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Ann Thorac Surg 2006;81:1243-1248
© 2006 The Society of Thoracic Surgeons
a Dalhousie University, Halifax, Nova Scotia, Canada
b Papworth Hospital, Cambridge
c Dendrite Clinical Systems, Reading, United Kingdom
d University College, London (on behalf of the Society of Cardiothoracic Surgeons of Great Britain & Ireland), United Kingdom
Accepted for publication December 1, 2005.
* Address correspondence to Dr Baskett, Room 2269, 1796 Summer St, Halifax, Nova Scotia, Canada, B3H 3A7 (Email: rogerbaskett{at}hotmail.com).
| Abstract |
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METHODS: A total of 71,470 CABG patients (19922001) in 27 centers in the United Kingdom were studied. The proportion of patients with arterial revascularization was compared. In-hospital mortality was compared for various grafting strategies: all-arterial (n = 5,401), all non-all-arterial patients (n = 66,069), one artery any number of veins (n = 49,801). The groups were compared for in-hospital mortality using multivariate logistic regression to assess the independent effect of the grafting strategies on mortality; logistic EuroSCORE-predicted mortality was compared to actual mortality, and all arterial and one artery and veins patients were compared with propensity score analysis.
RESULTS: There was a significant increase in the proportion of all-arterial patients over time (3.2% to 11.7%, p< 0.001) with evidence of variability across centers. Crude mortality for all-arterial patients was 2% vs 3% for all non-all-arterial patients (p < 0.001). In multivariate analysis, all-arterial was associated with a slight but insignificant increase in in-hospital mortality (odds ratio [OR] 1.13; [95% confidence interval {CI} 0.861.48], p = 0.36). There was a trend toward higher mortality in the all-arterial group when compared with the one artery and veins group (OR 1.19 [95% CI 0.911.56], p = 0.10). The one artery and veins group was the only group where actual mortality was significantly lower than predicted by EuroSCORE (p < 0.001). In propensity analysis the mortality was 1.51% for one artery and veins and 1.74% of all-arterial patients (p = 0.56).
CONCLUSIONS: The use of arterial grafting has increased over time, varies by center, and appears to be safe in terms of in-hospital mortality.
| Introduction |
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However, concern has been raised about the immediate safety of total arterial grafting and its widespread applicability [13, 14]. Few studies have compared complete arterial revascularization with conventional LIMA and venous conduits (the standard operation in most centers), and none have been multicentered studies [14, 15]. The results are inconclusive and there is little knowledge about the use and safety of total arterial revascularization in general cardiac surgical practice.
The objectives of this study were to examine the trend in the use of total arterial revascularization over time in a large contemporary CABG database. In addition, the safety (in terms of in-hospital mortality) of this grafting strategy was compared with conventional single artery and venous grafting, as well as other combinations of arterial and venous grafting, in a multicenter database.
| Material and Methods |
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Patients with single CABG (n = 4,195) or with inadequate detail of procedural data (n = 21,626) were excluded. An examination of those with and without adequate procedural data found no significant differences in risk factors or mortality. Thus this analysis is of 71,470 isolated CABG cases with two grafts or more. In-hospital mortality was compared for the different grafting strategies: all-arterial (AA, n = 5,401), all non-AA patients (AxV, n = 66,069) and this group was further subdivided based on the number of arterial grafts used (1 artery and veins (A1V), 2 arteries and veins (A2V), 3 arteries and veins (A3V), and veins only (VV). All-arterial use was compared across centers and over time using the
2 test. All analyses were performed with S-Plus statistical software (Insightful Corp, Hampshire, UK). Odds ratios (OR) reported are adjusted for all other covariates plus or minus the 95% confidence intervals (95% CI).
To investigate the safety of AA, the data were analyzed in four different ways.
2 test (or linear-by-linear association for categoric variables) and t tests for continuous variables. Logistic regression analysis [17] was used to assess the independent effect of the different grafting strategies on in-hospital mortality. These are expressed as OR ± 95% CI. In addition, expected mortality was calculated from the logistic regression model for in-hospital mortality and presented as observed to expected mortality ratios.
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| Results |
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Risk Profile
The lowest risk profile was in patients with more than one arterial graft who were younger, who had fewer comorbidities, and who had fewer urgent and emergency operations. The highest risk profile was in the VV group (Table 1).
Risk-Adjusted Mortality
Logistic EuroSCORE was calculated for the different grafting strategies. The VV group had a significantly worse than predicted mortality (Table 2). Both the AA and the A1V groups had results that were better than predicted by EuroSCORE, although only in the A1V group did this difference reach statistical significance (Table 2).
In our logistic regression analysis the VV group also had a significantly higher mortality than the reference A1V group (Table 3). The AA group had a slight but nonsignificant increased risk of death compared with the A1V group (Tables 2 and 3).
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| Comment |
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We have demonstrated in a large contemporary multicenter database that the use of complete arterial revascularization has increased dramatically over time, but appears to vary substantially by center. The crude mortality for patients undergoing complete arterial revascularization was 2.04%, similar to previous single-center series, which range from 0.2% to 3.0% [6, 1012, 14, 21]. After adjusting for patient profile differences among the various grafting strategies, there was no significant difference in in-hospital. The absolute difference is very small (0.23%) in the propensity analysis, and would require groups of nearly 50,000 propensity-matched patients for this to reach statistical significance.
There are theoretical reasons for a possible increased mortality with arterial grafts. All-arterial grafting is technically more demanding and there is undoubtedly a learning curve for the procedure [13, 14, 23]. Patients with critical proximal lesions may be at some early risk if the arterial conduits used do not "deliver" immediately due to small size or liability to vasospasm. In addition, selection of patients for this grafting strategy and differences in perioperative management are yet to be completely elucidated [3, 14, 23].
Looking at the various grafting strategies, the patients grafted with only venous conduits had a significantly higher observed and predicted mortality than all the other groups. This may be related more to risk profile than the choice of conduit, as this group often contains salvage procedures and multiple comorbidities, which may either prohibit or be perceived to prohibit the harvest of arterial conduits. The all-arterial and the single artery and vein graft patients had lower than predicted mortalities, but only the A1V group did significantly better than EuroSCORE, emphasizing the remarkable safety record of the "standard" operation. Patients who received a mix of two or three arterial grafts and veins were quite similar to the all-arterial graft patients, yet had higher than predicted mortality. Some of these patients may have had attempted complete arterial grafting and subsequently required adjuvant vein grafts due to perioperative complications, or arteries were used due to lack of adequate venous conduit.
There is relatively scant previous work comparing all-arterial grafting with conventional single artery and venous grafts. In a small single-center series Legare and colleagues [14] found increased morbidity but not mortality with complete arterial grafting. Three small single-center randomized trials (from the same center) have recently compared complete arterial grafting with single artery and venous grafting. All three studies demonstrated no difference in in-hospital mortality but significantly better freedom from angina and the need for PCI at 12 months in the all-arterial group [15, 24]. Despite this, total arterial grafting has not become the universal standard. This is perhaps because of the relatively small body of evidence supporting its long-term superiority, together with recent work suggesting that the intermediate outcome with vein grafts may in fact be much better in the current era [25]. In addition the procedure is more complex and takes longer to perform. In fact, previous studies have noted a poor uptake of arterial grafting which is likely due to a perceived higher morbidity and mortality as well as a lack of definitive evidence of benefit [22].
Limitations
There are a number of important weaknesses in this study. The database is voluntary and there is no formal validation process, although a recent study using the STS registry found that unaudited databases can be highly accurate [26]. We were only able to look at in-hospital mortality and not morbidity, which may be significantly higher in the all-arterial patients [14]. The use of complete arterial revascularization is correlated with center and a year, and not all centers contributed consistently for all the years of the study. In addition, surgeon specific detail was not available; clearly some centers (and surgeons) are much more committed to arterial grafting than others. Furthermore this is a fairly low-risk group of patients. Therefore we cannot comment on the outcomes in higher risk patients. This low-risk group of all-arterial patients may in fact reflect good judgment by the surgeons as they attempt to master a new technique.
In addition, the AA patients and the conventional A1V patients were quite different in terms of number of distal grafts and the proportion of cases that were redo cases (Table 4). This may indicate that some AA patients had complete arterial revascularization because of venous conduit unavailability rather than a desire on the part of the surgeon to undertake such a strategy for its supposed benefits. Using propensity analysis, we were able to adjust for the differences in center, year, proportion of redo cases, and number of distal grafts, and the results were consistent with the other analyses. Unfortunately we did not have the level of procedural detail to identify which grafts were placed to which vessels and about the extent of coronary disease, although the number of distal anastomoses performed is probably a reasonable surrogate for extent of disease.
In summary, the present study demonstrates an apparent increasing interest in the use of complete arterial grafting in CABG surgery in the United Kingdom. However, there is great variation across centers and likely between individual surgeons. Despite the purported benefits of complete arterial revascularization, its overall use by surgeons in the United Kingdom remains very low. This method of revascularization is safe in terms of in-hospital mortality in low-risk patients. Further study is needed to examine differences in in-hospital morbidity and long-term results in comparison with the more prevalent standard grafting strategy of single artery and veins.
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