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Eur J Cardiothorac Surg 2002;21:1015-1019
© 2002 Elsevier Science NL

Bilateral pedicled internal thoracic artery grafting

Department of Cardiovascular Surgery, Kumamoto Central Hospital, Kumamoto City, Japan

Received 15 October 2001; received in revised form 10 January 2002; accepted 15 March 2002.

* Corresponding author. Department of Cardiothoracic Surgery, St. George Hospital, Gray Street, Kogarah, NSW 2217 Australia. Tel.: +61-2-9585-8417; fax: +61-2-9585-8417
e-mail: masashiura{at}hotmail.com

	Abstract

Top Abstract 1. Introduction 2. Patients and methods 3. Operative technique 4. Results 5. Discussion References

 
Background: Pedicled bilateral internal thoracic artery grafting (BITA) has been discouraged in historical high-risk groups such as diabetes mellitus (DM), renal failure, old age, and obesity because of reported high incidence of mediastinitis. However, considering the fact that there are abundant short and long-term results including angiography study about the conventional pedicled grafts, it might be worthwhile reassessing the results of pedicled BITA grafting with modern techniques by a disciplined surgical team before abandoning the method. Methods: Between September 1989 and September 1999, 1371 patients underwent isolated coronary artery bypass grafting (CABG) in Kumamoto central hospital. Of these patients, 558 patients who had bilateral ITA strategy (mean age 63.0±9.2 years, 13–79) were studied. The method of harvest of ITAs is consistently the use of conventional pedicled grafts. The use of bone wax and unnecessary electrocautery injury to the periostium or cartilage were avoided as much as possible. The only change in the surgical technique in the study period is the application of the pinpoint hemostasis for the presternal tissues from August 1997 (late period). Results: In late period, there were significantly more patients with sternal sepsis risk factors such as diabetes mellitus (early: late; 19.3% vs. 34.8%, P<0.00003), and renal failure (0.3 vs. 9.7%, P<0.0001) as well as patients who had gastroepiploic artery grafting (16.9 vs 48.5%, P<0.0001) and those who required aortic non-touch technique (2.1 vs. 7.9%, P<0.001). The percentage of the patients receiving BITA grafting among the isolated CABG patients increased in the late period from 31.7% (331/1043) to 69.2% (227/328) (P<0.001), reflecting that a more aggressive approach towards bilateral ITA and arterial grafting has been taken in the late period. Overall operative mortality was 1.1% (n=6). Mediastinitis occurred in seven patients (1.3%). Of these, only one mediastinitis occurred in late period (0.4%). No mediastinitis occurred in 23 chronic renal dialysis patients. Among the 143 DM patients, there were three mediastinitis (2.1%). Of three, only one occurred in late period, yielding 1.3% mediastinitis rate. There was one mediastinitis (0.7%) among 134 elderly patients more than 70 years of age. Univariate analysis identified obesity as a risk factor for mediastinitis. And there was a trend of decreasing mediastinits in late period but did not reached a statistical significance (P<0.2). Multivariate analysis identified obesity and arteriosclerosis obliterates as independent risk factors. Neither diabetes mellitus, dialysis, female gender, nor old age were significant independent predictors of mediastinitis. Despite the significantly high percentage of high-risk patients in late group, there were no significant difference in mortality and morbidity between the two groups. Conclusion: Pedicled BITA grafting is feasible with acceptable morbidity and shouldn't be abandoned even in high-risk patients such as DM, old age, and dialysis, especially combined with pinpoint-hemostasis, avoiding excessive use of bone wax, and strict aseptic technique. These point require a surgical team familiar with these techniques to maintain adequate skills in conduit procurement.

Key Words: Coronary artery bypass grafting • Bilateral internal thoracic artery • Mediastinitis

	1. Introduction

Top Abstract 1. Introduction 2. Patients and methods 3. Operative technique 4. Results 5. Discussion References

 
Mediastinitis is a devastating complication after cardiac surgery. The use of bilateral internal thoracic artery (BITA) has been identified as a major determinant for mediastinitis after coronary artery bypass grafting (CABG) from previous studies [1]. Other recognized risk factors for mediastinitis included diabetes mellitus (DM), obesity, chronic obstructive pulmonary disease (COPD), old age, and chronic renal failure [1–5]. Borger et al. reported that BITA grafts increased the risk of deep sternal wound infection (DSWI) in all subgroups of CABG patients, particularly in diabetics who had a 14.3% incidence of DSWI after BITA grafting [4]. Because of these disappointing results in BITA grafting, BITA grafting has been discouraged in historical high-risk groups except if skeletonized BITA is used, as increasing number of favorable short time results using skeletonized BITA have been reported [6,7]. However, given the fact that there are abundant short- and long-term results about the conventional pedicled grafts and skeltonizing the ITAs is more time consuming than pedicled ITAs, it might be worthwhile reassessing the results of pedicled BITA grafting with modern techniques by a disciplined surgical team before the technique is abandoned. Thus the purpose of this study is to report the overall results of pedicled BITA grafting especially in high-risk group such as DM, old age, chronic renal failure in the institution where pedicled BITA grafting has been performed consistently.

	2. Patients and methods

Top Abstract 1. Introduction 2. Patients and methods 3. Operative technique 4. Results 5. Discussion References

 
Between September 1989 and September 1999, 1371 patients underwent isolated CABG in Kumamoto central hospital. Of these patients, 558 patients who had bilateral ITA strategy (mean age 63.0±9.2 years, 13–79) were studied. The patient's characteristics were summarized in the Table 1.

	3. Operative technique

Top Abstract 1. Introduction 2. Patients and methods 3. Operative technique 4. Results 5. Discussion References

 
The method of harvest of ITAs is the use of conventional pedicled grafts and not particularly special but a few key points were as followed: (1) extreme care was taken in avoiding any unnecessary electrocautery injury to the periostium or cartilage (in other words, harvest in the right plane); (2) harvesting of ITA grafts were performed mainly by the senior staff but if performed by the junior staff, under strict control and guidance of senior staff; (3) the use of bone wax was avoided as much as possible.

No skeletonized or semi-skeletonized technique were used in the study period. The power of the electrocautery varies according to the each surgeon's preference between 15 and 35 W. The only change in the surgical technique in the study period is the application of the pinpoint hemostasis for the presternal tissues as described by Nishida et al. [8]. From August 1997,presternal soft tissues were divided with the scalpel and hemostasis was performed with a pinpoint use of electrocautery to minimize the damage of the presternal tissue. However, the technique of the harvesting the ITA grafts itself has not been changed.

From August 1997, we confirmed satisfactory results of an initial pilot study of several patients in high-risk categories such as dialysis, old age, and DM, we then cautiously expanded the indication of BITA grafting to such historically known high-risk categories. This resulted in a significant number of patients with DM (early: late; 19.3 vs. 34.8%, P<0.00003), hyperlipidemia (26.3 vs. 43.2%, P<0.00003) and renal failure (0.3 vs. 9.7%, P<0.0001) being included. Patients who had gastroepiploic artery (GEA) grafting were also more frequent in late period. Modification of operation for increased aortic disease such as grafting on beating heart, the use of ventricular fibrillation or hypothermic circulatory arrest become more frequent in late period, reflecting the fact that aortic non-touch techniques using in situ arterial grafts were used more frequently in such high-risk patients in late period (2.1 vs. 7.9%, P<0.001). The percentage of the patients receiving BITA grafting among the isolated CABG patients increased in the later period from 31.7 (331/1043) to 69.2% (227/328) (P<0.001). The results reflect that a more aggressive approach towards bilateral ITA and arterial grafting has been taken in the late period.

3.1. Data definition
Body mass index (BMI) was calculated as weight (kg)/(height in meters) [2]. Emergency operation was defined if operation was performed immediately after the coronary angiogram. DM was defined as being treated medically either by diet, oral hypoglycaemics or insulin. The timing (period) of operation was defined as late if operation was performed after August 1997.

Mediastinitis was defined as infection involving the mediastinal area, with sternal instability and positive organism culture. Postoperative low output syndrome was documented if IABP was used postoperatively or inotrope was required more than 3 days postoperatively.

Postoperative respiratory failure was defined as prolonged ventilation >48 h. A perioperative myocardial infarction (PMI) was documented if a new Q wave appeared on the ECG or if creatinine kinase MB levels rose beyond 100 IU/L.

3.2. Statistical analysis
Univariate analysis was performed to clarify the risk factors of mediastinitis in pre-, intra- and post-operative variables.

Univariate testing of variables was performed with the Fisher's exact test for discrete variable comparisons. The Mann–Whitney U test was used for continuous variable comparisons.

To further clarify the risk factors, the multivariate analysis was performed among the variables. P<0.05 was considered significant.

All analyses were performed using the SAS Institute ver. 6.12 (Cary, N. C.) software.

	4. Results

Top Abstract 1. Introduction 2. Patients and methods 3. Operative technique 4. Results 5. Discussion References

 
Overall operative mortality was 1.1% (n=6). Mediastinitis occurred in seven patients (1.3%). Of these, only one mediastinitis occurred in the late period (0.4%). The mediastinitis rate in each categorized group were summarized in Table 2. No mediastinitis occurred in 23 chronic renal dialysis patients (nine with DM) or in 119 female patients. Among the 143 DM patients, there were three mediastinitis (2.1%). Of these three, only one occurred in late period, yielding 1.3% mediastinitis rate. There was one mediastinitis (0.7%) among 134 elderly patients more than 70 years of age. Univariate analysis identified obesity as a risk factor for mediastinitis. There was a trend of increasing rate of mediastinitis in younger patients, male gender, postoperative stroke, postoperative respiratory failure, and low cardiac output syndrome but none of these reached a statistical significance (P<0.2) And there was a trend of decreasing mediastinitis in late period but this also did not reach a statistical significance(P<0.2) (Table 2).

Patient's characteristics who had mediastinitis are summarized in Table 4. All except one recovered well with treatment of debridement and irrigation and closure of wounds. A 70-year old male with complications of intraoperative stroke, underwent an omental flap, this patient had persistent septicemia from the chest wound and died of multiple organ failure at 210 postoperative days.

	5. Discussion

Top Abstract 1. Introduction 2. Patients and methods 3. Operative technique 4. Results 5. Discussion References

Recently, the use of skeletonized BITA conduits has been reported to be potentially useful to expand the use of ITAs, in terms of the number of anastomoses per patient and of reducing the incidence of sternal complications. Jacob Gurevitch reported the outcomes of the impact of the routine use of double skeletonized internal mammary artery in 472 patients who underwent CABG [7]. One hundred sixty-nine (36%) of the patients were older than 70 years, and 145 (31%) were diabetic. Operative mortality was 1.7% (n=8). Sternal wound infection occurred in eight patients (1.7%). Neither DM nor old age (>70 years) were significant independent predictors of any early or late untoward events. None of the 70 diabetic patients more than 65 years of age developed sternal wound infection. Chronic lung disease was found to be the only independent predictor for sternal infections. As mentioned by them, the main disadvantage of this operative technique is that harvesting the skeletonized arterial graft is more time consuming than conventional one. In addition, less is known about the late results of skeletonized grafts whereas there are abundant short- and long-term results about the conventional pedicled grafts.

Antonio Calafiore reported the outcomes of 1146 patients who underwent isolated myocardial revascularization using BITAs, with 304 receiving pedicled grafts and 842 receiving skeletonized conduits. The skeletonized grafts group had a higher incidence of patients with diabetes (223 vs. 40, P<0.001). Postoperative complications were similar in both groups; the incidence of sternal wound healing problems was higher as a whole and with regard to diabetic patients (four of 40 [10%] vs. five of 223 [2.2%], P<0.05) in pedicled grafts group [6].

In search of better methods to decrease the mediastinitis in patients undergoing BITA grafting, we employed the following method; the pinpoint-electrocautery hemostasis techniques as well as avoidance of use of bone wax, and strict aseptic technique. Nishida reported that superficial or deep mediastinitis (or both) developed in only five (0.16%) of 3118 consecutive patients, if only the surgical team disciplined itself to divide presternal soft tissues with a scalpel and used electrocautery for pinpoint hemostasis [8]. However, in their study, there were a few BITA grafting patients and still little is known about pedicled BITA grafting using pinpoint hemostasis technique on mediastinitis. We have employed the use of conventional pedicled ITA even for BITA grafting and from August 1997, we started to use the pinpoint hemostasis-technique with expectation of reducing the mediastinitis in high-risk patients.We confirmed satisfactory results of an initial pilot study of several patients in high-risk categories such as dialysis, old age, and DM, we then cautiously expand the indication of BITA grafting to such historically known high-risk categories. This resulted in a significant number of diabetes and renal failure patients being included. In our series, no mediastinitis occurred in 23 chronic renal dialysis patients (nine with DM). Among the 143 DM patients, there were three mediastinitis (2.1%). Of the three, only one occurred in late period, yielding a mediastinitis incidence of 1.3%. The incidence of mediastinitis in DM patients with or without the pinpoint-electrocautery hemostasis techniques is lower than previously reported results of pedicled grafts and comparable to the recently published good results by skeletonized BITA grafting (3.1 and 1.3%; overall 2.1 vs. 2.2% by Calafiore et al.). In addition, although this study failed to demonstrate independent preventive effect for mediastinitis with pinpoint-electrcautery hemostasis techniques because time frame when each technique was used were different, there was a trend of decreasing incidence of mediastinitis in late period with the combination of the use of pinpoint-hemostasis technique, which supports continuing the use of pedicled BITA grafting with our currently used technique.

Jacob Gurevitch noted that when the IMA is isolated from the chest wall as a pedicle, cauterization damages the blood supply to the sternum, which in turn impedes sternal healing and exposes the sternum to the risks of early dehiscence and infection, particularly in operations in which both ITAs are used [7]. We believe that, even when ITA is harvested as a pedicle, the damage to the blood supply to the sternum could be minimized or reduced by avoiding injuries to the periostium and cartilage, which may partially explain our good results. Few reports exist regarding the bilateral ITA grafting in dialysis patients. Previous studies have demonstrated that ITA grafting does not increase the morbidity in dialysis patients [9]. Dialysis patients often have poor saphenous vein grafts and severe atherosclerosis of ascending aorta as reported in previous reports. Radial artery is usually not available in this group of patients because radial artery should be reserved for possible and present arterial-venous fistula for hemodialysis. In these situations, our results suggest bilateral ITA grafting could represent a useful option without increasing morbidity. In our experience, no mediastinitis occurred in 23 chronic dialysis patients including nine patients with DM. Definite conclusions could not be drawn because of the small number of patients, but the pinpoint-hemostasis technique has potential to provide reliable conduits to this high-risk group of patients.

In conclusion, pedicled BITA grafting is feasible with acceptable morbidity even in high-risk patients such as DM, old age, and dialysis, when especially combined with pinpoint-hemostasis, avoiding excessive use of bone wax, and strict aseptic technique. These points require a surgical team familiar with these techniques to maintain adequate skills in conduit procurement.

	References

Top Abstract 1. Introduction 2. Patients and methods 3. Operative technique 4. Results 5. Discussion References

 

1. Anonymous Risk factors for deep sternal wound infection after sternotomy: a prospective, multicenter study. J Thorac Cardiovasc Surg 1996;111:1200-1207.[Abstract/Free Full Text]
2. Baskett R.J., MacDougall C.E., Ross D.B. Is mediastinitis a preventable complication? A 10-year review. Ann Thorac Surg 1999;67:462-465.[Abstract/Free Full Text]
3. Bitkover C.Y., Gardlund B. Mediastinitis after cardiovascular operations: a case-control study of risk factors. Ann Thorac Surg 1998;65:36-40.[Abstract/Free Full Text]
4. Borger M.A., Rao V., Weisel R.D., Ivanov J., Cohen G., Scully H.E., David T.E. Deep sternal wound infection: risk factors and outcomes. Ann Thorac Surg 1998;65:1050-1056.[Abstract/Free Full Text]
5. He G.W., Ryan W.H., Acuff T.E., Bowman R.T., Douthit M.B., Yang C.Q., Mack M.J. Risk factors for operative mortality and sternal wound infection in bilateral internal mammary artery grafting. J Thorac Cardiovasc Surg 1994;107:196-202.[Abstract/Free Full Text]
6. Calafiore A.M., Vitolla G., Iaco A.L., Fino C., Di Giammarco G., Marchesani F., Teodori G., D'Addario G., Mazzei V. Bilateral internal mammary artery grafting: midterm results of pedicled versus skeletonized conduits. Ann Thorac Surg 1999;67:1637-1642.[Abstract/Free Full Text]
7. Gurevitch J., Paz Y., Shapira I., Matsa M., Kramer A., Pevni D., Lev-Ran O., Moshkovitz Y., Mohr R. Routine use of bilateral skeletonized internal mammary arteries for myocardial revascularization. Ann Thorac Surg 1999;68:406-411.[Abstract/Free Full Text]
8. Nishida H., Grooters R.K., Soltanzadeh H., Thieman K.C., Schneider R.F., Kim W.P. Discriminate use of electrocautery on the median sternotomy incision. A 0.16% wound infection rate. J Thorac Cardiovasc Surg 1991;101:488-494.[Abstract]
9. Nakayama Y., Sakata R., Ura M. Bilateral internal thoracic artery use for dialysis patients: does it increase operative risk?. Ann Thorac Surg 2001;71:783-787.[Abstract/Free Full Text]

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