Since platelet accumulation may be an important determinant of restenosis after angioplasty, the time course of 11Cr-labeled platelet accumulation after experimental angioplasty was evaluated in a deendothelialized, hypercholesterolemic rabbit preparation of atherosclerosis. Marked platelet accumulation (39.5 +-8.7 x 106 platelets/1 cm vessel length) was observed at 30 min and remained active until 4 hr after angioplasty. Total accumulation over 24 hr was 56.4 ± 4.7 X 106 platelets/1 cm length. Histologic dissection was directly related to the degree of platelet accumulation, with 64 ± 15 x 106 platelets/1 cm in the group with marked dissection and 8.7 3.7 x 106 platelets/1 cm in the group with minimal dissection (p < .05). Increasing angiographic dissection also resulted in a trend toward increased platelet accumulation, and angiographic change in luminal diameter showed a significant correlation with platelet accumulation. It is concluded that marked platelet accumulation occurs early after transluminal angioplasty and is related to the extent of dissection. Restenosis may result from a complex interaction of platelet accumulation, vascular damage, and blood flow. Circulation 75, No. 3, 636-642, 1987. PERCUTANEOUS transluminal angioplasty has been used increasingly for the nonsurgical treatment of occlusive atherosclerotic arterial disease in man. With a primary success rate approaching 90%, the major biological obstacle to be overcome remains the problem of restenosis, which occurs in up to 30% of successfully dilated lesions.1 Endothelial denudation and platelet adhesion have been observed both by light and scanning electron microscopy after arterial intimal damage. Platelet adhesion may be responsible for throm bosis and vasospasm occurring early after angioplasty. In addition, platelet-derived growth factor has a proliferative effect on smooth muscle cells, which may be an important factor in restenosis. Earlier studies from this laboratory have shown a diminution in the degree of restenosis in rabbits treated with either aspirin-dipyrid- Supported in part by grant 85-1028 from the American Heart Association and by The U.S. Navy (Office of Naval Research, contract N00014-79-C-0168, with funds provided by the Naval Medical Research and Development Command).Address for correspondence: James R. Thus, the aims of this study were to use 51Cr-labeled platelets (1) to delineate the time during which active platelet accumulation occurs after experimental angioplasty, and (2) to relate the level of platelet accumulation after angioplasty to the degree of neointimal dissection determined both angiographically and histologically.
MethodsAnimal preparation. Sixty-eight New Zealand white rabbits (weight 3 kg) were prepared with bilateral iliofemoral balloon deendothelialization followed by 6 weeks of a 2% cholesterol diet to create significant iliac atheroslcerosis as previously described.5 Experimental design (figure 1). After 6 weeks on the atherogenie diet all animals were anesthetized with pentobarbi...
Carotid stenting has become an accepted alternative to endarterectomy, but fear of embolic stroke has impeded its generalized application. The retina provides a unique observatory for the study of emboli, which may occur either directly or indirectly via collaterals to the ophthalmic artery. Systems under development for cerebral protection differ in their capacity to trap small emboli and in their protection of the collateral circulation. We evaluated 118 sequential patients undergoing carotid stenting using fundoscopy, fluorescein retinal angiography, and visual field examination. The site and size of emboli was assessed, and degree of edema estimated. All patients were treated using distal protection during carotid stent implantation: 38 patients with the Théron system (using routine flushing toward the external carotid) and 80 patients with the Percusurge system (aspiration only). Retinal embolization occurred in 6 of the 118 patients (4%), of whom 2 were symptomatic (1.7%). Using the Théron system, 5 of 38 patients (13.2%) had emboli while 1 of 80 (1.25%) had emboli using the Percusurge system (P = 0.019). Symptoms occurred only with emboli >20 microm. Symptomatic retinal embolization is uncommon during carotid stenting, but is more likely when external to internal carotid collaterals are not protected. Cerebral protection system designs should take into consideration the existence of collaterals and the need to protect against smaller sized emboli, which may cause blindness in the retinal circulation.
The major limitation of percutaneous coronary intervention (PCI) is restenosis. Restenosis is considered to be an overreaction of the natural healing process after traumatic balloon dilatation. An elaborate web of cellular and molecular responses, including the interaction of platelets, leukocytes, and the coagulation-fibrinolysis system, as well as the secretion of various growth factors and pro-inflammatory cytokines, contributes to neointimal hyperplasia and the development of restenosis. Moreover, platelet and neutrophil activation after stenting appears to be different from that after balloon angioplasty alone. Pharmacotherapy targeting the cell-to-cell interaction between platelets and neutrophils may potentially offer an effective treatment strategy against restenosis after PCI.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.