Ann Thorac Surg 2005;80:1137-1139
© 2005 The Society of Thoracic Surgeons
How to do it
Safe Coronary Artery Occlusion With a New Tourniquet in Off-Pump Bypass Grafting
Hirokuni Arai, MD, PhD
*
,
Keiji Oi, MD,
Hiroyuki Tanaka, MD, PhD,
Noriyuki Tabuchi, MD, PhD,
Makoto Sunamori, MD, PhD
Department of Cardiothoracic Surgery, Tokyo Medical and Dental University Graduate School of Medicine, Tokyo, Japan
Accepted for publication March 25, 2004.
* Address reprint requests to Dr Arai, Department of Cardiothoracic Surgery, Tokyo Medical and Dental University Graduate School of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan. (Email: hiro.tsrg{at}tmd.ac.jp).
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Abstract
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Coronary artery occlusion during off-pump coronary artery bypass grafting may lead to mechanical trauma of the arterial wall. My colleagues and I describe a safe coronary artery occlusion technique in off-pump bypass grafting that uses a new spring-equipped tourniquet, which enables precise adjustment of the least force necessary to occlude the coronary flow. This prevents snare-induced vessel wall damage.
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Introduction
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Off-pump coronary artery bypass grafting (OPCAB) is an increasingly accepted procedure for myocardial revascularization that offers excellent clinical results. Satisfactory anastomosis during OPCAB requires temporary occlusion of target coronary arteries. The most common technique for local hemostasis is that of encircling sutures and tourniquets. However, local coronary artery occlusion can lead to focal endothelial denudation, local microthrombosis, and arteriosclerotic plaque rupture [1–3]. Such potential for local trauma to native vessels must be minimized; otherwise, this may represent a major drawback of OPCAB. My colleagues and I describe a new device that enables safe coronary artery occlusion and minimizes vascular trauma during OPCAB.
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Technique
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This new spring-equipped tourniquet (Sumitomo Bakelite Co, Ltd, Tokyo, Japan) is a coronary occluder that reduces trauma by enabling fine adjustment of the coronary artery snaring force (Fig 1). The tourniquet consists of 3 portions: a polyvinyl chloride tube, a fine spring, and a plastic cap. A telescoping cylinder is fixed to the cap and moves within the proximal lumen of the tube. A fine spring is positioned between the tube and the cap portions. These 2 portions can slide back and forth within the compression range of the spring. The force-compression characteristics of the spring indicate a spring rate of 9 g of force per millimeter.
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Fig 1. (Left) The spring-equipped tourniquet. The plastic cap portion telescopes into the polyvinyl chloride tube portion. These 2 portions are interposed by a fine spring and can slide back and forth within the elastic compression range of the spring. (Right) The force-compression characteristics of the spring indicate a spring rate of 9 g of force (gf) per millimeter.
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After standard anesthesia, the heart is exposed by using either median sternotomy or small left thoracotomy. The target coronary artery is mechanically stabilized. Snaring sutures (4-0 polypropylene) are placed with a 21-mm half-circle blunt needle (Azwell Inc, Tokyo, Japan), passing only once under the coronary artery proximally and distally near the anastomotic site. The sutures are placed deep into the myocardium to create a cushion of subjacent epimyocardial tissue and are buttressed with thick pledgets to avoid direct coronary vessel wall compression. The proximal ends of the snaring suture are passed through the tourniquet tube. After arterial incision, the tourniquet is slid down while the ends of the suture are simultaneously pulled up. The coronary artery is indirectly compressed by the expansion force of the spring. The force of spring expansion is equal to suture tension, ie, the compression force on the coronary artery. Because the relation between the sliding distance and the force exerted by the spring is in direct proportion, the force necessary for coronary artery compression can be set as desired by controlling the sliding distance. By finely adjusting spring compression, optimal coronary occlusion with the minimum force necessary to interrupt blood flow is obtained (Fig 2). To maintain hemostasis, the suture is fixed by closing the cap. The anastomosis is performed with a running 7.5-0 polypropylene suture (Azwell, Inc).
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Fig 2. (Left) The coronary artery is gently occluded with the spring-equipped tourniquet. The plastic cap locks the snare sutures; the coronary artery is indirectly compressed by spring pressure. Optimal coronary occlusion is established by fine adjustment of spring compression. (Right) Solid and open arrows indicate spring expansion force and coronary artery compression force, respectively.
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The force generated by the spring at maximal compression is equivalent to approximately 100 g, which is similar to that of an internal mammary artery clamp jaw (125 g) [4]. In our experience, interruption of blood flow in a nondiseased coronary artery requires approximately half-length compression of the spring (ie, 50 g).
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Results
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We have applied this technique to 219 distal anastomoses in 85 consecutive OPCAB cases. Postoperative coronary angiography, which was performed 2 to 4 weeks after operation in 56 of these cases (155 distal anastomoses; 2 snared sites per anastomosis), revealed no marked snare-induced stenosis in any coronary artery to which this device was applied. Very mild (< 25%) stenosis was observed in only 2 (0.6%) of 310 snared sites.
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Comment
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For local hemostasis during coronary anastomosis in OPCAB, snares of either polypropylene or silicone elastomer suture are generally applied. Hangler and colleagues [1] reported the effects of local occlusion of the human coronary artery in recipient hearts during clinical heart transplantation. Scanning electromicroscopy revealed severe endothelial injury in 70% to 80% of snared sites in which polypropylene sutures were used. Silicone elastomer snares also induced endothelial injury in approximately 30% of snared sites. Gundry and colleagues [5] reported that catheterization, which was performed 32 ± 26 months after operation, showed appreciable stenoses at the site of vessel loops in 20% (3 of 15) of left anterior descending artery anastomoses. We suspect that one reason for the relatively high incidence of snare-induced injury in these studies may be the unnecessarily excessive force applied to the snared sites. In each case, the coronary artery was manually snared, and the applied force was not uniform. To prevent such snare-induced injury, some surgeons avoid using the distal snare, if possible. However, to obtain the bloodless surgical field necessary for precise anastomosis, the distal snare is often essential.
Intraluminal shunting may be another alternative to avoid snare-induced coronary artery damage. However, introduction of an intracoronary shunt into a coronary lumen may cause dissection or harm endothelial integrity, thus resulting in functional coronary artery impairment. Chavanon and colleagues [6] found in porcine coronary artery that intraluminal shunts created a markedly higher degree of endothelial dysfunction than did the extravascular occlusion technique.
With these observations in mind, we devised a new spring-equipped tourniquet that has 3 major advantages. First, this device enables precise adjustment of the minimum force required to occlude coronary flow while avoiding excessive coronary arterial wall stress. Second, surgeons can visually ascertain the approximate force applied to the coronary artery by noting the compressed spring length, because the applied force is in proportion to this length. Third, the maximal spring compression force is limited to approximately 100 g to avoid excessive occlusion. Although postoperative angiography in this study was performed relatively soon after operation, no considerable snare-induced stenosis resulting from our technique was observed.
In conclusion, this new spring-equipped tourniquet enables safe and delicate snaring of the coronary artery and contributes to the minimization of snare-induced coronary artery injury during OPCAB.
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Acknowledgments
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We acknowledge the technical contributions of Haruhiko Masuda (Sumitomo Bakelite Co, Ltd).
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References
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- Hangler HB, Pfaller K, Antretter H, Dapunt OE, Bonatti JO. Coronary endothelial injury after local occlusion on the human beating heart Ann Thorac Surg 2001;1:122-127.
- Demaria RG, Fortier S, Carrier M, Perrault LP. Early multifocal stenosis after coronary artery snaring during off-pump coronary artery bypass in a patient with diabetes J Thorac Cardiovasc Surg 2001;122:1044-1045.[Free Full Text]
- Gerola LR, Moura LA, Leão LE, Soares HC, Branco JN, Buffolo E. Arterial wall damage caused by snaring of the coronary arteries during off-pump revascularization Heart Surg Forum 2000;3:103-107.[Medline]
- Fonger JD, Yang XM, Cohen RA, Haudenschild CC, Shemin RJ. Human mammary artery endothelial sparing with fibrous jaw clamping Ann Thorac Surg 1995;60:551-555.[Abstract/Free Full Text]
- Gundry SR, Romano MA, Shattuck OH, Razzouk AJ, Bailey LL. Seven-year follow-up of coronary artery bypasses performed with and without cardiopulmonary bypass J Thorac Cardiovasc Surg 1998;115:1273-1278.[Abstract/Free Full Text]
- Chavanon O, Perrault LP, Menasché P, Carrier M, Vanhoutte PM. As originally published in 1996: endothelial effects of hemostatic devices for continuous cardioplegia or minimally invasive operations. Updated in 1999 Ann Thorac Surg 1999;68:1118-1120.[Free Full Text]
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Abstract
Introduction
