SHORT AND MEDIUM TERM RESULTS WITH CORONARY ENDOPROSTHESES

Mechanical stenting of the coronary wall by an endoprosthesis is a method of treating and preventing the 2 major complications of balloon angioplasty: acute occlusion by dissection and secondary restenosis. Forty-four self expanding stents were implanted in 42 patients presenting with post-angioplasty restenosis (35 cases), stenosis of an aortocoronary bypass graft (4 cases) or symptomatic post-angioplasty coronary dissection (3 cases). The primary results featured a high early occlusion rate of the endoprosthesis (28.5 %, 12 cases). Better patient selection to include patients with stable angina and coronary arteries with a diameter > 3 millimeters, and the administration of an association of platelet antiaggregant therapy with heparin and oral anticoagulants has led to an improvement in these results. The early occlusion rate in the first 23 patients implanted without these selection criteria was 43 % (10 cases) whereas it was only 10.5 % (2 cases) in the last 19 selected patients who were prescribed effective medical therapy. The medium term results of the 27 patients implanted without complications at 6 months showed restenosis in 5 cases and reocclusion (asymptomatic) in 1 case (22.2 % at control angiography at the 6th month). Restenosis was only observed in cases in which the endoprosthesis did not completely cover the coronary lesion (3 out of 3 cases) or when the endoprosthesis was implanted in a saphenous vein graft (2 out of 4 cases) and the only case of reocclusion occurred on a stent implanted in a coronary artery responsible for previous myocardial infarction. In the 21 patients in whom the stenosis had been totally covered by the stent there were no cases of restenosis. Implantation of a coronary endoprosthesis is feasible providing patients are strictly selected to exclude conditions of low transprosthetic flow and under cover of an association of antiaggregant and anticoagulant therapy. The medium term results are encouraging with respect to prevention of restenosis when the stent completely covers the lesion and the totality of the coronary segment submitted to the mechanical strain of the balloon dilatation. However, systematic implantation of coronary endoprosthesis is not reasonable except in the critical situation of symptomatic dissection. It is now imperative that comparative clinical trials be undertaken to evaluate the efficacy of coronary endoprosthesis in the prevention of restenosis and to identify the patients most likely to benefit from this technique.