A 60-year-old man underwent directional coronary atherectomy (DCA) of the mid portion of a large, anatomically dominant left circumflex coronary artery, resulting in propagating transverse dissection and subsequent complete distal occlusion. Intravascular ultrasound imaging (IVUS) of the dissected segment demonstrated the entry point of the dissection, and systolic compression of the true vessel lumen, prior to angiographic deterioration of distal coronary flow.