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THE IMPORTANCE OF THE AZYGOS VEIN IN SUPERIOR VENA CAVA-PULMONARY ARTERY ANASTOMOSIS
THE IMPORTANCE OF THE AZYGOS V E I N I N SUPERIOR V E N A C A V A — P U L M O N A R Y ARTERY ANASTOMOSIS W. Sterling Edwards, M.D., and L. M. Bargeron, Jr., M.D. (by Birmingham,
invitation),
Ala.
S
INCE its inception for partial bypass of the right heart, the major operative complication of superior vena cava-right pulmonary artery shunt has been severe cerebral edema. Glenn and Patino 2 in 1954 described an end-to-side anastomsis of the right pulmonary artery to the vena eava at the azygos orifice, after which the vena eava, central to the shunt, was ligated. Eobicsek" described a similar procedure in 1956 except that an end-to-end anastomosis of the supe rior vena eava to the distal right pulmonary artery was accomplished. Clinical experience in Russia 1 with the end-to-end method, which requires complete occlusion of the superior vena eava for 12 to 30 minutes, was followed by a high early mortality rate from brain damage. All patients in this series left the operating room with marked cyanosis and edema of the face and petechiae covering the upper half of the body. Glenn's end-to-side method allows the shunt to be constructed with only partial occlusion of the superior vena eava, so that the pressure elevation in the cerebral veins never reaches the dangerous levels seen when the vena eava is completely occluded. Glenn selected as his optimum site for pulmonary anastomosis the proximal stump of the divided azygos vein. This approach results in a lower morbidity and mortality from cerebral edema than the end-to-end method but has not eliminated it entirely. Glenn reports five postoperative instances of "superior caval syndrome" in a series of 20 operations; 4 of these were moderately severe and one was fatal. Our experience consists of 20 cases of superior vena cava-right pulmonary artery anastomosis. Of these, 16 were for tricuspid atresia, one for pulmonary artery atresia with auricular septal defect, one for Ebstein's syndrome, and 2 for tetralogy of Fallot with diffuse main pulmonary stenosis. The first ten of these operations were done exactly as described by Glenn and associates with implantation of the pulmonary artery to the stump of the divided azygos vein. Of these 10 patients, 3 infants died in the recovery room 1 to 10 hours after operation with severe facial edema and cyanosis and failure to regain consciousness. These symptoms we interpreted as due to cerebral
From the Department of Surgery, Medical College of Alabama, Birmingham, Ala. Supported by U. S. Public Health Service Grant No. H-1987(C8). Read at the Forty-third Annual Meeting of The American Association for Thoracic Sur gery at Houston, Texas, April 8-10, 1963.
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edema from high superior vena caval pressure. In the next 6 consecutive pa tients, the anastomosis was made directly caudal to the azygos vein which was not ligated, with the hope that it would serve as a decompression channel and prevent high superior caval pressure in the early period of recovery. Operative measurements of pressure in the superior vena cava were made through a 20 gauge needle connected to a water manometer in 4 of these 6 patients. After the shunt was completed and the vena cava ligated at its junction with the auricle, superior caval pressure was always elevated above 200 mm. H 2 0 with the azygos open. Temporary occlusion of the azygos vein always resulted in a further rise of 25 to 100 mm. H 2 0 which indicates that the azygos vein does
Fig. 1.—Diagram of technique for delayed ligation of the azygos vein after end-to-side superior vena cava-right pulmonary anastomosis.
permit retrograde drainage from the superior vena cava and prevents excessive pressure elevation. The immediate postoperative course in these 6 patients was much more satisfactory than in the previous group; there was little evidence of facial swelling and only mild cyanosis of the upper body. There was one death in an adult with Ebstein's anomaly but this was not associated with cere bral symptoms or edema. One 16-year-old girl with tricuspid atresia and severe cyanosis showed only slight improvement in cyanosis, and a second thoracotomy was performed for ligation of the azygos vein. Her cyanosis rapidly improved thereafter. Glenn 3 has demonstrated by venous angiography that retrograde flow occurs in the azygos vein if it is left patent after vena caval pulmonary artery shunt.
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It seemed to us from the above experience that a nonoperative technique was needed by which the azygos vein could be permanently ligated 8 or 9 days after the construction of the superior vena cava-pulmonary artery anastomosis. This would allow the azygos vein to serve as a decompression channel during the early postoperative course and prevent excessive superior vena caval pres sure elevation, but would then permit closure of the azygos vein to obtain maximum pulmonary blood flow after the danger of cerebral edema had passed. This has been satisfactorily achieved by the technique shown in Fig. 1. OPERATIVE TECHNIQUE
Through a right lateral thoracotomy, end-to-side anastomosis of the distal end of the right pulmonary artery to the side of the superior vena cava is carried out as in Glenn's technique except that the azygos vein is not ligated or divided and the anastomosis is made just caudal to the junction of the azygos vein with the vena cava. Two technical points of importance are as follows: (1) the shunt should be constructed very close to the azygos vein to allow ligation of the vena cava without constriction of the shunt by the ligature; (2) great care must be taken in placing the partial occlusion clamp and making the incision in the vena cava on the exact lateral surface of the vena cava to prevent angulation of the anastomosis. After completion of the shunt, a 2-0 silk ligature is looped twice around the azygos vein but left quite loose. A 1 cm. incision is made in the right posterior chest wall in the third intercostal space, down to, but not through, the fascia. The two ends of the azygos ligature are brought through the chest wall with separate needles to this subcutaneous incision. Here they are threaded over a sterile button and a single knot is tied loosely. The long ends of this thread and the button are placed subcutaneously just above the fascia and the skin edges are approximated over them with a single suture. An additional mattress suture is placed through the lips of this skin incision but not tied and the ends are left long. The purpose of the button is to simplify identification of the azygos liga ture at the time of delayed ligation and to prevent its incorporation in healing scar tissue. Eight days after operation, when the sutures are removed from the primary incision, the small posterior incision is opened with the use of local anesthesia if necessary. The button is located and removed. Gentle traction on the azygos loop is now applied until there is a feeling of resistance. This ligature is tied down on the fascia and cut. The mattress skin suture buries this ligature. DISCUSSION
Delayed ligation has been done in this fashion in the last three vena caval pulmonary artery shunts with excellent results in all. One 7-year-old boy with tricuspid atresia had a delayed azygos ligation 8 days after operation and developed chylothorax 12 days postoperatively which required thoracic duct ligation 4 days later. Inspection of the azygos vein at this second thoracotomy
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showed it to be securely occluded without tension on the shunt. These 3 patients have had a benign course with no evidence of facial swelling or cerebral edema and all have had almost complete disappearance of cyanosis after recovery. The patient with late chylothorax which required thoracic duct ligation was the second such case in our series of 20 vena caval pulmonary artery shunts. We now routinely ligate the thoracic duct at the time of the initial procedure, identifying it just above the diaphragm by injecting 1 c.c. of sky blue dye in the wall of the esophagus. SUMMARY
A technique is described for delayed ligation of the azygos vein one week after superior vena eaval-pulmonary artery anastomosis for partial bypass for congenital lesions of the right heart. This allows temporary decompression of the vena cava through the azygos vein and prevents excessive elevation of the superior vena caval pressure with cerebral edema. Delayed ligation permits maximum flow through the shunt after the dangers of cerebral edema have passed. We believe this technique to be especially valuable in infants, particu larly those with a relatively small pulmonary artery. REFERENCES 1. Bakulev, A. N., and Kolesnikov, S. A.: Anastomosis of Superior Vena Cava and Pul monary Artery in t h e Surgical Treatment of Certain Congenital Defects of the H e a r t , J . THORACIC SURG. 37: 693-702, 1959.
2. Glenn, W. W. L., and Patino, J . F . : Circulatory By-pass of the Right Heart. I . Preliminary Observations on the Direct Delivery of Vena Caval Blood into the Pulmonary Arte rial Circulation. Azygous Vein-Pulmonary Artery Shunt, Yale J . Biol. & Med. 27: 147, 1954. 3. Glenn, W. W. L., and others: Exhibit at the Clinical Congress, American College of Sur geons, Atlantic City, N . J., October, 1962. 4. Robicsek, F . , Temesvari, A., and Kadar, R. L . : A New Method for the Treatment of Congenital Heart Disease Associated With Impaired Pulmonary Circulation, Acta. med. scandinav. 154: 151, 1956. DISCUSSION DR. J O H N E. F E N N , New Haven, Conn.—I would like to comment on Dr. Edwards' excellent paper. We have also been interested in the management and function of the azygos vein following vena cava-pulmonary a r t e r y anastomosis. I n each of t h e 29 patients who have undergone operations a t t h e Yale-New Haven Medical Center, t h e azygos vein has been divided and the stump of the azygos has been used as the site of anastomosis for the distal divided right pulmonary artery. Thirteen of the patients have shown some sign of increased superior vena cava pressure but in the majority this has amounted to no more than mild periorbital edema which has cleared spontaneously within the first few postoperative days. To explore t h e role of t h e azygos vein i n animals undergoing vena cava-pulmonary artery anastomosis, we have performed venous and osseous angiograms with the azygos vein intact and divided. [Slide] This slide shows angiograms obtained in one animal with an intact azygos vein in which the direction of flow in the azygos is caudad with filling of the inferior vena cava. The osseous angiogram on the right side confirms the downward direction of flow in the azygos, again opacifying the inferior vena cava. The pressure in the superior vena cava
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was 120 mm. of saline and the venous flow through the anastomosis was 27 per cent of cardiac output. I n this situation some of the blood passes from the superior to the inferior vena cava through the azygos vein. If the flow of blood through t h e vena cava-pulmonary artery shunt is thereby reduced significantly the possibility of thrombosis of the anastomosis may be increased. [Slide] The next slide shows angiograms from another animal. Filling of the azygos system in the venous angiogram is poor despite opacification of the right pulmonary artery. Osseous angiography indicates that flow in the azygos is bidirectional with filling of the intrathoracic azygos system and the right pulmonary artery. The pressure in the superior vena cava was 135 mm. of saline. The shunt flow in this animal was 26 per cent of cardiac output. I t is possible that a valve a t the junction of the azygos vein and the vena cava may have impeded the passage of dye into the azygos. These studies show that the direction of blood flow in the i n t a c t azygos vein in animals with a vena eava-pulmonary artery shunt cannot be predicted, although in the majority of experiments the flow was from the superior cava into the azygos vein. We therefore believe that in all patients the azygos vein must be divided. In patients in whom the pulmonary a r t e r y - v e n a cava anastomosis is small, as in the infant, the pressure in the superior vena cava may rise to more than 200 mm. of saline which may cause cerebral edema. To provide for temporary decompression of the vena cava through the azygos system as the authors suggest may be a satisfactory solution to this problem. In New Haven, it has been our practice, in the infant who requires a shunt, to approach the heart through the midsternum so that an end-to-end extrapleural shunt is made between the vena cava and the right pulmonary artery. If the pulmonary artery is less than one half the diameter of the superior vena cava, an end-to-side anastomosis is performed between the right pulmonary artery and the ascending aorta. We would like to ask the authors why they think temporary decompression of the superior vena cava through the azygos is effective. Does it allow time for expansion of other venous collaterals to the inferior vena cava or does it permit time for full re-expansion of the right lung with reduction in resistance to flow through the pulmonary circulation? Also, we would like to ask if postoperative angiograms have been done 6 months or more following delayed ligation of the azygos vein. Please let me express my thanks to The Association for the privilege of the floor. DR. K E N N E T H HARDY, Oakland, Calif.—We, too, like the authors, have felt that preservation of the azygos vein would be important in these patients with vena caval pulmonary artery anastomoses, because of the occurrence in 2 eases of chylothorax in our series. Besides the decompressive effect of azygos runoff initially in preventing upper body edema, we had reason to believe that flows might eventually be such that we would gain, in addition to superior vena caval return to the right lung, additional systemic saturation by the added 10 per cent to 15 per cent increment of normal azygos return. Such reasoning has proved to be somewhat naive, and our hopes have not been fulfilled in this latter regard. [Slide] This baseline angiogram in a patient in whom the azygos was sacrificed, ac cording to the technique of Glenn, reveals the entire upper body return opacifying the right lung. [Slide] I n 2 % seconds after the beginning of injection, dye has traversed the left atrium and left ventricle and is now seen going to the systemic circulation, a desired result in this procedure. Having used the technique of costal interosseous venography in the evaluation for surgery of patients with bronehogenic carcinoma, we thought that if we could opacify the right lung in patients in whom the azygos vein had been preserved by the technique of azography, as described by Schobinger and others, we would gain some insight into the part played by azygos flow in these patients. [Slide] This patient had had a Glenn procedure 15 months previously, with preserva tion of the azygos vein and good clinical response, with systemic saturation improved from
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48 to 72 per cent. Much to our surprise, however, we see good opacification of the lumbar veins but only faint outline of the proximal azygos system, in contrast to the normal azygogram which normally readily demonstrates cephalad flow in this system. [Slide] A subclavian venous angiogram in the same patient demonstrates patency of the vena cava-pulmonary a r t e r y anastomosis and faint flooding of the pulmonary bed, but marked overflow spilling into the greatly hypertrophied and expanded azygos system, with flow in a caudal or retrograde direction. [Slide] The last slide made at 5 seconds after injection reveals filling of the inferior vena cava with return of a majority of upper body blood to the right heart, which partially defeats the purpose for which the operation was originally performed. This case substantiates the contention of the authors that the azygos system acts decompressively in the Glenn anastomosis, and that the azygos vein should be ligated in a staged manner. DR. F R E D E R I C K H. TAYLOR, Charlotte, N. C—Our group has been interested in this procedure for some time. I suspect it is very difficult to partially occlude the superior vena cava in a very tiny infant and still allow adequate blood flow to go downward to the heart while a side-to-end anastomosis is being done. Our approach to this problem has been a little different from Dr. E d w a r d s ' in that we use an end-to-end vena cava-pulmonary artery anastomosis; however, we leave the azygos vein open during the anastomosis. [Slide] This decompresses the superior vena cava during the few minutes of crossclamping necessary in order to do an end-to-end anastomosis below the azygos vein. This slide shows the end-to-end anastomosis. Glenn Young at Duke University divides the superior vena cava inferior to the side-to-end anastomosis, allowing for swinging out laterally and perhaps a straighter flow of blood. I think Young's technique arrives at more or less the same end as ours. [Slide] We ligate the azygos vein immediately after the anastomosis because, as we have found in this case, a so-called agyzos steal syndrome can occur. This child did not do well after anastomosis and several months later did require ligation of the azygos vein to improve her condition of cyanosis. One other thing we found very useful is the use of a bucket seat-like affair for these children in the immediate postoperative period. This period of facial cyanosis does subside in a day or two, but we have not found it necessary to leave an 8- to 10-day decompression azygos vein patent. DR. H A R V E Y W. K A U S E L , Albany, N . Y.—I do not wish to abuse this privilege by giving another paper. I enjoyed Dr. E d w a r d s ' presentation. We have been quite pleased with this procedure. We have run into some of these difficulties, and I think possibly one solution is that in the operations we have performed the hematoerit determinations in the patients have been excessively high—66 to 78 or in that range—and we have found that, by judicious phlebotomy over a period of 3 or 4 days prior to surgery, many of these problems have been overcome by getting the hematoerit readings down to an acceptable level of around 55. The chylous effusions that have occurred, and which I suspect have occurred more fre quently than we have been told, have responded to tube drainage, and we. have not had to divide the duet. Interestingly enough, in 1922, I believe Dr. Lee, at Johns Hopkins, showed that the only way to produce experimental chylous effusion in dogs was to ligate the superior vena cava. DR. B E N S O N B . ROE, San Francisco, Calif.—Dr. Edwards has, as usual, given an ex cellent presentation, but I must disagree with him, for, unless the anatomy to the extent of either pulmonary vascular resistance or the actual size of the right pulmonary artery will not handle the flow, it is not necessary to carry out this sort of delayed closure.
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0±
Further, I should like to challenge the fact that closing it at the end of 9 days is going to create any different situation from closing it initially. The same factors that determine the pressure elevation will be present then as initially. I suggest, as has been suggested by others, that the difficulties, particularly in small children, are technical ones of anastomosing two thin-walled, small vessels under awkward circumstances. [Slide] I f you will heparinize your patient (which, incidentally, will reduce one of the problems of intravascular thrombosis of the pulmonary vascular bed which has been reported as a difficulty) and insert a catheter into the superior vena cava through the atrial appendage and place tourniquets above and below the site of anastomosis, then the anastomosis can be done open with much better access and with a much wider lumen achieved. If you were to do angiograms on these small children postoperatively, you would find some narrowing of the anastomosis which may be the cause of difficulty. DR. EDWARDS (Closing).—In answer to the question about angiography of the azygos vein, we have done several venous angiograms, and, as Dr. Glenn found, there is retrograde flow down the azygos vein if it is left patent after production of a shunt. For this reason, we believe it advisable to close the azygos vein in the late postoperative period. Our program of leaving the azygos vein open immediately after operation is designed to minimize the dangerously high pressure elevation in the superior vena cava which is present for 24 to 48 hours. The slow fall in venous pressure after this period is almost certainly due to opening of collateral veins. Dr. Roe's caval catheter inserted through the right atrial appendage is an ingenious method of preventing high cerebral venous pressure while the shunt is constructed. I believe, however, that Glenn's end-to-side technique with only partial occlusion of the vena cava obviates the need for this catheter. We have without difficulty constructed a Glenn shunt in a one-month-old child. We believe the dangerous period in the Glenn method is the first 24 to 48 hours postoperatively until collateral veins dilate. In support of our theory that an open azygos vein during this period prevents excessive cerebral venous pressure, we can cite pressure measurements made continuously for 48 hours with the azygos vein open and closed and the much smoother postoperative course of those in whom the azygos vein was not ligated.
invitation),
Ala.
S
INCE its inception for partial bypass of the right heart, the major operative complication of superior vena cava-right pulmonary artery shunt has been severe cerebral edema. Glenn and Patino 2 in 1954 described an end-to-side anastomsis of the right pulmonary artery to the vena eava at the azygos orifice, after which the vena eava, central to the shunt, was ligated. Eobicsek" described a similar procedure in 1956 except that an end-to-end anastomosis of the supe rior vena eava to the distal right pulmonary artery was accomplished. Clinical experience in Russia 1 with the end-to-end method, which requires complete occlusion of the superior vena eava for 12 to 30 minutes, was followed by a high early mortality rate from brain damage. All patients in this series left the operating room with marked cyanosis and edema of the face and petechiae covering the upper half of the body. Glenn's end-to-side method allows the shunt to be constructed with only partial occlusion of the superior vena eava, so that the pressure elevation in the cerebral veins never reaches the dangerous levels seen when the vena eava is completely occluded. Glenn selected as his optimum site for pulmonary anastomosis the proximal stump of the divided azygos vein. This approach results in a lower morbidity and mortality from cerebral edema than the end-to-end method but has not eliminated it entirely. Glenn reports five postoperative instances of "superior caval syndrome" in a series of 20 operations; 4 of these were moderately severe and one was fatal. Our experience consists of 20 cases of superior vena cava-right pulmonary artery anastomosis. Of these, 16 were for tricuspid atresia, one for pulmonary artery atresia with auricular septal defect, one for Ebstein's syndrome, and 2 for tetralogy of Fallot with diffuse main pulmonary stenosis. The first ten of these operations were done exactly as described by Glenn and associates with implantation of the pulmonary artery to the stump of the divided azygos vein. Of these 10 patients, 3 infants died in the recovery room 1 to 10 hours after operation with severe facial edema and cyanosis and failure to regain consciousness. These symptoms we interpreted as due to cerebral
From the Department of Surgery, Medical College of Alabama, Birmingham, Ala. Supported by U. S. Public Health Service Grant No. H-1987(C8). Read at the Forty-third Annual Meeting of The American Association for Thoracic Sur gery at Houston, Texas, April 8-10, 1963.
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edema from high superior vena caval pressure. In the next 6 consecutive pa tients, the anastomosis was made directly caudal to the azygos vein which was not ligated, with the hope that it would serve as a decompression channel and prevent high superior caval pressure in the early period of recovery. Operative measurements of pressure in the superior vena cava were made through a 20 gauge needle connected to a water manometer in 4 of these 6 patients. After the shunt was completed and the vena cava ligated at its junction with the auricle, superior caval pressure was always elevated above 200 mm. H 2 0 with the azygos open. Temporary occlusion of the azygos vein always resulted in a further rise of 25 to 100 mm. H 2 0 which indicates that the azygos vein does
Fig. 1.—Diagram of technique for delayed ligation of the azygos vein after end-to-side superior vena cava-right pulmonary anastomosis.
permit retrograde drainage from the superior vena cava and prevents excessive pressure elevation. The immediate postoperative course in these 6 patients was much more satisfactory than in the previous group; there was little evidence of facial swelling and only mild cyanosis of the upper body. There was one death in an adult with Ebstein's anomaly but this was not associated with cere bral symptoms or edema. One 16-year-old girl with tricuspid atresia and severe cyanosis showed only slight improvement in cyanosis, and a second thoracotomy was performed for ligation of the azygos vein. Her cyanosis rapidly improved thereafter. Glenn 3 has demonstrated by venous angiography that retrograde flow occurs in the azygos vein if it is left patent after vena caval pulmonary artery shunt.
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It seemed to us from the above experience that a nonoperative technique was needed by which the azygos vein could be permanently ligated 8 or 9 days after the construction of the superior vena cava-pulmonary artery anastomosis. This would allow the azygos vein to serve as a decompression channel during the early postoperative course and prevent excessive superior vena caval pres sure elevation, but would then permit closure of the azygos vein to obtain maximum pulmonary blood flow after the danger of cerebral edema had passed. This has been satisfactorily achieved by the technique shown in Fig. 1. OPERATIVE TECHNIQUE
Through a right lateral thoracotomy, end-to-side anastomosis of the distal end of the right pulmonary artery to the side of the superior vena cava is carried out as in Glenn's technique except that the azygos vein is not ligated or divided and the anastomosis is made just caudal to the junction of the azygos vein with the vena cava. Two technical points of importance are as follows: (1) the shunt should be constructed very close to the azygos vein to allow ligation of the vena cava without constriction of the shunt by the ligature; (2) great care must be taken in placing the partial occlusion clamp and making the incision in the vena cava on the exact lateral surface of the vena cava to prevent angulation of the anastomosis. After completion of the shunt, a 2-0 silk ligature is looped twice around the azygos vein but left quite loose. A 1 cm. incision is made in the right posterior chest wall in the third intercostal space, down to, but not through, the fascia. The two ends of the azygos ligature are brought through the chest wall with separate needles to this subcutaneous incision. Here they are threaded over a sterile button and a single knot is tied loosely. The long ends of this thread and the button are placed subcutaneously just above the fascia and the skin edges are approximated over them with a single suture. An additional mattress suture is placed through the lips of this skin incision but not tied and the ends are left long. The purpose of the button is to simplify identification of the azygos liga ture at the time of delayed ligation and to prevent its incorporation in healing scar tissue. Eight days after operation, when the sutures are removed from the primary incision, the small posterior incision is opened with the use of local anesthesia if necessary. The button is located and removed. Gentle traction on the azygos loop is now applied until there is a feeling of resistance. This ligature is tied down on the fascia and cut. The mattress skin suture buries this ligature. DISCUSSION
Delayed ligation has been done in this fashion in the last three vena caval pulmonary artery shunts with excellent results in all. One 7-year-old boy with tricuspid atresia had a delayed azygos ligation 8 days after operation and developed chylothorax 12 days postoperatively which required thoracic duct ligation 4 days later. Inspection of the azygos vein at this second thoracotomy
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showed it to be securely occluded without tension on the shunt. These 3 patients have had a benign course with no evidence of facial swelling or cerebral edema and all have had almost complete disappearance of cyanosis after recovery. The patient with late chylothorax which required thoracic duct ligation was the second such case in our series of 20 vena caval pulmonary artery shunts. We now routinely ligate the thoracic duct at the time of the initial procedure, identifying it just above the diaphragm by injecting 1 c.c. of sky blue dye in the wall of the esophagus. SUMMARY
A technique is described for delayed ligation of the azygos vein one week after superior vena eaval-pulmonary artery anastomosis for partial bypass for congenital lesions of the right heart. This allows temporary decompression of the vena cava through the azygos vein and prevents excessive elevation of the superior vena caval pressure with cerebral edema. Delayed ligation permits maximum flow through the shunt after the dangers of cerebral edema have passed. We believe this technique to be especially valuable in infants, particu larly those with a relatively small pulmonary artery. REFERENCES 1. Bakulev, A. N., and Kolesnikov, S. A.: Anastomosis of Superior Vena Cava and Pul monary Artery in t h e Surgical Treatment of Certain Congenital Defects of the H e a r t , J . THORACIC SURG. 37: 693-702, 1959.
2. Glenn, W. W. L., and Patino, J . F . : Circulatory By-pass of the Right Heart. I . Preliminary Observations on the Direct Delivery of Vena Caval Blood into the Pulmonary Arte rial Circulation. Azygous Vein-Pulmonary Artery Shunt, Yale J . Biol. & Med. 27: 147, 1954. 3. Glenn, W. W. L., and others: Exhibit at the Clinical Congress, American College of Sur geons, Atlantic City, N . J., October, 1962. 4. Robicsek, F . , Temesvari, A., and Kadar, R. L . : A New Method for the Treatment of Congenital Heart Disease Associated With Impaired Pulmonary Circulation, Acta. med. scandinav. 154: 151, 1956. DISCUSSION DR. J O H N E. F E N N , New Haven, Conn.—I would like to comment on Dr. Edwards' excellent paper. We have also been interested in the management and function of the azygos vein following vena cava-pulmonary a r t e r y anastomosis. I n each of t h e 29 patients who have undergone operations a t t h e Yale-New Haven Medical Center, t h e azygos vein has been divided and the stump of the azygos has been used as the site of anastomosis for the distal divided right pulmonary artery. Thirteen of the patients have shown some sign of increased superior vena cava pressure but in the majority this has amounted to no more than mild periorbital edema which has cleared spontaneously within the first few postoperative days. To explore t h e role of t h e azygos vein i n animals undergoing vena cava-pulmonary artery anastomosis, we have performed venous and osseous angiograms with the azygos vein intact and divided. [Slide] This slide shows angiograms obtained in one animal with an intact azygos vein in which the direction of flow in the azygos is caudad with filling of the inferior vena cava. The osseous angiogram on the right side confirms the downward direction of flow in the azygos, again opacifying the inferior vena cava. The pressure in the superior vena cava
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was 120 mm. of saline and the venous flow through the anastomosis was 27 per cent of cardiac output. I n this situation some of the blood passes from the superior to the inferior vena cava through the azygos vein. If the flow of blood through t h e vena cava-pulmonary artery shunt is thereby reduced significantly the possibility of thrombosis of the anastomosis may be increased. [Slide] The next slide shows angiograms from another animal. Filling of the azygos system in the venous angiogram is poor despite opacification of the right pulmonary artery. Osseous angiography indicates that flow in the azygos is bidirectional with filling of the intrathoracic azygos system and the right pulmonary artery. The pressure in the superior vena cava was 135 mm. of saline. The shunt flow in this animal was 26 per cent of cardiac output. I t is possible that a valve a t the junction of the azygos vein and the vena cava may have impeded the passage of dye into the azygos. These studies show that the direction of blood flow in the i n t a c t azygos vein in animals with a vena eava-pulmonary artery shunt cannot be predicted, although in the majority of experiments the flow was from the superior cava into the azygos vein. We therefore believe that in all patients the azygos vein must be divided. In patients in whom the pulmonary a r t e r y - v e n a cava anastomosis is small, as in the infant, the pressure in the superior vena cava may rise to more than 200 mm. of saline which may cause cerebral edema. To provide for temporary decompression of the vena cava through the azygos system as the authors suggest may be a satisfactory solution to this problem. In New Haven, it has been our practice, in the infant who requires a shunt, to approach the heart through the midsternum so that an end-to-end extrapleural shunt is made between the vena cava and the right pulmonary artery. If the pulmonary artery is less than one half the diameter of the superior vena cava, an end-to-side anastomosis is performed between the right pulmonary artery and the ascending aorta. We would like to ask the authors why they think temporary decompression of the superior vena cava through the azygos is effective. Does it allow time for expansion of other venous collaterals to the inferior vena cava or does it permit time for full re-expansion of the right lung with reduction in resistance to flow through the pulmonary circulation? Also, we would like to ask if postoperative angiograms have been done 6 months or more following delayed ligation of the azygos vein. Please let me express my thanks to The Association for the privilege of the floor. DR. K E N N E T H HARDY, Oakland, Calif.—We, too, like the authors, have felt that preservation of the azygos vein would be important in these patients with vena caval pulmonary artery anastomoses, because of the occurrence in 2 eases of chylothorax in our series. Besides the decompressive effect of azygos runoff initially in preventing upper body edema, we had reason to believe that flows might eventually be such that we would gain, in addition to superior vena caval return to the right lung, additional systemic saturation by the added 10 per cent to 15 per cent increment of normal azygos return. Such reasoning has proved to be somewhat naive, and our hopes have not been fulfilled in this latter regard. [Slide] This baseline angiogram in a patient in whom the azygos was sacrificed, ac cording to the technique of Glenn, reveals the entire upper body return opacifying the right lung. [Slide] I n 2 % seconds after the beginning of injection, dye has traversed the left atrium and left ventricle and is now seen going to the systemic circulation, a desired result in this procedure. Having used the technique of costal interosseous venography in the evaluation for surgery of patients with bronehogenic carcinoma, we thought that if we could opacify the right lung in patients in whom the azygos vein had been preserved by the technique of azography, as described by Schobinger and others, we would gain some insight into the part played by azygos flow in these patients. [Slide] This patient had had a Glenn procedure 15 months previously, with preserva tion of the azygos vein and good clinical response, with systemic saturation improved from
816
EDWARDS AND BARGERON
J. Thoracic and
Cardiovas. Surg.
48 to 72 per cent. Much to our surprise, however, we see good opacification of the lumbar veins but only faint outline of the proximal azygos system, in contrast to the normal azygogram which normally readily demonstrates cephalad flow in this system. [Slide] A subclavian venous angiogram in the same patient demonstrates patency of the vena cava-pulmonary a r t e r y anastomosis and faint flooding of the pulmonary bed, but marked overflow spilling into the greatly hypertrophied and expanded azygos system, with flow in a caudal or retrograde direction. [Slide] The last slide made at 5 seconds after injection reveals filling of the inferior vena cava with return of a majority of upper body blood to the right heart, which partially defeats the purpose for which the operation was originally performed. This case substantiates the contention of the authors that the azygos system acts decompressively in the Glenn anastomosis, and that the azygos vein should be ligated in a staged manner. DR. F R E D E R I C K H. TAYLOR, Charlotte, N. C—Our group has been interested in this procedure for some time. I suspect it is very difficult to partially occlude the superior vena cava in a very tiny infant and still allow adequate blood flow to go downward to the heart while a side-to-end anastomosis is being done. Our approach to this problem has been a little different from Dr. E d w a r d s ' in that we use an end-to-end vena cava-pulmonary artery anastomosis; however, we leave the azygos vein open during the anastomosis. [Slide] This decompresses the superior vena cava during the few minutes of crossclamping necessary in order to do an end-to-end anastomosis below the azygos vein. This slide shows the end-to-end anastomosis. Glenn Young at Duke University divides the superior vena cava inferior to the side-to-end anastomosis, allowing for swinging out laterally and perhaps a straighter flow of blood. I think Young's technique arrives at more or less the same end as ours. [Slide] We ligate the azygos vein immediately after the anastomosis because, as we have found in this case, a so-called agyzos steal syndrome can occur. This child did not do well after anastomosis and several months later did require ligation of the azygos vein to improve her condition of cyanosis. One other thing we found very useful is the use of a bucket seat-like affair for these children in the immediate postoperative period. This period of facial cyanosis does subside in a day or two, but we have not found it necessary to leave an 8- to 10-day decompression azygos vein patent. DR. H A R V E Y W. K A U S E L , Albany, N . Y.—I do not wish to abuse this privilege by giving another paper. I enjoyed Dr. E d w a r d s ' presentation. We have been quite pleased with this procedure. We have run into some of these difficulties, and I think possibly one solution is that in the operations we have performed the hematoerit determinations in the patients have been excessively high—66 to 78 or in that range—and we have found that, by judicious phlebotomy over a period of 3 or 4 days prior to surgery, many of these problems have been overcome by getting the hematoerit readings down to an acceptable level of around 55. The chylous effusions that have occurred, and which I suspect have occurred more fre quently than we have been told, have responded to tube drainage, and we. have not had to divide the duet. Interestingly enough, in 1922, I believe Dr. Lee, at Johns Hopkins, showed that the only way to produce experimental chylous effusion in dogs was to ligate the superior vena cava. DR. B E N S O N B . ROE, San Francisco, Calif.—Dr. Edwards has, as usual, given an ex cellent presentation, but I must disagree with him, for, unless the anatomy to the extent of either pulmonary vascular resistance or the actual size of the right pulmonary artery will not handle the flow, it is not necessary to carry out this sort of delayed closure.
Vol. 46, No. 6 December, 1963
V E N A CAVA-PULMONARY A R T E R Y ANASTOMOSIS
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0±
Further, I should like to challenge the fact that closing it at the end of 9 days is going to create any different situation from closing it initially. The same factors that determine the pressure elevation will be present then as initially. I suggest, as has been suggested by others, that the difficulties, particularly in small children, are technical ones of anastomosing two thin-walled, small vessels under awkward circumstances. [Slide] I f you will heparinize your patient (which, incidentally, will reduce one of the problems of intravascular thrombosis of the pulmonary vascular bed which has been reported as a difficulty) and insert a catheter into the superior vena cava through the atrial appendage and place tourniquets above and below the site of anastomosis, then the anastomosis can be done open with much better access and with a much wider lumen achieved. If you were to do angiograms on these small children postoperatively, you would find some narrowing of the anastomosis which may be the cause of difficulty. DR. EDWARDS (Closing).—In answer to the question about angiography of the azygos vein, we have done several venous angiograms, and, as Dr. Glenn found, there is retrograde flow down the azygos vein if it is left patent after production of a shunt. For this reason, we believe it advisable to close the azygos vein in the late postoperative period. Our program of leaving the azygos vein open immediately after operation is designed to minimize the dangerously high pressure elevation in the superior vena cava which is present for 24 to 48 hours. The slow fall in venous pressure after this period is almost certainly due to opening of collateral veins. Dr. Roe's caval catheter inserted through the right atrial appendage is an ingenious method of preventing high cerebral venous pressure while the shunt is constructed. I believe, however, that Glenn's end-to-side technique with only partial occlusion of the vena cava obviates the need for this catheter. We have without difficulty constructed a Glenn shunt in a one-month-old child. We believe the dangerous period in the Glenn method is the first 24 to 48 hours postoperatively until collateral veins dilate. In support of our theory that an open azygos vein during this period prevents excessive cerebral venous pressure, we can cite pressure measurements made continuously for 48 hours with the azygos vein open and closed and the much smoother postoperative course of those in whom the azygos vein was not ligated.