Harmonic Shears for Skeletonized Internal Thoracic Arteries and Great Saphenous Vein Harvesting

Introduction

Although the routine use of the internal thoracic artery (ITA) and great saphenous vein (SV) is well established among cardiac surgeons (1, 2), there is considerable debate regarding the optimal harvesting technique for these conduits (3, 4). The ITA can be harvested either by itself or as a pedicle. Likewise, the SV vein can be harvested either with an open procedure or endoscopically.

There is an increasing interest in ultrasonic energy, because it provides several advantages over the conventional diathermy. The harmonic scalpel has been shown to be a tool for numerous surgical procedures and has also been used in cardiac surgery (5, 6). Skeletonized ITA harvesting is a recent applied technique and the use of an ultrasonic device for harvesting either SV can potentially enhance the efficacy of the procedure and minimize the morbidity associated with surgical interventions. The authors aim to share their experience of graft vessel harvesting using harmonic shears (Long Harmonic Shears, Ethicon, Cincinnati, Ohio, USA).

Operative Technique
The authors report a study group comprised of 30 consecutive patients who underwent isolated coronary artery bypass graft (CABG). The long harmonic shears consist of an ultrasonic generator and a soft grip scissor with two hand controls (Figure 1), a maximum power level of 5 to provide faster cutting, and a lower power level providing greater coagulation (Figure 2). New advanced technology that reduces unnecessary power application, which could potentially lead to excess thermal injury, provided for fine dissection and sealing of vessels.

After sternotomy, the harmonic shears allowed exposure of the innominate vein and dissection of the remnant of the thymus gland free from the pericardium. Thymic vessels were simultaneously cut and cauterized. The pleura was easily divided away from the pericardium, incised and cauterized at the same time (Video 1).

Both ITAs were harvested using a completely skeletonized technique. This minimizes chest wall trauma, achieves maximum length, and makes constructing the “Y” graft and performing the subsequent sequential grafting easier. The left internal mammary artery (IMA) was dissected first, and when bilateral IMAs were used, the right IMA was further dissected with the same method (Videos 2 and 3).

During exposure of the heart and before cannulation, the SV was harvested with the same device. After sternotomy, the IMA must be identified at the point where it crosses the costal cartilage. The longitudinal inner thoracic fascia was incised through electrocautery at the medial level of the artery, near the internal thoracic vein, while the dissection was performed with ultrasonic shears. After the fascia was gently pulled down, the dissection stared at the middle third of the artery. The artery was gently pulled away from the medial internal thoracic vein and the sternal wall with harmonic shears, and it was harvested from its distal bifurcation proximally to above the first intercostal branch. Loose adipose and connective tissue was cut and coagulated promptly at power level 5. When an arterial branch was visualized, it was further dissected proximally and distally to gain length for a safe division, at least 1 mm away from its origin at the arterial trunk with power level 3. When the artery was fully dissected, it was rinsed with warm papaverine solution and wrapped in a papaverine-soaked gauze.

After bilateral ITA skeletonization and before cannulation, the SV should be harvested proximal to the medial malleolus or close to the saphenofemoral junction, lateral and distal to the groin skin crease (Videos 4 and 5).

When surgical myocardial revascularization involves two artery grafts, the vein length that is harvested should be sufficient for only one graft on the right coronary artery. Once the incision along the route of the vein was made with a scalpel, a plane was created around the vein using the harmonic shears. The SV is covered by a thin layer of adherent tissue anteriorly and posteriorly. The perivascular fat on either side of the saphenous nerve was avoided from the plane. Each side branch was carefully inspected and clamped with a Ligaclip® after cutting with harmonic shears, if required. This technique provides quick harvesting and very simple leg hemostasis, even in patients with double antiplatelet therapy and after heparin administration. When the vein was completely dissected out, some saline solution was provided to test the vein. The ITA flow was estimated and the arteries were distally clamped with small atraumatic vascular clamps. The graft vessels should be inspected for inadequate hemostasis, wall trauma, and hematomas. The length of time taken for ITA and SV harvest was substantially decreased with harmonic shears.
Comment

The success of an aortocoronary bypass operation is, in general and to a large degree, dependent on the structural integrity of the grafts used. The damage done to the endothelium during the preparation of the grafts is presently considered to be of prime importance for early graft failure (7). New ultrasonic technology provides for fine dissection and sealing of vessels, reducing unnecessary power application that could potentially lead to excess thermal injury. Reviews about harmonic shears provided no harvesting damage, excellent graft quality as evaluated intraoperatively, no bleeding from graft branches, and good long-term clinical outcomes. Harvest time is quicker than the conventional technique, although in principle, techniques that are less damaging usually take more time. In conclusion, the authors recommend using harmonic shears during the preparation of the vessels graft, because of the advantages such as reduced injury, causing less bleeding, and shorter time for harvesting. Although the experience remains limited, the preliminary observations of the efficacy of these instruments justify their further use.

References

1. Motwani JG, Topol EJ. Aortocoronary saphenous vein graft disease: pathogenesis, predisposition, and prevention. Circulation. 1998;97(9):916-931.
2. Sur S, Sugimoto JT, Agrawal DK. Coronary artery bypass graft: why is the saphenous vein prone to intimal hyperplasia? Can J Physiol Pharmacol. 2014;92(7):531-545.
3. Ouzounian M, Hassan A, Buth KJ, et al. Impact of endoscopic versus open saphenous vein harvest techniques on outcomes after coronary artery bypass grafting. Ann Thorac Surg. 2010;89(2):403-408.
4. Cheng K, Rehman SM, Taggart DP. A review of differing techniques of mammary artery harvesting on sternal perfusion: time for a randomized study? Ann Thorac Surg. 2015;100(5):1942-1953.
5. Kieser TM, Rose MS, Aluthman U, Narine K. Quicker yet safe: skeletonization of 1640 internal mammary arteries with harmonic technology in 965 patients. Eur J Cardiothorac Surg. 2014;45(5):142-150.
6. Cavozza C, Campanella A, Audo A. New ultrasonic device for internal thoracic artery harvesting. Multimed Man Cardiothorac Surg. 2017 Aug.
7. Verrier ED, Boyle EM Jr. Endothelial cell injury in cardiovascular surgery. Ann Thorac Surg. 1996;62(3):915-922.

Figure Legends

Figure 1. Ultrasound generator. The generator monitor shows two numbers corresponding to device action: the lower power level 3 provides greater coagulation, the higher power level 5 (maximum) provides faster cutting.

Figure 2. Harmonic shears with two manual controls, for cutting or coagulation.