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Ann Thorac Surg 2002;74:1086-1090
© 2002 The Society of Thoracic Surgeons
a Department of Cardiovascular Surgery, University Hospital, Geneva, Switzerland
b Hahnemann Medical Center, Philadelphia, Pennsylvania, USA
c Texas Heart Institute, Houston, Texas, USA
d Tulane Medical Center, New Orleans, Louisiana, USA
e M. F. Miller Statistical Services, Langhorne, Pennsylvania, USA
f University of North Carolina, Chapel Hill, North Carolina, USA
g State University of New York Health Center, Brooklyn, New York, USA
h The Cardiovascular Research Foundation, New York, New York, USA
i Hôpital de la Tour, Geneva, Switzerland
Accepted for publication June 5, 2002.
* Address reprint requests to Dr Christenson, Clinic for Cardiovascular Surgery, University Hospital, 24 rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland
e-mail: jtchristenson{at}hotmail.com
| Abstract |
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Methods. This report describes IABC use in cardiac surgery, examines trends in complications over time, and compares outcomes in preoperative versus postoperative use in a single prospective worldwide registry over the past 3 years.
Results. The frequency of IABC use appears to be increasing with time as the complication rates have dramatically fallen. The overall IABC-related complication rate was 6.5% (460/7,101), and the rate of major complications (requiring surgery or transfusion) was 2.1% (148/7,101). Hospital mortality was significantly lower in patients treated preoperatively with IABC compared with patients treated postoperatively (8.8% vs 28.2%, p < 0.0001), although this may be due to a selection bias in the postoperative group.
Conclusions. Preoperative IABC therapy leads to better patient outcomes in high-risk CABG patients. Improved IABC technology and better surveillance have led to increased use with lower complication rates. Although selection bias is inherent in retrospective studies, the Benchmark Counterpulsation Outcomes Registry outcomes are in close concordance to prospective randomized studies previously reported.
| Introduction |
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This report describes IABC use in cardiac surgery, examines trends in complications over time, and compares outcomes in preoperative versus postoperative IABC use in a unique voluntary single worldwide registry (Benchmark Counterpulsation Outcomes Registry) [19] over the past 3 years. Registry data were also compared with data from The Society of Thoracic Surgeons (STS) National Database, another large voluntary data base.
| Material and methods |
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The society of thoracic surgeons national database
After receiving written permission from The Society of Thoracic Surgeons (STS) National Database, data sets from the STS Adult Cardiac National Database were harvested from the years 1996 and 1997. The STS National Database had more than 500 participating sites and more than 1.5 million cumulative procedures registered in 1998. The following data were extracted: distribution of IABC use in relation to various cardiac surgery procedures and estimated vascular complications from incidence of complication summary, including vascular/aortic dissection, iliac/femoral dissection, and acute limb ischemia. These data probably represent an overestimation of vascular complications in relation to IABC use, as not all vascular complications that occur in relation to cardiac surgery are related to IABC. Furthermore, data regarding preoperative and intrapostoperative IABC use were analyzed, and mortality was calculated for each subset by univariate analysis using preoperative IABC and intrapostoperative IABC as risk variables.
Definitions
All-cause hospital mortality was defined as mortality occurring from any cause during IABC or after IABC. Preoperative IABC is preoperative insertion of the intraaortic balloon catheter and the start of IABC before aortic crossclamping in high-risk coronary patients. Intra/postoperative IABC was defined by intraoperative catheter insertion and the start of IABC, due to difficulties weaning the patient from cardiopulmonary bypass once surgery was terminated, or by IABC start during the recovery phase due to postcardiotomy failure.
We defined IABC-related complications as follows: the overall complication rate includes all reported complicationsvascular complications (limb ischemia, limb loss, arterial dissection, and vessel perforation), hemorrhage (balloon insertion site bleeding), infection, and septic complications (verified by positive cultures), balloon entrapment and rupture, and secondary complications related to malpositioning of the balloon catheter itself. Major complications were defined by any complication requiring surgical intervention or blood transfusion, or left permanent sequel. For example, major limb ischemia was defined as a loss of pulse or sensation, or abnormal limb temperature or pallor, requiring surgical intervention. Minor limb ischemia was defined as decreased arterial blood flow as manifested by diminishing pulse that resolves with balloon removal, and not resulting in any impairment of body function. Major bleeding was defined as bleeding that occurred in direct relation to the balloon catheter (perforation of artery or insertion site bleeding), associated with hemodynamic compromise that required blood transfusion or surgical intervention. Minor hemorrhage involved minor hematomas or oozing from puncture site, and did not require blood transfusion or surgical intervention.
High-risk coronary patients were defined as patients who present with at least two of the following preoperative criteria: left ventricular ejection fraction less than 0.30, left main stenosis greater than 70%, unstable angina at the time of surgery despite optimal medical treatment, diffuse coronary artery disease requiring four or more distal anastomosis to achieve complete revascularization, or reoperations or re-reoperations (ie, second, third, or fourth reoperation) [10].
Statistical analysis
We employed the
2 test (Fishers exact test) for nominal measurements, the median or Mann-Whitney tests for ordinal measurements, and an independent group Students t test for metric measurements to assess the differences among groups and subgroups and determine the presence of statistical significance where appropriate. A level of p less than 0.05 was required to consider a result statistically significant. Wherever possible, all data were presented as mean ± standard deviation.
| Results |
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IABC-related complications
The overall reported IABC-related complication rates from different time intervals, using similar definitions and large study populations showed a trend to diminish, mainly due to fewer major vascular complications (Table 1).
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Complications: preoperative versus postoperative IABC in high-risk coronary patients
A more detailed analysis of the Benchmark registry data showed that any kind of limb ischemia related to IABC use (minor as well as major) was significantly higher in the intrapostoperative IABC group compared with the preoperative IABC therapy group (4.5% and 2.6% respectively, p = 0.028). Also, major limb ischemia (ie, requiring surgical intervention) had a significantly higher incidence for intrapostoperative IABC treatment (1.8%) than for preoperative IABC therapy (0.8%; p = 0.012). However, there was no evidence that the overall complication rate was lower or higher in the preoperative IABC group.
Preoperative IABC took a median of 4 hours less of IABC treatment time compared with postoperative IABC. This was not a statistically significant difference at the 0.05 level, but showed a clear trend. However, least-square sums statistics showed p = 0.0089 on the hypothesis that mean 1 was equal to mean 2. In high-risk patients, on the other hand, there was a significantly shorter IABC therapy time for preoperative IABC (n = 1,247) compared to postoperative IABC (n = 1,370; 41.0 ± 32.0 hours and 50.1 ± 48.5 hours, respectively; p = 0.0293).
Hospital mortality
Table 4
presents hospital mortality rates, used as the outcome variable, for patients undergoing various types of cardiac surgical procedures and who either received preoperative IABC therapy or intrapostoperative IABC treatment. In the Benchmark Registry and the STS National Database, hospital mortality was significantly lower when preoperative IABC therapy was initiated (8.8% and 9.5%, respectively) compared with when IABC was introduced as intrapostoperative treatment (28.2% and 23.6%, p < 0.0001). Still, mortality rates were clearly higher in the preoperative IABC therapy patients than in patients where the variable IABC was not present (2.5 to 2.9%; STS National Database) (Table 4).
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Compiled data regarding IABC-related complications may be skewed and may not show the true picture. However, by comparing data from two major large registries, we demonstrate that recently published data correspond well with registry data, both from the most important cardiac surgery registry (the STS National Database) and a more specific global registry (the Benchmark Counterpulsation Outcomes Registry). The concordance between these two registries is striking.
Importantly, major complications (requiring surgical intervention or blood transfusion for access site bleeding) continued to decrease over time. Improved balloon catheters, smaller catheters, better education and surveillance of patients treated with IABC, increased use, and more experience may be factors to explain this trend. Early detection and adequate reaction to limb ischemia in IABC treatment ultimately results in fewer severe complications and lowered risk of limb loss.
The Benchmark registry demonstrated that both preoperative and intra/postoperative IABC therapy were associated with low complication rates. In fact, major limb ischemia was significantly lower for preoperative IABC therapy, most likely due to the shorter treatment times. This was an important finding because it helps to alleviate concerns about high complication rates previously suggested in relation to prophylactic IABC use. Moreover, preoperative IABC therapy was associated with low mortality rates, despite the high-risk status of most of these patients, which corresponds with findings from earlier studies [6, 11, 19].
Holman and coworkers [7] recently reported that preoperative IABC was beneficial, but they did not show survival advantage over intra/postoperative IABC use. Fasseas and colleagues [14], on the other hand, reported on Benchmark registry patients with left main coronary disease and found decreased mortality with prophylactic IABC use. Data from the Benchmark registry and the STS National Database also clearly demonstrate survival benefits for the preoperative IABC group; however, this may be due to a selection bias in the intra/post operative group. These results also find support in numerous retrospective and prospective studies [1, 6, 9, 11, 21].
As the number of high-risk coronary patients admitted for cardiac surgery has increased, IABC use has also increased at many cardiac centers, particularly for preoperative IABC therapy [68, 21, 22]. For example, Creswell and coworkers [1] reported an increase in IABC use from 6.4% in 1986 to 12.7% in 1990. However, as reported by Ghali and associates [22], great variations in IABC use between centers in the United States exists, with rates varying from 7.8% to 20.8% (on average 13.4%). Regional and global variations in the use of IABC are also described, such as the comparison of the IABC use in the United States with Europe [23].
There are many reasons for the large variations in IABC use. These include the fact that controversy persists about indications for IABC use, and that the use of IABC is regarded and registered as a complication rather than a therapy. Certainly, economic factors may also play an important role in the decision-making process of using IABC, although recent studies have clearly demonstrated that IABC therapy is cost-effective [6, 10]. In addition, prospective users have been deterred from initiating IABC by numerous reports in the literature of a high incidence of balloon-related complications. Various complications have been reported in relation to the use of IABC, such as vascular complications (limb ischemia and limb loss, acute vascular dissection, embolization), bleeding complications from the insertion site, infection and septic complications, and neurologic complications [20].
In the present study, better patient outcomes along with improved IABC technology led to increased use and lower complication rates. Recent registry data demonstrates that preoperative IABC therapy is associated with increases in survival. Although selection bias is inherent in retrospective studies, the Benchmark Registry outcomes are in close accordance with prospective randomized studies previously reported.
Study limitations
The information presented in this study is observational only. In addition, data from the Benchmark Registry and the STS database are not necessarily comparable because of slightly varying patient demographics and indications. There may also be a selection bias for patients treated intra/postoperatively.
The present study has, based on data from a large patient population over a short time span, clearly demonstrated a low complication rate related to IABC usage in cardiac surgery. Particularly encouraging is the seemingly lower complication rate in patients when IABC was used as prophylactic therapy.
| Acknowledgments |
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| Footnotes |
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| References |
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