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Ann Thorac Surg 2007;84:25-31
© 2007 The Society of Thoracic Surgeons
a Division of Cardiovascular Surgery, St. Vincent Mercy Medical Center, Toledo, Ohio
b Division of Cardiovascular Surgery, St. Luke’s Hospital, Maumee, Ohio
c Department of Surgery, University of Toledo, College of Medicine, Toledo, Ohio
d Department of Medicine, University of Toledo, College of Medicine, Toledo, Ohio
Accepted for publication February 20, 2007.
* Address correspondence to Dr Habib, Cardiopulmonary Research, St. Vincent Mercy Medical Center, 2213 Cherry Street, ACC Bldg, Suite 309, Toledo, OH 43608 (Email: robert_habib{at}mhsnr.org).
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Abstract |
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Methods: We reviewed our experience in 288 CABG/CE patients (63 ± 10 years, 207 men). A total of 1,056 grafts (275 internal thoracic artery [ITA] [26%]; 221 radial [21%], 560 vein [53%]) were constructed including 325 (31%) placed to CE targets.
Results: Eighteen of 288 patients died in-hospital (6.3%). Unadjusted one-year and five-year survival for the 270 discharged patients was 95.2% and 83.0%, respectively. Survival (0 to 7 years) was significantly better for patients with radial (n = 154) versus no-radial (n = 134) artery grafting (p = 0.021). Multivariate Cox regression analysis associated increased number of arterial grafts (hazard ratio [HR] = 0.64 [0.44 to 0.92]; HR [95% confidence interval]) to improved survival, while RCA endarterectomy (HR = 1.8 1.0 3.3; p = 0.054) was associated with worse survival. Repeat angiography (495 days [median]) in 68 patients encompassed 78 CE (38 vein, 24 ITA, and 16 radial) and 162 non-CE (84 vein, 40 ITA, and 38 radial) grafts. Graft failure was similar (p = 0.37) for radial (10 of 54 [19%]) and ITA (7 of 64 [11%]), and worst for vein (50 of 122 [41%]; p < 0.001). For CE targets, graft failure was worse for vein (55% vs 35%; p = 0.05) and unchanged for arterial (13% vs 15%; p = 0.88) grafts.
Conclusions: Combined CABG/CE is associated with good long-term outcomes. Increased arterial grafting achieved by radial artery utilization confers a survival benefit in this high-risk population. The latter is probably derived from superior radial versus vein graft patency.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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Paralleling recent advances in percutaneous coronary interventions (PCI), the current CABG population has seen an increased preponderance of severe diffuse coronary atherosclerosis. Conventional grafting techniques are often not sufficient for complete myocardial reconstruction, a recognized predictor of short-term and long-term outcomes [4, 5]. Because of this PCI-induced shift in the coronary disease profile of CABG patients, there is renewed interest in adjunct techniques to facilitate more complete revascularization such as CE and transmyocardial revascularization [6].
Recently, investigators have reported good-to-excellent perioperative and long-term CABG/CE outcomes, with evidence of varying results depending on the coronary vessel requiring endarterectomy [7–10]. However, these distinctly better outcomes may be related to the contemporaneous shift in grafting conduit choice. Specifically, CABG experienced a parallel transition from an early practice of near-exclusive vein grafting to the current practice of one or more arterial conduits with the left internal thoracic artery (LITA) to the left anterior descending artery (LITA-LAD) pedicle graft as a cornerstone [11, 12]. Presently, there is a paucity of data addressing the possible role of increased use of arterial grafts in CABG/CE outcomes and, in particular, the effects of it on late survival and patency of grafts placed to endarterectomized vessels.
We hypothesized that better outcomes achieved in recent CABG/CE series are in substantial part explained by a contemporaneous increase in arterial grafting. Accordingly, the aim of this study was to determine the efficacy of aggressive utilization of the radial artery as a second arterial conduit, in addition to ITA, as opposed to vein grafting in patients undergoing CABG/CE surgery.
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Patients and Methods |
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Coronary Endarterectomy (CE)
Vessels chosen for CE were 1.5 mm or greater external lumen and always supplied viable myocardium. Utilized CE techniques were similar to those described by Mills [13]. Endarterectomy was performed on vessels with multiple discrete high-grade lesions and with short, intervening nondiseased segments, making runoff of these graftable blind segments suboptimal and thus potentially compromising long-term graft durability. Alternatively, vessels with diffuse calcific atherosclerosis along a significant portion of the epicardial vessel lumen resulting in minimal internal lumen (<1 mm diameter) were also endarterectomized. All grafts not documenting the typical biphasic flow were revised. In 16 patients, the target vessel could not be reconstructed, due to inherent fragility of the vessel wall. In this situation, the target vessel was ligated. Generally, radial artery grafts were preferentially used to targets with high-grade stenosis (>75%) to minimize the risk of failure due to competitive flow.
All patients received postoperative aspirin initiated on intensive care unit (ICU) arrival, and were given heparin, 5,000 units subcutaneous twice a day or three times a day, starting on postoperative day 1 until discharge. Starting in the late 1990s, in an attempt to optimize graft patency, CABG/CE patients were started postoperatively on warfarin for six weeks with a target international normalized ratio of 2.5 to 3.0. More recently, six to eight weeks of clopidogrel was substituted for warfarin as follows: (1) patients who are on preoperative clopidogrel, a 75 mg daily dose was reinstituted on postoperative day 1 (POD 1); or (2) patients who are not on preoperative clopidogrel, 150 mg was given on arrival in the ICU through the nasogastric tube, and a 75 mg clopidogrel dose was started on POD 1.
Data Collection and Analysis
Collected clinical data included demographics, risk factors and comorbidities, preoperative medications, and operative data, as well as postoperative complications and outcomes. All entries were based on the Society of Thoracic Surgeons (STS) definitions. Patient survival data were secured from our service patient follow-up and verified from individual patient queries of the United States Social Security Death Index database (http://ssdi.genealogy.rootsweb.com) in April 2005. Allowing for a three-month lag in this database, this corresponds to a minimum of 13 (12/2003) and a maximum of 109 (1/96) months follow-up.
Graft Patency
Post-CABG coronary recatheterization data were obtained from multiple sources including cardiac surgery and cardiac catheterization databases. Angiography reports were reviewed and the relevant data entered into a dedicated database. For this study, a coronary graft was considered to be an anastomotic failure (or nonpatent) in case of the following: (1) complete or 100% occlusion; (2) stenosis of 75% or greater; or (3) if extensive conduit narrowing or "string sign" was present. Angiography data for restudied symptomatic patients only are presented in two forms. First, graft failure frequencies for the various coronary targets are contrasted for (1) CE versus non-CE targets, and (2) in terms of conduit type (arterial versus vein grafts). Second, Kaplan-Meier graft survival was estimated where grafts found to be patent are censored out of the analysis at time of last repeat angiography.
Statistical Methods
Continuous data were expressed as mean ± SD unless otherwise stated. Univariate comparisons were done with the 
2 or Fisher exact test for categoric variables and the unpaired t test for continuous variables. Kaplan-Meier plots were determined for survival (alive), catheterization free survival, and revascularization free survival and compared by the log-rank test. We determined the effects of explanatory variables on survival by multivariate Cox proportional hazard analysis. Given the near-universal LITA use and the variance in number of arterial grafts (
5), we modeled arterial grafting by a single numerical variable (number of arterial grafts). The increase in arterial grafts is primarily determined by the number of radial grafts but also incorporates the infrequent use of right ITA grafts. The number of radial grafts ranged between 0 and 4. Model selection was first done with backward elimination (Wald statistic), and variables significant at a p less than 0.1 level were retained in the model as predictors and confirmed using forward and stepwise selection (SPSS version 13.0 software; SPSS Inc, Chicago, IL).
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Results |
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Patient Outcomes: Perioperative Morbidity and Mortality
Selected postoperative data are summarized in Table 2. Briefly, the observed complication rates were commensurate with the high-risk characteristics of this population. Patients with multiple CE showed a significantly greater risk of myocardial infarction (MI; electrocardiogram changes; p < 0.05) that coincided with relatively greater postoperative creatinine kinase-myocardial band (CK-MB; [mean, 63 v 45 ng/mL, p = 0.07]). In-hospital mortality occurred in a total of 18 patients (6.25%) with a median age of 67 years. Of these, a disproportionate number followed repeat-CABG (6 of 26; 23.1%) versus first-time CABG (12 of 262; 4.58%) (p < 0.001). The LAD endarterectomy patients tended to less in-hospital mortality (3 of 95 [3.2%]; p < 0.1). In-hospital mortality for RCA (8.5%), posterior descending artery (PDA; 8.2%), and CX (5.4%) did not differ.
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Figure 1A shows the 0 to 84 months Kaplan-Meier death-free (alive), revascularization-free, and recatheterization-free survival estimates for the 270 patients discharged alive. These estimates, respectively, were 95.2%, 92.6%, and 85.5% at one year and 83.0%, 73.4%, and 59.9% at five years after CABG/CE. The unadjusted survival was significantly better for radial versus no-radial (p = 0.021; Fig 1B). Survival was similar whether patients underwent single or multiple endarterectomies (p = 0.84; data not shown). Unadjusted survival was worse in the RCA endarterectomy subcohort but was not significant (p = 0.12).
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0.35) was added as a predictor of late death. Here too, RCA-CE was associated with borderline worse survival (hazard ratio [HR] = 1.98; p = 0.066). Also, an increasing number of arterial grafts, achieved primarily by radial grafting, was associated with relatively greater survival benefit (HR = 0.55; p = 0.003).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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Investigators have reported that increased use of arterial grafts for CABG is associated with improved long-term outcomes, and have explained their findings by greater arterial graft patency [eg, 11, 12]. Good early and late CABG/CE outcomes with endarterectomy performed in one or more of the three main coronary beds have been reported [7–10] but, to date, no studies have investigated the potential varying efficacy of utilizing arterial versus vein conduits for grafting endarterectomized coronaries. More specifically, we have found no studies comparing the long-term results of radial versus vein grafting in CABG/CE patients in the setting of high ITA utilization. Predicated on our previous report of superior CABG with LITA-LAD outcomes (including graft patency) with radial compared with vein grafts, we hypothesized that, just as in nonendarterectomy CABG patients, radial patency would be superior to vein with potential impact on survival.
In our study, CABG/CE patients represented 5.9% of the isolated CABG population, an experience in line with the 2% to 22% CE rate reported by others [7–10]. The CABG/CE patients were characterized by a distinctly higher risk profile (Table 1), and their in-hospital mortality rate of 6.3% was within the 2% to 8.6% range reported in recent series [7–10]. Note, a disproportionate number of these early deaths occurred in reoperations (6 of 26; 23%). Although a small number of reoperative CABG/CE, given our experience we advise caution in case of reoperative CABG when a high likelihood of CE requirement for revascularization is suspected. We support either a nonoperative approach or consideration of transmyocardial revascularization. Hospital deaths in primary CABG/CE (12 of 262; 4.6%) closely approximated the 4.55% STS-predicted mortality in those same patients. This is perhaps a favorable result because the STS model does not include a specific factor to reflect the advanced nature of the coronary atherosclerosis encountered in CE patients, and hence will underestimate true CABG risk.
Overall, perioperative MI was relatively infrequent (3.5%) and fell within the 2% to 6% range reported by others [7–10]. But this incidence of MI rose to 9.1% in the subset CABG/CE patients who required multiple endarterectomies. Also, the rate of MI was highest in patients with CE performed in the LAD territory (5.3%) and lowest in those with CE in the PDA territory (1.2%). Interestingly, this trend is opposite the acute mortality data. A potential explanation for this trend is the reliance on the "traction technique," with incomplete extraction of plaque from the diagonal and septal perforators in patients who required a LAD endarterectomy. Such incomplete extraction may predispose to acute closure of these small branches that increases the risk of ischemia despite patency of the primary target vessel.
The long-term results in this CABG/CE patient series were gratifying, both from a survival and a graft patency perspective. The five-year Kaplan-Meier survival for the 270 discharged patients was 83% (Fig 1), and 77.5% when in-hospital deaths are included. Survival in discharged patients tended to be best in the LAD-CE subcohort (87%) and worst in RCA-CE (76%) patients. These results compare favorably with the results reported by others. Shapira and colleagues [7], in 151 patients, reported a five-year survival of 70% (including 2% hospital mortality). Byrne and colleagues [10] reported a 74% five-year survival in 190 LAD-CE patients discharged alive from the hospital. Sundt and colleagues [8] reported a 75% five-year survival in 177 CABG/CE patients.
Multivariate analysis indicated (Table 3) that long-term CABG/CE survival was improved by increasing the number of arterial grafts by the utilization of radial artery conduits (risk ratio = 0.55). This result in CABG/CE is consistent with recent data in isolated CABG which indicated that using radial as a second arterial graft in CABG with LITA-LAD improves long-term survival significantly [12]. Survival was adversely affected by increasing patient’s age, insulin-dependent diabetes mellitus, peripheral vascular occlusive disease, ejection fraction less than 0.35, and RCA endarterectomy. This finding of diminished survival in RCA endarterectomy (Table 3) is surprising, as the MI rate in these patients is lower. A possible explanation of this may be that RCA system targets received 80% vein grafts compared with 64% and 26% to the CX and LAD systems, respectively. In the setting of rare (if any) ITA grafting to the RCA, we speculate that the lower long-term survival is a reflection of generally diminished graft patency and not a result of RCA endarterectomy per se.
Our enthusiasm for radial artery grafts in CABG patients in general is further supported by the data in complex CABG/CE patients. Indeed, this study demonstrated superior radial artery patency compared with vein in CE patients. Overall, grafts of 25% of discharged CABG/CE patients were restudied, and the angiography results indicated that graft failure was not affected by its placement to endarterectomized (33%) or nonendarterectomized (25%) target vessels. However, the conduit subanalyses (Table 4) revealed that the superiority of the arterial grafts is in fact more pronounced for the severely diseased CE targets, especially in the LAD and CX territory. As in previous CABG reports, we confirm the inferior radial artery durability to RCA targets.
In conclusion, this study assessed the efficacy of radial artery grafting in CABG patients with advanced atherosclerotic disease requiring CE. We report good overall long-term survival in a large series of high-risk CABG/CE. Our data exhibit varying results depending on the coronary vessel requiring CE with the best results in the case of LAD-CE compared with less favorable RCA-CE results. Importantly, we showed the following: (1) that use of multiple arterial grafting confers significant survival benefits similar to that described in CABG without CE; (2) that this benefit is likely derived from superior arterial versus vein graft patency. Lastly, in this high-risk group of patients, complete coronary revascularization can be accomplished safely and effectively with radial artery grafting to endarterectomized and nonendarterectomized vessels. Radial artery graft patency exceeded that of SVGs to all targets, with evidence supporting the preferential use of radials to revascularize LAD system and CX system targets.
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Acknowledgments |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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References |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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This article has been cited by other articles:
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