Comparison of conventional electrocautery vs Plasmablade™ for internal thoracic artery harvesting

Abdulkadir Bilgiç; Emrah Uğuz; Kemal Eşref Erdoğan; Aydan Kılıçaslan; Mecit Gökçimen; Mete Hıdıroğlu; Erol Şener

doi:10.5606/e-cvsi.2016.492

Abstract

Objectives

In this study, we aim to investigate whether internal thoracic artery harvesting with the PlasmaBlade™ is more effective and safer than electrocautery in preserving the integrity of the intima and pedicle of the internal thoracic artery.

Patients and methods

Between January 2014 and March 2014, a total of 40 patients were randomized to undergo internal thoracic artery harvesting with the PlasmaBlade™ (group 1; n=20) or electrocautery (group 2; n=20). Internal thoracic artery sections (intima and pedicle) were stained with hematoxylin-eosin, van Gieson's and Masson's trichrome stains. Their integrity was morphologically assessed using the light microscopy.

Results

Histological examination showed that endothelium was well preserved and endothelial injury scores were significantly lower in group 1, compared to group 2 (p=0.020). Bleeding scores for the vessel wall and the pedicle were also significantly lower in group 1, compared to group 2 (p=0.020). The mean injury zone width was significantly shorter in group 1 (0.335 mm and 0.730 mm in group 1 and 2, respectively) (p=0.000).

Conclusion

The PlasmaBlade™ is safer and more effective in preserving the integrity of the intima and pedicle of the internal thoracic artery than electrocautery for internal thoracic artery harvesting in coronary artery bypass grafting. A well-preserved endothelial function may provide higher graft patency rates.

Keywords:

Coronary artery bypass surgery, electrocautery, graft harvesting, internal thoracic artery

Introduction

After Kolesov performed the first internal thoracic artery (ITA) - left anterior descending artery (LAD) anastomosis,[1] ITA was recognized as the most optimal conduit for coronary artery bypass grafting (CABG). Thanks to its positive effects on early and long-term patency rates and high cardiac survival rates, it has been explicitly suggested by many authors.[2] Despite the developments in transcatheter methods and new generation drug eluting stents, it is still incomparable with other alternative methods in terms of the patency rates of LAD-ITA anastomosis.[3]

Internal thoracic artery has a unique molecular and cellular resistance against atherosclerosis.[4,5] However, endothelial injury during harvesting may activate the coagulation cascade, thereby, leading to early graft thrombosis.[2] Furthermore, the endothelial injury may facilitate the atherosclerotic process, and, as a result, it may cause graft stenosis or occlusion in the long-term.[2] Therefore, the internal elastic lamina must be intact for a high-rate long-term ITA patency.

Internal thoracic artery harvesting with electrocautery has become a standard procedure since first described in 1967.[1] To further increase the utilization of this artery, a variety of topical and systemic vasodilator agents have been proposed and less invasive ITA harvesting techniques have been developed.[4-6]

The PlasmaBlade™ (PEAK Surgical, Inc., Palo Alto, CA, USA) which was developed to cause minimal thermal damage during tissue cutting and coagulation has been introduced as a novel surgical device with pulsed-plasma technology.[7-11]

In this study, we aim to investigate whether ITA harvesting with the PlasmaBlade™ is more effective and safer than conventional electrocautery in preserving the integrity of the intima and pedicle of the ITA.

Methods

Between January 2014 and March 2014, a total of 40 patients who were hospitalized for CABG were randomized to undergo ITA harvesting with the PlasmaBlade™ (group 1; n=20) or electrocautery (group 2; n=20). The socio-demographic and basic characteristics in respect of accompanying diseases are provided in Table 1.

The primary objective of our study was to find out whether Plasmablade is superior to electrocautery in means of preventing endothelial and perivascular connective tissue injury by histopathologic examination of the ITA samples under light microscope. The study protocol was approved by the Ankara Atatürk Training and Research Hospital Ethics Committee. A written informed consent was obtained from each patient. The study was conducted in accordance with the principles of the Declaration of Helsinki.

Surgical technique

Internal thoracic artery graft harvesting was initiated with placing the ITA retractor following the median sternotomy. Endothoracic fascia was opened throughout the ITA. The conventional cautery (Valleylab™ Force FX™ monopolar electrocautery, Covidien; Mansfield, Mass) was used at a low-power (diatermy coagulation 20 W). In the other group, the PlasmaBlade™ was used. A special care was taken to avoid dissection, avulsion, or spasm during excision.

The subclavian vein was exposed proximally to the ITA and the proximal branches of the ITA were divided. It was distally released up to 1 cm proximal to the bifurcation together with the accompanying satellite veins and fatty tissues. Homeostasis was implemented using hemostatic titanium clips on the ITA branches (SLS-Clip™ System Vitalitec International Inc., Plymouth, Massachusetts, USA).

The branches were divided approximately 2 mm distal from the origin of the ITA. Following systemic heparinization for minimum three minutes, the graft was separated from the thoracic wall. The ITA segment was removed from the distal section of the ITA prior to use of the papaverine solution. Then, the papaverine solution is sprayed onto the graft and the ITA was kept in a warm papaverine and physiological saline-impregnated gauze. In our clinic, the bifurcation is kept in place to protect the sternal blood flow and collateral circulation. Approximately 1 cm long distal segment, the ITA is not used prior to bifurcation. The study specimens were obtained removing a 1 cm long ITA tissue proximal to this segment.

Pathological examination

The specimens were fixed in the solution containing 10% buffered formaldehyde. All specimens were sectioned, stained with hematoxylin-eosin (H-E), Masson's trichrome (MTK), and elastic van Gieson (EVG) stains and were examined under the light microscopy (Leica DM6000 B, Leica Microsystems Inc., Buffalo Grove, IL, USA). The specimens stained with MTK were examined to identify the extent of the thermal injury on the collagen in the vascular wall, while the specimens stained with EVG were analyzed to determine the impact of the thermal injury on elastine in the ITA wall. The specimens stained with H-E underwent histological examination.

Endothelial injury, congestion, free bleeding, and the width of the injury zone were evaluated in the histopathological examination under the light microscopy. Scoring systems which were described in previous studies were used.[12,13]

During the histopathological examination, endothelial injury was scored to be 0= no injury, 1= mild injury (slight desquamation in the endothelium, minimal exposure in the basal lamina), 2= moderate injury (intimal or endothelial contusion), and 3= severe injury (endothelial separation), regarding the endothelial cell loss, exposed basal lamina, and intimal and medial edema.

Congestion was scored to be 1, in case of congestion in 30% of the vascular structures; to be 2, in case of congestion in 60% of the vascular structures, and to be 3, in case of 90% or higher congestion of vascular structures.

Free bleeding was scored to be 1, in case of bleeding in less than 10% of the perivascular soft tissue to be 2, if it involves 20-50%, and to be 3, if it is more than 50%.

The width of the injury zone was examined to compare the impact of collateral thermal injury which the PlasmaBlade™ and conventional cautery caused in the soft tissues during dissection.

Statistical analysis

Based on the results of the preliminary power analyses, the obligatory sampling width required for the comparison of the endothelial injury between the groups was calculated as 40 with 20 patients in each group. In such case, the expected value for the power of the test was found to be approximately 81.31%.

Statistical analysis was carried out using SPSS for Windows version 15.0 software program (SPSS Inc., Chicago, IL, USA). The demographic data were expressed in mean ± standard deviation. The Mann- Whitney U test and Spearman's correlation analysis were performed. A p value of <0.05 was considered statistically significant.

Results

The baseline and demographic characteristics of the patients are shown in Table 1.

The bleeding status was compared under four categories between two groups, as described above.

The first, second, and third-degree bleeding were found to be 50%, 30%, and 20% in group 1 respectively.

In group 2, the patients with no bleeding, first, second, and third-degree bleeding were found to be 5%, 10%, 25%, and 60%, respectively.

Using the Pearson's chi-square test, the patients with no bleeding were combined with the patients with first-degree bleeding in a single category and the patients were re-examined under three categories (Table 2). In group 1, less severe bleeding was seen, indicating a statistical significance (Fisher's exact test=7,860 and p=0.020) (Figure 1).

The mean width of the injury zone was 0.335 mm and 0.730 mm in group 1 and group 2, respectively (Figure 2). In group 1, the width of the injury zone was significantly lower (Student's t test=4.902 and p=0.000) (Table 3). Desquamation was also seen in the collagen tissue due to collateral thermal injury in the MTK stained ITA samples harvested with electrocautery (Figure 3).

No endothelial injury was observed in 95% (n=19) of the patients in group 1 and in 60% of the patients (n=12) in group 2 (p=0.020). In both groups, there was no second or third-degree endothelial injury (Table 4).

Collateral heat did not cause damage to the collagen tissue in MTK stained ITA samples harvested with the PlasmaBlade™ (Figure 4).

When the congestion scores were reviewed, firstdegree congestion was found in 45%, second-degree congestion in 50%, and third-degree in 5% of the patients in group 1, while these were found to be 20%, 65%, and 15% in group 2, respectively. The congestion scores of both groups are presented in Table 5.

The congestion was examined under three categories. Using the Fisher chi-square, the categories were combined to have two categories. However, there was no statistically significant difference in the congestion scores between the groups (p=0.605).

Discussion

Since CABG was first brought into daily practice, several attempts have been made to develop an ideal graft. However, the superiority of the arterial grafts into the venous grafts was proven: the ITA was introduced in 1960s, and since then, it has been the optimal conduit of choice.[2, 4, 6,14-16] The ITA has higher long-term patency rates, compared to other grafts.[13-15] While the typical atherosclerotic changes and intimal hyperplasia can develop faster in the venous grafts, they are seen much rarely and later with the ITA grafts.[17-21]

Currently, one of the most commonly used techniques in the ITA harvesting is pedicled preparation of the conduit with the surrounding soft tissue, satellite veins, and endothoracic fascia.[2-4,14] This method facilitates harvesting and reduces the possibility of vascular injury.[4] In addition, sustainability of venous and lymphatic drainage ensures the protection of vasa vasorum and continued activity of the conduit.[4,5] Since the very first cases for CABG, it has been prepared using electrocautery.[22] The main goal of using electrosurgery is to ensure a clean and clear incision and coagulation with minimum collateral heat injury.[23,24] The PlasmaBlade™ tissue dissection devices are introduced as novel surgical devices with pulsed-plasma technology to avoid adverse effects of conventional electrocautery.[23,24] It has been developed to induce minimal thermal damage during the tissue dissection and coagulation and the device is called as PEAK® Surgery System together with PULSAR® Generator.[23-25] Most electrosurgical cutting tools use continuous radio-frequency (RF) waveforms which thermally vaporize the soft tissue through heating and via an electric arc.[23-25] This results in cutting and coagulation which leaves a wide zone of collateral thermal tissue damage. As the PlasmaBlade™ device receives RF energy in short pulses via a highly insulated cutting electrode, it has an ability to cut at a much lower mean temperature than conventional electrosurgery.[4]

Furthermore, the basic operating principle of this system is that it creates a vapor cloud with the device end contacting with the tissue. The ionization of the water molecules in the vapor cloud creates a specific environment for the dissection. It has been shown that the dissection is performed at a lower temperature (approximately 45 ˚C) with a lower power, a lower voltage, and a lower current due to the ionization of the water molecules.[23,24] The mean temperature for the conventional cautery is 250 to 350 ˚C.[23,24] Unlike conventional electrocautery systems, this device does not provide a fixed voltage. Its pulsed-voltage values ranging between +300 and -100 within nanoseconds ensure maximum ionization of the water molecules.

As the device end is covered with a glass-based silicon agent, the active region becomes narrow and only the crescent-shaped region which is approximately 0.5 mm thick at the tip is active.[7-11] As the impedance of the tissue decreases within this specifically created environment, less tissue necrosis and thermal damage occur and such a dissection is obtained closer to that performed with a scalpel.[23-25]

A variety of preclinical and clinical studies were carried out in different surgical zones while and after developing the peak surgery system.[23] The studies were initially started with in vivo and ex vivo preclinical testing on animals and, then, clinical studies were performed.[23] It has been shown through these studies that such a dissection which has a scalpel precision and causes hardly any thermal damages at lower power levels can be performed using the PEAK surgery system and that the system has a hemostasis capability equal to the conventional electrocautery at higher power levels.[23]

No matter how much lower the power is kept in conventional electrocautery during ITA harvesting, the resulting collateral heat may cause damage to both the surrounding tissue and the ITA itself. The traction induced by the perivascular hematoma and electrocautery burn creates a local turbulent flow in the artery. Such turbulent flow may accelerate atherosclerosis due to the endothelial damage as previously reported in the literature and pose an adverse effect on the graft patency.[5] In our study, severe bleeding areas in the perivascular tissue were found significantly higher in the electrocautery group. Therefore, we believe that less perivascular bleeding in the pedicle with the PlasmaBlade™ system may reduce the turbulent flow and increase the patency rates.

It has been shown that an intact elastic lamina following the ITA harvesting may prevent atherosclerosis. In our study, the width of the injury zone was found to be significantly lower in the patients treated with the PlasmaBlade™ rather than electrocautery. Thus, it suggests that the PlasmaBlade™ may reduce collateral thermal injuries, and accordingly, increase the graft patency rates.

In another study, Lehtola et al.[26] demonstrated that an endothelial injury and mural thrombosis developed, when the tip of the electrocautery contacted with the ITA wall or the hemostatic metallic clips, which might be a reason for early and late graft failures. In this study, histopathological examination of the electrocautery group revealed thermal damage-induced extensive cautery artefacts in the arterioles of the ITA.

Several preclinical studies have shown that the PlasmaBlade™ requires less than half of the energy produced in the conventional electrocautery devices to achieve similar dissection and coagulation results due to the advance level insulation of its electrode configuration, and its pulsed electric wave forms.[23] This ensures that the temperature during the procedure is less than half of the temperature of the conventional devices, thereby, providing a decrease in the heat transfer by more than a half and a decrease by 50 to 90% in the depth of the thermal injury of the surrounding tissues.[23] Similarly, in our study, the width of the injury zone and severe perivascular bleeding were significantly lower in the PlasmaBlade™ group than the conventional electrocautery group.

Moreover, postoperative sensorial abnormalities on the thoracic wall (i.e. hypoesthesia, hyperalgesia, and allodynia) are associated with the utilization of electrocautery, which may adversely affect the wound healing.[27] It is well-known that the surgical smoke impairs the image quality and the cautery smoke increases the risk of cancer.[28] In addition, the requirement for the cautery tip to be frequently cleaned may be challenging; however, more importantly, burn injuries have been reported in case of improper grounding.[28] In the literature, the advantages of the PlasmaBlade™ have been published.[23] Nonetheless, the ability of the PlasmaBlade™ to provide surgical hemostasis and its effects on postoperative bleeding and blood product utilization should be further evaluated in clinical studies. The major concern of bilateral ITA harvesting is the sternal wound infections, particularly in diabetic patients.

Therefore, it should also be investigated whether the Plasmablade™ would make a difference in wound infections.

In conclusion, our study results suggest that the PlasmaBlade™ is safer and more effective in preserving the integrity of the intima and pedicle of the internal thoracic artery than electrocautery for internal thoracic artery harvesting in coronary artery bypass grafting. No matter how much easier electrocautery makes internal thoracic artery harvesting, therefore, novel technologies such as PlasmaBlade™ are needed to be developed to minimize side effects. A well-preserved endothelial function may provide higher graft patency rates.

Declaration of conflicting interests

The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Funding

The authors received no financial support for the research and/or authorship of this article.

References

Kolessov VI. Mammary artery-coronary artery anastomosis as method of treatment for angina pectoris. J Thorac Cardiovasc Surg 1967;54:535-44.

Onan B, Yeniterzi M, Onan IS, Ersoy B, Gonca S, Gelenli E, et al. Effect of electrocautery on endothelial integrity of the internal thoracic artery: ultrastructural analysis with transmission electron microscopy. Tex Heart Inst J 2014;41:484-90.

Windecker S, Kolh P, Alfonso F, Collet JF, Cremer J, Falk V, et al. ESC/EACTS Guidelines on myocardial revascularization. European Heart Journal 2014;35:2541-619.

Huddleston CB, Stoney WS, Alford WC Jr, Burrus GR, Glassford DM Jr, Lea JW, et al. Internal mammary artery grafts: technical factors influencing patency. Ann Thorac Surg 1986;42:543-9.

Chaikhouni A, Crawford FA, Kochel PJ, Olanoff LS, Halushka PV. Human internal mammary artery produces more prostacyclin than saphenous vein. J Thorac Cardiovasc Surg 1986;92:88-91.

Orejola WC, Villacin AB, Defilippi VJ, Mekhjian HA. Internal mammary artery harvesting using the harmonic scalpel. ASAIO J 2000;46:99-102.

Palanker D, Vankov A, Jayaraman P. On mechanisms of interaction in electrosurgery. New Journal of Physics 2008;10:123022

Palanker DV, Vankov A, Huie P. Electrosurgery with cellular precision. IEEE Trans Biomed Eng 2008;55:838-41.

Palanker D, Vankov A, Freyvert Y, Huie P. Pulsed electrical stimulation for control of vasculature: temporary vasoconstriction and permanent thrombosis. Bioelectromagnetics 2008;29:100-7.

Vankov A, Palanker D. Nanosecond plasma-mediated electrosurgery with elongated electrodes. J Appl Phys 2007;101:124701.

Palanker DV, Marmor MF, Branco A, Huie P, Miller JM, Sanislo SR, et al. Effects of the pulsed electron avalanche knife on retinal tissue. Arch Ophthalmol 2002;120:636-40.

Yoshikai M, Itoh T, Kamohara K, Yunoki J, Fumoto H. Intimal injury of ultrasonically skeletonized internal thoracic artery by a vessel clamp: morphological analysis. Interact Cardiovasc Thorac Surg 2007;6:331-4.

Vuong PN, Berry C, editors. The Pathology of Vessels. Berlin: Springer-Verlag; 2002.

Barner HB, Swartz MT, Mudd JG, Tyras DH. Late patency of the internal mammary artery as a coronary bypass conduit. Ann Thorac Surg 1982;34:408-12.

Lytle BW, Loop FD, Cosgrove DM, Ratliff NB, Easley K, Taylor PC. Long-term (5 to 12 years) serial studies of internal mammary artery and saphenous vein coronary bypass grafts. J Thorac Cardiovasc Surg 1985;89:248-58.

Singh RN, Sosa JA, Green GE. Long-term fate of the internal mammary artery and saphenous vein grafts. J Thorac Cardiovasc Surg 1983;86:359-63.

Smith SH, Geer JC. Morphology of saphenous veincoronary artery bypass grafts: Seven to 116 months after surgery. Arch Pathol Lab Med 1983;107:13-8.

Grondin CM. Graft disease in patients with coronary bypass grafting. Why does it start? Where do we stop? J Thorac Cardiovasc Surg 1986;92:323-9.

Sezgin A, İkizler M, Mercan Ş, Gültekin B, Akay T, Taşdelen A, et al. Arteriyel greftlerin hazırlanmasında ultrasonik disseksiyonla klasik tekniğin karşılaştırılması. Turk Gogus Kalp Dama 2001;9:197-200.

Dignan RJ, Yeh T Jr, Dyke CM, Lee KF, Lutz HA, Ding M, et al. Reactivity of gastroepiploic and internal mammary arteries. Relevance to coronary artery bypass grafting. J Thorac Cardiovasc Surg 1992;103:116-22.

Barbour DJ, Roberts WC. Additional evidence for relative resistance to atherosclerosis of the internal mammary artery compared to saphenous vein when used to increase myocardial blood supply. Am J Cardiol 1985;56:488.

Green GE, Stertzer SH, Reppert EH. Coronary arterial bypass grafts. Ann Thorac Surg 1968;5:443-50.

Loh SA, Carlson GA, Chang EI, Huang EJ, Gurtner GC. Comparative healing of surgical incisions created by a standard electrosurgery, PEAK electrosurgical cutting tool, and standard scalpel blade. Podium presentation at the American College of Surgeons Annual Meeting. October 9, 2007, New Orleans, LA; 2007.

Ihnken KA, Schwartz SP, Huang E, Vose JG. Comparison of porcine internal thoracic artery harvest with the PEAK PlasmaBlade compared to harmonic scalpel and traditional electrosurgery. Podium Presentation at the Cardiovascular Research & Education Foundation Annual Meeting. February 12-15, 2009, San Diego, CA; 2009

Blumenthal P, Jacobson MT, Huang E, Carlson GA, Berek JS. Evaluation of PEAK PlasmaBlade for obstetric and gynecologic surgery vs. traditional electrosurgery. American College of Obstetrics and Gynecology 2008 Annual Meeting. May 3-7, 2008, New Orleans, LA; 2008.

Lehtola A, Verkkala K, Järvinen A. Is electrocautery safe for internal mammary artery (IMA) mobilization? A study using scanning electron microscopy (SEM). Thorac Cardiovasc Surg 1989;37:55-7.

Bar-El Y, Gilboa B, Unger N, Pud D, Eisenberg E. Skeletonized versus pedicled internal mammary artery: impact of surgical technique on post CABG surgery pain. Eur J Cardiothorac Surg 2005;27:1065-9.

Hockberg J, Murray GF. Principles of operative surgery. In: Sabiston DC, Lyerly HK, editors. Textbook of Surgery. Philadelphia: W.B. Saunders; 1997. p. 253-63.