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Ann Thorac Surg 2002;74:1548-1552
© 2002 The Society of Thoracic Surgeons

Original article: cardiovascular

Changing pattern in beating heart operations: use of skeletonized internal thoracic artery

Raymond Cartier, MDa*, Marzia Leacche, MDa, Pierre Couture, MDb

a Department of Surgery, Montreal Heart Institute, Montreal, Quebec, Canada
b Department of Anesthesia, Montreal Heart Institute, Montreal, Quebec, Canada

Accepted for publication July 11, 2002.

* Address reprint requests to Dr Cartier, Department of Surgery, Montreal Heart Institute, 5000 Belanger St E, Montreal, Quebec, Canada, H1T 1C8.
e-mail: rc2910{at}aol.com


   Abstract
Top
 Abstract
Introduction
 Patients and methods
 Results
 Comment
 References
 
BACKGROUND: The use of skeletonized internal thoracic artery (ITA) was reported to be technically and hemodynamically beneficial in conventional coronary artery bypass grafting with cardiopulmonary bypass assistance. The purpose of this study is to evaluate the impact of changing from conventional to skeletonized ITA harvesting on early off-pump coronary artery bypass grafting outcome.

METHODS: Between 1996 and 2001, 640 patients underwent systematic off-pump coronary artery bypass grafting (single surgeon experience). The ITA was pedicled (P) in the first consecutive 440 patients and skeletonized (S) in the subsequent 200 consecutive patients. Mean age, preoperative risk factors, sex, number of involved territories, and incidence of reoperations were similar in both groups.

RESULTS: In group S, number of ITAs per patient (1.7 ± 0.08 versus 1.2 ± 0.05; p < 0.001), bilateral ITA (46% versus 27%; p < 0.001), ITA sequential grafts (27% versus 1%; p < 0.001), and T grafts (16% versus 3%; p < 0.001) were higher. Deep sternal infections were comparable in both groups (group S: 1%, group P: 1.2%; p = 0.38). Perioperative myocardial infarction, maximal creatinine kinase-MB level, and requirement for more than 24 hours of inotropic support were comparable in both groups. Thirty-day mortality was also similar (S: 1.7%, P: 1.6%).

CONCLUSIONS: Changing to routine use of skeletonized ITA in off-pump coronary artery bypass grafting is a safe alternative to routine pedicled ITA. In our experience, this procedure has facilitated the use of ITA anastomosis without increasing sternal wound complications.


   Introduction
Top
 Abstract
 Introduction
Patients and methods
 Results
 Comment
 References
 
Off-pump coronary artery bypass grafting (OPCAB) has emerged as an established alternative technique of coronary artery revascularization that complements the standard technique of revascularization [1–4]. Aging of the surgical population, increased associated comorbidity, and more advanced ischemic heart disease have all been contributing elements that have promoted and facilitated the acceptance of OPCAB among the cardiovascular community. Nevertheless, OPCAB is still seen as a technically more demanding procedure that does not grant the surgeon similar technical possibilities as the conventional technique. Operating on a nonvented beating heart may occasionally produce a demand for longer conduits, particularly in cases of dilated ischemic cardiomyopathy. The use of skeletonized internal thoracic artery (ITA) has been well recognized to improve the length of the ITA allowing more distal and sequential grafting [5, 6]. This was also shown to reduce deep sternal infections, especially in bilateral harvesting among diabetic and obese patients [7, 8]. Furthermore, beneficial effects on immediate ITA flow after harvesting were reported with skeletonization compared with standard pedicle harvesting [9, 10]. However, skeletonization is a more tedious technique than pedicle harvesting. It also has the potential risk of conduit injury and perioperative ischemia.

The purpose of this study is to evaluate the effects of changing from conventional pedicled to systematic skeletonized ITA harvesting on early outcome of OPCAB in a single surgeon practice.


   Patients and methods
Top
 Abstract
 Introduction
 Patients and methods
Results
 Comment
 References
 
Between September 1996 and May 2001, 640 patients (single surgeon experience) underwent OPCAB for ischemic disease at the Montreal Heart Institute. They represented 95% of the entire cohort operated on for ischemic disease during the same time by the same surgeon. In the first 440 consecutive patients, ITAs were harvested as a pedicle (group P); whereas in the last 200 consecutive patients, ITAs were skeletonized (group S). Anesthetic management consisted of adequate patient fluid repletion, minimal use of ß-blockers, use of {alpha}-agonists to maintain systemic pressure greater than 100 mm Hg, and intravenous nitroglycerin whenever signs of ischemia were present. ß-Agonists were avoided to avoid exaggerated inotropism during stabilization, and only half of the heparin was reversed at the end of the procedure. Off-pump coronary artery bypass grafting was performed with mechanical stabilization (Cor-Vasc; CoroNéo Inc, Montreal, Quebecc, Canada). Pericardial traction sutures were used for posterior exposure as previously described [11]. Silicone loops were used for vessel occlusion. Revascularization strategy consisted of bypassing first the vessel with the culprit lesion immediately followed with the proximal aortic anastomosis when a saphenous vein or a radial artery was used. Endovascular shunt was only used when early ischemia was recorded during the preocclusion test (1 to 2 minutes).

To achieve ITA skeletonization, the endothoracic fascia was first divided between the internal thoracic vein and the ITA and used to pull down the artery and facilitate the dissection. Generally, collaterals were clipped proximally and cauterized distally. Electrocautery was constantly kept at a very low power (10 on a scale of 60) during the entire dissection. After heparin administration the ITA was clipped and divided distally. The conduit was then wrapped in a sponge humidified with a mixture of verapamil (10 mg/100 mL).

Results are expressed as mean and standard deviation for the continuous variables and percentage for discrete variables. Student’s t test was used to analyze continuous variables, and Fisher’s exact test was used for discrete variables. Statistical analysis was performed using a computer software package (SPSS, Chicago, IL). Statistical differences were considered significant if the p value was less than 0.05.


   Results
Top
 Abstract
 Introduction
 Patients and methods
 Results
Comment
 References
 
Demographics
Patient demographics are depicted in Table 1. Both groups had comparable sex distribution, risk factors for ischemic heart disease, preoperative functional class, number of ischemic territories involved, left main disease, preoperative left ventricular ejection fraction, history of unstable angina, recent (<4 weeks) myocardial infarction, and previous coronary artery bypass grafting. However, skeletonized patients were a little older.


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  		Table 1. Demographic Data for Skeletonized and Pedicled Cohorts

 
Surgical data
Both groups had a comparable number of grafts per patient, ischemic time (total of all anastomotic ischemic times), and rate of complete revascularization (Table 2). Nevertheless, in the skeletonized group, more grafts per ischemic territory were performed, operative blood losses were significantly lower, and a trend toward lesser transfusion rate was observed.


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  		Table 2. Surgical Data for Both Cohorts

 
Internal thoracic artery grafting
Internal artery grafting was used equally in both groups (96.3%; Fig 1). However, single ITA grafting was more common in group P (71% versus 37%) and double ITA to coronary artery bypass (bilateral or sequential) was more frequently used in group S (37% versus 24%). Triple arterial bypass with ITA conduits was used in 15% of group S and in less than 1% in group P. Bilateral ITA harvesting occurred more frequently in group S (48% versus 27%; p < 0.01) along with sequential grafting (26% versus 0.75%; p < 0.001) and T grafts (16% versus 3%; p < 0.001). When only diabetic patients were considered, bilateral harvesting was more frequent in the S patients (S [n = 55]: 35% versus P [n = 107]: 12%; p < 0.001). Interestingly, fewer vein grafts were performed in group S compared to group P (1.34 ± 0.94 versus 1.67 ± 0.97; p < 0.0001).



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  		Fig 1. Internal thoracic artery (ITA) to coronary artery bypass distribution for both cohorts. *p < 0.01. Open bars = pedicled; solid bars = skeletonized.

 
Perioperative data
Operative mortality, prevalence of perioperative myocardial infarction (defined by creatinine kinase-MB count > 100 IU), postoperative maximal creatinine kinase-MB count (P: 21 ± 50, S: 15 ± 33 IU; p = not significant), and need for new use of intraaortic balloon pump during or after operation were comparable for both cohorts (Table 3). Mechanical ventilation time and postoperative stay in the intensive care unit and postoperative hospital care facilities were shorter in group S, but this did not reach statistical significance. Nevertheless, surgical time was significantly longer in group S by approximately 20 minutes. When only one ITA was used, surgical time was not significantly different (P [n = 311]: 161 ± 41 minutes, S [n = 83]: 168 ± 50 minutes; p = 0.19). Similar observation was made with bilateral harvesting (P [n = 112]: 203 ± 43 minutes, S [n = 89]: 211 ± 42 minutes; p = 0.19). However, when only double ITA grafting was considered (either sequential or bilateral), time was comparable (P [n = 107]: 204 ± 41 minutes versus S [n = 75]: 201 ± 47 minutes; p = 0.65; Fig 2).


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  		Table 3. Perioperative Data for Both Cohorts

 


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  		Fig 2. Saphenous vein graft (SVG) distribution in both cohorts. *p < 0.001; #p = 0.05. Open bars = pedicled; solid bars = skeletonized. (ITA = internal thoracic artery.)

 
Deep sternal infection and dehiscence
Postoperative incidence of deep sternal infections, defined by any infections involving the sternum or the mediastinum (P: 1.2% versus S: 1%, p = not significant), sternal dehiscence (P: 2.1% versus S: 1.8%, p = not significant), and reoperation for bleeding (P: 3.8% versus S: 4.1%, p = not significant) were comparable for both groups. When all patients were considered, univariate analysis only identified diabetes (p = 0.05) as a contributing factor to deep sternal infections and bilateral ITA harvesting (p = 0.097) as a factor related to sternal dehiscence.


   Comment
Top
 Abstract
 Introduction
 Patients and methods
 Results
 Comment
References
 
There is an increasing body of evidence that the use of bilateral ITA graft could improve long-term outcome after coronary artery bypass grafting [12–14]. Using bilateral ITA in OPCAB can further improve patient outcomes by decreasing surgical manipulations of the ascending aorta and potential perioperative complications such as aortic dissection and cerebrovascular accident caused by plaque dislodgement [1, 15]. In the past, bilateral ITA harvesting has been shadowed by the specter of sternal infection and dehiscence, especially in patients with diabetes, obesity, and chronic obstructive pulmonary disease [16]. Internal thoracic artery skeletonization has been shown, both experimentally and clinically, to better preserve sternal vascularization and help prevent sternal wound complications [17]. In an animal model, Parish and coworkers [17] demonstrated better residual blood flow with ITA skeletonization than with the pedicle technique. Cohen and colleagues [18], using single photon emission computed tomography, confirmed the observation of Parish and coworkers [17] in a clinical setting. Galbut and colleagues [19] have reported a 1.5% rate of sternal complication with bilateral ITA skeletonization and have confirmed the excellent clinical long-term results with this technique. Calafiore and colleagues [20] reported a patency rate at 35 months of 100% in 33 patients who received bilateral ITA grafting for the anterior and posterior wall, confirming the safety and efficacy of the technique.

A common concern with skeletonization has been ITA injury during harvesting with postoperative spasm and ischemia [21, 22]. Noera and colleagues [23], looking at three different techniques of ITA harvesting including pedicle and skeletonization, could not find any difference in ITA blood flow or incidence of intramural hematoma. Other authors have reported similar results in clinical and experimental settings [24, 25]. Choi and Lee [9] clinically observed a higher immediate blood flow after ITA skeletonization compared with conventional technique when no intraluminal papaverine injection was used. Wendler and colleagues [10] observed similar findings after endoluminal perfusion of papaverine. Although the authors gave no specific explanation for this observation a parallel could be drawn with Leriche periarterial sympathectomy used in the early 20th century to improve peripheral vascular flow [26].

In the current series, clinical results were comparable with both techniques. Number of grafts per patient, operative mortality, perioperative myocardial infarction, average postoperative creatinine kinase-MB, use of intraaortic balloon pump, mechanical ventilation time, transfusion rate, and hospital stay were similar. Use of at least one ITA was similar in both groups, confirming the low occurrence of conduit injury. More bilateral harvesting and sequential ITA grafting were performed in the S cohort, which clinically translated as a lower use of vein grafts compared with the conventional technique. However, ITA skeletonization has its drawbacks. Because of the delicate aspect of the dissection, operative time was slightly prolonged although this was not clinically relevant (8 minutes). The 20-minute difference observed between the two groups was mostly related to the higher incidence of bilateral ITA harvesting in the S group. In our experience, the use of skeletonization led to a higher use of ITA grafting mainly owing to increased length of conduits and increased self-confidence with bilateral ITA harvesting in diabetic patients.

Postoperative prevalence of deep sternal infections and sternal dehiscence were comparable with both techniques. Considering the rate of bilateral ITA harvesting in group S patients was twice the rate observed in group P patients and a higher incidence of diabetes was found in the former, this observation appears reassuring. However, univariate analysis still indicated that diabetes was a risk factor for deep sternal complication, as previously reported [16].

Of course, this study has weaknesses. Patients were not randomized, and both techniques were not performed in the same time frame. Nevertheless, all operations were performed by a single surgeon, and all patients were considered without any selection in contrast with a randomized study, in which candidates are selected before the operation and then not always reflecting the surgeon’s daily practice.

In conclusion, changing from pedicled to systematic skeletonized ITA harvesting was found to be a safe strategy in OPCAB. In our experience, it has allowed a greater use of arterial conduits without increasing sternal complications.


   References
Top
 Abstract
 Introduction
 Patients and methods
 Results
 Comment
 References
 

  1. Cartier R., Brann S., Dagenais F., Martineau R., Couturier A. Systematic off-pump coronary artery revascularization in multivessel disease: experience of three hundred cases. J Thorac Cardiovasc Surg 2000;119:221-229.[Abstract/Free Full Text]
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  5. Cunningham J.M., Gharavi M.A., Fardin R., Meek R.A. Considerations in the skeletonization technique of internal thoracic artery dissection. Ann Thorac Surg 1992;54:947-951.[Abstract]
  6. Wendler O., Hennen B., Markwirth T., et al. T grafts with right internal thoracic artery to left internal thoracic artery versus the left internal thoracic artery, and radial artery. Flow dynamics in the internal thoracic artery main stem. J Thorac Cardiovasc Surg 1999;118:841-848.[Abstract/Free Full Text]
  7. Matsa M., Paz Y., Gurevitch J., et al. Bilateral skeletonized internal artery grafts in patients with diabetes mellitus. J Thorac Cardiovasc Surg 2001;121:668-674.[Abstract/Free Full Text]
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  9. Choi J.B., Lee S.Y. Skeletonized and pedicled internal thoracic artery grafts: effects on free flow during bypass. Ann Thorac Surg 1996;61:909-913.[Abstract/Free Full Text]
  10. Wendler O., Tscholl D., Huang Q., Schafers H.J. Free flow capacity of skeletonized versus pedicled internal thoracic artery grafts in coronary artery bypass grafts. Eur J Cardiothorac Surg 1999;15:247-250.[Abstract/Free Full Text]
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  14. Taggart D.P., D’Amico R., Altman D.G. Effect of arterial revascularization on survival: a systematic review of studies comparing bilateral and single internal mammary arteries. Lancet 2001;358:870-875.[Medline]
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