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Ann Thorac Surg 1997;64:9-14
© 1997 The Society of Thoracic Surgeons
Baylor College of Medicine and Veterans Affairs Medical Center, Houston, Texas
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Abstract |
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 TopFootnotes Abstract IntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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Methods. The study group was 498 consecutive bilateral ITA operations, constituting the 10-year experience of a single surgeon. Follow-up averaged 7.1 years (mode 7.3 years), and was 94.2% complete. These patients were divided into two groups, 311 patients (group I) who underwent the traditional operation (left ITA to the left anterior descending artery, right ITA to the right coronary artery), and 187 patients (group II) who received revascularization of branches of the left coronary artery (left ITA to the circumflex system and right ITA to the left anterior descending artery).
Results. The study groups were similar in age, severity of disease, number of bypassed arteries, ejection fraction, diabetes, hypertension, and duration of operation. There were more male patients in group II (91.4% versus 82.3%). A multivariate analysis showed that the location of ITA bypass grafts influenced survival independent of gender (p = 0.0288). Operative morbidity and mortality were similar between groups. Ninety-three patients had repeat angiography with equivalent patency rates of the ITA conduits (91.7% versus 89.6%; p = 0.67). The Kaplan-Meier actuarial survival estimate demonstrated a significant improvement in survival of patients in group II who received both ITA bypass grafts to left-sided arteries (p = 0.021), with the survival curves diverging at 6 years. More patients in group II were in New York Heart Association class I or II, but the difference was not statistically significant (94.6% versus 91.6%). Only 2 patients required reoperation.
Conclusions. It appears that maximum long-term benefit from bilateral ITA operations is achieved by grafting the ITA conduits to coronary arteries that supply more left ventricular muscle.
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Introduction |
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TopFootnotesAbstractIntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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For more than 25 years, coronary bypass grafting has been the surgical treatment of choice for ischemic heart disease. With the current focus on outcome analysis, surgeons continue to search for methods to reduce morbidity and resource utilization with emphasis on improving long-term quality survival. These efforts were advanced considerably when the internal thoracic artery (ITA) was shown to have higher long-term patency [1] and survival [2] than the saphenous vein as a coronary bypass conduit. It has been hypothesized that results are further improved when both ITAs are used, but convincing clinical data addressing this issue have accumulated slowly, and although the technique has been practiced since the late 1960s, most thoracic surgeons choose not to use two ITAs.
There are three basic arrangements of in situ bilateral ITA bypass grafts. The first and most widely used method grafts the left ITA to the anterior descending coronary (LAD) and the right ITA to the right coronary artery (RCA). The second operative technique grafts the left ITA to the LAD and routes the right ITA through the transverse sinus, typically to branches of the circumflex artery [3]. The third method departs most radically from conventional single ITA procedure by placing the right ITA anterior to the LAD, and grafting the left ITA to a circumflex artery branch. Although many clinicians consider each artery of the so-called three-vessel heart equally important, the average RCA is not the clinical equivalent of the left-sided branches [4]. We were early proponents of ITA grafting and chose, as we began to use both ITAs, to employ either the standard pattern (left ITA to the LAD and right to the RCA, or to cross over the midline with the right ITA and bypass the circumflex artery with the left ITA. This technique, originated by Puig and colleagues, [3] of placing the right ITA through the transverse sinus was questioned by Rankin and associates [5] early in our experience. In this study we evaluated long-term clinical results between two groups of patients based upon whether the right ITA was grafted to the RCA or the left ventricular arteries.
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Patients and Methods |
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TopFootnotesAbstractIntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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The total number of coronary grafts was 1,692, averaging 3.4 bypass grafts per patient. Each patient received bilateral ITA grafts, and in 72 patients 82 ITAs were used for sequential grafts. The remainder of bypass grafts were constructed with autologous saphenous vein. The patients were divided into two groups: 311 patients (group 1) underwent the traditional operation (left ITA to the LAD and right ITA to the RCA), and 187 patients (group 2) received revascularization of branches of the left coronary system with both ITAs (left ITA to the circumflex system and right ITA to the LAD). Both groups had supplemental reversed saphenous vein grafts to additional lesions. Internal thoracic artery conduit placement decisions were based upon what were considered to be the two clinically most important coronary arteries. This decision was not difficult when two-vessel disease was being treated or the left main coronary artery was involved with a normal RCA. In patients with so-called triple-vessel coronary artery disease, choice of the pattern of ITA placement was based upon the relative angiographic size of the circumflex artery distribution versus the right coronary system.
We established direct communication with 94.2% of the patients, their families, or their physicians. The status of the remainder was determined by social security number through the National Social Security Death Index Network. We were able to obtain follow-up longevity data for 100% of the study sample. After a mean observation period of 7.1 years, 87.2% of the 498 study patients are alive.
Stratified cumulative survival was calculated by the Kaplan-Meier product-limit method. Tests for homogeneity over strata were calculated using the likelihood ratio test. Multivariate analyses were conducted using proportional-hazards regression. Frequency data were analyzed using the 
2 test. All computations were performed using SAS version 6.11. Individual variables calculated included sex, age at operation, Canadian Cardiovascular Society Angina Scale classification (CCSC), preoperative functional class, emergent or elective surgery, occurrence of preoperative myocardial infarction within 1 week of the operation, premorbid conditions (diabetes, hypertension, and congestive heart failure), preoperative medications, preoperative ejection fraction, percentages of all stenoses of named coronary arteries, (left main, left anterior descending, diagonal, circumflex, right coronary, posterolateral, and posterior descending), weight, ischemic time, total pump time, blood transfused in the operating room, blood transfused perioperatively, duration of ventilation, days in intensive care unit, type of cardioplegia (blood or electrolyte), and incidence of perioperative infarction (as determined by new Q waves). Operative mortality included all deaths occurring while hospitalized or within 30 days of the operation.
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Surgical Technique |
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TopFootnotesAbstractIntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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The operative technique did not substantially change during the study period. All distal ITA anastomoses were completed under 3.5x magnification using running 7-0 Prolene (Ethicon, Somerville, NJ), with three interrupted sutures for the toe. Running 8-0 Prolene was used for proximal sequential anastomoses. Care was taken in all cases to anchor the pedicles precisely with stay sutures to prevent tension or buckling of the anastomoses. Excessive angulation of the distal ITA was avoided assiduously when the heart was replaced to its normal position. Notation of routes, angulation, and tension are especially important when grafting the right and circumflex coronary arteries, as the heart may become distorted during grafting relative to its normal contour. Proper angulation of the right ITA when grafted to the LAD is equally important to insure nonturbulent flow (Fig 1
). The dissected LAD often presents a ridge of tissue that must be notched to ensure the distal right ITA of a straight lie (Fig 2). When the left ITA is grafted to circumflex artery branches, placement of the anastomosis too close to the atrioventricular groove should be avoided to prevent kinking (Fig 3).
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Results |
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TopFootnotesAbstractIntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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). There were no significant differences in age, hypertension, diabetes, smoking, average anginal class, preoperative myocardial infarction, or urgency of the operation. Group 1 had more female patients (17.9% versus 9.6%; p = 0.01). The extent of coronary artery disease was slightly more ominous in group 2, which had a significantly larger percentage of patients with left main disease (9.9% vs. 20.2%; p = 0.001) (Table 2). In contrast, group 1 was composed of more patients with double-vessel disease (42.6% versus 32.4%; p = 0.03). The majority of patients in both groups had normal ventricular function, but group 2 had a higher percentage of patients with an ejection fraction less than 0.50 preoperatively (33.4% versus 43.1%; p = 0.04).
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Operative Mortality and Morbidity |
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TopFootnotesAbstractIntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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). The major parameters of operative morbidity, including mediastinal wound infection, stroke, necessity of intraaortic balloon pump, perioperative myocardial infarction, or return to operating room for control of bleeding were not significantly different. The perioperative resource utilization indicators were comparable for both groups in terms of blood transfused either in the operating room or postoperatively, duration of mechanical ventilation, and time in the intensive care unit. The number of bypass grafts constructed in both groups was essentially equal.
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Follow-up and Survival |
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TopFootnotesAbstractIntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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) began to diverge at 6 years and became significant at 8 years. At 9.6 years 70.1% of patients in group 1 and 93.1% of patients in group 2 were alive. This is statistically significant by log-rank analysis (p = 0.021) and by Wilcoxon analysis (p = 0.0042).
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). Two patients underwent reoperation, both from group 1. All late deaths were considered in the analysis to be associated with cardiac disease, despite clear evidence of other causes in 4 patients; one death was secondary to a ruptured abdominal aortic aneurysm and three deaths were related to cancer.
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Graft Patency |
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TopFootnotesAbstractIntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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Comment |
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TopFootnotesAbstractIntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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Multiple descriptive uncontrolled studies, the longest a 17-year follow-up by Galbut and colleagues [7], show excellent survival in patients with bilateral ITA grafts [8–12]. The 5-year survival rate in these populations ranges consistently between 88% [7] and 97.2% [8], and at 10 years between 80% [7] and 90.2% [8]. Long-term studies that divided the total consecutive patient population based upon whether one or two ITAs were grafted demonstrated superior clinical outcomes in the bilateral ITA graft groups [13, 14].
Fiore and colleagues [15] and Naunheim and associates [16] followed up the same computer-matched cohorts of 100 patients having bilateral ITA operations and 100 patients receiving single ITA grafts for 15 years and found no significant differences in survival. The patients in these studies had the same ITA placement as our group 1 (left ITA to the LAD with right ITA to the RCA). A subsequent study confirming this work matched groups of 80 patients without circumflex artery disease whose LAD lesions were grafted with the left ITA, and the patients whose RCA lesions received either the right ITA or a vein graft [17]. The study found no survival advantage upon follow-up at 8 years. Another large-sample computer-matched retrospective study from the Mayo Clinic compared single ITA operations to patients with both ITAs grafted to arteries supplying the left ventricle (our group 2). This study concluded that the patients whose left ventricles were supplied by both ITAs had significantly better 10-year survival rates (p = 0.039) [18].
Concurrent studies with consecutive patients with bilateral ITA and single ITA operations grouped by the number of ITA graft procedures performed are likely to be influenced by selection bias, which cannot be excluded by computer-matched retrospective techniques. Concern that the bilateral ITA operation is a more demanding, more complicated procedure could influence case selection toward younger, healthier patients. Although the present study also has a nonrandomized consecutive design, the influence of patient selection bias is at least partially limited because individual anatomic variations, rather than the complexity of the surgical options, determined placement of the right ITA graft. The preoperative and perioperative data in the present study were also collected prospectively by the surgeon, thereby possibly reducing the likelihood of inaccuracy.
In the present study the survival benefits from performing bypass grafts on stenotic left-sided coronary arteries with both ITA conduits began to appear after the sixth year, but took 8 years to reach statistical significance. Most of those who died had not undergone repeat angiography; had they done so, direct association with graft failure might have been established. Instead, repeat coronary angiograms were done in survivors with symptoms and perhaps accounts for comparable graft patency rates in the two groups. However, any added benefit at 8 or more years from using a superior conduit to treat the RCA is not apparent.
Longevity is the most important and objective endpoint of successful outcome, but the survivor's quality of life is of almost equivalent importance. The survivors in both groups had continued excellent relief from angina, with the majority (92.9% versus 95.3%; p = 0.61) in CCSC angina class I or II. Only two patients in the series, both in group 1, underwent repeat operations. The reason for such a low reoperation rate is not readily apparent, but is consistent with other reports of bilateral ITA operations [7, 13, 17].
The perioperative mortality and morbidity were essentially the same in both groups, as might be anticipated in operations of equivalent complexity and identical surgical care. The similar operative results would also indicate discursively that the two groups were evenly matched for operative risk.
The choice of whether to place the in situ right ITA through the transverse sinus to circumflex branches or anteriorly to the LAD depends on the patient's anatomy and the preference of the surgeon. Findings by Rankin and coworkers [5] regarding inadequate flow in right ITA grafts placed through the transverse sinus must be weighed against the excellent long-term patency rates reported recently in a large series by the Puig group [3], and confirmed by others on a short-term basis [12, 19]. Advantages of this approach are that it revascularizes the left ventricular myocardium and protects the patent right ITA from the potential hazards of reoperation.
The danger of reoperation in patients with patent ITA grafts may be considerably overstated. Lytle and associates [20] reported that of 428 patients with patent left ITA grafts to the LAD, 3.3% had graft damage requiring replacement, and all patients with damaged arteries survived. In 11 patients undergoing reoperations with patent right ITA grafts crossing the midline, one graft (9%) was damaged and repaired, and the patient survived [21]. As an additional safeguard for reoperation the graft pedicle can be surrounded with polytetrafluoroethylene either as a membrane [22] or a tube graft [23] as a precaution. A guiding principle in vascular surgery has always been to do the operation that would provide the best long-term results initially and deal with theoretical future considerations as they occur.
A number of surgeons experienced in the use of ITA graft procedures advise that the right ITA be used as a free graft when one wishes to bypass left coronary artery branches with both ITAs [10, 21, 24, 25]. Very recently, a study of 1,454 patients whose right ITAs were used as a free graft found a 94% survival rate at 7 years, and 95% patency of the free grafts at 40 months [24]. Using the right ITA as a free graft likewise provides better assurance during reoperation, and adds additional length beyond any of the in situ routes. This method nevertheless adds another anastomosis. Tector, a pioneer in ITA use, and colleagues [25] developed a method of attaching the free right ITA to the left ITA, thereby creating a bypass circuit composed entirely of ITA, and avoiding the need for an aortic anastomosis or interposed vein.
In conclusion, the present study supports the concept that placing both ITAs to left-ventricular arteries is the preferred method for the bilateral ITA operation. There are no data, only conjecture, supporting the superiority of any one of the possible three methods for using in situ bilateral ITAs to revascularize left-sided vessels. Evidently, bypassing the left ventricular mass with conduits that will perfuse longer is the lesson, and the several methods of accomplishing this appear equally adequate.
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Footnotes |
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TopFootnotesAbstractIntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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Address reprint requests to Dr Jones, Department of Surgery, Veterans Administration Medical Center, 2002 Holcombe Blvd, Houston, TX 77030 (e-mail: mesj{at}bmc.tmc.edu).
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References |
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TopFootnotesAbstractIntroductionPatients and MethodsSurgical TechniqueResultsOperative Mortality and...Follow-up and SurvivalGraft PatencyCommentReferences |
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