Failure of ticlopidine to inhibit deposition of indium-111-labeled platelets on Dacron prosthetic surfaces in humans

Carotid endarterectomy with a polyurethane patch versus primary closure: A prospective randomized study

INTRODUCTION

The use of synthetic patch angioplasty during carotid endarterectomy (CEA) has been advocated to reduce restenosis, stroke, and death, but the type of material used is still being debated. This study compared rate of restenosis, neurologic events, and perioperative death in patients undergoing CEA with primary closure versus polyester urethane patch closure.

PATIENTS AND METHODS

In a prospective randomized study, we compared patch angioplasty with polyester urethane (Vascular-patch, B. Braun Medical AG, Tuttlingen, Germany) to primary closure between February 1999 and March 2002 in 404 operations. Early (30-day) stroke and mortality rate, long-term restenosis, and neurologic events were compared in the two groups during 2.5 to 5 years of follow-up (median follow-up, 2 years).

RESULTS

Primary closure was used in 216 operations, and patch angioplasty was used in 206. Clamping time was significantly shorter in the primary closure group ( P < .001). Perioperative mortality and neurologic events were similar in both groups (1.9% vs 3.9%, P = .21, odds ratio [OR], 2.1; 95% confidence interval [CI], 0.56 to 9.85). The rate of residual stenosis (> or =50%) at 0 or 3-month follow-up was significantly lower in the patch group (2 operations, 1.1%) compared with the primary closure group (17 operations, 8.9%) ( P = .001, OR, 0.114; 95% CI, 0.026 to 0.5). Multivariable logistic regression showed that only primacy closure was found to influence residual stenosis. Restenosis of 70% was significantly less in the patch angioplasty group (2.2% vs 8.6%) ( P = . 01, hazard ratio, 0.246; 95% CI, 0.08 to 0.75). No correlation was found between restenosis and gender, preoperative symptoms, or risk factors.

CONCLUSIONS

Patch angioplasty with polyester urethane significantly reduced the restenosis rate ( P = . 01) compared with primary closure. Even though clamping time was longer, patching was not associated with more perioperative complications.

Evaluation of thrombogenicity of fluoropassivated polyester patches following carotid endarterectomy

The use of a patch after carotid endarterectomy (CE) is recommended to reduce the incidence of restenosis. Most studies on this subject report the implantation of saphenous vein or PTFE patches, because polyester has always been considered to be a thrombogenic material. The purpose of this study was to evaluate the thrombogenicity of a knitted polyester patch passivated by fluoropolymer surface treatment (FPD patch), which experimental studies have demonstrated to be less thrombogenic than other materials. This prospective, randomized study was performed in 22 patients who underwent CE. In 11 patients the arteriotomy was sutured directly, while in the other 11 an FPD patch was applied. Patients' 111in-oxine labeled platelets were reinjected on the first postoperative day, and scintigraphies were performed after 4, 24, and 48 hr, respectively. The study confirmed that an FPD patch is no more thrombogenic than a simple carotid endarterectomy. The application of the patch, therefore, can be recommended to reduce restenosis without any adjunctive thromboembolic risk.

Application of new coatings for vascular grafts based on polyacrylic systems with antiaggregating activity

A study has been made of the behaviour of knitted and woven Dacron mesh used in the preparation of vascular grafts when coated with either a layer of poly(2-hydroxyethyl methacrylate) or co-polymers of 2-hydroxyethyl methacrylate with 5, 10 or 20 wt% of an acrylic derivative of salicylic acid, 2-methacryloyloxybenzoic acid. In vitro studies were carried out to quantify the loss of polymer under flow conditions, and ex vivo studies were done in dogs to quantify the deposition of 111In-oxine-labelled platelets. The treated materials showed a lesser deposition of platelet thrombi when compared with the control group.

Collaborative overview of randomised trials of antiplatelet therapy--I: Prevention of death, myocardial infarction, and stroke by prolonged antiplatelet therapy in various categories of patients. Antiplatelet Trialists' Collaboration

OBJECTIVE

To determine the effects of "prolonged" antiplatelet therapy (that is, given for one month or more) on "vascular events" (non-fatal myocardial infarctions, non-fatal strokes, or vascular deaths) in various categories of patients.

DESIGN

Overviews of 145 randomised trials of "prolonged" antiplatelet therapy versus control and 29 randomised comparisons between such antiplatelet regimens.

SETTING

Randomised trials that could have been available by March 1990.

SUBJECTS

Trials of antiplatelet therapy versus control included about 70,000 "high risk" patients (that is, with some vascular disease or other condition implying an increased risk of occlusive vascular disease) and 30,000 "low risk" subjects from the general population. Direct comparisons of different antiplatelet regimens involved about 10,000 high risk patients.

RESULTS

In each of four main high risk categories of patients antiplatelet therapy was definitely protective. The percentages of patients suffering a vascular event among those allocated antiplatelet therapy versus appropriately adjusted control percentages (and mean scheduled treatment durations and net absolute benefits) were: (a) among about 20,000 patients with acute myocardial infarction, 10% antiplatelet therapy v 14% control (one month benefit about 40 vascular events avoided per 1000 patients treated (2P < 0.00001)); (b) among about 20,000 patients with a past history of myocardial infarction, 13% antiplatelet therapy v 17% control (two year benefit about 40/1000 (2P < 0.00001)); (c) among about 10,000 patients with a past history of stroke or transient ischaemic attack, 18% antiplatelet therapy v 22% control (three year benefit about 40/1000 (2P < 0.00001)); (d) among about 20,000 patients with some other relevant medical history (unstable angina, stable angina, vascular surgery, angioplasty, atrial fibrillation, valvular disease, peripheral vascular disease, etc), 9% v 14% in 4000 patients with unstable angina (six month benefit about 50/1000 (2P < 0.00001)) and 6% v 8% in 16,000 other high risk patients (one year benefit about 20/1000 (2P < 0.00001)). Reductions in vascular events were about one quarter in each of these four main categories and were separately statistically significant in middle age and old age, in men and women, in hypertensive and normotensive patients, and in diabetic and nondiabetic patients. Taking all high risk patients together showed reductions of about one third in non-fatal myocardial infarction, about one third in non-fatal stroke, and about one third in vascular death (each 2P < 0.00001). There was no evidence that non-vascular deaths were increased, so in each of the four main high risk categories overall mortality was significantly reduced. The most widely tested antiplatelet regimen was "medium dose" (75-325 mg/day) aspirin. Doses throughout this range seemed similarly effective (although in an acute emergency it might be prudent to use an initial dose of 160-325 mg rather than about 75 mg). There was no appreciable evidence that either a higher aspirin dose or any other antiplatelet regimen was more effective than medium dose aspirin in preventing vascular events. The optimal duration of treatment for patients with a past history of myocardial infarction, stroke, or transient ischaemic attack could not be determined directly because most trials lasted only one, two, or three years (average about two years). Nevertheless, there was significant (2P < 0.0001) further benefit between the end of year 1 and the end of year 3, suggesting that longer treatment might well be more effective. Among low risk recipients of "primary prevention" a significant reduction of one third in non-fatal myocardial infarction was, however, accompanied by a non-significant increase in stroke. Furthermore, the absolute reduction in vascular events was much smaller than for high risk patients despite a much longer treatment period (4.4% antiplatelet therapy v 4.8% control; five year

Prevention of thrombus formation on biomaterials exposed to blood using different antiplatelet drugs: experimental study in dogs

An ex vivo shunt, established in dogs between both femoral arteries and right atrium, has been used to quantify the platelet deposition on six prosthetic materials used in the construction of cardiovascular prostheses: highly porous knitted Dacron (intervascular HP 800, 1400 mL/cm2/min/120 mm Hg), low-porosity woven Dacron (intervascular LP 200, 200 mL/cm2/min/120 mm Hg), double velour knitted Dacron, Avcothane 51 elastomere, and the mesothelial and epipericardial surfaces of bovine pericardium. In the search for a method to prevent platelet thrombi formation on these materials, we studied four groups of dogs: group 1 (control), group 2 (5 mg/kg body weight (BW)/day acetylsalicylic acid), group 3 (20 mg/kg BW/day acetylsalicylic acid), and group 4 (5 mg/kg BW/day acetylsalicylic acid plus 5 mg/kg BW/day dipyridamole). Platelets were labeled with 111In-oxine. The least thrombogenic material was Avcothane 51 elastomere. The only effective treatment for reduction of platelet deposition on the six materials was 5 mg/kg BW/day of acetylsalicylic acid. The dose used in group 3 only decreased the deposition of platelets on three of the six materials studied. The treatment employed in group 4 did not significantly reduce the deposition of platelets on any of the materials when compared with the control group.

Effect of ticlopidine on blood loss, platelet turnover and platelet deposition on prosthetic surfaces in patients undergoing aorto-femoral bypass grafting

Sixty patients in whom a prosthetic aorto-femoral bypass graft was inserted were pretreated with ticlopidine (250 mg b.i.d.) or placebo in a double-blind study. Blood loss and transfusion need were higher in ticlopidine treated patients. Platelet survival was partially corrected and platelet deposition on prosthetic surfaces was inhibited with ticlopidine. The study suggests that ticlopidine does not increase excessively the bleeding risk during peripheral vascular surgery and that the antiplatelet drug may have beneficial effects in the early phase after insertion of prosthetic vascular graft.

Role of platelets and thrombosis in mechanisms of acute occlusion and restenosis after angioplasty

The vascular disruption produced by angioplasty initiates platelet deposition through the processes of platelet adhesion and recruitment of circulating platelets to form an enlarging mural platelet thrombus. Thrombin produced by simultaneous activation of the coagulation cascade by subendothelial connective tissue structures enhances platelet deposition and stabilizes the forming thrombus with enmeshing fibrin. Platelet recruitment involves the expression of the glycoprotein IIb/IIIa receptor for fibrinogen and other cytoadhesive proteins including fibronectin, thrombospondin and von Willebrand factor. Platelet deposition and thrombus formation caused by angioplasty appear to be important in the development of 2 complications: acute thrombotic occlusion and restenosis. Experimental mechanical vascular injury produces a predictable, although rather variable, amount of vascular narrowing due to transient smooth muscle cell proliferative intimal lesion formation. This intimal thickening by proliferating smooth muscle cells is in part mediated by platelet mitogens, particularly platelet-derived growth factor, which are released into the damaged vessel from platelets at the time of angioplasty. Platelet-derived growth factor may also be released from other associated vascular and blood cells in response to mechanical injury, e.g., endothelium, monocyte/macrophage and smooth muscle cells themselves. The actual mitogens, and their cells of origin, that mediate restenosis after therapeutic angioplasty remain to be established. Various oral antiplatelet agents have been shown to reduce arterial thrombotic occlusion in a number of controlled clinical trials, e.g., aspirin in transient ischemic attacks and unstable angina, aspirin and dipyridamole in saphenous vein coronary artery bypass and progression of peripheral vascular disease and dipyridamole in artificial heart valves. Acute arterial thrombosis may require more potent, immediate and transient intervention, e.g., monoclonal antibody to platelet receptor expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of suloctidil on tomographically quantitated platelet accumulation in Dacron aortic grafts

Platelet deposition contributes to the thrombotic and embolic complications of prosthetic materials in man. To determine if the investigational platelet inhibitory drug suloctidil (200 mg 3 times daily) reduces platelet deposition on Dacron aortic grafts, a randomized, double-blind, crossover trial was conducted in 12 men with grafts that had been in place more than 9 months. Platelet deposition in the graft was assessed by quantitative analysis of planar images obtained at 24, 48 and 72 hours after injection of indium-111-labeled platelets. Also, a tomographic method of imaging and quantitating labeled platelet deposition in the graft was developed. Tomographic imaging was performed at 24 and 72 hours after platelet injection and was quantitated by a graft/blood ratio that compared indium-111 platelet activity in summed 1.8-cm-thick transaxial tomographic slices of the aortic graft to indium-111 platelet activity in well-counted whole blood. Compared with placebo, suloctidil failed to decrease the tomographic graft/blood ratio at 24 hours (6.2 +/- 1.3 vs 5.7 +/- 0.8) and 72 hours (11.4 +/- 2.9 vs 10.7 +/- 2.2). Similarly, the graft/blood ratio determined by planar imaging was not different between placebo and suloctidil therapy at 24 hours (1.7 +/- 0.3 vs 1.6 +/- 0.2), 48 hours (2.2 +/- 0.4 vs 2.4 +/- 0.4) or 72 hours (2.6 +/- 0.5 vs 2.8 +/- 0.5) after labeled platelet injection. Thus, suloctidil does not significantly reduce platelet deposition on chronically implanted Dacron grafts in humans.

The effect of sulfinpyrazone on platelet deposition on Dacron vascular grafts in man

To determine if sulfinpyrazone inhibits platelet deposition on chronically implanted (greater than 9 months) Dacron aortic bifurcation grafts in man, we performed indium-111 platelet imaging over 24 to 96 hours after labeled platelet injection in 10 males with grafts before and during sulfinpyrazone therapy (200 mg four times daily). Platelet accumulation was quantitated by a graft/blood ratio that compared indium-111 platelet image activity in the graft to platelet activity in well-counted whole blood. In addition, independent visual analysis compared platelet accumulation in the graft area to adjacent native arteries. By quantitative evaluation, sulfinpyrazone did not decrease the graft/blood ratio compared to baseline at 24 hours (3.2 +/- 0.4 vs 3.3 +/- 0.5, mean +/- SEM), 48 hours (4.6 +/- 0.6 vs 4.6 +/- 0.9) , 72 hours (6.8 +/- 0.8 vs 6.7 +/- 1.3), or 96 hours (9.7 +/- 1.6 vs 9.7 +/- 1.6) after labeled platelet injection. Visual interpretation also revealed no decrease in deposition in any patient during sulfinpyrazone therapy. We conclude that sulfinpyrazone does not inhibit platelet deposition on chronically implanted Dacron arterial graft surfaces in man. The techniques described provide a useful method of evaluating antithrombotic drug effects in patients with intravascular prosthetic materials.