Abstract-Distal to a chronic coronary artery stenosis, structural remodeling of the microvasculature occurs. The microvascular functional changes distal to the stenosis have not been studied in detail. We tested the hypothesis that microvascular structural remodeling is accompanied by altered regulation of coronary vasomotor tone with increased responsiveness to endothelin-1. Vasomotor tone was studied in coronary microvessels from healthy control swine and from swine 3 to 4 months after implantation of an occluder that causes a progressive coronary narrowing, resulting in regional left ventricular dysfunction and blunted myocardial vasodilator reserve. Arterioles (Ϸ200-m passive inner diameter at 60 mm Hg) were isolated from regions perfused by the stenotic left anterior descending and normal left circumflex coronary arteries and studied in vitro.
Background. Intracoronary stents may be effective when used as "bail-out" devices for acute complications after percutaneous transluminal coronary angioplasty. Furthermore, preliminary reports have demonstrated some promising results with stents with regard to the reduction of restenosis. Several stent devices are available for preclinical and clinical evaluation. The use of these stainless-steel stents has been limited by poor visibility during fluoroscopy and thrombogenicity during the first days to weeks after implantation. We therefore investigated the immediate and short-term effects on arterial patency of a new, radiopaque, balloon-expandable coil stent in normal coronary arteries of pigs.Methods and Results. In 10 animals, a stent was placed in two of the three epicardial coronary arteries. During the implantation procedure, the animals received heparin; after the procedure, no antithrombotic drugs were administered. After 1 week (five animals and 10 stents) or 4 weeks (five animals and 10 stents), repeat angiography was performed, followed by pressurefixation of the coronary arteries for light and electron microscopic examination. Angiographic analysis revealed that all stented coronary segments were patent and without signs of intraluminal defects. Scanning electron microscopy showed complete endothelial covering of all stents within 7 days. Light microscopy showed a reduced tunica media locally under the stent wires, which resulted from exerted pressure. The neointima on top of the stent wires measured 56 ,m (range, ,um) after 1 week and 139 ,um (range, 84-250 jum) after 4 weeks.Conclusions. Results from this study show that this radiopaque endoprosthesis can be safely placed in normal coronary arteries of pigs. After 4 weeks, all stents were patent and there was no need for additional antithrombotic treatment, whereas neointimal proliferation was limited.
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