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Ann Thorac Surg 2005;79:564-569
© 2005 The Society of Thoracic Surgeons

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Original article: Cardiovascular

Revascularization of the Right Coronary Artery in Bilateral Internal Thoracic Artery Grafting

^a Department of Thoracic and Cardiovascular Surgery, Tel-Aviv Sourasky, Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
^b Department of Tel-Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel

Accepted for publication July 6, 2004.

^* Address reprint requests to Dr Pevni, Department of Thoracic and Cardiovascular Surgery, Tel-Aviv Sourasky Medical Center, 6 Weizman St, 64239 Tel-Aviv, Israel (E-mail: pevnid{at}yahoo.com).

	Abstract

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
BACKGROUND: Bilateral internal thoracic artery (BITA) grafting with a composite T-graft enables right coronary artery (RCA) system revascularization with the distal end of the free right internal thoracic artery (RITA). This study compares this grafting technique to left-sided BITA grafting and RCA revascularization with the right gastroepiploic artery (RGEA) and saphenous vein grafts (SVG).

METHODS: From April 1996 to July 1999, 1000 consecutive patients underwent left-sided revascularization with BITA. In 231 patients RCA grafting was performed with free RITA, in 246 with RGEA, in 142 with SVG, and 381 did not receive any graft to the RCA (no-graft group).

RESULTS: Female gender, old age (> 70), emergency, and congestive heart failure were less prevalent in the RGEA group, and prior percutaneous transluminal coronary angioplasty was more prevalent in the no-graft group. Thirty-day mortality (3.6%, 4.9%, 2%, and 3.4% in the RITA, SVG, RGEA, and no-graft groups, respectively) and occurrence of perioperative complications (sternal infection, myocardial infarction, cerebrovascular accident, and bleeding) were similar. Overall, however, the trend was toward a higher complication rate in the RITA group (10.3%, 4.9%, 5.6%, and 7.3% respectively, p = 0.06). Midterm follow-up (40 to 78 months) showed similar 6-year survival (Kaplan-Meier) (88%, 87%, 89.5%, and 85.5%, respectively) and similar return of angina (10.8%, 6.3%, 10.6%, and 9.5%, respectively) in the four groups.

CONCLUSIONS: Early and midterm results in patients undergoing left-sided BITA grafting are not affected by the conduit used for RCA grafting.

	Introduction

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Recent studies have reported a survival benefit and decreased rates of reinterventions when bilateral internal thoracic arteries (BITAs) are used for left-sided myocardial revascularization [1–3]. BITAs have been recognized as optimal conduits because of superior patency and freedom from arteriosclerosis [1–3]. These reports have led many surgeons to now routinely use BITAs for myocardial revascularization of the left coronary system. The conduits used for revascularization of the right coronary artery (RCA) system include the saphenous vein, the right internal thoracic artery (RITA) in situ or the free radial artery (RA), and the right gastroepiploic artery (RGEA) [4–6].

The influence of the choice of conduit type to the RCA system on clinical results remains unclear, and the complementary conduit of choice to this system has yet to be determined. No superior patency rate for any one of these grafts to the RCA has been established [4–6]. The use of the RA or RGEA as the conduit for a moderate stenosis of the RCA is limited because of its association with a high risk of graft failure owing to competitive flow [7, 8]. Limited flow capacity of the RGEA has also been reported [9]. One evaluation of the saphenous vein graft (SVG) to the RCA territory revealed surprisingly good clinical and angiographic results after long-term follow-up [4].

Thus, the debate on the complementary graft of choice to RCA system is still ongoing. Our previous investigation had a follow-up of up to 4.5 years and did not demonstrate any clinical benefit of RGEA grafts over SVGs [10]. It is well known that rapid degeneration of SVGs occurs after 5 to 7 years, and so the short follow-up of that study was a serious limitation.

In the current study, we report a longer follow-up (40 to 78 months) of patients undergoing left-sided BITA revascularization. We evaluated results of the different RCA grafting techniques and compared them with those of BITA patients who did not require RCA grafting.

	Material and Methods

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
From April 1996 to July 1999, 1000 consecutive patients underwent left-sided (left anterior descending [LAD] and circumflex) revascularization with BITAs that were dissected as skeletonized arteries [11]. BITAs comprised 71% of the 1408 coronary artery bypass grafting (CABG) procedures performed in the Tel Aviv Sourasky Medical Center during this time. RCA grafting was performed with a free RITA in 231 patients (Fig 1A), with a RGEA in 246 (Fig 2A), and with a SV in 142 (Fig 2B), while 381 patients did not require any graft to the RCA (the no-graft group patients with a nonstenotic or a small RCA) (Fig 1B). The RCA was grafted distally to the bifurcation (ie, the posterior descending artery [PDA] or the posterolateral branch of the RCA).

View larger version (30K): [in this window] [in a new window]   Fig 1. Composite T-graft; (A) with the right internal thoracic artery (RITA) to the posterior descending artery (PDA); (B) without any graft to the right coronary artery. (AO = aorta; D = diagonal artery; LAD = left anterior descending artery; LITA = left internal thoracic artery; M = marginal artery; PA = pulmonary artery.)

View larger version (29K): [in this window] [in a new window]   Fig 2. In situ crossover arrangement; (A) with the right gastroepiploic artery (R+GEA) to the posterior descending artery (PDA); (B) with a saphenous vein graft (SVG) to the PDA. (Cx-Marg = left circumflex artery-marginal branch; D = diagonal artery; LAD = left anterior descending artery; LITA = left internal thoracic artery; RITA = right internal thoracic artery.)

We do not use the cross technique in patients who have a short RITA, a very long ascending aorta, an enlarged right ventricle, or a too distal or unpredictable LAD anastomotic site. In most of the reported cases (648 patients of the 1000), we used the composite arterial grafting technique. The composite graft can be prepared before the patient is connected to cardiopulmonary bypass. Most of the composite grafts included end-to-side anastomosis of the free RITA on an in situ LITA (Fig 1). The free RITA can sometimes reach the RCA's anastomotic site (posterolateral or PDA). However, in most patients that required sequential anastomoses, the RITA was not long enough to reach the PDA and we preferred using a third conduit (RGEA or SV).

The type of conduit selected for RCA grafting was not related to the configuration of the ITAs. Our strategy was to use RITAs and RGEAs as grafts to the RCA branches only in the presence of a significant stenosis (ie, > 80%).

To decrease the risk of spasm of the arterial grafts, we treated all of our patients with a high-dose intravenous infusion of isosorbide dinitrate (Isoket; 4 to 20 mg/h) during the first 48 hours postoperatively. From the second postoperative day, the patients whose RGEA was used were treated with calcium-channel blocker (diltiazem; 90 to 180 mg/d, orally) for at least 3 months.

Statistical Analysis
Data are expressed as the mean ± standard deviation or as a proportion. The ² test and 2-sample t tests were used to compare discrete and continuous variables, respectively. Multivariable logistic regression analysis was used to predict early mortality, sternal infection, and return angina by various risk factors. The odds ratio (OR) and the 95% confidence interval (CI) are given. The Cox proportional hazard model was used to evaluate the influence of preoperative variables on late and overall mortality. Postoperative survival is expressed by the Kaplan-Meier method, and survival curves were compared by the Log-Rank test. All analyses were performed by means of SPSS 9.0 software (SPSS, Chicago, IL).

	Results

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
The relative numbers of female patients, patients older than 70 years, emergent operations, and patients with congestive heart failure (CHF) were significantly lower in the RGEA group, and prior PTCA was more prevalent in the no-graft group. Otherwise, the four groups were similar in most of the preoperative patient characteristics (Table 1). The operative data for the four study groups are displayed in Table 2. The use of composite T-graft and sequential grafting was more common among patients who underwent revascularization of the right coronary system with free RITAs. The mean number of grafts per patient was significantly lower in the no-graft group (2.52 in the no-graft group vs 3.32, 3.72, and 3.55 in the RITA, SVG, and RGEA groups, respectively). Consequently, the average aortic cross-clamping time was significantly lower in the no-graft group.

An increased mortality rate in this series was noted in patients whose operations were emergent, in patients supported preoperatively with intraaortic balloon counterpulsation, in patients with CHF, peripheral vascular disease (PVD), an ejection fraction (EF) of less than 35%, and in patients operated on within the first 7 days of an acute myocardial infarction (MI). After adjustment for other demographic, clinical, and surgical predictors, however, only preoperative PVD (OR, 2.9; 95% C.I., 1.09 to 7.95) and CHF (OR, 3.3; 95% C.I., 1.4 to 7.7) emerged as independent risk factors for 30-day mortality. Postoperative morbidity included 10 cases (1%) of perioperative MI, 16 (1.6%) strokes, 16 (1.6%) reoperations for bleeding, and 22 (22%) cases of sternal wound infection.

The occurrence of perioperative complications (sternal infection, perioperative MI, stroke, and bleeding) was similar among the four subgroups. Overall, however, a trend was noted towards a higher complication rate in the RITA group (p = 0.06, Table 3). The occurrence of sternal infection was increased in patients with COPD (9.6% vs 1.5% without this risk factor, p < 0.001) and in patients with diabetes mellitus (4.4% vs 1.2% in nondiabetic patients, p = 0.004). RCA grafting did not affect the occurrence of sternal infection (Table 3). COPD (OR 5.95; 95% CI, 2.1 to 16.9) and diabetes mellitus (OR, 4.65; 95% CI, 1.7 to 12.5) were also found to be independent predictors of sternal infection in the multivariable logistic regression analysis.

View larger version (19K): [in this window] [in a new window]   Fig 3. Kaplan-Meier survival curves of the four right coronary artery (RCA) revascularization subgroups: right internal thoracic artery (RITA); right gastroepiploic artery (RGEA); saphenous vein graft (SVG) and without graft to RCA (No graft).

Eighty-seven patients underwent cardiac catheterization during the follow-up period. The procedure was indicated in 78 because of chest pain, and 9 patients consented to elective catheterization within the framework of our learning to use a composite T-graft. Of the 176 BITA anastomoses in this subgroup, 160 (91%) were patent. Only 43 grafts to the PDA were demonstrated angiographically (6 to 36 months after the operation). This included 19 RGEA grafts, 18 SVGs, and 6 free RITA grafts. All SVGs were defined as intact; however, four RGEA grafts and one free RITA graft were occluded. The angiographic "string sign," related to competitive flow, was observed in 2 patients with RGEA grafts and in 1 free RITA patient.

Reinterventions included 4 reoperations and 20 PTCA balloon procedures and stents. There was a similar reintervention rate in the RCA revascularization groups (Table 4).

	Comment

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
This study describes the results of early and midterm left-sided CABG with BITAs. We have been routinely performing left-sided BITA grafting in our department since 1996. The report is based on a relatively large number of patients (1000) and focuses mainly on the clinical results of left-sided BITA grafting compared with various techniques currently being used for RCA grafting. Our results showed that skeletonized BITA grafting is also safe in subgroups of high-risk patients. Despite 41% of our patient cohort being older than 70 years, survival was good and the postoperative complication rate was relatively low. The independent predictors of overall mortality were age older than 70 years, CHF, PVD, and diabetes mellitus. The 6-year angina return rate was also relatively low (9.6%), and the only independent predictor of angina return was PVD.

Recent studies have demonstrated that the use of left-sided BITA grafting is the single factor associated with greater freedom of reintervention, return of angina, and survival benefit [1–3]. Skeletonization of the internal thoracic artery and the use of a composite graft technique provide the possibility of performing multiple anastomoses with the BITA [11].

Despite the benefits of left-sided BITA grafting that had been demonstrated in several studies, the complementary graft of choice for the RCA has yet to be determined [5, 10]. The use of the RITA as a conduit to the RCA was recently associated with a less-than-optimal patency rate and showed no benefit over other grafts [5, 6, 12]. Tatoulis and colleagues reported that the 5-year patency rate of RITA to the LAD was 95% compared with 83% to the RCA [13]. The RA has also been proposed for RCA grafting [14, 15], but disappointing 5-year patency rates (73% to 83%) were demonstrated, especially when the RCA stenosis was less than 80% [7, 13, 16].

The coronary competitive flow may limit the use of the RGEA as a graft to the RCA system, and most authors recommended an RGEA graft when the degree of coronary artery stenosis exceeds 70% [8, 17]. In addition, Ochi and colleagues [9] demonstrated a limited flow capacity in the presence of an angiographically intact patent graft and concluded that only RGEA grafts exceeding 2.6 mm in luminal diameter would be consistently adequate. The reported mean luminal diameter of an RGEA, however, is 2.2 mm [18]. The size of an RGEA is associated with wide individual variability, and no reliable method exists for predicting its size before harvesting. In our experience, the RGEA could be applied in only 20% to 30% of the patients. Moreover, in our previous study, we did not find any benefit in the clinical outcome when an RGEA was used as a graft to the RCA compared with the SVG. [10].

In the present study, we failed to find any benefit of using either an free RITA or an RGEA graft compared with the SVG to the RCA. Moreover, the clinical outcome of patients who received a ITA graft to the RCA did not differ from the outcome of those patients who did not require RCA grafting. Early results of the patients in our four groups were similar. The independent risk factors for early mortality were CHF and PVD. The occurrence of postoperative complications was also similar for all groups, with more sternal infection affecting patients with COPD and diabetes mellitus. The 6-year survival was also similar in all four groups and was not associated with the type of conduit to the RCA.

This study has several limitations. Coronary angiography was performed mainly in symptomatic patients. These limited data do not allow any conclusion to be drawn with regard to patency rate. The groups were not closely matched. The RGEA group contained more young patients, and this graft was not used in emergent cases. Also, the tendency to prefer the SVG in higher-risk subgroups may influence later results. The RA as a graft to the PDA was not included in this study because we have been routinely using the RA only as of 1999.

The follow-up period was not long enough and whether arterial grafts to the RCA system can further improve clinical results of left-sided BITA grafting will probably be established after longer periods of follow-up. It well known that the rapid degradation of a SVG occurs after 5 to 7 years. We did not find in the current study (follow-up up to 78 month) any benefit for the free RITA over RGEAs and SVs when it was used as conduit for the RCA.

Therefore our current policy for RCA revascularization is different from the policy applied during the study period. We did not use the radial artery during the study period. We started using this conduit in 2000. Whenever possible, we prefer to use arterial conduits such as the RA for the RCA, rather than the SV, (RCA stenosis > 75%). Based on the results of this study, we use RITAs almost exclusively for left-sided revascularization. Our study did not show any benefit from using this graft for RCA revascularization. In addition, there was a trend towards a higher complication rate in the RITA group. We still prefer to use the RGEA in young patients with critical RCA stenosis because its long patency rate is supposedly superior to SVGs [17]. We use the SVG when RCA stenosis is less than 75% or in patients where the use of the RA (positive Allen test, dialysis) is contraindicated.

Conclusion
Early and mid-term results in patients undergoing left sided BITA grafting are apparently not affected by the conduit used for RCA grafting.

	Acknowledgments

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Esther Eshkol is thanked for editorial assistance.

	References

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 

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