Early and late results of intracoronary arterial stenting after coronary angioplasty in dogs.

Abstract

Intimal dissection with acute closure represents the major complication associated with percutaneous transluminal coronary angioplasty (PTCA). Intracoronary stent devices offer the possibility of treatment for this sequela. We developed a balloon catheter-mounted, flexible coil stent for use in such cases. To determine the utility of this device and its immediate and long-term influence on arterial patency, 39 mongrel dogs had the stent placed after PTCA of the left circumflex or left anterior descending coronary arteries. Thirteen animals were treated before and after the procedure with warfarin. In this group there were three early deaths associated with stent thrombosis. Twenty-six animals were subsequently treated before and after with aspirin and dipyridamole. There were no early thrombotic events associated with stent placement in these animals. Late arteriographic examination revealed patent vessels in all dogs. Diameter stenosis for warfarin-treated dogs was 8 + 5% (mean + SD) at 2 months (n = 9), 6 + 4% at 6 months (n = 5), and 11 + 7% at 12 months (n = 3).Diameter stenosis for aspirin/dipyridamole-treated dogs was 9 + 3% at 2 months (n = 8), 8 + 5% at 6 months (n = 12), and 5% at 12 months (n = 1). Light and scanning electron microscopic analyses of stented arteries demonstrated incorporation of the stent wires into the arterial wall. Early findings included mild thrombosis localized to areas of wire entrenchment followed by rapid regrowth of endothelial and/or pseudoendothelial cells over trenches, exposed wires, and elastica. Late histologic studies revealed that the stented segments had thinning of the media, mild neointimal proliferation over stented wires, and an otherwise normal intimal surface. Flexible intracoronary stents can be placed safely, rapidly, and accurately from a femoral arterial entry site and can maintain long-term patency in the dog. Further testing in other preparations will elucidate the effects of stenting in atherosclerotic vessels. Circulation 76, No. 4, 891-897, 1987. CURRENTLY AVAILABLE balloons used in percutaneous transluminal coronary angioplasty (PTCA) are capable of producing a cylindrical lumen of predetermined diameter within most arteries dilated. Early ischemic complications usually relate to closure of the vessel lumen immediately after balloon deflation or in the following 24 hr. Lumen reduction results from encroachment by dissecting intima, plaque, and medial structures, elastic recoil of the vessel wall, and occasionally arterial spasm. Once blood flow is reduced, thrombosis and total occlusion may occur.

Restenosis after coronary angioplasty. Potential biologic determinants and role of intimal hyperplasia.

“…75,76 Third, moderate (e.g., >40-50% cross-sectional area) stenoses in experimental models are associated with significant poststenotic regions exposed to disturbed flow and low wall shear stress. 77 If these observations are applied in the setting of coronary angioplasty, we may postulate the following events.…”

A view of vascular stents.

“…Thus, once the metal is stretched beyond a certain limit, it cannot collapse. '4-28 Gianturco later developed a stent with features of spring loading and balloon expandability ( Figure 1C), which was reported by Roubin et al 29 The potential advantages of the Palmaz design over others were 1) ease of delivery, 2) an expansion ratio up to 6:1, 3) a streamlined profile (0.003 in. ), 4) a minimal amount of metal comprising the surface area when expanded (10%), and 5) reliable expansion.…”

Intravascular Stenting

“…Neointimal thickness was reported as being 50 JLm. The efficacy of this stent was confirmed by Robinson et al 18 in the iliac arteries of atherosclerotic rabbits using balloon dilatation of the contralateral artery as control. They showed that stenting achieved a wider lumen with less intimal proliferation than balloon dilatation alone, and that this effect was maintained over the four-week period of study.…”