Myocardial ischemia is a heart condition in which not enough blood supply and oxygen reaches the heart muscle. Damage to the major blood vessels of the heart (coronary artery disease), minor blood vessels of the heart (microvascular heart disease), or damage to the heart muscle (hypertrophic cardiomyopathy) can cause myocardial ischemia. Any of theses three conditions can cause patients to experience chest pain and other symptoms as well as cause the heart to function improperly.