A 74-year-old male underwent cardiac catheterization that revealed a chronic total occlusion of the proximal left anterior descending coronary artery (LAD). The right coronary artery provided only faint collateral circulation to the LAD. Multislice computed tomography (MDCT) disclosed that a conus artery took off directly from the aorta and provided good collateral circulation to the LAD. Percutaneous coronary intervention of the LAD was successfully performed using contralateral injection via the isolated conus artery. Whenever sufficient collateral filling is not visualized in a chronically occluded LAD, an isolated conus artery should be considered. MDCT is a helpful tool in this setting.