Ann Thorac Surg 1998;65:951-954
© 1998 The Society of Thoracic Surgeons
Midterm Results of Free Internal Thoracic Artery Grafting for Myocardial Revascularization
Tadashi Tashiro, MDaa,
Katsuhiko Nakamura, MDaa,
Shungo Sukehiro, MDaa,
Masanao Nakamura, MDaa,
Ryuichi Shibano, MDaa,
Tadashi Motomura, MDaa,
Michio Kimura, MDaa
a Department of Cardiovascular Surgery, University of Fukuoka School of Medicine, Fukuoka, Japan
Accepted for publication September 4, 1997.
Address reprint requests to Dr Tashiro, Department of Cardiovascular Surgery, University of Fukuoka School of Medicine, 7-45-1 Nanakuma, Jonanku, Fukuoka 814-80, Japan
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Abstract
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Background. This study investigated the midterm results after free internal thoracic artery (FITA) grafting for coronary artery bypass grafting.
Methods. Between 1988 and 1995, coronary artery bypass grafting and postoperative graft angiography were performed in 337 patients, of whom 56 patients were treated with 57 FITA grafts. We examined the postoperative graft patency of FITA grafts compared with in situ internal thoracic artery (IITA) grafts, and the late results in the patients receiving at least one FITA graft (FITA group) were compared with those in the patients receiving only IITA graft (IITA group).
Results. The early postoperative graft patency rate was 93.2% for the FITA grafts and 96.0% for the IITA grafts (not significant [NS]). Patients underwent sequential graft angiography at 29.5 months postoperatively (25 FITA and 89 IITA). The late graft patency rate was 100% and 92.1%, respectively (not significant). The cardiac death-free survival rate at 5 years was 93.5% in the FITA group and 96.6% in the IITA group (not significant), and the angina-free survival rate at 5 years was 80.6% and 83.2%, respectively (not significant).
Conclusions. The FITA provides late results comparable with those attained with IITA.
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Introduction
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The internal thoracic artery (ITA) is commonly used for coronary revascularization because of its excellent graft patency and survival rates [1–3]. The ITA is commonly used as an in situ graft, but it is increasingly used as a free graft to obtain additional ITA length, attributable to injured ITA, or to avoid crossing the midline when using a right ITA [4–6]. However, little information exists about the late or midterm results obtained with free ITA (FITA) grafts. In this study, we evaluated the patency of the FITA graft and the survival rates compared with those obtained with the in situ ITA (IITA) after intermediate-term follow-up.
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Patients and methods
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Population
Between January 1988 and December 1995, coronary artery bypass grafting (CABG) was performed in 375 patients. The patients underwent operations either at St. Mary’s Hospital (Kurume, Japan) until March 1994 or at Fukuoka University Hospital after March 1994 and were performed by the same surgeon (T.T.). There were 15 deaths in the entire group (hospital mortality, 4.0%): two (7.7%) among patients receiving only vein grafts, two (3.2%) among patients receiving FITA graft, and 11 (3.8%) among patients receiving IITA grafts. Twenty-three patients refused to undergo postoperative cardiac catheterization or were assessed as inappropriate candidates for postoperative cardiac catheterization because of advanced age. Postoperative graft angiography was performed in the remaining 337 patients. Patients who had received only saphenous vein grafts were excluded because of the small number of patients (n = 15). Retrospectively we studied these 322 patients, in 56 of whom a total of 73 distal anastomoses had been made using 57 FITA grafts. We compared the postoperative angiographic graft patency of the FITA grafts with that of IITA grafts, and the postoperative survival rate in the patients who had received at least one FITA graft (FITA group) with that in the patient who received only an IITA graft (IITA group). Patient data for the FITA and IITA groups are shown in Table 1.
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Table 1. Clinical Characteristics of the Free Internal Thoracic Artery and In Situ Internal Thoracic Artery Groups
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Statistical analysis of categoric variables was performed on cross-tables using the Pearson’s 
2 test. Continuous variables were analyzed with the two-sample t test or the Mann-Whitney U test. Survival curves were estimated by the Kaplan-Meier method. Differences in survival rates between the two groups were analyzed using the log rank test. In all statistical tests a two-sided p value of less than 0.05 was considered to be significant.
Free internal thoracic artery indication
During the operation if the IITA did not extend as far as the planned site of coronary anastomosis, the ITA was transected at its origin. In 55 (96.5%) of the 57 FITA grafts, the reason for using the graft as a free graft was to gain additional length. Two (3.5%) FITA procedures were performed because of injury to the ITA at harvesting.
Operative technique
All operations were performed through a median sternotomy incision. The ITA was freed from the chest wall distally to the fifth intercostal space and proximally to the subclavian vein. After intravenous administration of heparin, the distal edge of the artery was cut. A standard extracorporeal perfusion technique and moderate hypothermia or normothermia were used. The myocardium was protected with cold crystalloid potassium cardioplegia until 1991, and with continuous warm blood cardioplegia after 1992. Both distal and proximal anastomoses were completed during the arrest period with single cross-clamping technique. The distal anastomoses of the ITA to the coronary artery were made by continuous suturing with a single 7-0 polypropylene suture. When a FITA was used, the proximal anastomoses of the FITA to the aorta, punched out with a 3-mm aortic punch, were made with continuous suturing with a single 6-0 polypropylene suture. All the FITA were sutured directly to the aorta. Sequential anastomoses to the left anterior descending coronary artery system were made using 16 FITA and 20 IITA grafts.
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Results
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Angiographic study
Early postoperative cardiac catheterization was performed at a mean interval of 32.4 days (range, 13 to 65 days) postoperatively in 322 patients. The early postoperative graft patency is shown in Table 2. There were no significant differences between the FITA group and the IITA group, but significant difference were found between the FITA and the saphenous vein graft group (p < 0.001), and between the IITA and the saphenous vein graft group (p < 0.001).
Eighty-four patients underwent sequential coronary angiography 6 months to 7 years (mean, 29.5 months) postoperatively. Twenty-five FITA anastomoses and 89 IITA anastomoses that were patent in the early postoperative study were examined on follow-up study. The patency rate was 100% in the FITA grafts and 92.1% in IITA grafts (not significant [NS]).
Follow-up study
Five patients (1.5%) were lost to follow up. The late results were evaluated in 317 patients at an average interval of 46 months (range, 3 to 103 months). The median follow-up interval was 46.2 months in the FITA group and 45.8 months in IITA group (NS). The overall survival rates at 5 years was 83.1% and 83.0% (NS), respectively (Fig 1). Cause of late death were shown in Table 3. The cardiac death-free survival rate at 5 years was 93.5% and 96.6% (NS), respectively (Fig 2), and the angina-free survival rate at 5 years was 80.6% and 83.2% (NS), respectively (Fig 3).
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Fig 1. Overall survival estimates for free internal thoracic artery (FITA) and in situ internal thoracic artery (IITA) groups.
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Fig 2. Cardiac survival estimates for free internal thoracic artery (FITA) and in situ internal thoracic artery (IITA) groups.
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Fig 3. Angina-free cardiac survival estimates for free internal thoracic artery (FITA) and in situ internal thoracic artery (IITA) groups.
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Comment
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There is no doubt that the ITA is the most suitable conduit for CABG. Internal thoracic artery grafting provides excellent long-term patency and survival rate [1–3]. It is common to use at least one ITA routinely for CABG. However, in some circumstances, for example when the ITA is too short or injured, it is impossible to use this artery for CABG. In this event, the ITA can be used as a free graft. Loop and colleagues [4] and Barner [5] reported independently the successful use of FITA grafting in 1973. These important early reports established the FITA as an additional arterial conduit for CABG. However, little information exists about the late or midterm results of FITA grafts.
Loop and colleagues [6] reported that the early (<18 months postoperatively) closure rate after FITA grafting was high, whereas it was low in the late (>18 months postoperatively) period. The higher rate of early closure was attributed to technical problems of the construction of the aortic anastomosis, particularly in the presence of thickened, calcified, or fragile aortic wall. At the late study, FITA grafts showed no evidence of graft atherosclerosis. Loop and colleagues concluded that FITA, like IITA, appeared to have relative resistance to atherosclerosis.
In our study, although the difference was not significant, the early postoperative patency rate of FITA grafts (92.5%) was slightly poorer than that of IITA grafts (96.2%). For FITA grafting, two (distal and proximal) anastomoses were necessary. This would increase the risk of early occlusion. The late patency rate of ITA grafts that were patent at the early study was 100% in the FITA and 94.2% in the IITA grafts. Thus, if the FITA was patent at the early examination, it could be expected to be patent at the late period. This result demonstrated that the FITA has a similar relative resistance to atherosclerosis as IITA.
Thus, we believe that to improve the patency rate of FITA, it is important to construct good quality proximal anastomoses. Several techniques for proximal anastomosis of FITA have been described [4–7]. Direct anastomosis to the aorta and anastomosis to either the saphenous vein patch of the aorta or the hood of the saphenous vein graft were reported in earlier studies [4–6]. We anastomosed all the FITAs directly to the aorta. Proximal anastomosis of FITA was completed during aortic cross-clamping. We believe that for the proximal anastomosis of the FITA it is important to perform anastomosis during aortic clamping. Under aortic cross-clamping, a healthy 1 cm2 section of the aortic wall for proximal anastomosis can be found easily, and anastomosis can be carried out confidently as well. Proximal anastomosis under cross-clamping seems to provide improved graft patency rate for FITA grafts.
Tector and colleagues [8] reported total revascularization of the heart using the FITA anastomosed in a T shape to the IITA. Several researchers [8, 9] recommend the anastomosis of FITA to another IITA. They believe that hemodynamic stress may result in disruption of the endothelium and the internal elastic lamina of free grafts and result in early intimal hyperplasia. However, Verhelst and coworkers [10] have suggested that the physiologic adaptation of the FITA is comparable to that of the IITA. Van Son [11] and Daly [12] and their colleagues have confirmed that the vasa vasorum of the ITA extends to the adventitia, implying that use of an ITA as a free graft should not induce any wall ischemia.
In our experience, the FITA and IITA grafts show no significant difference in postoperative graft patency, actuarial survival rate, or angina-free survival rate in the late period. We therefore conclude that grafting of the FITA by direct anastomosis to the aorta provides late results comparable with those attained with IITA grafting.
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References
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- Lytle B.W., Loop F.D., Cosgrove D.M., Ratliff N.B., Easley K., Taylor P.C. Long-term (5 to 12 years) serial studies of internal mammary artery and saphenous vein coronary bypass grafts. J Thorac Cardiovasc Surg 1985;89:248-258.[Abstract]
- Cameron A., Kemp H.G., Green G.E. Bypass surgery with internal mammary artery graft: 15 year follow-up. Circulation 1986;74(Suppl 3):30-36.
- Loop F.D., Lytle B.W., Cosgrove D.M., et al. Influence of the internal mammary graft on 10-year survival and other cardiac events. N Engl J Med 1986;314:1-6.[Abstract]
- Loop F.D., Spampinato N., Cheanvechai C., Effler D.B. The free internal mammary bypass graft: use of the IMA in the aorta-to-coronary artery position. Ann Thorac Surg 1973;15:50-55.[Medline]
- Barner H.B. The internal mammary artery as a free graft. J Thorac Cardiovasc Surg 1973;66:219-221.[Medline]
- Loop F.D., Lytle B.W., Cosgrove D.M., Golding L.A.R., Taylor P.C., Stewart R.W. Free (aorto-coronary) internal mammary artery graft. Late results. J Thorac Cardiovasc Surg 1986;92:827-831.[Abstract]
- Schimert G., Vidne B.A., Lee A.B. Free internal mammary artery graft, an improved surgical technique. Ann Thorac Surg 1975;19:474-477.[Abstract]
- Tector A.J., Amundsen S., Schmal T.M., et al. Total revascularization with T grafts. Ann Thorac Surg 1994;57:33-39.[Abstract]
- Calafiore A.M., Di Giammarco G., Luciani N., et al. Composite arterial conduits for a wider arterial myocardial revascularization. Ann Thorac Surg 1994;58:185-190.[Abstract]
- Verhelst R., Etienne P.Y., El Khoury G., Noirhomme P., Rubay J., Dion R. Free internal mammary artery graft in myocardial revascularization. Cardiovasc Surg 1996;4:212-216.[Medline]
- Van Son J.A.M., Smedts J., Vincent J.G., Van Lier H.J.J. Comparative anatomic studies of various arterial conduits for myocardial revascularization. J Thorac Cardiovasc Surg 1990;99:703-707.[Abstract]
- Daly R.C., McCarthy P.M., Orszulak T.A., Schaff H.V., Edward W.D. Histologic comparison of experimental coronary artery bypass grafts. Similarity of in-situ and free internal mammary artery grafts. J Thorac Cardiovasc Surg 1988;96:19-29.[Abstract]
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Abstract
Introduction
