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Ann Thorac Surg 2004;77:1262-1265
© 2004 The Society of Thoracic Surgeons
a Division of Cardiothoracic Surgery, Brody School of Medicine at East Carolina University, Greenville, North Carolina USA
Accepted for publication September 23, 2003.
* Address reprint requests to Dr Bolotin, Department of Surgery, Tel Aviv Medical Center, 6 Weizman St, Tel Aviv, Israel
e-mail: bolotin{at}tasmc.health.gov.il
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Abstract |
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METHODS: Nine dogs underwent bilateral robotic internal thoracic artery harvesting through three ports placed in the left chest. One internal thoracic artery was harvested as a pedicle in each dog, and the other was skeletonized. Internal thoracic artery blood flow was measured in each graft, and comparative endothelial histologic studies were performed. Data are mean ± the standard error of the mean.
RESULTS: All 18 internal thoracic arteries were harvested successfully. Skeletonized internal thoracic artery harvests required more time (48.0 minutes ± 1.8) than pedicle internal thoracic artery harvests (39.0 minutes ± 1.4; p < 0.05). Internal thoracic artery flows during the final intervals were similar (skeletonized = 30.0 mL/min ± 2.4 vs pedicle = 31.5 mL/min ± 1.8; p = 0.9). Free internal thoracic artery bleeding flow was similar in both groups (skeletonized = 162.0 mL/min ± 3.0 vs pedicle = 189.0 mL/min ± 2.4; p = 0.4). Histologically, both groups were similar with minimal endothelial damage.
CONCLUSIONS: Robotically skeletonized harvesting is safe, but it requires more time (48.0 minutes ± 1.8) than pedicle internal thoracic artery harvesting. Despite muted tactile feedback with robotics, neither technique was associated with histologic or functional damage. These encouraging results may represent an advantage for complete arterial revascularization in robotic coronary bypass patients.
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Introduction |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Material and methods |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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All animals were anesthesized with intravenous sodium thiopental (Pentothal, 15 mg/kg; Abbott SPA, Rome, Italy), intubated, and maintained with 1% to 2% isoflurane and O2 and N2O (1:2 mixture). Throughout the experiments, lung ventilation was achieved using a positive-pressure respirator (MDS [Matrx, Orchard Park, NY]). Arterial invasive blood pressure using the Hewlett Packard 78534C, GMBH (Hamburg, Germany), electrocardiogram using the Hewlett Packard 78534C, GMBH (Hamburg, Germany), and pulse oximeter using the Escort 20401 (Arleta, CA) were monitored throughout the experiment. Body temperature was kept constant using a heating blanket.
Internal thoracic artery harvesting surgical technique
The animals were positioned on their side with the left chest up. The first port for the robotic camera (12 mm) was placed in the fourth intercostal space at the midaxillary line. CO2 insufflation was used to maintain an insufflation pressure between 6 to 10 mm Hg before introducing the endoscope by using a high-flow laparoflator (Linvatec, Largo FL) connected to the camera port. After adequate visualization of the pleural cavity was achieved, the two instrument ports (5 mm) were placed under endoscopic vision in the second and sixth intercostal spaces, two centimeters posterior to the camera port. The right internal thoracic artery was harvested first through the left chest, followed by the left internal thoracic artery harvesting through the same ports. To avoid internal thoracic side bias, five procedures were started with skeletonizing the right internal thoracic, followed by pediculated harvesting of the left internal thoracic artery, whereas the other four procedures were started with pediculated right side internal thoracic artery harvesting. Two surgeons performed the experiments. The harvesting technique was similar to the open clinical technique; mainly the cautery dissection was used in the pedicled group and the blunt dissection with clip division of the arterial branches was used in the skeletonized group. There was no use of papaverine during the harvesting procedures.
Instrumentation and data collection
A Doppler flow probe (Transonic Systems, NY) was introduced into the chest through the first intercostal space and placed around each internal thoracic artery using the robotic arms. The flow in the internal thoracic artery was monitored before and during the harvesting (every 10 minutes), at the end of the harvesting, and 5 minutes later. Free internal thoracic bleeding was measured at the end of each experiment. Surface electrocardiogram, invasive blood pressure, blood saturation, and systemic temperature were monitored continuously throughout the experiments.
The histologic examination
Vessels were fixed in 10% neutral buffered formalin. Cross-sections for evaluation were obtained sequentially every 10 mm. Tissues were routinely processed, and 4-micron sections were stained with hematoxylin and eosin. Sections were evaluated by a pathologist who was blinded to the harvesting techniques. Each section was evaluated semiquantitatively on a scale from 0 to 4 (0 = none, 1 = minimal, 2 = mild, 3 = moderate, and 4 = severe) for the following criteria: vacuolation of the tunica media, loss of endothelium, margination of white blood cells, loss of the internal elastic lamina, splitting of the internal elastic lamina, thrombosis, adventitial hemorrhage, periadventitial hemorrhage, vasa vasorum heat-associated damage, vasa vasorum thrombosis, and vasa vasorum margination of white blood cells.
Data and statistical analysis
Hemodynamic data were gathered on a personal computer using Sonosoft 3.1.3 (Sono Metrics, Ontario, Canada) software. Robotic pedicled internal thoracic artery harvesting was compared with skeletonized harvesting using the Student's paired t test. Results are expressed as mean ± standard deviation. Differences were considered significant at a p value less than 0.05.
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Results |
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Skeletonized ITA harvests required more time (46.6 ± 1 minute) than pediculated ITA harvests (35.5 ± 1 minute; p = 0.005). No learning curve was observed regarding the time needed to harvest the internal thoracic artery in either technique. There was no significant difference between the two surgeons; surgeon 1 required 45.8 ± 2 minutes for the skeletonization and 37.5 ± 2 minutes for the pedicle, whereas surgeon 2 required 47.4 ± 2 minutes for the skeletonization and 34.0 ± 3 for the pedicle (p = 0.74 and p = 0.86, respectively).
Internal thoracic artery blood flow at 5 minutes after harvesting was found to be similar when comparing the two techniques (skeletonized = 33.0 ± 1.4 mL/min vs pediculed = 36.1 ± 1.6 mL/min; p = 0.97). Free ITA bleeding flow was similar in both groups (skeletonized = 171.1 ± 10 mL/min vs pediculed = 187.5 ± 9 mL/min; p = 0.43).
There was a trend toward higher flow in the skeletonized group at the first part of the harvesting process (10 and 20 minutes) and a trend toward reduction in flow at the second half of the harvesting process (30 and 40 minutes) (Fig 1). However, these differences did not reach statistical significance, and 5 minutes after the completion of the harvesting process the flow between the two groups was found to be similar.
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Comment |
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Skeletonization of the internal thoracic artery was reported by Keeley [1] in order to achieve graft lengthening and potential use for sequential anastomosis. Other authors have reported an increased graft length as well as higher immediate blood flow in the skeletonized internal thoracic group as compared with the pedicled group, and also a larger anastomotic diameter in the skeletonized group [2, 3]. This higher immediate blood flow may increase the safety of arterial revascularization by reducing the risk of internal thoracic hypoperfusion syndrome [11]. Other groups have reported an improvement in pulmonary function tests and deep sternal wound infections in the elderly, diabetic patients with the routine use of bilateral skeletonized internal thoracic arteries [12, 13]. Calafiore and coworkers [14] reported the clinical advantages of bilateral skeletonized internal thoracic grafting in regard to the increased number of distal anastomosis and lower sternal wound complications as compared with bilateral pedicled internal thoracic artery grafting. This combination of potentially more distal anastomosis with the use of off-pump technology may represent a future advantage of the skeletonized technique in robotic-assisted totally arterial multivessel off-pump surgery [4, 5].
In the current study, robotic skeletonization was found to be more time consuming than robotic pediculed ITA harvesting. A difference of 11 minutes between the two techniques may be of importance, because totally endoscopic coronary artery bypass procedures are generally more time consuming. No learning curve was demonstrated in our study, probably because of the small number of procedures as compared with the clinical reports [15].
The minimal and comparable histologic damage is similar to previous reports comparing the two harvesting techniques in median sternotomy patients [16, 17]. The trend toward more vasa vasorum damage (heat changes and vasa vasorum thrombosis) in the skeletonized group may represent a potential hazard toward long-term changes. However, the overall number is quite low (0.1and 0.6, less than minimal) and therefore should probably not represent clinical significance.
The dog is a well-accepted animal model for ITA harvesting; however, several anatomical differences make the dog's ITAs easier to harvest. The major differences include the following: the first third of the dog's ITA is loosely in the mesentery, there are fewer side branches in the dog's ITA in the latter two thirds, and the vessel is covered mainly by muscle. Therefore clinical robotic harvesting is needed to verify our results.
In conclusion, based on our animal model, robotic skeletonization of the internal thoracic artery is feasible and safe, and it may represent a future advantage for total arterial robotic coronary artery bypass grafting.
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= pediculated; 
= skeletonized. (pre = preoperative.)