ventricular dysfunction in 1 patient. Four of the patients developed multiple organ failure. The only death that occurred in group 2 was due to a left ventricular dysfunction after postoperative hemorrhage caused by hypocoagulation from nonsurgical bleeding. Except for postoperative low cardiac output, other major postoperative complications were few and evenly distributed between the groups. However, the average intubation time, as well as the average stay in intensive care unit and total hospital stay, was significantly shorter in group 2 (Table 5).

Complications There were no IABP-related deaths in either group. Complications related to IABP occurred in 5 of 60 patients in the entire series, thus resulting in an 8.3% complication rate, without group differences. The complications were limb ischemia in all cases. No infections or hemorrhage occurred. None of the complications occurred preoperatively in group 2. Time when complications were diagnosed, treatment, and outcome are presented in Table 6.

Comment In high-risk coronary patients, difficulties in weaning from CPB because of severely disturbed cardiac performance postoperatively is known to be associated with a high postoperative mortality rate [1, 3, 10]. Despite massive pharmacologic support combined with postoperative IABP support, mortality and morbidity rates remain high [2, 3, 6, 11]. These data were confirmed in this prospective randomized study. Group 1 patients (controls) had an overall hospital mortality rate of 20% (6 of 30) and if specifically looking at patients who presented with low cardiac output postoperatively in this group of patients, the mortality rate was 24% (6 of 25). One explanation for this high mortality rate is that the studied group contained numerous patients who had salvage operations. Indications for preoperative IABP treatment before myocardial revascularization include patients presenting with at least two of the high-risk criteria described previously. Most patients presented with three or more high-risk criteria (Table 2). In the cohort of high-risk coronary patients not receiving preoperative IABP (group 1), 83% (25 of 30) presented with low cardiac output postoperatively, and 23 of 25 patients (92%) required postoperative insertion of an IABP in addition to massive pharmacologic support. In patients who had an IABP inserted postoperatively, the treatment was required for a substantially longer time, which not only increases the total procedural cost (by prolonged stay in the intensive care unit and massive pharmacologic support) but also could increase the risk of IABP-related complications. It is therefore justified to propose preoperative IABP treatment in high-risk patients. However, preoperative IABP treatment should be reserved for a selected group of high-risk patients because it is associated with documented complications. In the

Table 6. Complications Related to Intraaortic Balloon Pump Group

Time (h)

1 1 1

48 26 6

2 T2

14

2 T12

4

Type

Treatment

Leg ischemia, intimal dissection Leg ischemia Leg ischemia, misplacement of catheter, superficial femoral artery Leg ischemia, acute compartment syndrome Leg ischemia

Removal of catheter, interposition graft Removal of catheter, thrombectomy Removal of catheter, intraaortic balloon pump insertion in common femoral artery contralateral side Removal of catheter, thrombectomy, fasciotomy Removal of catheter

Outcome No ischemia No ischemia No ischemia

No ischemia, mild peroneal palsy No ischemia

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present study there were no IABP-related deaths, but vascular complications occurred in 8.3% (5 patients), without group differences, which corresponds with results of earlier reports [6, 10, 11, 16]. Our relatively low IABP complication rate, without major sequels, may be due to our experience using IABP, short insertion times, particularly in the preoperatively treated group of patients, and close surveillance of the peripheral circulation with special emphasis on early signs of acute ischemia or acute compartment syndrome. In our practice we do not routinely perform angiography of the peripheral circulation in high-risk patients, mainly because of the risk of contrast overload, as well as higher cost. Angiography of the peripheral circulation is advocated only in patients with symptoms and signs of significant peripheral vascular impairment. The study groups and subgroups were all comparable with regard to preoperative patient characteristics, angiography, and operative data, except that group 2 patients had a significantly shorter CPB time ( p ⫽ 0.001), indicating less difficulty in weaning from CPB as an result of better cardiac performance. As previously documented, and confirmed by the present study, preoperative IABP treatment results in improved cardiac index, resulting in a less ischemic or often a nonischemic myocardium at the time of aortic crossclamping [14], which is likely the most accurate explanation for the postoperative benefits. Furthermore, preoperative IABP treatment in high-risk patients has been found to be highly cost-effective [11, 14]. However, the most beneficial timing for introducing preoperative IABP treatment in high-risk coronary patients has not been established previously. We determined the optimal timing for preoperative IABP treatment on preoperative and postoperative cardiac performance (cardiac index measurements), hospital mortality rate, postoperative morbidity, as well as required stay in intensive care unit and total length of hospital stay in high-risk patients who had CABG. Group 2 T24 and T12 had the IABP inserted in the intensive care unit and received IABP treatment 24 and 12 hours, respectively, before aortic cross-clamping, whereas group 2 T2 received the IABP in the operating suite and received 2 hours of preoperative IABP treatment before cross-clamping. There were no differences in preoperative patient characteristics or angiographic data among the three subgroups. Operative data were without statistically significant group differences. The average CPB time in the group 2 subgroups did not differ statistically, but there was a tendency toward shorter CPB time in group 2 T24. An initial tendency to better cardiac indices was observed in groups 2 T12 and 2 T24 compared with group 2 T2 at 30 minutes and 12 hours after weaning from CPB, but there were no significant differences. After 24 hours postoperatively, cardiac indices from all groups were directly comparable. These findings confirm a previous report suggesting that longer preoperative IABP treatment further improve cardiac performance [6]. However, all other study endpoints, such as hospital mortality rate, postoperative morbidity rate, intubation time, required stay in intensive care unit postoperatively and total hospital stay did not differ between the subgroups.

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Despite the small number of patients in each subgroup, only 2 hours of preoperative IABP therapy were necessary to produce the benefits in a cohort of high-risk patients who had CABG. This timing for preoperative IABP therapy allows insertion of the IABP catheter in the operating room and does not require additional stay in intensive care unit, but achieves the same end results as longer treatment periods. We are grateful to the perfusionist Jaenine Reuse.

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