Ischemic heart disease is characterized by a reduction in blood supply to the heart muscle, usually due to coronary artery disease. It has several causes including atherosclerosis, thrombosis, and decreased coronary blood flow. Symptoms range from stable angina during exertion to unstable angina that can occur at rest. Physical examination may show signs of ischemia but can be normal. Diagnosis involves ECG, exercise tolerance testing, and cardiac imaging tests. Angiography can confirm the diagnosis by detecting coronary artery blockages.