An open design, multicentre, randomized trial of percutaneous transluminal coronary angioplasty versus stenting, with a heparin-coated stent, of totally occluded coronary arteries: rationale, trial design and baseline patient characteristics. Total Occlusion Study of Canada (TOSCA) Investigators.
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BACKGROUND: Percutaneous transluminal coronary angioplasty (PTCA) of totally occluded coronary arteries is performed in a variety of clinical settings and for a variety of indications. Most commonly it is performed for relief of symptoms of myocardial ischemia. Studies have also suggested that PTCA of occluded arteries beyond the acute phase of myocardial infarction may improve left ventricular function even in the absence of objective evidence of ischemia. One of the major limitations of total occlusion PTCA is a high rate of reocclusion, reported to be as high as 40%. Recently, small studies have suggested that stenting may improve the long term outcome after PTCA of total coronary occlusions. OBJECTIVES: To determine in a prospective, randomized trial whether long term patency and clinical outcome following successful PTCA of a totally occluded coronary can be improved by the use of of a heparin-coated stent. PATIENTS AND METHODS: Subjects were randomly assigned to one of two strategies once the guide wire had crossed the occluded segment of the target artery: PTCA alone, or PTCA followed by insertion of Palmaz-Shatz heparin-coated stent(s). Randomization was stratified according to duration of the coronary occlusion: six weeks or less, and more than six weeks. The primary end-point is failure of sustained patency (Thrombolysis in Myocardial Infarction [TIMI] flow grade less than 3) at six months. Secondary end-points are change in minimal luminal diameter, target vessel revascularization at one year, cardiovascular events at one year, and change in global and regional left ventricular function. BASELINE CHARACTERISTICS: All 410 patients have been randomly assigned to the PTCA alone (n = 208) or PTCA plus stent (n = 202) group. Mean age was 58 +/- 11 years and 18% were female. Prior myocardial infarction had been documented in 67% of patients. The duration of occlusion was six weeks or less in 40% and more than six weeks in 60% of patients. In 64% of patients TIMI flow was grade 0 and in 36% it was grade 1. STUDY IMPLICATIONS: The trial will demonstrate whether the use of a heparin-bonded stent can improve long term patency and clinical outcome in patients undergoing clinically indicated PTCA of totally occluded coronary arteries. If a significant reduction in reocclusion and clinical events is demonstrated, the Total Occlusion Study of Canada (TOSCA) would offer a more effective long term revascularization strategy in future trials testing the open artery hypothesis.
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