There is still no consensus for management of CAE. Previously improvement of coronary flow has been demonstrated by mibefradil in patients with slow coronary flow. A new trial is needed to explore the effect of calcium channel blockers (CCB) in isolated CAE. Diltiazem improves myocardial perfusion by blocking calcium channels in coronary arteries. This agent has been widely used in coronary catheter labs to prevent and treat no-reflow.