Ann Thorac Surg 2004;77:1530-1534
© 2004 The Society of Thoracic Surgeons
Original articles: cardiovascular
Rationale for off-pump coronary revascularization to small branches—angiographic study of 1,283 anastomoses in 408 patients
Kaoru Matsuura, MDa,
Junjiro Kobayashi, MDa*,
Osamu Tagusari, MDa,
Ko Bando, MDa,
Kazuo Niwaya, MDa,
Hiroyuki Nakajima, MDa,
Toshikatsu Yagihara, MDa,
Soichiro Kitamura, MDa
a Department of Cardiovascular Surgery, National Cardiovascular Center, Osaka, Japan
Accepted for publication October 16, 2003.
* Address reprint requests to Dr Kobayashi, Department of Cardiovascular Surgery, National Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Osaka, Japan 565-8565
e-mail: jkobayash{at}hsp.ncvc.go.jp
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Abstract
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BACKGROUND: Off-pump coronary artery bypass grafting (OPCAB) has gained wide acceptance in tandem with the development of the stabilizer and associated operative techniques. However bypass grafting to the small branches of a beating heart is technically demanding and remains controversial. In the present study we evaluated the graft patency and quality of anastomoses to small coronary arteries by early postoperative angiography.
METHODS: Between March 2000 and December 2002 a total of 1,328 anastomosed sites to coronary branches were studied angiographically in 404 patients representing 88.6% of all cases who underwent OPCAB in this period. The coronary artery branches were categorized as large (>1.5 mm, group L: 1,028 anastomoses sites) or small (< 1.5 mm, group S: 300 sites) by intraoperative measurement. As in situ grafts the internal thoracic artery (ITA) and the gastroepiploic artery (GEA) were used at 504 and 28 distal anastomosis sites respectively. The radial artery (RA) was used as a composite graft for 739 distal anastomosis sites. Sequential bypass grafting was performed at 388 anastomosis sites in side-to-side fashion. Arterial grafts were used in 96.1% of total bypass grafting.
RESULTS: The percentage of male gender was 78.3% in group S and 87.2% in group L (p = 0.025). The ITA was used in 43.7% of group L and 18.3% of group S (p < 0.0001). The RA was used in 49.4% of group L and 77% of group S (p < 0.0001). The overall patency and stenosis free rates (FitzGibbon Type A) were 97.2% and 96.2%. Graft patency and stenosis free rates in group S (96.7% and 93.3%) were as good as those in group L (97.5% and 97.1%). In group S, the patency and stenosis free rates of SV grafts were 71.4% and 57.1%. On the other hand, those of ITA grafts were 100% and 98.3% (p = 0.53 vs. saphenous vein graft [SVG]) and RA grafts were 95.8% and 92.1% (p = 0.61 vs. SVG) respectively. In group S, the graft patency and stenosis free rates of bypass to the obtuse marginal (OM) (93.7% and 87.5%) were slightly lower than those to other implantation sites left anterior descending (LAD: 100% and 97.3%; PL: 96.5% and 92.3%; DI: 98.0% and 96%; PDA: 97.0% and 97.0%; right coronary artery [RCA]: 100% and 100%) although there was no statistical significance. The graft patency and stenosis free rates were slightly better with side-to-side anastomosis than with end-to-side anastomosis (side-to-side: 98.1% and 95.8% vs. end-to-side 96.3% and 86.3%) in group S.
CONCLUSIONS: OPCAB to small coronary artery branches with arterial grafts provided satisfactory graft patency and stenosis free rates.
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Introduction
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Off-pump coronary artery bypass (OPCAB) has been widely applied as an attractive countermeasure to percutaneous catheter intervention in coronary artery disease (CAD). Recently, OPCAB has become a standard surgical option for CAD owing to the development of equipments such as the stabilizer and associated operative techniques [1–3]. Meanwhile patients with small coronary arteries represent a significant proportion of those undergoing coronary artery revascularization. In some previous reports percutaneous catheter intervention in small coronary arteries was associated with high success and low complication rates but had higher incidence of repeat revascularization even when stents were used [4–9]. Although bypass grafting to small branches on the beating heart is technically demanding and remains controversial, few reports have addressed the problems and outcomes of OPCAB for small coronary arteries [10]. In the present study we evaluated graft patency and quality of anastomoses to small coronary arteries in OPCAB by early postoperative angiography and compared these findings with those of the treatment of larger coronary arteries.
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Material and methods
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Between March 2000–December 2002, a total of 1,328 anastomosed sites on coronary branches were studied angiographically in 404 patients representing 88.6% of all cases who underwent isolated OPCAB during this period. Male patients accounted for 83% (n = 336) and female for 17% (n = 68). The coronary artery branches were categorized by size as large (
1.5 mm; group L: 1,028 anastomosis sites) or small (< 1.5 mm; group S: 300 sites) by intraoperative measurement. To be precise a coronary artery was recorded as small, intraoperatively, when the maximum intraarterial shunt diameter that could be passed from the coronary arteriotomy in a distal direction was 1 mm or 1.25 mm, in conjunction with severe distal arteriosclerosis. As an intraoperative arterial shunt, we apply two different products; the Clear View (Medtronic, Fridley, MN) for the 1 mm and 1.25 mm sizes, and the AnastaFLO (Edwards Life Science, Irvine, CA) for the 1.5 mm and larger sizes. As all those anastomosis, that underwent coronary endarterectomy, could not accept even the 1 mm intraoperative arterial shunt, they were all included in Group S.
Our basic strategy for OPCAB has been previously described [1, 11]. We prefer multiple and complete coronary revascularization with composite and sequential grafting using all available arterial grafts—especially in-situ arterial grafts. Aortic no-touch is also the basic strategy [11]. Additionally in 17 cases using vein grafts we used aortic connecters that automatically anastomosed the saphenous vein graft (SVG) to the ascending aorta so as to avoid the complications related to the aortic clamp. Of these cases, nine were studied angiographically postoperatively. Six cases were in group L and six cases were in group S. In the early years we used the ITA-SVG composite grafts for 28 patients. Surgical technique and details of intraoperative and postoperative management were described previously [1, 11]. To prevent arterial spasm, continuous intravenous infusion of diltiazem (0.5–1.0 µg/kg) or nicardipine (0.1–0.2 µg) was used intraoperatively and during the first 16 hours after the operation. Diltiazem (100–200 mg/d) or amlodipine (2.5–5.0 mg/d) was then prescribed for oral administration in conjunction with aspirin (162 mg/d) beginning on the next morning [11].
The number of patients who underwent bypass grafting for small arteries was 179 (44.3%) whereas those who only had large arteries done numbered 225 (55.6%). The percentage of male gender was 78.2% (n = 140) in group S and 87.1% (n = 196) in group L (p = 0.025). In this series, bypass grafting with an arterial graft accounted for 96.1% of all anastomoses (n = 1277). The distribution of graft material is given in Figure 1.
The internal thoracic artery (ITA) was used in 44% of group L and in 18% of group S (p < 0.0001) and the radial artery (RA) was used in 49% of group L and in 78% of group S (p < 0.0001). The distribution of anastomosis sites is given in Figure 2.
Anastomosis of the left anterior descending branch (LAD) comprised 36% of group L and 11% of group S (p < 0.0001), that of the posterolateral branch (PL) was 24% in group L and 43% in group S (p < 0.0001), and that of the RCA was 2% in group L and 0.3% in group S (p = 0.0171). The distribution of the anastomosis method is given in Figure 3.
Side-to-side anastomosis,—that is, sequential bypass—was performed in 27% of group L and 37% of group S (p = 0.0019). The proportion of patients using SVG who had undergone medical treatment for diabetes mellitus preoperatively was 31% (15/49) in group L and 29%(2/7) in group S. Side-to-side anastomosis was performed in 27% of group L (13/49) and 0% of group S (0/7).
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Fig 1. Distribution of graft material. (A) Group S. (B) Group L. (GEA = gastroepiploic artery; ITA = internal thoracic artery; RA = radial artery; SVG = saphenous vein graft.)
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Fig 2. Distribution of anastomosis site. (A) Group S (%). (B) Group L (%). (LAD = left anterior descending branch; OM = obtuse marginal artery; PL = posterolateral branch; RCA= right coronary artery.)
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Angiographic study
Coronary and graft angiography was performed at 10–21 days (mean 14 days) after the OPCAB. Patients with renal dysfunction (serum creatinine > 2.0 mg/dL) were evaluated only by stress thallium myocardial scintigraphy and they were excluded from this study. Graft patency and stenosis were independently assessed by the single cardiologist team. Graft stenosis was regarded as significant if it was applied to FitzGibbon type A [12].
Statistical methods
All data were reviewed retrospectively. All values are expressed as mean ± standard deviation (SD). A comparative analysis was performed between the different patient groups. Differences were analyzed using the univariate analysis (the Mantel–Haenszel 
2 test, the two-tailed t test, Fischer exact test, or the Mann–Whitney U test, as appropriate). A value of p less than 0.05 was used to indicate significance.
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Results
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The overall patency was 97.2% (1292/1328), and the stenosis free rate was 96.1% (1,276/1,328). Patency was 97.5% (1,002/1,028) in group L and 96.7% (290/300) in group S (p = 0.963). The stenosis free rate was 96.7% (996/1,028) in group L and 93.3% (280/300) in group S (p = 0.706). The patency and stenosis free rates stratified by graft material are given in Figure 4.
The patency rates of the ITA graft were 98.2% (441/448) in group L and 100% (55/55) in group S (p > 0.999). The stenosis free rates of it were 96.7% (434/449) in group L and 98.2% (54/55) in group S (p > 0.999). The patency rates of the SVG were 95.9% (47/49) in group L and 71.4% (5/7) in group S (p = 0.763). The patency rate of the SVG was 71.4% and that of the ITA was 100% (p = 0.763, vs. SVG), the gastroepiploic artery [GEA] was 100% (p = 0.713, vs. SVG), and the RA was 96.5% (p = 0.772, vs. SVG) in group S. The stenosis free rates of the SVG were 98% (48/49) in group L and 57.1% (4/7) in group S (p = 0.530). Among the SVG anastomosis with aortic connector devices, one bypass graft was occluded and this was in group L. The patency rates of the RA were 97.4% (495/508) in group L and 96.5% (223/231) in group S (p = 0.954) whereas the stenosis free rates of the RA were 97.4% (484/508) in group L and 93.5% (216/231) in group S (p = 0.909).
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Fig 4. Patency and stenosis free rate stratified by graft material. (GEA = gastroepiploic artery; ITA = internal thoracic artery; RA = radial artery; SVG = saphenous vein graft.)
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The patency and stenosis free rates stratified by the anastomosis site are given in Figure 5.
The patency of the LAD site was 99.2% (365/368) in group L and 100% (34/34) in group S (p > 0.999). The stenosis free rate of the LAD was 97.8% (360/368) in group L and 97.1% (33/34) in group S (p > 0.999). In both groups S and L, there was no significant difference in patency rate between anastomosis sites. The stenosis free rate of the OM (86.2%) was lower than that of other sites in group S.
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Fig 5. Patency and stenosis free rate stratified by anastomosis site. (LAD = left anterior descending branch; OM = obtuse marginal artery; PL = posterolateral branch; RCA = right coronary artery.)
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The patency and stenosis free rates stratified by the anastomosis site are given in Figure 6.
The rates of patency and freedom from stenosis in side-to-side anastomosis were better than those in end-to-side anastomosis in both groups L and S although the difference was not significant.
Coronary endarterectomy was carried out in 8 patients, all of whom could not accept the 1.5 mm or larger shunt and the patency rate was 87.5% (7/8).
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Comment
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Recently OPCAB has been rapidly revived because of its cost effectiveness and the availability of commercial stabilizing devices and, of course, the further development of the operative technique [1–3, 13, 14]. However OPCAB is still a somewhat more or less technically demanding procedure than is conventional CABG despite local site stabilization and anesthetic management such as induced bradychardia. Natural motion and counteraction of the heart to derangement during heart elevation is still a serious concern in the pursuit of an accurate anastomosis. This uneasiness could cause distress to the surgeon especially when the target artery is small [10]. The results of this study show that the quality of OPCAB to small coronary arteries is as good as that to large arteries with respect to early graft patency and freedom from stenosis.
The definition of small coronary branch has not been established clearly before and several previous reports set up their criteria [4–10]. Ramstrom and associates reported the coronary artery bypass graft to small vessel disease which was recorded intraoperatively when the maximum diameter of the probe that could be passed from the coronary arteriotomy in a distal direction was 1 mm or 1.5 mm in conjunction with severe distal arteriosclerosis [10]. To refer this report, we used the intracoronary shunt for the measurement of coronary artery branches. The size of a coronary vessel we measured in this study may not the real diameter of the coronary branches, but the surgical diameter of the coronary branches, because the coronary vasospasm could reduce its size after the vessel is touched. However we adopted the surgical diameter for the definition of small coronary artery because the surgical diameter is the very matter of great importance for surgeons.
Our basic strategy of OPCAB has been described previously [1, 11]. The essential philosophy of our institution comprises the aorta no-touch technique using an in-situ graft and composite and sequential grafting methods combined with total arterial revascularization using only internal thoracic artery and composite radial artery grafts. In fact, bypass grafting with an arterial graft accounts for 96.1% of all anastomoses (n = 1277). Furthermore when using vein grafts we have recently adopted the application of the aortic connecters that automatically anastomose the SVG with the ascending aorta so as to avoid the complications of the aortic clamp; this yields the benefit of reduced cerebrovascular accidents by avoiding aortic manipulation [15].
Previous reports have shown that the results of CABG are generally less favorable in women than in men [10, 16]. Although many factors are present the smaller diameter of female coronary arteries, which can cause technical difficulties, has often been proposed as a dominant factor. In this report the percentage of female gender was significantly larger in group S. This result shows that women have a risk that is associated with small arteries.
In a previous report the patency was inversely related to the size of the grafted vessel in the LAD and circumflex (CX) areas in OPCAB [17]. However, in our series, the patency and stenosis free rate of small arteries were proven to match those of larger arteries even with OPCAB. Moreover, as described in previous reports, women have a higher prevalence of varicose or stripped saphenous veins [10]. Assuming this to be true, and given our recent preference for arterial grafts over vein grafts, there is less likelihood of trouble with diseased vessels.
This study provides us with information about the distribution of the small coronary arteries. The small coronary arteries were more inclined to be located in the posterolateral (PL) than in the LAD. Although this represents not a clinical result but an anatomical one, it possesses clinical significance because we prefer to employ total arterial bypass grafting.
Patency and quality of the anastomoses were excellent although late follow-up will be necessary. Some pitfalls emerge with regard to the patency and stenosis free results. Poor long-term patency of vein grafts in CABG and the gross atheromatous changes seen on angiography have been reported. In this study early patency of the SVG in small arteries has no significant difference with that of the ITA or the RA. The patency and stenosis free rate of small SVG did not have something to do with the morbidity of diabetes mellitus, application of aortic connector, or the type of anastomosis method. Also the stenosis free rate of the OM in small arteries was slightly lower than at other anastomosis sites. This supports the technical difficulty of anastomosis at the OM including the lifting and stabilization of the heart. The patency and stenosis free rates of side-to-side anastomosis were comparable to but slightly better than those of end-to-side anastomosis. This demonstrates the benefit of the diamond shape anastomosis which enlarges the anastomotic area.
There is the main limitation in this study that the angiographies were done early after the procedure. The angiographic study done at 6 or 12 months after surgery is the subject to be done in the future.
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Conclusion
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OPCAB to small coronary artery branches with arterial grafts provides satisfactory graft patency and freedom from stenosis.
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References
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Abstract
Introduction
