Ann Thorac Surg 2002;73:511-515
© 2002 The Society of Thoracic Surgeons
Original article: cardiovascular
Feasibility and suitability of the routine use of bilateral internal thoracic arteries
Takashi Hirotani, MD*a,
Shogo Shirota, MDa,
Yasunori Cho, MDa,
Shigeyuki Takeuchi, MDa
a Department of Cardiovascular Surgery, Tokyo Saiseikai Central Hospital, Tokyo, Japan
Accepted for publication November 6, 2001.
* Address reprints requests to Dr Hirotani, Department of Cardiovascular Surgery, Tokyo Saiseikai Central Hospital, 1-4-17 Mita, Minato-ku, Tokyo 108-0073, Japan
e-mail: hero.takashi{at}nifty.ne.jp
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Abstract
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Background. It has been demonstrated that bilateral use of internal thoracic arteries (ITAs) confers better long-term results in patients than does unilateral use. However, routine use of bilateral ITAs has usually been avoided.
Methods. Since 1997, we have used bilateral ITAs extensively for patients who required multivessel bypasses. Recently, 243 consecutive patients, including 127 diabetic patients, were reviewed.
Results. Every patient received at least one ITA graft, and 200 patients (82%) received bilateral ITAs. The majority (93%) of ITA grafts were used as in situ grafts. The hospital mortality rate was 0.41%, and deep sternal infections were observed in 5 patients (2.0%). There was no difference in the incidence of chest wound infection between the group treated with bilateral ITA grafting and that treated by unilateral ITA grafting.
Conclusions. These observations suggest that ITAs can be used bilaterally for treatment in the majority of patients who require multivessel bypass, with low mortality and morbidity.
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Introduction
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The use of the internal thoracic artery (ITA) as the first conduit of choice for coronary artery bypass grafting (CABG) has recently been expanded with its bilateral use, and there is increasing evidence that the bilateral use of ITAs confers better long-term results on patients than does single use [1–3]. However, for various reasons, there has been some reluctance to use bilateral ITAs: inadequate length of the right ITA (RITA) to be bypassed to a distal branch of the left circumflex (LCX) or right coronary artery (RCA); increased likelihood of sternal infections; technical difficulty; the prolonged time for harvesting conduits; and the possibility of the RITA being injured during reentry when it is placed anterior to the heart for revascularization of the left anterior descending (LAD) artery. In diabetic patients particularly, the majority of surgeons have avoided using bilateral ITAs for fear of deep sternal infections and subsequent lethal mediastinitis [4–6]. However, diffuse coronary artery disease involving distal vessels is more common in diabetic patients. Therefore, in diabetic patients, bypass grafting using arterial grafts is desirable. A recent bypass angioplasty revascularization investigation (BARI) study demonstrated that in diabetic patients, there was a relationship between the presence of an ITA graft and the mortality associated with cardiac diseases, and that the benefits of CABG concerning survival were limited to the use of ITA grafts [7]. Based on these considerations, since 1997, we have tried to expand the use of ITA and routinely to use bilateral ITAs for treatment in patients who required multiple CABG, even when these patients were diabetic and required insulin. In the present study, we evaluated the feasibility and suitability of the routine use of bilateral ITAs for patients requiring multiple CABG.
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Material and methods
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The present study included all patients who were referred to us for multiple CABG, except for those requiring simultaneous valvular surgery and those with postinfarction ventricular septal defects. The subjects were 243 consecutive patients who received multiple coronary artery bypass grafts during the period from January 1997 through April 2001. They consisted of 183 men and 60 women who ranged in age from 38 to 90 years (mean 64.2 years). Profiles of the subjects are summarized in Table 1.
The frequency of urgent operation was higher in patients who received unilateral ITA grafts than in those who underwent bilateral ITA grafting (p = 0.031). There were no significant differences in other variables between the two groups. At the time of surgery, 127 patients (52%) had diabetes mellitus that had been diagnosed by endocrinologists at our Tokyo Saiseikai Diabetic Center, and there was no difference in the incidence of diabetes mellitus between the patients with bilateral ITA grafting and those with unilateral ITA grafting. Of these 127 patients, 63 (50%) were under treatment with insulin. The distributions of these insulin-dependent diabetic patients were similar between the patients with bilateral ITA grafting and those with unilateral ITA grafting. The patients were defined as being diabetic on the basis of published criteria, namely, a fasting serum glucose level equal to or higher than 140 mg/dL.
Use of internal thoracic artery
The use of bilateral ITAs was indicated for all patients with multivessel disease whenever they had recipient vessels for bilateral ITAs regardless of the urgency of the operation. In addition, diabetes mellitus has not been considered to be a valid reason for ruling out the bilateral use of ITAs. We decided not to use bilateral ITAs when a recipient vessel for RITA grafting was absent, when one of two ITA grafts was regarded as unsuitable for some reason (injury to ITA grafts during harvesting, obstruction of subclavian arteries, or extremely narrow ITA), when it was difficult to harvest one of two ITA grafts for some reason (prior radiation, prior trauma, or chronic empyema), or when patient’s life was not expected to be long for some reason (highly advanced age, coexistence of advanced malignant disease).
The left ITA (LITA) was usually used for revascularization of the LAD artery. However, when the RITA was used for the LAD artery, the LITA was used for either the LCX or diagonal artery. The RITA was usually bypassed to the proximal RCA or through the transverse sinus to the LCX artery. The RITA was also used for the LAD or diagonal artery anterior to the heart in some patients depending on the combination of bilateral ITAs. The ITA was used as an in situ graft in principle, but either all or part of the ITA was used as a free graft between the ascending aorta and coronary artery or between two segments of the same coronary artery beyond the stenotic lesion (CCBG) when the RITA could not be used for an in situ graft because of inadequate length or when the distal part of the ITA could be used for CCBG after its proximal part was used for an in situ graft [8].
In principle, we preferred to use bilateral ITA grafts individually rather than use a single ITA graft as a sequential bypass graft when two different coronary arteries were the target vessels. We especially avoided using an ITA graft anastomosed to the LAD artery as a sequential bypass graft, because such ITA grafts were considered key grafts in the success of the operation and thus should be protected against winding or insufficient flow.
Operative technique
All operations were performed by one surgeon to exclude selection bias on the part of the surgeon regarding patients’ allocation to single or double ITA grafting. After performing median sternotomy, a single or bilateral ITA was mobilized from its origin to the distal end close to the bifurcation as a pedicle with surrounding tissue. The common trunks of sternal branches and intercostal branches arising from the ITA were carefully preserved. Insofar as possible, branches were cut less than 1 mm from their origin so as not to obstruct the sternal circulation from the intercostal arteries. Cardiopulmonary bypass was performed under moderate hypothermia. Myocardial protection was carried out with antegrade crystalloid cardioplegia and topical cooling. Both proximal and distal anastomoses were performed during a single period of aortic occlusion. Grafting was attempted on all vessels measuring 1.2 mm or more in diameter that showed 75% or greater obstruction.
Morbidity
Perioperative myocardial infarctions were determined from persistent elevation of CK-MB enzyme, new Q waves, or ST elevation on electrocardiograms. Arrhythmias were defined as complications if they were considered life threatening or if they required medication. Strokes were diagnosed from the physical findings and documented by computerized tomography of the brain. Respiratory failure due to any causes was noted when mechanical ventilatory support was required for at least 48 hours. If discharge from wounds, except for blood, was observed, they were defined as being infected, regardless of the results of culture. Minor chest wound infections included those limited to the subcutaneous tissue. Major chest wound infections included all cases in which tissues were infected down to the sternal wire or beyond and that required reexploration of the wound and refixation of the sternum. Stratification of leg wound infections was not based on the depth of infectious involvement.
Postoperative coronary angiography was routinely conducted in all patients with normal renal function, after obtaining their consent. Angiograms were independently reviewed by one of six cardiologists, and each graft was independently graded according to the scale of FitzGibbon and colleagues [9].
Data analysis
Quantitative variables approximating the normal range of distribution were expressed as means ± standard deviation and analyzed by Student’s unpaired t test or the Mann-Whitney U test. Nominal variables were analyzed nonparametrically by 
2 test. The predictors of postoperative complications were determined by multivariate logistic regression analyses. Statistical significance was defined as a p value of less than 0.05.
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Results
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The number of distal anastomoses ranged from two to seven (mean 3.3 ± 1.0). The mean aortic cross-clamping time was 115 ± 37 minutes. All patients received at least one ITA graft, and 200 patients (82%) underwent bilateral ITA grafting. All ITA grafts were used with surrounding tissue. Among 443 ITA grafts, 414 ITA grafts were used as in situ grafts, and 29 ITA grafts were used as free grafts either between the roof of a saphenous vein graft near its proximal anastomosis and the coronary artery (n = 9) or between the two segments of the same coronary artery beyond the stenotic lesion (n = 20). Gastroepiploic arteries (GEAs) were used in 26 patients. Table 2
shows the coronary arteries revascularized with the RITA, LITA, saphenous vein, and GEA. In 39 patients, sequential anastomoses were performed with at least one ITA graft. Forty-three patients did not receive bilateral ITA grafts for the following reasons: the absence of a recipient vessel for RITA grafting in 26 patients (the target vessel was a combination of the LAD and a distal LCX artery in 8 patients, LAD and a distal RCA in 10, and LAD and both a distal LCX and RCA in 8); highly advanced age (
85 years) in 7; injury to ITA grafts during harvesting of the ITA in 3; extremely narrow ITA in 1; obstruction of the left subclavian artery in 3; chronic empyema due to tuberculosis in 1; coexistence with advanced malignant disease in 1; and progressive course of acute myocardial infarction during harvesting of RITA in 1.
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Table 2. Coronary Arteries Revascularized With Internal Thoracic Artery, Saphenous Vein, and Gastroepiploic Artery Grafts
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Mortality
Only one patient died before discharge from the hospital or within 30 days after the operation. This patient underwent CABG for postinfarction unstable angina and died of pulmonary infarction 10 days after operation. The patient received bilateral ITA grafts in addition to two saphenous vein grafts.
Morbidity
Operative complications and their incidences are shown in Table 3. There was no difference in the incidence of chest wound infection between patients with bilateral and unilateral ITA grafting. Also, in 127 diabetic patients, the incidence of this complication did not differ significantly according to whether ITAs were used bilaterally or unilaterally. Further, there was no difference irrespective of whether the diabetic patients required insulin or not (Table 4).
In 10 patients (4.1%), minor chest wound infection was observed and was treated conservatively. In 5 patients (2.1%), major chest wound infection was found. All of these patients underwent reexploration of the wound and refixation of the sternum. All recovered sufficiently and were discharged from the hospital within 3 weeks after the second operation.
To determine the predictors of relatively frequent postoperative complications (chest wound infection, perioperative myocardial infarction, stroke, and arrhythmia) multiple logistic regression analyses were conducted using the following variables: age, gender, extent of coronary lesions, the presence of diabetes mellitus at surgery, left ventricular dysfunction defined as a left ventricular ejection fraction of less than 30%, preoperative use of intraaortic balloon pumping, urgency of operation, past history of myocardial infarction, previous performance of CABG, number of distal anastomoses, aortic cross-clamp time, existence of congestive heart failure at operation, and number of ITA grafts used. Results showed no predictors of chest wound infection, stroke, and arrhythmia, but the number of distal anastomoses was found to be an independent predictor of perioperative myocardial infarction (p = 0.0028; odds ratio = 2.30; 95% confidence interval, 1.33 to 3.96), although the statistical reliability may be low because of low frequency outcomes.
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Early graft patency
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The angiographic investigations conducted approximately 2 to 3 weeks after surgery in 236 patients (97% of the subjects) showed a patency rate of 96.3% for all grafts. The patency rate for all ITA grafts was 97.5%, significantly superior (p = 0.0054) to that (93.6%) for all saphenous vein grafts. Table 5
shows FitzGibbon scores (grade A = excellent, grade B = fair, grade O = occluded) for each type of conduit placed. Regarding sequential grafts, three side-to-end anastomoses were occluded among 39 ITA sequential grafts. The other 36 ITA sequential grafts, with 72 anastomoses, were perfectly patent (patency rate = 96.2%). Among 29 free ITA grafts, one graft used for CCBG was occluded. The remaining 19 free ITA grafts used for CCBG and nine free ITA grafts used for bypass grafts between the roof of the saphenous vein grafts and the coronary artery were perfectly patent (patency rate = 96.6%).
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Comment
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Reports have recently shown the long-term benefits of bilateral ITA grafting [1–3], and various methods of applying right ITA grafts have increased the indications for bilateral ITA grafting [10, 11]. However, some objections to the use of bilateral ITAs for CABG remain. Many clinical conditions have been considered unsuitable for the use of bilateral ITA grafts, including diabetes mellitus, instability, acute myocardial infarction, obesity, female gender, advanced age, and poor left ventricular function. However, recent advances in anastomotic techniques and perioperative management have increased the use of bilateral ITA grafts for CABG. The routine use of bilateral ITAs for CABG would be justified if mortality and morbidity were indicated to be similar to those for the use of unilateral ITA. In our hospital, we use bilateral ITAs extensively in the patients who require multiple CABG. As a result, 82% of 243 consecutive patients who required multiple CABG received bilateral ITA grafts. In addition, the majority (93%) of ITA grafts were used as in situ grafts, which were expected to have the greatest long-term benefits among all bypass conduits.
In fact, however, many surgeons do not recommend the routine use of bilateral ITA grafts for CABG. It appears that the increasing risk of sternal infection probably due to sternal ischemia [12, 13] is the main reason for avoiding bilateral ITA grafting. In the present study, bilateral ITA grafting was achieved without any increase in mortality or morbidity. We carefully preserved the common trunks of sternal branches and intercostal branches arising from the ITA during harvesting of the ITA, and the sternum was fixed firmly with stainless bands or Kirschner wires [14]. In addition, when the patients were diabetic, the blood glucose level was managed by employing regular insulin injection every 6 hours according to a sliding scale during both the preoperative and postoperative periods. It appears that these techniques contributed to the relatively low incidence of chest wound infection in the present series.
Favorable short-term patency of ITA grafts was also demonstrated in the present study. The patency rate of ITA grafts was much superior to that of SV grafts. In addition, such favorable patency was also demonstrated even when the ITA was used as a sequential graft or free graft. However, the ITA appears to be better when used as an in situ graft with a single anastomosis rather than as a sequential graft or free graft, because of the possibility of torsion of the ITA graft or technical error at the anastomotic site.
This study was limited by its small size, the tendency of subjects to be relatively low risk patients, and the lack of randomization. Further, information on body mass index, which occasionally affects the decision criteria for whether or not to use bilateral ITAs, was omitted.
In summary, this report demonstrates that bilateral ITA grafting is feasible in the majority of patients undergoing multiple CABG and can be achieved without any increase in mortality or morbidity.
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References
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Abstract
Introduction
