Microporous Expanded Polytetrafluoroethylene Arterial Prosthesis for Construction of Aortopulmonary Shunts: Experimental and Clinical Results Alan B. Gazzaniga, M.D., Martin P. Elliott, M.D., Donald R. Sperling, M.D., William R. Dietrick, M.D., Jack I. Eisenman, M.D., D. Michael McRae, M.D., a n d Robert H. Bartlett, M.D. ABSTRACT A new microporous, expanded polytet- expanded polytetrafluoroethylene (PTFE).* rafluoroethylene arterial prosthesis was evaluated in Long-term patency has been documented in dogs. The material appears to produce an adequate animals, and tissue ingrowth is minimal to prosthesis for aortopulmonary anastomosis in ani- nonexistent [ 3 ] .This report presents our limited mals and can conduct a high rate of blood flow. The laboratory experience and recent clinical results graft has been used in 3 patients with pulmonary using this material to construct aortopulmonary atresia aged 2 days, 2 months, and 6 months. Thus far shunts in infants. all patients are well, growing, and have a loud shunt murmur. The desirable features of this type of anas- Experimental Materials and Methods tomosis are presented. Two dogs weighing between 20 and 25 kg were
anesthetized intravenously with sodium penDespite improved results in the early correc- tobarbital, the trachea was intubated, and ventltion of complex congenital heart defects, there lation was maintained with a Bird respirator. remains a group of cyanotic infants who can The thorax was entered through the right fourth survive only if a systemic-pulmonary artery intercostal space, and the right pulmonary artery anastomosis is constructed. The subclavian- and aorta were isolated. The pulmonary artery pulmonary artery (Blalock-Taussig), aorta-left was opened 6 mm in a longitudinal fashion, and pulmonary artery (Potts), and aorta-right pul- a 4 mm PTFE graft was beveled and anastomosed monary artery (Waterston-Cooley) shunts have to the right pulmonary artery using 6-0 synthetic all proved useful and are indicated in certain cardiovascular sutures. The proximal end of the situations. In recent years the aorta-right pul- graft was then sewn end-to-side to the aorta. In 1 monary artery anastomosis as originally de- animal, after construction of the shunt there was scribed by Waterston [141 has become popular an excellent bruit over the pulmonary artery. In in infants because of the low incidence of the second animal a faint bruit was present, and thrombosis when properly constructed [13]. there was an acute angle between the graft and This anastomosis, however, can easily be con- the aorta. The dogs were allowed to recover and structed too large, and complications including underwent aortography in six weeks. In a third dog an aorta-main pulmonary artery left ventricular failure and unilateral lung edema shunt was constructed through a transsternal can occur [1, 101. This anastomosis has proved incision at the level of the fourth intercostal difficult to close properly at the time of correcspace. Systemic pressure was measured by way tion [5]. of the internal mammary artery using a Statham Recent technological advances have allowed strain gauge connected to a Beckman multhe production of an arterial prosthesis with a tichannel recorder. Left atrial pressure (LAP) diameter of 4.0 mm, made from microporous, was monitored by inserting a catheter into the left atrium through the right lower lobe vein. From the Department of Surgery, University of California, Systemic blood flow was measured with a 14 mm Irvine, College of Medicine, Irvine, CA. Micront flow probe around the aorta proximal to Accepted for publication Sept 16, 1975. Address reprint requests to Dr. Gazzaniga, Department of Surgery, University of California, Irvine, College of Medicine, Irvine, CA 92664.
322
*IMPRA Inc, Phoenix, AZ. tMicron Instruments Inc, Los Angeles, CA.
323
Gazzaniga et al: Microporous Expanded PTFE Arterial Prosthesis
In the dog in which short-term hemodynamic studies were performed, mean systemic blood flow with the shunt clamped was 3.2 liters per minute proximal to the aortic graft anastomosis. When the graft was open systemic blood flow rose to a mean flow of 4.4 L/min, or an increase of 1,200 mlimin with the shunt open. Systemic arterial pressure fell from 150 to 130 mm Hg and Results In the dogs that underwent aorta-right pulmonary diastolic pressure from 75 to 60 mm Hg. Mean artery shunting, aortography was performed six LAP went from 21 to 30 mm Hg when the shunt weeks after the anastomosis. The angiogram in 1 was opened. These marked hemodynamic dog is shown in Figure 1; the distribution of changes indicated high flow through the 4.0 mm blood from the aorta is mainly to the right pul- arterial prosthesis. These same results were obmonary artery. This animal was killed two tained with repeated opening and closing of the weeks later. The graft was patent, with a smooth shunt. Prior to sacrifice, a catheter was placed in lining throughout. Histological examination the main pulmonary artery and pressure was showed a thin endothelial cell layer with fibro- measured. With the shunt open the systolic blasts in the wall (Fig 2). In the second animal, pulmonary artery pressure was 80 mm Hg, patency could not be documented by aortog- which fell to 60 mm Hg with clamping. The raphy and the animal was killed. At postmortem diastolic pressure was unchanged. examination the kinking at the aortic anastomosis was seen to have led to obstruction and Clinical Material and Methods Because of the technical problems of anastomosfinally to total occlusion of the graft. ing the arterial prosthesis to the right pulmonary artery and aorta without angulation and because Fig 1 . Subtractioiz roentgenogmni of nortogram of the preferential flow to the right lung, we showing PTFE shiiiit (arrow)inn dog. Bloodflozued elected to use aorta-main pulmonary artery mainly to the right lung. shunts in patients whenever feasible. Three patients aged 2 days, 2 months, and 6 months with pulmonary atresia underwent systemicpulmonary artery shunts using the 4.0 mm PTFE. Clinical summaries are shown in the Table. The 2-day- and 2-month-old infants were moribund prior to operation. In Patient 1the pH was 6.9 just prior to operation, and the pulmonary valve was opened by blind incision and dilation. The patient’s heart had arrested several times prior to the valvulotomy. The graft was anastomosed to the aorta and main pulmonary artery. Nine months postoperatively the patient had a loud shunt murmur with an arterial oxygen saturation of 85%. Patient 2 had complex intracardiac anatomy that included a common atrium and single ventricular chamber with a right aortic arch. The patient had undergone a previous aorta-right pulmonary artery shunt during the newborn period. The shunt at six months was inadequate in size, and the baby had an arterial oxygen saturation of 67% with a hematocrit of 74%. the shunt. All pressures and flows were continuously monitored. The animal was observed for three hours, during which the shunt was clamped and released at half-hour intervals to assess the change in aortic flow, LAP, and systemic blood pressure.
324 The Annals of Thoracic Surgery Val 21 No 4
Fig 2. P/iotor~iicrograpliof prostliesis
iti a
April 1976
dog
d l O i l r i i l g fibi’Ob/nSt e!lligf’l?tiOfl i i l t O g r ~ 7 j ilW// t arldfl
tliiri eriifotlirlial layer of cells. (Orig i i i n g ~ 1 0 0 . )
Aortography showed a moderate-sized left pulmonary artery and the ascending aorta projecting into the left chest. The left subclavian artery had a high takeoff and was not long enough for anastomosis to the pulmonary artery. The baby
underwent left pulmonary artery-aorta PTFE shunt. Upon opening the shunt there was a bruit in the left pulmonary artery. The patient had a benign postoperative convalescence. Eight months postoperatively h e had a loud shunt murmur and an arterial oxygen saturation of 88% at rest. Patient 3 was 2 months old and had pulmonary atresia with a ventricular septal defect. The
Clinical Data on 3 Patients Who Received PTFE Grafts Arterial 0, Sat ( %)
Patient No., Age, & Sex
wt
1, 2 days, F
2.9
2, 6 mo, M
4.0
3, 2 mo, M
3.2
Pulmonary atresia with single ventricle and previous aorta-right pulmonary artery shunt Pulmonary atresia with ventricular septal defect
(kg) Diagnosis
Preop
Postop
Operation
Outcome
Pulmonary atresia 40 with intact septum
92
Well 9 mo postop
67
86
Closed pulmonary valvulotomy & aorta-main pulmonary artery shunt Aorta-left pulmonary artery shunt
Well 8 mo postop
45
85
Aorta-main pulmonary artery shunt
Well 8 mo postop
325
Gazzaniga et al: Microporous Expanded PTFE Arterial Prosthesis
ductus arteriosus was closed, and the entire pulmonary blood flow was from small bronchial arteries arising from the descending aorta. The patient had an arterial oxygen saturation of 45% while breathing 40% oxygen, was obtunded, and was being fed by gavage. At operation the main pulmonary artery was approximately 2 to 3 mm in diameter. Vascular tapes were passed around the right and left pulmonary arteries, and the main pulmonary artery was divided at its origin from the heart (Fig 3). The artery was then opened along its anterior surface down to the left pulmonary artery. The 4.0 mm PTFE graft was anastomosed to the artery using 7-0 synthetic cardiovascular suture. The graft was then brought around and sewn onto the aorta. There was a thrill in the pulmonary artery at the conclusion of the procedure, and the patient was discharged home in seven days. Eight months postoperatively he had an arterial oxygen saturation of 85% at rest.
Comment Prior to use of the PTFE graft in patients, our laboratory evaluation was limited to familiarizing ourselves with its handling characteristics and determining if this material, when free in the mediastinum, would become incorporated by fibroblasts. In the dogs with aorta-right pulmonary artery shunts, the graft had had ingrowth of fibroblasts and the lumen was lined with a thin layer of cells. A kink was present following the anastomosis in 1 dog, and this ultimately led to thrombosis of the graft. Because kinking is hard to eliminate when constructing an anastomosis to the right pulmonary artery and because flow on arteriography was principally to the right lung, clinical use of this material favored an aorta-main pulmonary artery shunt. Consequently, hemodynamic measurements were made in l animal that had an aorta-main pulmonary artery shunt using a 4.0 mm graft. Changes equivalent to those of direct aorta-right pulmonary artery (Waterston) shunts of 5 to 6 mm were produced [6]. The PTFE prosthesis is circular, with a diameter of 4.0 mm,
326 The Annals of Thoracic Surgery Vol 21 No 4 April 1976
whereas a 4.0 mm direct aorta-right pulmonary artery side-to-side anastomosis may not be perfectly circular. Therefore, the 4.0 mm graft material sewn to the main pulmonary artery has a higher flow rate than the comparable direct 4.0 mm aorta-right pulmonary artery anastomosis. The PTFE vascular prosthesis is made by an extrusion process and differs from woven or knitted synthetic arterial grafts because of its small pore size. This prevents tissue growth into the lumen but allows for fibroblast incorporation to bind it to surrounding structures. The lumen, as shown in 1dog experiment (see Fig 2), is covered throughout its entire length with a thin layer of what appear to be endothelial cells. The material handles well and does not require preclotting, but care must be taken to puncture the material with as small a needle as possible. Blood should not sit in the graft while the anastomosis is being made since the clots that form are difficult to remove. There has been extensive laboratory study of expanded PTFE as a vena caval graft and as an artery substitute. In 1972 Soyer and associates [121 reported the use of expanded PTFE as a venous prosthesis in pigs, replacing the portal vein and inferior vena cava. Patency rates were excellent, and there was no luminal ingrowth. Similar results have been reported recently by Smith and colleagues [ l l ] using the material to replace the inferior vena cava in dogs. Matsumoto and associates [81 utilized expanded PTFE as an arterial small vessel replacement in dogs and used a 3 mm ID graft for replacement of femoral arteries. They reported a 100°/~patency rate with follow-up of four to eleven months. Campbell and associates [31 used expanded 4.0 ID PTFE but varied the wall thickness and pore size. They achieved a high patency rate when using the material for an artery substitute and concluded that pore size was the critical factor in patency. Their work led to development of the material used in our patients. Clinical use of expanded PTFE is limited, and no long-term patency rates are available. The application of expanded PTFE as a conduit for construction of aortopulmonary shunts in infants is the result of our dissatisfaction with currently accepted techniques. The complications of construction and subsequent closure
of aortopulmonary or subclavian-pulmonary shunts are well known [4,7,10 1. These difficulties have stimulated some surgeons to do earlier correction of certain cyanotic congenital heart defects [2, 41. However, intracardiac correction in an older child presents fewer technical difficulties for the surgeon and less risk for most patients than the same correction done in infants. The desirable features of an aorta-main pulmonary artery shunt are that blood flow is distributed to both lungs and that symmetrical and bidirectional flow may promote growth and enlargement of small pulmonary arteries. An aorta-right pulmonary artery shunt in most instances preferentially sends blood to the right lung, especially if there is kinking of the pulmonary artery [9, 101. This can produce underdevelopment of the left pulmonary artery and further narrowing of the pulmonary outflow tract. Subsequent takedown of this anastomosis has been more involved than was anticipated when the anastomosis was first proposed [5]. The intraoperative benefits of the main pulmonary artery-aorta shunt are apparent once the operation is performed. With the usual type of anastomosis, there is retraction of the lung hilus with occlusion of blood flow to one lung during the anastomosis. Blood flow to the lung is not interrupted during partial occlusion of the main pulmonary artery when an end-to-side shunt is performed. The conduct of the operation is smoother and faster, and there are fewer periods of bradycardia. No autogenous vessels such as the subclavian artery are sacrificed, and there is minimal dissection of the pulmonary arteries. The U-shaped anastomosis shown in Figure 3 appears to be satisfactory, and the graft is positioned so that kinking is minimized. It is possible to construct an anastomosis that does not involve as much length of graft, but this may produce too high a flow rate in an infant. The long-term patency rates and fate of PTFE grafts in humans are unknown. Histological examination in animals confirms minimal to absent tissue ingrowth and lining of the graft with endothelial-like cells. The graft is located anteriorly and should be accessible for closure at subsequent correction. Whether its incorporation into surrounding structures will make sub-
327
Gazzaniga et al: Microporous Expanded PTFE Arterial Prosthesis
sequent operations technically hazardous is unknown.
8. Matsumoto H, Hosegawa T, Fuse K, et al: A new vascular prosthesis for a small caliber artery. Surgery 74:519, 1973 9. Oldham HN, Simpson L, Jones RH, et al: DifReferences ferential distribution of pulmonary blood flow 1. Albers WH, Nadas AS: Unilateral pulmonary following aortopulmonary anastomosis. Surg edema and pleural effusion after systemicForum 21:201, 1970 pulmonary artery shunts for cyanotic congenital 10. Reitman MJ, Galioto FM, Gala1 ME, et al: Ascendheart disease. Am J Cardiol 19:861, 1967 ing aorta to right pulmonary artery anastomosis. 2. Barratt-Boyes BG: Primary definitive intracardiac Circulation 49:952, 1974 operations in infants: tetralogy of Fallot, Ad- 11. Smith DE, Hammon J, Anane-Sofah J, et al: Segvances i n Cardiovascular Surgery. Edited by JW mental venous replacement: a comparison of Kirklin. New York, Grune & Stratton, 1973, p 155 biological and synthetic substitutes. J Thorac 3. Campbell CD, Goldfarb D, Detton DD, et al: ExCardiovasc Surg 69:589, 1975 panded polytetrafluoroethylene as a small artery 12. Soyer T, Lempinen M, Cooper P, et al: A new substitute. Trans Am SOC Artif Intern Organs venous prosthesis. Surgery 72:864, 1972 20:86, 1974 13. Waldhausen JA, Friedman S, Tyers GFO, et al: 4. Castaneda AR, Lamberti J, Sade RM, et al: Open Ascending aorta-righ t pulmonary artery anasheart surgery during the first three months of life. tomosis. Circulation 38:463, 1968 J Thorac Cardiovasc Surg 68:719, 1974 14. Waterston DJ: Treatment of Fallot’s tetralogy in 5. Ebert PA, Gay WJ Jr, Oldham HN: Management children under 1 year of age. Rozhl Chir 41:181, of aorta-right pulmonary artery anastomosis dur1962 ing total correction of tetralogy of Fallot. Surgery 71:231, 1972 6. Gazzaniga AB, James JM, Achauer BM, et al: Editor’s Note Changes in left atrial and systemic pressures and The authors’ experience with the material described is blood flow following graded aortopulmonary not great, and the experimental data are very limited. However, we believe this new material for inanastomosis. Ann Thorac Surg 18:372, 1974 7. Kirklin JW, Karp RB: The Tetralogy of Fallot. trathoracic shunts should be brought to the attention of our readers. Philadelphia, Saunders, 1970
anesthetized intravenously with sodium penDespite improved results in the early correc- tobarbital, the trachea was intubated, and ventltion of complex congenital heart defects, there lation was maintained with a Bird respirator. remains a group of cyanotic infants who can The thorax was entered through the right fourth survive only if a systemic-pulmonary artery intercostal space, and the right pulmonary artery anastomosis is constructed. The subclavian- and aorta were isolated. The pulmonary artery pulmonary artery (Blalock-Taussig), aorta-left was opened 6 mm in a longitudinal fashion, and pulmonary artery (Potts), and aorta-right pul- a 4 mm PTFE graft was beveled and anastomosed monary artery (Waterston-Cooley) shunts have to the right pulmonary artery using 6-0 synthetic all proved useful and are indicated in certain cardiovascular sutures. The proximal end of the situations. In recent years the aorta-right pul- graft was then sewn end-to-side to the aorta. In 1 monary artery anastomosis as originally de- animal, after construction of the shunt there was scribed by Waterston [141 has become popular an excellent bruit over the pulmonary artery. In in infants because of the low incidence of the second animal a faint bruit was present, and thrombosis when properly constructed [13]. there was an acute angle between the graft and This anastomosis, however, can easily be con- the aorta. The dogs were allowed to recover and structed too large, and complications including underwent aortography in six weeks. In a third dog an aorta-main pulmonary artery left ventricular failure and unilateral lung edema shunt was constructed through a transsternal can occur [1, 101. This anastomosis has proved incision at the level of the fourth intercostal difficult to close properly at the time of correcspace. Systemic pressure was measured by way tion [5]. of the internal mammary artery using a Statham Recent technological advances have allowed strain gauge connected to a Beckman multhe production of an arterial prosthesis with a tichannel recorder. Left atrial pressure (LAP) diameter of 4.0 mm, made from microporous, was monitored by inserting a catheter into the left atrium through the right lower lobe vein. From the Department of Surgery, University of California, Systemic blood flow was measured with a 14 mm Irvine, College of Medicine, Irvine, CA. Micront flow probe around the aorta proximal to Accepted for publication Sept 16, 1975. Address reprint requests to Dr. Gazzaniga, Department of Surgery, University of California, Irvine, College of Medicine, Irvine, CA 92664.
322
*IMPRA Inc, Phoenix, AZ. tMicron Instruments Inc, Los Angeles, CA.
323
Gazzaniga et al: Microporous Expanded PTFE Arterial Prosthesis
In the dog in which short-term hemodynamic studies were performed, mean systemic blood flow with the shunt clamped was 3.2 liters per minute proximal to the aortic graft anastomosis. When the graft was open systemic blood flow rose to a mean flow of 4.4 L/min, or an increase of 1,200 mlimin with the shunt open. Systemic arterial pressure fell from 150 to 130 mm Hg and Results In the dogs that underwent aorta-right pulmonary diastolic pressure from 75 to 60 mm Hg. Mean artery shunting, aortography was performed six LAP went from 21 to 30 mm Hg when the shunt weeks after the anastomosis. The angiogram in 1 was opened. These marked hemodynamic dog is shown in Figure 1; the distribution of changes indicated high flow through the 4.0 mm blood from the aorta is mainly to the right pul- arterial prosthesis. These same results were obmonary artery. This animal was killed two tained with repeated opening and closing of the weeks later. The graft was patent, with a smooth shunt. Prior to sacrifice, a catheter was placed in lining throughout. Histological examination the main pulmonary artery and pressure was showed a thin endothelial cell layer with fibro- measured. With the shunt open the systolic blasts in the wall (Fig 2). In the second animal, pulmonary artery pressure was 80 mm Hg, patency could not be documented by aortog- which fell to 60 mm Hg with clamping. The raphy and the animal was killed. At postmortem diastolic pressure was unchanged. examination the kinking at the aortic anastomosis was seen to have led to obstruction and Clinical Material and Methods Because of the technical problems of anastomosfinally to total occlusion of the graft. ing the arterial prosthesis to the right pulmonary artery and aorta without angulation and because Fig 1 . Subtractioiz roentgenogmni of nortogram of the preferential flow to the right lung, we showing PTFE shiiiit (arrow)inn dog. Bloodflozued elected to use aorta-main pulmonary artery mainly to the right lung. shunts in patients whenever feasible. Three patients aged 2 days, 2 months, and 6 months with pulmonary atresia underwent systemicpulmonary artery shunts using the 4.0 mm PTFE. Clinical summaries are shown in the Table. The 2-day- and 2-month-old infants were moribund prior to operation. In Patient 1the pH was 6.9 just prior to operation, and the pulmonary valve was opened by blind incision and dilation. The patient’s heart had arrested several times prior to the valvulotomy. The graft was anastomosed to the aorta and main pulmonary artery. Nine months postoperatively the patient had a loud shunt murmur with an arterial oxygen saturation of 85%. Patient 2 had complex intracardiac anatomy that included a common atrium and single ventricular chamber with a right aortic arch. The patient had undergone a previous aorta-right pulmonary artery shunt during the newborn period. The shunt at six months was inadequate in size, and the baby had an arterial oxygen saturation of 67% with a hematocrit of 74%. the shunt. All pressures and flows were continuously monitored. The animal was observed for three hours, during which the shunt was clamped and released at half-hour intervals to assess the change in aortic flow, LAP, and systemic blood pressure.
324 The Annals of Thoracic Surgery Val 21 No 4
Fig 2. P/iotor~iicrograpliof prostliesis
iti a
April 1976
dog
d l O i l r i i l g fibi’Ob/nSt e!lligf’l?tiOfl i i l t O g r ~ 7 j ilW// t arldfl
tliiri eriifotlirlial layer of cells. (Orig i i i n g ~ 1 0 0 . )
Aortography showed a moderate-sized left pulmonary artery and the ascending aorta projecting into the left chest. The left subclavian artery had a high takeoff and was not long enough for anastomosis to the pulmonary artery. The baby
underwent left pulmonary artery-aorta PTFE shunt. Upon opening the shunt there was a bruit in the left pulmonary artery. The patient had a benign postoperative convalescence. Eight months postoperatively h e had a loud shunt murmur and an arterial oxygen saturation of 88% at rest. Patient 3 was 2 months old and had pulmonary atresia with a ventricular septal defect. The
Clinical Data on 3 Patients Who Received PTFE Grafts Arterial 0, Sat ( %)
Patient No., Age, & Sex
wt
1, 2 days, F
2.9
2, 6 mo, M
4.0
3, 2 mo, M
3.2
Pulmonary atresia with single ventricle and previous aorta-right pulmonary artery shunt Pulmonary atresia with ventricular septal defect
(kg) Diagnosis
Preop
Postop
Operation
Outcome
Pulmonary atresia 40 with intact septum
92
Well 9 mo postop
67
86
Closed pulmonary valvulotomy & aorta-main pulmonary artery shunt Aorta-left pulmonary artery shunt
Well 8 mo postop
45
85
Aorta-main pulmonary artery shunt
Well 8 mo postop
325
Gazzaniga et al: Microporous Expanded PTFE Arterial Prosthesis
ductus arteriosus was closed, and the entire pulmonary blood flow was from small bronchial arteries arising from the descending aorta. The patient had an arterial oxygen saturation of 45% while breathing 40% oxygen, was obtunded, and was being fed by gavage. At operation the main pulmonary artery was approximately 2 to 3 mm in diameter. Vascular tapes were passed around the right and left pulmonary arteries, and the main pulmonary artery was divided at its origin from the heart (Fig 3). The artery was then opened along its anterior surface down to the left pulmonary artery. The 4.0 mm PTFE graft was anastomosed to the artery using 7-0 synthetic cardiovascular suture. The graft was then brought around and sewn onto the aorta. There was a thrill in the pulmonary artery at the conclusion of the procedure, and the patient was discharged home in seven days. Eight months postoperatively he had an arterial oxygen saturation of 85% at rest.
Comment Prior to use of the PTFE graft in patients, our laboratory evaluation was limited to familiarizing ourselves with its handling characteristics and determining if this material, when free in the mediastinum, would become incorporated by fibroblasts. In the dogs with aorta-right pulmonary artery shunts, the graft had had ingrowth of fibroblasts and the lumen was lined with a thin layer of cells. A kink was present following the anastomosis in 1 dog, and this ultimately led to thrombosis of the graft. Because kinking is hard to eliminate when constructing an anastomosis to the right pulmonary artery and because flow on arteriography was principally to the right lung, clinical use of this material favored an aorta-main pulmonary artery shunt. Consequently, hemodynamic measurements were made in l animal that had an aorta-main pulmonary artery shunt using a 4.0 mm graft. Changes equivalent to those of direct aorta-right pulmonary artery (Waterston) shunts of 5 to 6 mm were produced [6]. The PTFE prosthesis is circular, with a diameter of 4.0 mm,
326 The Annals of Thoracic Surgery Vol 21 No 4 April 1976
whereas a 4.0 mm direct aorta-right pulmonary artery side-to-side anastomosis may not be perfectly circular. Therefore, the 4.0 mm graft material sewn to the main pulmonary artery has a higher flow rate than the comparable direct 4.0 mm aorta-right pulmonary artery anastomosis. The PTFE vascular prosthesis is made by an extrusion process and differs from woven or knitted synthetic arterial grafts because of its small pore size. This prevents tissue growth into the lumen but allows for fibroblast incorporation to bind it to surrounding structures. The lumen, as shown in 1dog experiment (see Fig 2), is covered throughout its entire length with a thin layer of what appear to be endothelial cells. The material handles well and does not require preclotting, but care must be taken to puncture the material with as small a needle as possible. Blood should not sit in the graft while the anastomosis is being made since the clots that form are difficult to remove. There has been extensive laboratory study of expanded PTFE as a vena caval graft and as an artery substitute. In 1972 Soyer and associates [121 reported the use of expanded PTFE as a venous prosthesis in pigs, replacing the portal vein and inferior vena cava. Patency rates were excellent, and there was no luminal ingrowth. Similar results have been reported recently by Smith and colleagues [ l l ] using the material to replace the inferior vena cava in dogs. Matsumoto and associates [81 utilized expanded PTFE as an arterial small vessel replacement in dogs and used a 3 mm ID graft for replacement of femoral arteries. They reported a 100°/~patency rate with follow-up of four to eleven months. Campbell and associates [31 used expanded 4.0 ID PTFE but varied the wall thickness and pore size. They achieved a high patency rate when using the material for an artery substitute and concluded that pore size was the critical factor in patency. Their work led to development of the material used in our patients. Clinical use of expanded PTFE is limited, and no long-term patency rates are available. The application of expanded PTFE as a conduit for construction of aortopulmonary shunts in infants is the result of our dissatisfaction with currently accepted techniques. The complications of construction and subsequent closure
of aortopulmonary or subclavian-pulmonary shunts are well known [4,7,10 1. These difficulties have stimulated some surgeons to do earlier correction of certain cyanotic congenital heart defects [2, 41. However, intracardiac correction in an older child presents fewer technical difficulties for the surgeon and less risk for most patients than the same correction done in infants. The desirable features of an aorta-main pulmonary artery shunt are that blood flow is distributed to both lungs and that symmetrical and bidirectional flow may promote growth and enlargement of small pulmonary arteries. An aorta-right pulmonary artery shunt in most instances preferentially sends blood to the right lung, especially if there is kinking of the pulmonary artery [9, 101. This can produce underdevelopment of the left pulmonary artery and further narrowing of the pulmonary outflow tract. Subsequent takedown of this anastomosis has been more involved than was anticipated when the anastomosis was first proposed [5]. The intraoperative benefits of the main pulmonary artery-aorta shunt are apparent once the operation is performed. With the usual type of anastomosis, there is retraction of the lung hilus with occlusion of blood flow to one lung during the anastomosis. Blood flow to the lung is not interrupted during partial occlusion of the main pulmonary artery when an end-to-side shunt is performed. The conduct of the operation is smoother and faster, and there are fewer periods of bradycardia. No autogenous vessels such as the subclavian artery are sacrificed, and there is minimal dissection of the pulmonary arteries. The U-shaped anastomosis shown in Figure 3 appears to be satisfactory, and the graft is positioned so that kinking is minimized. It is possible to construct an anastomosis that does not involve as much length of graft, but this may produce too high a flow rate in an infant. The long-term patency rates and fate of PTFE grafts in humans are unknown. Histological examination in animals confirms minimal to absent tissue ingrowth and lining of the graft with endothelial-like cells. The graft is located anteriorly and should be accessible for closure at subsequent correction. Whether its incorporation into surrounding structures will make sub-
327
Gazzaniga et al: Microporous Expanded PTFE Arterial Prosthesis
sequent operations technically hazardous is unknown.
8. Matsumoto H, Hosegawa T, Fuse K, et al: A new vascular prosthesis for a small caliber artery. Surgery 74:519, 1973 9. Oldham HN, Simpson L, Jones RH, et al: DifReferences ferential distribution of pulmonary blood flow 1. Albers WH, Nadas AS: Unilateral pulmonary following aortopulmonary anastomosis. Surg edema and pleural effusion after systemicForum 21:201, 1970 pulmonary artery shunts for cyanotic congenital 10. Reitman MJ, Galioto FM, Gala1 ME, et al: Ascendheart disease. Am J Cardiol 19:861, 1967 ing aorta to right pulmonary artery anastomosis. 2. Barratt-Boyes BG: Primary definitive intracardiac Circulation 49:952, 1974 operations in infants: tetralogy of Fallot, Ad- 11. Smith DE, Hammon J, Anane-Sofah J, et al: Segvances i n Cardiovascular Surgery. Edited by JW mental venous replacement: a comparison of Kirklin. New York, Grune & Stratton, 1973, p 155 biological and synthetic substitutes. J Thorac 3. Campbell CD, Goldfarb D, Detton DD, et al: ExCardiovasc Surg 69:589, 1975 panded polytetrafluoroethylene as a small artery 12. Soyer T, Lempinen M, Cooper P, et al: A new substitute. Trans Am SOC Artif Intern Organs venous prosthesis. Surgery 72:864, 1972 20:86, 1974 13. Waldhausen JA, Friedman S, Tyers GFO, et al: 4. Castaneda AR, Lamberti J, Sade RM, et al: Open Ascending aorta-righ t pulmonary artery anasheart surgery during the first three months of life. tomosis. Circulation 38:463, 1968 J Thorac Cardiovasc Surg 68:719, 1974 14. Waterston DJ: Treatment of Fallot’s tetralogy in 5. Ebert PA, Gay WJ Jr, Oldham HN: Management children under 1 year of age. Rozhl Chir 41:181, of aorta-right pulmonary artery anastomosis dur1962 ing total correction of tetralogy of Fallot. Surgery 71:231, 1972 6. Gazzaniga AB, James JM, Achauer BM, et al: Editor’s Note Changes in left atrial and systemic pressures and The authors’ experience with the material described is blood flow following graded aortopulmonary not great, and the experimental data are very limited. However, we believe this new material for inanastomosis. Ann Thorac Surg 18:372, 1974 7. Kirklin JW, Karp RB: The Tetralogy of Fallot. trathoracic shunts should be brought to the attention of our readers. Philadelphia, Saunders, 1970
