A scanning electron microscopic study of angiographic catheters and guide wires

Clot Formation in Angiographic Catheters — An in Vitro Comparative Study

Clot formation was compared in 6 brands of angiographic catheters, each of which was tested in 3 states: untreated, heparinized, and albumin-coated. Forty-six samples of each brand in each state (in total 828) were filled with blood from 23 donors and incubated at +37 °C for 5 or 15 min. Physiologic saline was then injected through the catheters at a flow rate of 5 and 50 ml/s, respectively, and any expelled clots identified on a filter. Heparinization reduced the number of clotted catheters at 5 min, but not at 15 min. The only significant difference related to catheter brands was found between the heparinized nylon and polyurethane catheters at 5-min incubation with fewer clotted polyurethane catheters. This difference was not found between the same materials made by two other manufacturers. Albumin coating had no effect on clot formation, but clots were more easily expelled by low-flow injections in albumin-coated and, to a lesser degree, in heparinized than in untreated catheters.

Intraarterial abciximab for treatment of thromboembolism during coil embolization of intracranial aneurysms: outcome and fatal hemorrhagic complications

Object

Experience with intraarterial abciximab for the treatment of thromboembolism during endovascular coil embolization is limited. The authors report the outcome of intraarterial abciximab use, with an emphasis on fatal hemorrhagic complications.

Methods

Between March 2003 and May 2006, the authors treated 606 aneurysms by using endovascular coil embolization, and in 32 (5.3%) of these aneurysms (31 patients) an intraarterial thrombus developed. Sixteen of these aneurysms were ruptured and the other 16 were unruptured. Arterial thrombi were totally occlusive in 3 and partially occlusive in the remaining 29 cases. Intraarterial abciximab was administered at a concentration of 0.2 mg/ml as a bolus of 4–15 mg over a period of 15–30 minutes.

Results

Complete thrombolysis was achieved in 17 (53%) and partial thrombolysis in 15 (47%) of 32 lesions. Twenty-eight patients (90.3%) were asymptomatic after abciximab thrombolysis, but 3 had postprocedural rebleeding that occurred after abciximab treatment; all of these patients had recently experienced an aneurysm rupture. Of these patients, 1 displayed severe thrombocytopenia and the other 2 showed a > 25% reduction in platelet count after abciximab treatment.

Conclusions

Intraarterial abciximab is effective for the treatment of thromboembolic complications that occur during intracranial aneurysm coil insertion. Nevertheless, attention should be paid to prevent potentially fatal complications such as thrombocytopenia and hemorrhage, especially in patients with a ruptured aneurysm.

Abciximab as an adjunct to high-risk carotid or vertebrobasilar angioplasty: preliminary experience

OBJECTIVE

Abciximab, a platelet glycoprotein IIb/IIIa receptor inhibitor, has been shown to reduce the risk of ischemic events associated with coronary intervention. However, its role in neurointerventional procedures needs to be defined. We prospectively evaluated our initial experience with the use of abciximab in a series of high-risk patients undergoing carotid, basilar, or vertebral artery angioplasty.

METHODS

Patients were given an intravenous abciximab bolus (0.25 mg/kg), followed by infusion (10 microg/min) for a period ranging from 12 to 24 hours, as an adjunct to angioplasty in 20 procedures (19 patients). These patients were considered to be at high risk for thromboembolic events because of recent ischemic symptoms and/or complex lesion morphology. Before, immediately after, and 24 hours after the procedure, each patient was evaluated by a neurologist for the presence of new neurological deficits. Any bleeding or other complications during hospitalization were also recorded. Bleeding was defined as major (hemoglobin decrease >5 g/dl), minor (hemoglobin decrease 3-5 g/dl), or insignificant.

RESULTS

Angioplasty was performed in the internal carotid artery (n = 13), vertebral artery (n = 4), or basilar artery (n = 2). Stents were placed across 13 lesions. In one patient, angioplasty could not be performed owing to technical difficulties; however, abciximab was administered because of extensive lesion manipulation. Intraprocedural heparin was given in 19 procedures (35-86 U/kg intravenously) and partially reversed in 6 procedures. Low-dose intra-arterial thrombolytic agents were administered in seven patients before the lesion was crossed. Two patients experienced transient neurological deficits either during (n = 1) or immediately after (n = 1) the procedure. Another patient had complete occlusion of the right vertebral artery after angioplasty with complete recanalization after 24 hours of abciximab infusion. Major or minor bleeding was not observed in any patient. Insignificant bleeding was observed in eight patients. Thrombocytopenia was observed in one patient who received concomitant administration of intravenous heparin and abciximab infusion.

CONCLUSION

We observed a low frequency of neurological events in high-risk patients undergoing angioplasty with or without stent placement. Abciximab seems to be a relatively safe adjunct for carotid or vertebrobasilar endovascular intervention either alone or in combination with low-dose thrombolytics. Partial reversal of intraprocedural heparin should be considered to reduce the risk of postprocedural bleeding.

Prevention and treatment of thromboembolic and ischemic complications associated with endovascular procedures: Part I--Pathophysiological and pharmacological features

Thromboembolic and ischemic complications frequently occur during and after endovascular procedures, because of associated arterial injury and the thrombogenic characteristics of arterial catheters, contrast agents, and implanted devices such as coils and stents. Platelet adhesion, activation, and aggregation occurring at the site of arterial injury are mediated by local factors, including thromboxane A2 (inhibited by aspirin) and adenosine diphosphate (inhibited by ticlopidine and clopidogrel). Concomitantly, thrombin is formed by serial activation of clotting factors via contact with subendothelial tissue factor. Thrombin cleaves fibrinogen into fibrin. Thrombin activation is indirectly blocked by heparin and its analogs. However, after thrombin is clot-bound (with fibrin), it is relatively protected from heparin and is effectively blocked only by direct thrombin inhibitors (hirudin and its analogs). The final common pathway in clot formation is the binding of fibrinogen to platelets via platelet glycoprotein IIb/IIIa receptors, which is inhibited by antibodies to platelet IIb/IIIa receptors. New treatment modalities, such as the use of direct thrombin inhibitors and antibodies to platelet glycoprotein IIb/IIIa, seem to be more effective for prophylaxis and treatment than conventional anticoagulation and antiplatelet therapies.

In vivo thrombogenicity of intravascular ultrasound imaging catheters

This study evaluates the frequency and significance of thrombus formation on the surface of intravascular ultrasound (US) imaging catheters. The investigation includes 63 consecutive patients who underwent 32 arterial and 38 venous intravascular procedures. At the end of the imaging procedure the US findings were observed during withdrawal of the catheter into the introducer sheath. Thrombus formation was demonstrated in 5 (7%). The largest thrombus fragments had a cross-sectional dimension of 2.2 x 1.0 mm. There was a significant correlation between the incidence of thrombus formation and the occurrence of malign neoplastic disease. No relation was found between the frequency of thrombus formation and the duration of the imaging procedure or the type of US catheter. It is concluded that the thrombogenicity of intravascular US imaging devices is not higher than that of conventional angiographic catheters. The observed "pull-out" thrombi were small and it is unlikely that they could have any clinical significance.

Effects of re-use on the physical characteristics of angiographic catheters

Five types of angiographic catheters used in current radiological and haemodynamic clinical practice at Sacré-Coeur Hospital in Montreal were studied for their mechanical sturdiness, and also with respect to the possibility that re-use could be associated with blood contamination by loose particles. Samples were taken both from new catheters and from catheters re-used up to 10 times. Routine cleaning and sterilization procedures showed no adverse effects on the maximum tensile strength and elongation at break of catheters. While some biological debris were occasionally present in re-used catheters, they appeared to be firmly fixed to the lumen surface, and they seemed unlikely to be carried into the blood stream during catheterization. On the other hand, new catheters exhibited a substantially higher loose particicle count than catheters which had been properly cleaned and sterilized. It is concluded that properly handled re-used angiographic catheters are just as safe for the patient as new catheters. The limit on the number of re-uses may depend on the care taken to avoid damage to the lumen surface during cleaning, on ageing on the catheter material and on economic considerations.

Clinical events following neuroangiography: a prospective study

Clinical events following cerebral angiography were prospectively evaluated in 1,002 procedures. The ischemic event rate between 0 and 24 hours was 1.3% (0.1% permanent). This incidence was higher (2.5%) in patients investigated for cerebrovascular disease, but the difference was not significant. In addition, 1.8% of the patients suffered ischemia (0.3% permanent) between 24 and 72 hours after angiography. Cerebral ischemic events occurred as a recurrence or worsening of a preexisting phenomenon. twice as often as de novo. All permanent ischemia was a worsening of a preexisting phenomenon. There was a significant increase in the incidence of neurologic events between 0 and 24 hours when the procedure lasted longer than 60 minutes and when there was systolic hypertension. Trends toward higher incidence were noted with the use of increased volume of contrast, with increased serum creatinine, when transient ischemic attacks or stroke were the indications, and when 3 or more catheters were used. The incidence of neurologic events between 24 and 72 hours increased significantly with the increase in the amount of contrast used, with age, and with diabetes. The occurrence of nonneurologic events (mostly hematomas) was significantly increased by multiple factors. This study shows that events can and do occur beyond the usual observation period of 24 hours but confirms the low risk of cerebral angiography when performed judiciously.

Roughness and thrombogenicity of the outer surfaces of intravascular catheters

Thirty-seven types of catheters made from plastics including silicone rubber, polyvinylchloride, polyethylene, and polyurethane were tested for thrombogenesis in the cephalic vein of sheep. The range in the mass of thrombus on the catheters at autopsy 9 days after insertion was 20-fold. There was considerable variation when catheters made from the same types of plastic were compared, but polyethylene catheters tended to be more thrombogenic than other types. Scanning electron microscopy (SEM) revealed a variety of surfaces ranging from very smooth to very rough. Roughness was frequently associated with the presence of radioopaque particles which in several catheters were concentrated into radio-opaque tracer strips. Within types of plastics, catheters with rougher surfaces were usually more thrombogenic than those with smooth surfaces.

Surface modification and evaluation of some commonly used catheter materials. I. Surface properties

Double catheter systems consisting of a stiff outer catheter and a flexible, buoyant, flow-directed, inner catheter which is often balloon-tipped have been employed with increasing frequency recently in both therapeutic and diagnostic procedures. Their use, however, has been restricted because of the excessive friction generated between the two catheters. In an attempt to decrease friction between polymers commonly used as catheter materials, oxidation of polyethylene, fluorinated ethylene-propylene copolymer, poly(vinyl chloride), silicone rubber, and polystyrene surfaces was induced by exposing the polymers to radio frequency glow discharge (RFGD) in a helium environment. All polymers were surface characterized utilizing x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and contact angle measurements before and after oxidation. This article describes the materials and methods used to fabricate and characterize the polymer surfaces and the results of the characterization. The results indicate that increases in oxygen concentration at the surface of the polymers and decreases in air-water contact angles occur with increased RFGD exposure time. Plateau values were usually obtained after 5-30 s exposure time, yet no apparent changes in surface topography were noted by scanning electron microscopy. The hydrophilic surfaces produced were stable for up to three months storage time in air.