Polytetrafluoroethylene Conduit Research Articles

Primary repair of pulmonary atresia with ventricular septal defect and major aortopulmonary collaterals: a useful approach

Background The ultimate goal of surgical therapy for pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries is to create unobstructed and separate in series pulmonary and systemic circuits. Our preference has been a 1-stage complete unifocalization technique, avoiding collateral anastomosis with either the native pulmonary arteries or other aortopulmonary collateral vessels. Methods and results Since 1998, 5 patients (median age 29.6 months) with pulmonary atresia, ventricular septal defect, and major aortopulmonary collateral arteries have undergone surgical correction, consisting of (1) exclusion of a descending thoracic aortic segment from which all major aortopulmonary collateral arteries originate, and (2) connection of this aortic segment to the native pulmonary artery using an interposition polytetrafluoroethylene conduit. The ventricular septal defect was closed in all patients, and the right ventricle was connected to the unifocalized pulmonary artery with a valved conduit. All patients survived the operation. Two patients required reexploration for postoperative bleeding. One patient remained on mechanical ventilation for 17 days due to a pulmonary infection. During follow-up (12-21 months), no patient required additional interventions. The postoperative right ventricular/left ventricular pressure ratio was 0.55 median. No significant stenosis within the reconstructed pulmonary circuit was identified. All patients remain free of symptoms, requiring no medications. Conclusion Intracardiac repair of pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries can be accomplished by a midline 1-stage repair including complete unifocalization of all pulmonary blood supply without individual collateral anastomosis in selected patients. This approach offers a convenient and satisfactory surgical option.

Transrenal arteriovenous dialysis graft creation: survival and patency in a swine model.

To investigate transrenal arteriovenous graft creation in an animal model and to report survival and patency. Arteriovenous grafts were created from the renal artery to the renal vein in 10 swine. Renal access was accomplished with a combined percutaneous and transvascular approach. A reinforced 6-mm polytetrafluoroethylene conduit was tunneled between both flank access points, and stent-grafts were deployed from each of the renal origins into the conduit. Clopidogrel (10 mg per kilogram of body weight) was administered intravenously during the procedure, followed by a daily oral dose (75 mg) for up to 2 weeks. Animals were monitored with auscultation and angiography for up to 1 month; necropsy was performed in all animals. Rapid arteriovenous flow at completion angiography was achieved in eight of 10 animals. Shunts were patent in five of six animals that were followed for 1 month. Diffuse pseudointimal hyperplasia was mild in three of six shunts and moderate in two (focal stenoses). Immediate thrombosis occurred in the first two animals when the clopidogrel bolus was administered after stent-graft deployment. These shunts were recanalized mechanically. Shunts were immediately patent in five of the six remaining shunts when the clopidogrel bolus was administered prior to stent-graft deployment. Complications occurred in four of 10 animals, three of which were euthanized within 1 week. The bowel was traversed in two animals, and renal vein laceration occurred during two procedures because of failure of the stent-graft delivery system. Transrenal arteriovenous graft creation in swine is technically feasible, and long-term patency is possible with antiplatelet therapy.

Carotid-carotid crossover bypass: is it a durable procedure?

Reconstruction of a diseased common carotid artery may necessitate direct repair via aortic artery-based revascularization. However, carotid-carotid artery crossover grafting is an alternative extra-anatomic option that obviates the need for median sternotomy. We analyzed our results with carotid-carotid artery crossover bypass surgery. Data were analyzed for all patients undergoing carotid-carotid crossover bypass surgery from 1995 to 2000. Data on patient demographics, indications for surgery, perioperative morbidity and mortality, and graft patency were retrieved from a vascular surgery data base and hospital records. Stroke-free survival and graft patency were determined with life table methods. Over 5 years, 24 carotid-carotid artery crossover bypass procedures were performed to treat both symptomatic (n = 19, 79%) and asymptomatic (n = 5, 17%) disease. Nine procedures (38%) were performed in men, 3 (13%) in patients with diabetes, 12 (50%) in active smokers, and 2 in patients with a history of Takayasu arteritis. Patient mean age was 63 years (range, 38-79 years). Twenty-three patients (96%) received polytetrafluoroethylene conduit grafts, and the remaining patients received vein grafts. Ten (42%) patients underwent concomitant endarterectomy. There were no perioperative deaths. One patient (4%) had asymptomatic early occlusion, one had transient neurologic deficit (4%), one (4%) required additional surgery because of bleeding, and one (4%) had a perioperative cerebrovascular accident (stroke). Three (17%) asymptomatic late occlusions were identified at 11, 57, and 64 months, respectively. Mean follow-up was 30 months (range, 1-70 months). Primary patency was 88%, and secondary patency was 92% at 3 years. Stroke-free survival was 94% at 4 years. Carotid-carotid artery crossover bypass surgery is a safe and durable procedure. Its use precludes the need for median sternotomy and provides acceptable stroke-free survival.

Infrapopliteal-Lower Extremity Revascularization with Prosthetic Conduit: A 20-Year Experience

The use of prosthetic conduits for lower extremity revascularization in the infrapopliteal location remains controversial. The objective of this report is to describe the immediate and long-term results in a series collected over two decades. Of the approximately 1,500 lower extremity revascularizations performed between 1978 and 1998, 81 infrapopliteal bypass cases using polytetrafluoroethylene (PTFE) as conduit in 77 patients were identified. Autogenous conduit was unavailable (86%) due to prior surgery: coronary artery bypass graft (25%), femoro-popliteal bypass (60%), or femoro-distal bypass (23%). All cases were done for critical ischemia using PTFE (6 mm, 95%; ring reinforced, 54%) under general (75%) or regional (25%) anesthesia. The distal anastomosis was to the anterior tibial artery (43%), posterior tibial artery (28%), tibioperoneal trunk (16%), or peroneal artery (12%), and vein patch was used in 25% of cases. Postoperative features included acute graft thrombosis in 11 cases (14%), all done under general anesthesia, perioperative death in 3 (4%), and a mean in-hospital stay of 17 days. Long-term follow-up has ranged from 1 to 144 months (mean, 22 months). At 36 months, primary patency was 20%, secondary patency 42%, and limb salvage 55% calculated by the Kaplan-Meier method. Univariate analyses revealed regional anesthesia was associated with prolonged primary patency (35% vs 15%, p=0.026) while the use of ring-reinforced PTFE conduit was associated with prolonged limb salvage (65% vs 40%, p=0.042). All other variables including gender, smoking, diabetes mellitus, renal failure, decade of operation, use of vein patch or postoperative warfarin were not significantly associated with either prolonged patency or limb salvage. Despite poor primary patency, distal prosthetic bypass can lead to long-term limb salvage. These data suggest distal anastomotic vein patches and postoperative anticoagulation may not be beneficial adjuncts. However, the use of regional anesthesia may decrease the incidence of perioperative thrombosis and the use of ring reinforced conduit may prolong limb salvage.

Expanded polytetrafluoroethylene entubulation of the rabbit inferior alveolar nerve

Objective. The purpose of this study was to evaluate the use of an expanded polytetrafluoroethylene conduit in the treatment of a 6.0-mm gap in the rabbit inferior alveolar nerve and compare the results with those of an autogenous interpositional tibial nerve graft. Study design. The inferior alveolar nerves of 5 adult New Zealand White female rabbits (10 nerves) were exposed bilaterally, and a 6-mm segment of each nerve was resected. On one side, chosen at random, the gap was immediately bridged through use of an 8.0 × 2.0-mm expanded polytetrafluoroethylene conduit; on the other side, the gap was grafted with an autogenous tibial nerve graft. Two randomly selected nerves served as sham-dissected controls. At 15 weeks after surgery, the animals were killed and the entire nerve segments were harvested and prepared according to standard fixation and embedding techniques. The sections were examined histomorphometrically to quantify the degree of axonal regeneration through definition of fascicular number, total fascicular surface area, axonal density, and mean axonal diameter at 3 locations along the repair site. Results. Light microscopic examination revealed the presence of disorganized neural tissue in both groups, with slightly more fibrovascular interfascicular tissue in the expanded polytetrafluoroethylene group. Histomorphometric analysis revealed no significant differences between groups for most of the measured variables. The mean axonal diameter varied between groups, and the fascicular number was greater in the expanded polytetrafluoroethylene group at the middle site. Conclusions. This study demonstrates that regeneration of the inferior alveolar nerve can occur across a 6.0-mm gap through an expanded polytetrafluoroethylene tube with results comparable to those of an autogenous nerve graft, significant donor site morbidity being avoided. The significant differences between groups were probably due to greater containment of regenerating axonal fibers in the expanded polytetrafluoroethylene group. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;89:292-8)

Ulnar nerve reconstruction with an expanded polytetrafluoroethylene conduit

The ulnar nerve of a 22-year-old woman was reconstructed by expanded polytetrafluoroethylene (ePTFE) conduit, 141 days after nerve transection at the distal forearm level. A 2.9 cm nerve gap was bridged by a corrugated, 3.9 cm long, 6 mm diameter ePTFE tube. At final evaluation 3 years later the patient achieved excellent motor and sensory recovery. Exploration of the tube, at that time, showed macroscopically normal nerve inside the conduit.

Physical Properties of Polytetrafluoroethylene Bypass Material after Balloon Dilation

To evaluate the performance characteristics of 3-mm and 6-mm polytetrafluoroethylene (PTFE) grafts after radial dilation comparable to their use in endovascular applications. PTFE conduits with 3- and 6-mm internal diameters were radially expanded three, four, and five times the original diameter with angioplasty balloons. Internal diameter, outer diameter, wall thickness, radial and longitudinal shortening, internodal distance, radial and longitudinal tensile strength, water entry pressure, and suture retention strength were measured and compared with nondilated samples. After dilation, the diameter of the 3- and 6-mm PTFE conduits recoiled approximately 23%, and the length shortened insignificantly. The wall thickness decreased to approximately half, and the internodal distance did not change. Porosity decreased as evidenced by a slight increase in the water entry pressure. Longitudinal and radial tensile strength, as well as suture retention strength, were decreased. Dilation of PTFE graft, as used in endovascular applications, by three to five times results in moderate elastic recoil. This needs to be taken into consideration if the material is used without a supporting inner stent. Because of the absence of significant change in porosity, perigraft fluid collections are not likely to occur. Significant decrease in suture retention strength after dilation poses a risk of localized tear and potential procedure failure.

The merit of polytetrafluoroethylene extensions and interposition grafts to salvage failing infrainguinal vein bypasses.

The purpose of this study was to evaluate the merit of polytetrafluoroethylene (PTFE) extensions and interpositions for the management of failing infrainguinal vein bypass grafts. The treatment of 133 failing vein grafts in 125 patients over a 10-year period was retrospectively reviewed. Twenty-two graft-threatening lesions were detected in patients who did not have a usable autogenous vein conduit as determined by preoperative and intraoperative evaluations. A PTFE extension or interposition graft was used for the necessary reconstruction in all cases. Ten lesions were within the vein graft, 11 were proximal to the graft in the femoral or popliteal artery segments, and one was distal to the graft in the popliteal artery. The treatment of these lesions included 19 extensions and three mid graft interpositions. The vein graft lesions developed significantly sooner (mean 10.6+/-2.5 months) after the bypass (p<0.05) than the arterial lesions (mean 28.0+/-6.1 months). The 3-year cumulative secondary patency rate for these vein grafts treated with PTFE extensions or interpositions was 84%+/-8%. This was not significantly different from the 3-year cumulative secondary patency rate for vein grafts treated with vein extensions or interpositions at our institution over the same time period (82%+/-10%). The 3-year limb salvage rates were 95% and 89%, respectively. These results indicate that PTFE extensions and interpositions can be used successfully to maintain the patency of failing vein grafts and may serve to prolong limb salvage in patients without any usable autogenous vein. Early reintervention with a PTFE conduit in this difficult group of patients is appropriate to salvage a failing vein graft.

Skeletal muscle ventricles in circulation: Decreased incidence of rupture

Skeletal muscle ventricles (SMVs) are muscular pumping chambers constructed for cardiac assist. Skeletal muscle ventricles can be connected to the circulation in a variety of configurations for both left and right heart assist; when connected to the aorta and stimulated to contract during diastole, they function in a similar fashion as an intraaortic balloon pump. Skeletal muscle ventricles were constructed in 18 dogs using the left latissimus dorsi muscle. In 10 of these dogs (group 1), the inner surface of the SMV was lined with autogenous pericardium obtained at the time of construction of the SMV. For the remaining 8, the SMVs were lined by fibrous tissue that forms in reaction to the synthetic mandrel around which the latissimus muscle is wrapped. After the muscles were electrically conditioned to a fatigue-resistant state, the mandrels were removed from the SMVs and the SMVs were connected to the descending thoracic aorta with a specially constructed base cap and two polytetrafluoroethylene conduits. Initial hemodynamic recordings revealed that the mean diastolic blood pressure increased by 24.7% in group 1 and by 29.8% in group 2. Diastolic augmentation was well maintained over time; augmentation in surviving group 1 animals was 30.0% after 18 months of pumping continuously in circulation. Long-term survival was greater in the dogs whose SMVs were constructed using an inner pericardial lining. At 90 days in circulation, 60% of the dogs in group 1 were alive with functioning SMVs, whereas only 13% of the dogs in group 2 were alive. The incidence of SMV rupture in the fibrouslined SMVs was 63%, whereas the incidence in the pericardial-lined SMVs was 0%. No evidence of thromboembolism occurred in either group. Lining the inner surface of an SMV with pericardium appears to provide structural integrity, which helps to prevent the complication of SMV rupture in this model of cardiac assist.

Composite and plain tubular synthetic graft conduits in right ventricle-pulmonary artery position: Fate in growing lambs

Our goal was to identify the most appropriate material for right ventricle-pulmonary artery conduits in growing animals. We used 100 lambs that were 3 to 4 weeks old (mean weight 11.7 kg). Follow-up was up to 24 months. Group I received plain tubular conduits: (1) Dacron knitted fabric, (2) collagen-coated knitted fabric, (3) Milliknit and Microknit material, (4) woven Dacron fabric, (5) three-dimensional Dacron fabric (crossweave 500 and 800), or (6) polytetrafluoroethylene. Group II received either a (1) woven Dacron fabric conduit with a built-in tissue valve or (2) polytetrafluoroethylene graft with a built-in St. Jude Medical valve. We did angiograms and catheterizations every 3 to 6 months and killed the lambs at 6, 12, 18, or 24 months. Tubular Dacron fabric woven or knitted grafts, regardless of matrix, pore size, thickness, or coating, caused formation of a thick acellular pseudointima buildup, which led to progressive obstruction starting as early as 3 months. Polytetrafluoroethylene grafts in groups I and II showed the formation of thin inner and outer capsules (0.5 mm) and none developed obstruction despite wall calcification. Conduits of woven Dacron fabric with a built-in tissue valve degenerated rapidly, leading to calcification thrombosis and obstruction within 3 months; no lamb survived 12 months. Polytetrafluoroethylene conduits with a St. Jude Medical valve in lambs receiving anticoagulants remained free of obstruction and continued to function well. It appears that synthetic conduits of polytetrafluoroethylene perform well in either of the situations here tested and may be the best choice at present. (J T HORAC C ARDIOVASC S URG 1995;110:427-35)

Occluded infrainguinal grafts: When to choose lytic therapy versus a new bypass graft

Background: The published results of thrombolysis for occluded bypass grafts, including a prospective multicenter trial, have been disappointing, prompting many investigators to proceed directly to a new bypass rather than attempt graft salvage. Our series of 61 occluded grafts treated with lytic therapy, however, identified a subgroup that justified attempted graft salvage. Method: The grafts consisted of saphenous vein 59% ( 36 61 ), other vein (arm or composite vein) 21% ( 13 61 ), and polytetrafluoroethylene (PTFE) 29% ( 13 61 ). The data analysis was designed to identify the graft subgroup that would benefit from lytic therapy by using cumulative survival analysis techniques with the Wilcoxon (Gehan) test for univariate analysis and Cox proportional hazards model for multivariate analysis. Specific variables examined by univariate analysis were graft age (defined as the interval from initial bypass to graft lysis), graft material, graft type (femoropopliteal versus femorotibial), diabetes, symptoms (claudication versus salvage) and duration of occlusion prior to lysis. Results: Complete lysis was achieved in 72% ( 44 61 ) of the grafts, and 86% ( 38 44 ) had an underlying stenosis that was treated by percutaneous balloon angioplasty ( 28 38 ) or surgery ( 7 38 ). Three stenotic outflow lesions were not treated. Cumulative 5-year patency for all 61 grafts was 23% ± 0.075 (SE). Only graft age <10 versus >10 months was significant ( P <0.004) by univariate analysis, and it was also the only significant variable found by multivariate analysis; it indicated a 1.58 increase in relative risk of occlusion for the younger grafts. The combination of a saphenous vein graft that was also >10 months old resulted in a 45% 5-year patency, compared to 21% for <10-month-old saphenous vein grafts ( P <0.008). A review of 161 bypass grafts performed at our institution over the past 10 years revealed a 52% 5-year secondary patency in previously bypassed limbs, which varied with graft material (67% saphenous, 50% alternative vein, 31% prosthetic). Lysed graft patency was comparable to that of a second bypass using other veins or PTFE conduit. Conclusions: In the absence of an intact saphenous vein for a second bypass, thrombolytic therapy is an alternative to surgery.

Transfemoral endovascular repair of iliac artery aneurysms

Purpose: This report evaluates the application of transfemoral endovascular repair of iliac artery aneurysms. Patients and methods: Over a 20-month period, 11 patients with serious comorbid illnesses and a total of 14 iliac artery aneurysms were treated with endovascular grafts composed of polytetra-fluoroethylene conduits combined with balloon expandable iliac artery stents (Palmaz). Nine right common, 3 left common, and 2 right internal iliac artery aneurysms were treated. The patients were men between 58 and 89 years of age (mean 72). Eight patients had isolated aneurysms and 3 had multiple iliac artery aneurysms. Results: Endovascular iliac grafts were successfully placed in all 11 patients. No procedural deaths occurred. Follow-up ranged from 3 to 21 months (mean 11). No acute or late graft thromboses occurred. Conclusions: Transluminally placed endovascular stented grafts can be used to successfully exclude iliac artery aneurysms from the circulation while maintaining lower-extremity arterial perfusion. However, longer follow-up in more patients is necessary to confirm the durability of this technique.

Value and limitations of secondary femoropopliteal bypasses with polytetrafluoroethylene

Secondary femoropopliteal bypasses with polytetrafluoroethylene (PTFE) grafts are widely regarded to be of questionable value. This has prompted some to abandon all attempts at secondary revascularization with PTFE and others to recommend that primary femoropopliteal bypasses be performed preferentially with PTFE grafts so that vein may be used for secondary procedures. Because we questioned both of these views, we reviewed all femoropopliteal bypasses done at our institution in the past 12 years and identified 73 secondary PTFE femoropopliteal procedures performed after a failed ipsilateral infrainguinal bypass (69 failed femoropopliteal; 4 failed femorodistal). Seventy (96%) secondary bypasses were performed for limb salvage and 3 (4%) for severe disabling claudication. Insertion of grafts to the popliteal artery was above the knee in 26 (36%) and below the knee in 47 (64%). Primary life-table graft patency at 4 years was only 38%. Forty-eight reinterventions in 34 limbs were required to restore or maintain graft patency in thrombosed or failing grafts. For thrombosed grafts, 20 interventions consisted of 9 simple thrombectomies and 11 thrombectomies with additional revision procedures (5 distal or proximal extensions, 6 patch angioplasties). Twenty-eight lesions threatening graft patency were treated by percutaneous transluminal angioplasty in 3, proximal or distal extensions in 20, and patch angioplasty in 5. As a result of these reinterventions, the overall secondary patency rate was 55% at 4 years, and the limb salvage rate was 74% at 4 years. Although aggressive follow-up and reintervention may be required, the use of secondary PTFE conduits in the femoropopliteal position is a viable option in patients undergoing limb salvage procedures who are at high risk. Many of these patients do not have adequate vein for use as a bypass graft.

Early Cannulation of Plasma TFE and Gore-Tex Grafts for Hemodialysis: A Prospective Randomized Study

Fifty-one consecutive vascular access procedures were randomized to either the Medtronic plasma TFE or Gore-Tex polytetrafluoroethylene (PTFE) conduits in patients requiring immediate dialysis from December 1989 to April 1990. There were 49 forearm loop fistulas and 2 upper arm grafts. Fifty of these fistulas were cannulated within 48 h of placement to avoid use of subclavian venous catheters for hemodialysis. Complications related to the early cannulation of these fistulas included 2 hematomas in the plasma TFE group, and 3 hematomas in the Gore-Tex group (p = 1.00). Two patients with Gore-Tex grafts were systemically heparinized prior to hematoma formation after thrombectomy of their accesses. There were no adverse sequelae in these 5 patients, and none of the hematomas interfered with further dialytic therapy. One patient in the plasma TFE group and 3 patients in the Gore-Tex group developed cellulitis within the first month of placement (p = 0.65). All were treated with intravenous vancomycin with resolution of the erythema. None of the plasma TFE and 3 of the Gore-Tex fistulas thrombosed within 30 days of placement (p = 0.22). All were salvaged by thrombectomy. Both the plasma TFE and Gore-Tex vascular conduits may be used after surgical placement for early dialytic therapy and are associated with minimal early complications. The early use of these fistulas may eliminate the need for subclavian venous cannulation in most patients with renal failure, thus diminishing the incidence of subclavian venous stenosis and thrombosis. Further observation of these grafts will be necessary to determine the effect of immediate cannulation on their long-term performance for hemodialysis.

Platelet reactivity in human aortic grafts: A prospective, randomized midterm study of platelet adherence and release products in Dacron and polytetrafluoroethylene conduits

Platelet-related phenomena at the blood-surface interface of randomly placed knitted Dacron (n = 6) and polytetrafluoroethylene (ePTFE) (n = 6) interposition aortic grafts were studied in patients undergoing abdominal aortic aneurysmectomy. Luminal accumulation of platelets was assessed by infusing indium-111-oxine (400 μCi) labeled autologous platelets and imaging grafts at 1 week, 3 months, and 6 months after surgery. Image analysis included an indium ratio technique (comparing aortic graft radioactivity to that of an iliac artery) and a red blood cell technetium subtraction technique (excluding blood pool radioactivity from graft radioactivity, with the heart or iliac artery serving as reference regions). Plasma levels of β-thromboglobulin and platelet factor 4 were correlated with platelet accumulations on the aortic prostheses. Differences in graft radioactivity or platelet-release products were not evident 1 week after surgery. Three months after implantation, Dacron and ePTFE conduits exhibited 87% and 47% (p < 0.05) more radioactivity with the indium ratio technique than the iliac artery. Similary, increased Dacron compared with ePTFE graft radioactivity was noted using technetium subtraction techniques: 71% vs 30% with a heart reference and 26% vs 11% with an iliac artery reference, respectively. Increases in graft radioactivity correlated with increases in both plasma β-thromboglobulin and platelet factor 4 at 3 months (r = 0.6 to 0.9; p < 0.05 to 0.001 depending on the imaging technique used). At 6 months, differences did not persist. In fact, technetium subtraction techniques suggested less Dacron conduit reactivity. It is speculated that differences in platelet accumulation and activation associated with different graft substrates may prove clinically important.

Platelet reactivity in human aortic grafts: A prospective, randomized midterm study of platelet adherence and release products in Dacron and polytetrafluoroethylene conduits

Platelet-related phenomena at the blood-surface interface of randomly placed knitted Dacron (n = 6) and polytetrafluoroethylene (ePTFE) (n = 6) interposition aortic grafts were studied in patients undergoing abdominal aortic aneurysmectomy. Luminal accumulation of platelets was assessed by infusing indium-111-oxine (400 microCi) labeled autologous platelets and imaging grafts at 1 week, 3 months, and 6 months after surgery. Image analysis included an indium ratio technique (comparing aortic graft radioactivity to that of an iliac artery) and a red blood cell technetium subtraction technique (excluding blood pool radioactivity from graft radioactivity, with the heart or iliac artery serving as reference regions). Plasma levels of beta-thromboglobulin and platelet factor 4 were correlated with platelet accumulations on the aortic prostheses. Differences in graft radioactivity or platelet-release products were not evident 1 week after surgery. Three months after implantation, Dacron and ePTFE conduits exhibited 87% and 47% (p less than 0.05) more radioactivity with the indium ratio technique than the iliac artery. Similarly, increased Dacron compared with ePTFE graft radioactivity was noted using technetium subtraction techniques: 71% vs 30% with a heart reference and 26% vs 11% with an iliac artery reference, respectively. Increases in graft radioactivity correlated with increases in both plasma beta-thromboglobulin and platelet factor 4 at 3 months (r = 0.6 to 0.9; p less than 0.05 to 0.001 depending on the imaging technique used). At 6 months, differences did not persist. In fact, technetium subtraction techniques suggested less Dacron conduit reactivity. It is speculated that differences in platelet accumulation and activation associated with different graft substrates may prove clinically important.

Aorta-coronary bypass grafting with polytetrafluoroethylene conduits: Early and late outcome in eight patients

During 1982 and 1983 we performed aorta-coronary bypass grafts on eight patients using 4 mm polytetrafluoroethylene conduits and predominantly the multiple sequential graft technique. Angiography was performed 1 week postoperatively and seven of eight patients had patent grafts and were angina free. At 1 year's follow-up 18 of 28 distal anastomoses were patent and five of eight patients were angina free. At 45 month's follow-up four of 28 distal anastomoses were patent and one of eight patients was angina free.

Injury to the left coronary artery during repair of tetralogy of Fallot: Successful aorta-coronary polytetrafluoroethylene graft

Inadvertent transection of an anomalous left coronary artery, which originated from the right coronary artery, occurred during repair of tetralogy of Fallot in a 2-year-old child. An aorta-coronary bypass graft was constructed with a size 4 polytetrafluoroethylene conduit. Early recatheterization showed patency of the polytetrafluoroethylene graft, but a myocardial scintiscan done 3 months after operation demonstrated reduced perfusion of the areas supplied by the left coronary system. Preoperative aortography or selective coronary angiography is mandatory to avoid this potentially lethal complication. Future surgical options are discussed.

Externally stented polytetrafluoroethylene valved conduits for right heart reconstruction: An experimental comparison with Dacron valved conduits

Valve-containing conduits have made possible the repair of many congenital anomalies that involve right ventricular-pulmonary arterial discontinuity. The distressing problem of neointimal peel formation with eventual conduit obstruction in patients with Dacron valved conduits has led to the need for premature replacement in many patients. Externally stented polytetrafluorethylene has demonstrated superior patency in the venous system experimentally and clinically and was believed to have potential advantages over Dacron for conduit construction. This study compares the transconduit resistance and the thickness of the neointimal peel in right ventricular-pulmonary arterial conduits constructed of externally stented polytetrafluoroethylene with those of woven Dacron. The 19 mm externally stented polytetrafluoroethylene conduits (Impra, Inc.) containing a Hancock porcine valve (Extracorporeal Inc.) were implanted in six adult mongrel dogs followed by proximal occlusion of the pulmonary artery. In six additional animals, a Dacron valved conduit of similar size and length was inserted. Cardiac output, transconduit gradient, and resistance were measured at operation and at 3 months. All conduits were subsequently explanted, opened longitudinally, and the thickness of the neointimal peel (excluding suture lines) measured. No hemodynamic differences were noted during the 3 month follow-up. However, the thickness of the neointimal peel was fourfold greater in Dacron conduits (609 +/- 144 mu) than in the conduits constructed of externally stented polytetrafluoroethylene (156 +/- 50 mu) (p less than 0.01). The thick peel in Dacron conduits extended into the outflow portion of the porcine valve cusps and prevented their full excision. The neointima in externally stented polytetrafluoroethylene conduits was thin and uniform and did not extend onto the leaflets or limit their mobility. This study demonstrated that the early hemodynamic performance of externally stented polytetrafluoroethylene conduits was comparable to that of Dacron conduits; Dacron conduits were subject to an accelerated rate of peel formation that affected leaflet mobility and may be a factor in early valve degeneration; a thin neointima formed in externally stented polytetrafluoroethylene conduits and valve leaflet motion was preserved. This study showed that externally stented polytetrafluoroethylene conduits offer advantages over Dacron valved conduits and warrant clinical application.

Polytetrafluoroethylene grafts as the first-choice arterial substitute in femoropopliteal revascularization.

We studied a series of femoropopliteal bypass operations in which polytetrafluoroethylene (PTFE) grafts were used as the first choice, regardless of the availability of saphenous vein. From Jan 1, 1979 to Dec 31, 1982, 63 PTFE femoropopliteal bypass grafts were placed in 55 patients without exploration of the saphenous vein. Forty-three grafts were placed for limb salvage, and 20 grafts were placed for disabling claudication. Patients were followed up for nine to 53 months (average, 23 months). The operative mortality was 1.8%. There were no infections. The overall patency at 30 months was 76.1%. The 30 months' cumulative patency rate for patients with claudication was 89.3%, and there were no amputations. The cumulative 30-month patency for limb salvage was 70.1%, and there was a limb salvage rate of 81.2%. Because the 30-month results were comparable with reported series using autogenous saphenous vein, we concluded that PTFE conduits may be considered the first-choice arterial substitute for femoropopliteal reconstruction. Until longer follow-ups are available, reversed autogenous saphenous vein should probably be the graft of first choice in younger patients (less than 60 years of age) without coronary artery disease who are undergoing femoropopliteal revascularizations.