EARLY AND LATE RESULTS OF INTRACORONARY ARTERIAL STENTING AFTER CORONARY ANGIOPLASTY IN DOGS

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 coils tent 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.