Endothelial cell seeding: problems and expectations.
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Animals↗
Biomedical subjects
A D Callow
Publications and source records attributed to A D Callow.
The microcosm of the arterial wall--a plea for research.
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Animals↗
Postoperative management of patients who undergo aortic surgery.
Because patients with occlusive or aneurysmal disease of the aorta frequently have coexisting disease in other important organ systems, complications after aortic surgery usually relate to the heart, lungs and kidneys. Postoperative care thus requires attention, in an intensive-care milieu, to respiratory, cardiac, renal and gastrointestinal systems, coagulation and, in rare instances, psychiatric problems.
Aged↗
Retroperitoneal approach to high-risk abdominal aortic aneurysms.
During a 14-month period we used a left-flank, retroperitoneal, retrorenal approach in 23 high-risk patients with abdominal aortic aneurysm (AAA). Fourteen patients underwent suprarenal/celiac cross clamp for juxtarenal/suprarenal AAA and/or associated occlusive disease. Other indications for this approach included diminished cardiac and/or pulmonary reserve, previous extensive abdominal surgery, obesity, and inflammatory AAA. There was only one death (4%) in this high-risk group and minimal operative morbidity. The flexibility afforded by this approach for high aortic exposure allowed expeditious proximal anastomoses with minimal postoperative renal dysfunction. Pulmonary complications, ileus, and pain were reduced and patient mobilization was rapid despite the complex nature of the operative procedures. We believe that this approach offers significant advantages for all cases of AAA but particularly for anatomically complex lesions and medically high-risk patients.
Aged↗
Antiplatelet therapy and vascular grafts. Studies in a baboon ex vivo shunt.
Antiplatelet therapy is currently recommended in an effort to improve patency rates of small-caliber vascular grafts. The effect of aspirin and heparin on acute platelet deposition was studied in a baboon ex vivo shunt. Two grafts, expanded polytetrafluoroethylene and knitted Dacron, were exposed to a flow rate of 25 mL/min after administration of aspirin or heparin. Indium 111-labeled platelet uptake by the grafts was determined over 2 1/2 hours. The amount of platelet deposition in the treated groups was significantly less than that of controls after 2 1/2 hours. There was no difference between the aspirin and heparin groups. The finding that heparin inhibited platelet deposition to a degree comparable with aspirin suggests that it may not be necessary to start antiplatelet therapy preoperatively. Intraoperative systemic heparinization will provide sufficient inhibition of platelet deposition. A protocol for perioperative antiplatelet therapy is outlined.
Animals↗
Adult human endothelial cell coverage of small-caliber Dacron and polytetrafluoroethylene vascular prostheses in vitro.
Culture of endothelial cells on synthetic vascular grafts has heretofore met with limited success. We report here a technique which allows attachment and subsequent growth of adult human vascular endothelial cells on the synthetic materials polytetrafluoroethylene (PTFE) and Dacron which are currently used for vascular reconstructive surgery. Studies were conducted on both untreated materials and those pretreated with the extracellular matrix proteins collagen and fibronectin. Collagen was applied to the graft materials with positive pressure and then allowed to gel in the interstices. Fibronectin was added to the collagen-lined lumen followed by a cell suspension. Cell coverage on the grafts was assessed by scanning electron microscopy after various lengths of time. Cells adhered poorly to and did not grow on untreated Dacron and PTFE. Protein-treated materials did allow cell attachment and growth but with distinct differences. On PTFE (n = 30), cells could form a confluent monolayer within 9 days while cell coverage was generally incomplete at this time on the more irregular surface of Dacron (n = 5). Thus, adult human endothelial cells can grow on collagen- and fibronectin-coated prosthetic materials. This approach to lining graft materials in vitro may be useful in improving the performance of small-caliber vascular grafts.
Adult↗
Arterial reconstructions: fundamental questions.
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Carotid Artery Diseases↗
The costs of surgery for limb-threatening ischemia.
The clinical courses of 106 patients with limb-threatening ischemia were traced for as long as 5 years to determine the cost of their care. Seventy-eight patients initially treated with vascular reconstruction accrued an average of $40,769 +/- $3726 in costs over a mean follow-up period of 805 +/- 57 days, during which they had an average of 2.4 +/- 0.2 hospitalizations or 67 +/- 6 inpatient days. Twenty-eight high-risk patients treated with primary amputation accrued $40,563 +/- $4729 in costs over a mean follow-up period of 663 +/- 97 days, during which they had an average of 2.2 +/- 0.3 hospitalizations or 85 +/- 10 inpatient days. Successful revascularization resulted in lower costs ($28,374) than did primary amputation ($40,563) or failed reconstruction ($56,809). Patients with ischemic tissue loss accrued costs more rapidly than did patients with rest pain only. The high cost of providing care for these patients and the advent of diagnosis related group reimbursement mandate that proposed treatment protocols be evaluated not only for their effectiveness but also for their cost-effectiveness.
Actuarial Analysis↗
The effect of flow on vascular endothelial cells grown in tissue culture on polytetrafluoroethylene grafts.
Vascular grafts lined with endothelial cells (EC) grown to confluence in culture before implantation may provide a thromboresistant flow surface. Growth of EC on and their adherence to currently available prosthetic materials under conditions of flow are two impediments remaining in the development of such a graft. To address these problems, 22 polytetrafluoroethylene grafts (PTFE) (5 cm by 4 mm inside diameter) were pretreated with collagen and fibronectin, seeded with 2 to 3 X 10(6) bovine aortic EC per graft, and placed in tissue culture (seeded grafts). Twenty-two grafts pretreated with collagen and fibronectin alone served as controls. After 2 weeks morphologic studies revealed that 20/22 seeded grafts were lined with a confluent endothelial layer. Indium 111-oxine was then used to label the EC-seeded grafts. After exposure to either low (25 ml/min) or high (200 ml/min) flow rates for 60 minutes in an in vitro circuit, examination of the luminal surface of the graft by light microscopy and scanning electron microscopy revealed minimal loss of EC. These findings were corroborated by radionuclide scans that showed an insignificant loss of the EC-associated indium label during exposure to flow (7% low flow, 11% high flow). Pretreatment of PTFE grafts with collagen and fibronectin thus promotes both attachment and adherence of EC even under flow conditions.
Animals↗
Correlation of B-mode ultrasound imaging and arteriography with pathologic findings at carotid endarterectomy.
Presently most noninvasive methods for assessing extracranial carotid disease have relied on hemodynamic change associated with significant stenosis. Recent evidence has suggested that both ulceration and/or plaque hemorrhage may frequently play an important role in the pathophysiology of carotid disease. To assess the ability of B-mode ultrasound to provide this anatomic information, in a prospective blinded manner we compared B-mode ultrasound and selective four-vessel arteriography to pathologic specimens obtained at the time of 89 carotid endarterectomies. The presence of ulceration, plaque characteristics (particularly hemorrhage), and luminal diameter were described for each modality. While arteriography detected only 16 of 27 ulcerations (sensitivity, 59%), B-mode ultrasound had a greater sensitivity (24/27, 89%). Both modalities had comparable specificities (arteriography, 73%; B-mode ultrasound, 87%). Moreover, B-mode ultrasound was highly sensitive for demonstrating plaque hemorrhage (27/29, 93%), as well as being quite specific (84%). Assessment of luminal reduction by B-mode ultrasound improved with technologist/interpreter experience and was significantly improved by adding real-time spectral analysis. Because of B-mode ultrasound's sensitivity for imaging ulceration and plaque hemorrhage, it offers significant advantages for the noninvasive detection of extracranial carotid disease.
Arterial Occlusive Diseases↗
Evaluation of arterial prostheses in a baboon ex vivo shunt: the effect of graft material and flow on platelet deposition.
Surface thrombogenicity is recognized as an important factor in the failure of small caliber vascular prostheses. The baboon ex vivo shunt was developed to study small caliber grafts under controlled conditions at different flow rates. The shunt was created by percutaneous insertion of catheters into the baboon femoral artery and vein. Platelet-graft interactions were studied using autogenous indium 111 labeled platelets. Two graft materials were placed in series and exposed to blood flow for 2 1/2 hours at flow rates of 25 and 200 ml/min. At the end of this period, the grafts were removed for morphologic examination. Platelet adhesion to the grafts, especially with the less thrombogenic materials (PTFE and HUV), was found to be independent of flow rate. PTFE was found to be the least platelet-reactive material, HUV was intermediate, and knitted Dacron was the most thrombogenic surface. Platelet deposition on the flow surface was confirmed by light microscopy and scanning electron microscopy.
Animals↗
Improvements in the diagnosis and management of aortoenteric fistula.
To assess the impact of an aggressive approach (early operation, graft removal, and extraanatomic bypass) adopted by us 5 years ago in patients with aortic synthetic grafts and gastrointestinal bleeding, we reviewed our 15 year experience with aortoenteric fistula in 13 patients. The courses of six patients from the recent series (1979 through 1984) were contrasted with those of seven patients from our earlier series (1968 through 1978). Twelve of 13 patients presented with gastrointestinal bleeding (usually low volume), and no patient presented in shock. Six of seven patients in Series I (earlier series) had positive blood cultures, whereas only two of six in Series II (recent series) had this finding. Of the 13 patients, 10 underwent preoperative endoscopy. It was only with consistent visualization of third and fourth portions of the duodenum that a diagnosis of aortoenteric fistula was established (three of four patients 75 percent). Although the upper gastrointestinal series was abnormal more frequently (five of seven patients, 71 percent) than arteriograms (three of nine patients, 33 percent), the latter was more specific for a predisposing lesion. At surgery, nine (70 percent) patients had an anastomotic fistula and four (30 percent), a false aneurysm. Although only one of seven patients in Series I survived (14 percent), four of six patients in Series II were alive at last follow-up in September 1984 (67 percent). Early diagnosis followed by prompt operation with removal of the synthetic graft and extraanatomic bypass is associated with an improved survival for patients with aortoenteric fistula, but the degree of preoperative sepsis as indicated by positive blood cultures appears to be an important prognostic sign.
Aged↗
Ultrasound characteristics of recurrent carotid disease: hypothesis explaining the low incidence of symptomatic recurrence.
The true incidence of recurrent disease after carotid endarterectomy (CENDX) is unknown, but noninvasive hemodynamic testing shows a paradox between the incidence of hemodynamically significant recurrent stenosis (RS) and the presence of symptomatic disease. We have shown that real-time B-mode ultrasound imaging can demonstrate the gross pathology of the arterial wall and plaque and their surface characteristics. Therefore we reviewed the clinical data and B-mode studies performed 6 months to 15 years after 276 carotid endarterectomies. Preoperative and perioperative risk factors and associated symptoms on follow-up were stored on computer. The patients were divided into three groups by the anatomy of their B-mode study. The majority of the studies were normal (203 [73.5%]), 42 (15.2%) showed mild disease, and 34 (12.3%) demonstrated significant RS. The RS group had a statistically significant increase in incidence of known lipid abnormalities (p less than 0.05), associated peripheral vascular disease, previous myocardial infarctions, and ulcerated plaque on the original carotid endarterectomy (p less than 0.01). The site of RS appeared related to the time of detection by B-mode ultrasound imaging. Internal carotid RS developed late (greater than 4 years), as did RS of the bifurcation. By contrast, stenosis at the common carotid level developed earlier. These findings suggest different pathogenic mechanisms--for the former, redevelopment of atherosclerosis; for the latter, accentuation of preexisting atherosclerosis perhaps by hemodynamic factors. Finally, in the 26 vessels with RS without occlusion, there was an 8% incidence of plaque ulcer or hemorrhage vs. a 62% incidence in 79 primary atherosclerotic plaques previously studied by both B-mode and pathologic examination. The low incidence of plaque characteristics associated with symptomatic disease may account for the low incidence of symptomatic disease associated with RS.
Arterial Occlusive Diseases↗
Healing pattern of small caliber dacron grafts in the baboon: an animal model for the study of vascular prostheses.
Although dogs have been used widely to study the healing of large caliber synthetic grafts, hypercoagulability probably makes the dog a poor model for studies of small caliber vascular prostheses. The baboon's coagulation system is similar to man's, but large caliber baboon grafts were reported to endothelialize rapidly. In this study the healing pattern of 4 mm internal diameter Dacron carotid interposition grafts in baboons was determined using specimens harvested at time points between 2 weeks and 18 months post-implantation and examined with light and scanning electron microscopy. The luminal surface of baboon grafts in the acute healing phase (less than 1 month) was comparable to that reported in the literature for dogs. Baboon grafts did not completely endothelialize until 10-12 weeks post-implantation. For work with small caliber vascular prostheses, the dog appears to have no advantage over the baboon as an animal model on the basis of graft healing.
Animals↗
A baboon flow-regulated shunt for the study of small caliber vascular grafts.
Synthetic vascular grafts often occlude when used in low-flow high-resistance reconstructions. In order to study the pathophysiology of graft failure a flow-regulated ex vivo shunt was designed for insertion into the baboon femoral artery and vein. Synthetic graft materials (4 mm i.d.) can be placed into the shunt circuit and studied at known rates of flow for uptake of 111In-labeled platelets. Segments of the grafts can be removed from the shunt circuit at specified time intervals for morphologic study with scanning electron microscopy (SEM). In this paper the shunt model is described in detail and early experiments with it are reported. Labeled platelet uptake and SEM studies suggest that flow rate and graft composition influence the deposition of platelets and other blood components on graft surfaces. At high-flow knitted Dacron attracts large numbers of platelets, and becomes covered with a nearly confluent platelet-protein carpet within 1 hr. At low flow platelet uptake and development of the platelet-protein carpet is slower. Polytetrafluoroethylene (PTFE) attracts few platelets at high-flow rates, but at lower-flow rates begins to develop a platelet-protein carpet similar to that seen on knitted Dacron. Flow-related factors influencing platelet deposition are discussed and further experiments to be carried out with this model are described.
Animals↗
Correlation of operative findings with angiographic and noninvasive hemodynamic factors associated with failure of polytetrafluoroethylene grafts.
The causes of autogenous saphenous vein (ASV) graft failure have been well described and are predominantly due to stenosis of the ASV graft during the first year after implantation. Distal atherosclerotic disease is a late cause of ASV graft failure. Furthermore, with failure of the ASV graft the clinical and hemodynamic status of the limb usually reverts to the preoperative state. To better define the causes and hemodynamic consequences of polytetrafluoroethylene (PTFE) graft failure, we reviewed the pathologic findings at surgery and compared these with arteriograms made prior to and after occlusion and sequential noninvasive hemodynamic studies in 36 patients with failed PTFE grafts (greater than 30 days after operation). Distal atherosclerotic disease was the most frequent cause of PTFE failure (23 of 36 limbs, or 64%), and it appeared as early as the first 6 months after implantation. Doppler pressures after PTFE failure deteriorated significantly (p less than 0.05) at the thigh, calf, and ankle levels. A blinded comparison of preoperative with postoperative arteriograms revealed significant progression of disease. Because of significant involvement of the popliteal artery in our series, treatment of intimal hyperplasia with patch angioplasty (seven cases, or 19%) was short lived and sequential extension was required. Distal atherosclerotic disease therefore appeared to be the most common cause of PTFE graft failure and occurred much earlier after implantation than with ASV graft failure. Deterioration of the hemodynamic state of the limb correlated with this high degree of distal atherosclerotic disease.
Blood Pressure↗
Aspirin decreases platelet uptake on Dacron vascular grafts in baboons.
The influence of a single dose of aspirin (5.4-7.4 mg/kg) on platelet uptake on 4-mm Dacron interposition grafts was studied in a baboon model using gamma camera scanning for 111-Indium labeled platelets. In vitro assessment of platelet function after aspirin administration revealed that in the baboon, as in the human, aspirin abolished arachidonic acid-induced platelet aggregation, prolonged the lag time between exposure to collagen and aggregation, and decreased plasma thromboxane B2 levels. Aspirin also prolonged the template bleeding time. Scans for 111-Indium labeled platelets revealed that pretreatment with a single dose of aspirin decreased platelet uptake on 4-mm Dacron carotid interposition grafts. This decrease in platelet uptake was associated with a significant improvement in 2-hour graft patency and with a trend toward improved 2-week patency.
Animals↗