Therapeutic dissection after successful coronary balloon angioplasty: no influence on restenosis or on clinical outcome in 693 patients. The MERCATOR Study Group (Multicenter European Research Trial with Cilazapril after Angioplasty to prevent Transluminal Coronary Obstruction and Restenosis)

OBJECTIVES: The objective of this study was to examine the relation between an angiographically visible coronary dissection immediately after successful coronary balloon angioplasty and a subsequent restenosis and long-term clinical outcome. BACKGROUND. The study population comprised all 693 patients who participated in the MERCATOR trial (randomized, double-blind, placebo-controlled restenosis prevention trial of cilazapril, 5 mg two times a day). METHODS. Cineangiographic films were processed and analyzed at a central angiographic core laboratory, without knowledge of clinical data, with use of an automated interpolated edge detection technique. Dissection was judged according to the National Heart, Lung, and Blood Institute classification. Angiographic follow-up was obtained in 94% of patients with 778 lesions. Two approaches were used to assess the restenosis phenomenon: 1) categoric, using the traditional cutoff criterion of greater than 50% diameter stenosis at follow-up, and 2) continuous, defined as absolute change in minimal lumen diameter (mm) between the postcoronary angioplasty and follow-up, adjusted for the vessel size (relative loss). Clinical outcome was ranked according to the most serious adverse clinical event per patient during the 6-month follow-up period, ranging from death, nonfatal myocardial infarction, coronary revascularization and recurrent angina requiring medical therapy to none of these. RESULTS. Dissection was present in 247 (32%) of the 778 dilated lesions. The restenosis rate was 29% in lesions with and 30% in lesions without dissection (relative risk 0.97; 95% confidence interval 0.77 to 1.23). The relative loss in both groups was 0.10 (mean difference 0; 95% confidence interval -0.03 to 0.03). Clinical outcome ranged from death in 4 patients (0.9%) without dissection and 1 patient (0.4%) with dissection; nonfatal myocardial infarction in 4 (0.9%) without and 8 (3.2%) with dissection; coronary revascularization in 73 (16.6%) withou