with the Spiral Composite Vein Graft

Transcription

1 Redacement of Superior Vena Cava with the Spiral Composite Vein Graft A Versatile Technique C. J. Chiu, M.D., J. Terzis, M.D., and M. L. MacRae, B.S. ABSTRACT A technique to construct a spiral vein graft is described. A graft with predictable diameter and length can be made, regardless of the degree of discrepancy in the size of vessels at the donor and recipient sites. The technique is simple and versatile, and when used to replace the superior vena cava in dogs, long-term patency can be obtained without anticoagulation or other adjunctive measures. Si bypass nce the early experimental work of Gluck in 1898 [3] and Carrel and Guthrie in 1906 [Z], the autogenous vein graft has been one of the most satisfactory materials available either to substitute for or to a segment of blood vessel. At present, except for the larger-caliber arteries for which synthetic graft materials appear to be acceptable, vein grafts find wide application in the replacement of veins and smaller-caliber arteries. The peripheral veins which can be sacrificed as donor vessels are often limited and variable in their diameters. Thus, discrepancy in vessel caliber becomes a problem when a vessel is used to replace one that is quite different in size, as for example when the saphenous vein is used to replace the superior vena cava. Although many techniques to construct a composite vein graft have been described, the spiral method discussed here appears to be unique in its simplicity and versatility. It produces a graft vessel with predictable caliber and length regardless of the degree of discrepancy between the donor and recipient vessels. In the following study this technique was used to replace the superior vena cava for two reasons. First, the results of operative procedures for replacing the superior vena cava have generally been unsatisfactory [9]. From the Division of Thoracic and Cardiovascular Surgery, McGill University, and University Surgical Clinic, The Montreal General Hospital, Montreal, Que.. Canada. Supported by grants from the Medical Research Council of Canada and Quebec Heart Foundation. The technical assistance of Dr. W. Mersereau and Misses C. Labelle and S. Holmes is very much appreciated. Accepted for publication Feb. 8, Address reprint requests to Dr. Chiu, The Montreal General Hospital, 1650 Cedar Ave., Montreal 109, Que., Canada. VOL. 17, NO. 6, JUNE,

2 CHIU, TERZIS, AND MACRAE Consequently, numerous experimental studies have been performed in order to design a technique with more predictable patency [4]. These techniques include utilization of various materials for replacing the superior vena cava, such as synthetic grafts [6], homografts [7], pericardium [l], and other autogenous tissues. Many adjuncts have also been advocated, including the construction of an arteriovenous fistula [5], administration of dextran [7], and other anticoagulant therapies. A simple method which obviates such adjuncts but still has predictable patency would clearly be preferable. The second reason or using the spiral composite vein graft is that it provides an endothelialized venous surface; with precise matching of the graft caliber, which is feasible with this technique, the rheological disturbance at the anastomotic site may be avoided. Thus, two out of three factors described in Virchow s triad [S] of venous thrombus formation may be minimized, perhaps resulting in an improved patency. Materials and Methods Thirteen dogs weighing from 15 to 20 kg. were anesthetized intravenously with pentobarbital (30 mg. per kilogram of body weight), intubated, and then ventilated with a positive-pressure respirator. Right lateral thoracotomy was performed, and the chest was entered through the third intercostal space. The azygos vein was ligated, and the superior vena cava was resected between the junction of the innominate veins and the azygos vein. The resected superior vena cava measured approximately 4 cm. in length. The left external jugular vein was used as the donor vessel. Utilizing a very simple formula, described below, the length of donor vein needed was readily determined. All the side branches were carefully ligated, and the vein was removed and opened longitudinally. A rod, cylinder, or plastic tube having approximately the same caliber as the recipient vessel-i.e., the superior vena cava-was used as a stent, and the donor vein was wrapped in a spiral fashion. Two stay-stitches at each end of the spiral held the vein on the stent, and running over-and-over stitches of fine nonabsorbable material (7-0 silk) were used to complete the spiral composite graft (Fig. 1). It was then grafted into the recipient site in the usual manner (Fig. 2). Magnifying loupes (2.5~) were found to be valuable in achieving precise suturing of the spiral composite graft. The chest wall was closed in layers, and no adjunct of any kind was used either during or following the operation. The dogs were observed up to one and one-half years after the operation. The patency of the reconstructed superior vena cava was ascertained with serial venous angiograms. In the construction of spiral composite vein grafts, the length of donor vein needed can be estimated simply as follows: Since the whole surface area of the donor vessel will be utilized to construct the graft, the surface area of 556 THE ANNALS OF THORACIC SURGERY

3 SVC Replacement with Spiral Vein Graft FIG. I. Completed spiral graft sutured with running 7-0 silk stitches. donor blood vessel removed and the surface area of the segment of recipient vessel to be replaced should be equal. Therefore, 2rRL = 2nd where R = radius of the recipient vessel L = length to be substituted at the recipient site r = radius of the donor vessel 1 = length of the donor vessel Hence, 1 = R/r x L Thus, the length of donor vessel needed equals the ratio of the calibers of the recipient and donor vessels times the length to be substituted at the recipient site. For example, if the superior vena cava is approximately three times larger than the peripheral vein to be utilized, in order to substitute 4 cm. of superior vena cava using spiral composite graft, at least 3 x 4, or 12, cm.2 of FIG. 2. Spiral graft replacing the superior vena cava. Note the matching of the graft and superior vena cava calibers. VOL. 17, NO. 6, JUNE,

4 CHIU, TERZIS, AND MACRAE SPIRAL AUTOGENOUS VEIN GRAFT FOR SUPERIOR VENA CAVA REPLACEMENT IN DOGS Dog. No. SVC Patency Period Observed Remarks day Died; anastomotic stenosis days Killed; intraoperative occlusion of SVC wk. Died; intraoperative cyanosis, hydrothorax 4 P 3 wk. Killed; endothelialized graft 5 P 4 wk. Died; empyema 6 P 5 wk. Died; infection 7 P 6 wk. Died: pneumonia 8 P 5 mo. Killed; vicious 9 P 10 mo. Alive &well 10 P 11 mo. Alive &well 11 P 11 mo. Alive &well 12 P 15 mo. Alive &well 13 P 15 mo. Alive &well SVC = superior vena cava; 0 = occluded: P = patent. peripheral vein will be required. Our experience shows that the donor vein contracts to a varying degree after removal. Although this may be overcome to some extent by a gentle stretch when it is wrapped around a cylinder in spiral fashion, it is safer to assume that the length of donor vein estimated represents the minimum that is required. Results The period of observation and patency of the new superior vena cava are summarized in the Table. As can be seen, the 3 dogs that died or were killed within three weeks of operation had occluded superior venae cavae. Technical factors, particularly anastomotic stenosis and kinking, appear to FIG. 3. Example of technical error. Too long a graft produces buckling and kinking with early occlusion. 558 THE ANNALS OF THORACIC SURGERY

5 SVC Replacement with Spiral Vein Graft FIG. 4. Specimen of spiral graft 6 weeks after replacement of the superior uena caua. The suture line is endothelialized, and the surface is smooth with no thrombus or stenosis. be the cause of these failures. Kinking of the superior vena cava may be due to an excessively long donor graft (Fig. 3); this can be avoided by estimating the required length of graft prior to its construction as described previously. Up to five months after operation, 5 other dogs either died or were killed. All the grafts were patent, the endothelial surfaces were smooth (Fig. 4), and no thrombosis or narrowing was found. Five other dogs were alive and well eleven to fifteen months after the operation: on angiography all the superior vena cava grafts in these dogs remained patent (Fig. 5). Comment The spiral composite vein graft described produces a graft with predictable diameter and length regardless of the degree of discrepancy in the size of vessels at the donor and recipient sites, and yet without excessively sacrificing the length of donor vessel. This technique is simple and versatile and may be applicable in many clinical situations. It was applied in the FIG. 5. Venous angiogram taken 15 months after replacement of the superior uena caua with a spiral composite vein graft. VOL. 17, NO. 6, JUNE,

6 CHIU, TERZIS, AND MACRAE superior vena caval position under the assumption that the autogenous vein, with its intact endothelial lining, is perhaps still the best graft available for substituting a segment of the vena cava. Our results indicate that if the graft is open for the first few days, it is likely to remain patent indefinitely. The failures occurred within a few days of operation, usually because of identifiable technical error. It is noteworthy that in this study, unlike other reported series, neither anticoagulation nor any other adjuncts were used. It would appear, therefore, that with a properly constructed graft, this technique may provide a valuable method of replacing the superior vena cava and may merit clinical trial in suitable cases. References 1. Brais, M., Butranou, E., Brassard, A., Stanley, P., and Chartrand, C. Effect of dextran on patency of pericardial tubular graft of the superior vena cava in the dog. J. Thorac. Cardiovasc. Surg. 65:296, Carrel, A., and Guthrie, C. C. Transplantation biterminale complete d un segment de veins sur une artere. C. R. SOC. Biol. (Paris) 59:412, Gluck, C. Die moderne Chirurgie des Circulations-Apparatus. Cited in L. A. Peer (Ed.), Transplantation of Tissues. Baltimore: Williams & Wilkins, Vol. 11, p Haimovici, H., Hoffert, P. W., Zinicola, N., and Steinman, C. An expenmental and clinical evaluation of grafts in the venous system. Surg. Gynecol. Obstet. 131:1173, Miller, R. E., Corneil, N. J., and Sullivan, F. J. Replacement of superior vena cava with autogenous tissue. Ann. Thorac. Surg. 15:474, Peter, M. Y., Hering, C. A., and Watkins, E., Jr. Experimental Teflon replacement of the superior vena cava and atriocaval junction. J. Thorac. Cardiovasc. Surg. 40:224, Rangarathnam, C. S., Plzak, L.F., Jr., Klein, L., and Wright, K. A. Superior Vena Cava Replacement-Superiority of Irradiated Caval Homografts over Heparin-Bonded Prosthetic Grafts. Presented at the 6th Annual Meeting of the Association for Academic Surgery, New Orleans, La., Nov. 2-4, Sabiston, D. C., Jr. Pulmonary Embolism. In J. H. Gibbon, Jr., D. C. Sabiston, Jr., and F. C. Spencer (Eds.), Surgery of the Chest (2d ed.). Philadelphia: Saunders, P Skinner, D. B., Salzman, E. W., and Scannell, J. G. The challenge of superior vena cava obstruction. J. Thorac. Cardiovasc. Surg. 49~824, THE ANNALS OF THORACIC SURGERY