These results show that the definition of unstable angina is important in determining the immediate outcome of directional atherectomy. In the absence of rest or postinfarction angina, the immediate results are not significantly different from those obtained in stable angina. Our results also suggest that both the immediate and short-term outcome in unstable angina are not greatly influenced by atherectomy but more so by the pathophysiology of unstable angina, which increases the complications of percutaneous interventions.