Coronary dissection is a major cause of abrupt arterial closure after coronary angioplasty but may also be associated with no discernible event. Deciding which dissections should receive further treatment is often a dilemma if the artery remains patent. This case-control study examined predictors of major ischemic complications after coronary dissections. Fifty-eight patients with coronary dissections, but a patent artery at the completion of the angioplasty procedure, subsequently had in-hospital abrupt arterial closure, acute myocardial infarction, emergency coronary bypass surgery, or died; they were matched to 58 control subjects with dissection but no event. Analysis of each angiogram was performed with the examiner unaware of patient's history. Baseline angiographic and clinical characteristics of cases and controls were similar except for an excess of current smokers among the cases (31 vs 16%; p = 0.048). Residual luminal diameter at the dissection site was 1.2 +/- 0.6 mm (cases) versus 1.6 +/- 0.6 mm (controls; p = 0.001) with relative stenosis of 59 +/- 21% vs 43 +/- 21%, respectively (p = 0.0001). Dissections among cases were longer than among controls (11 +/- 7 mm vs 7 +/- 4 mm; p = 0.001). No significant difference was found in dissection morphology using 2 classification schemes or in final Thrombolysis in Myocardial Infarction study flow grade. Transient occlusion during the procedure, however, occurred in 47% of cases versus 5% of controls (p = 0.0001). Transient occlusion, residual percent stenosis > or = 70%, and dissections > or = 6 mm were independently predictive of major ischemic events.