Complex sentence: Myocardial ischemia is an imbalance between myocardial oxygen supply and demand resulting in angina pectoris, myocardial stunning, myocardial hibernation, ischemic preconditioning, postconditioning, or under the most severe instances, acute coronary syndrome and myocardial infarction.
Split into simpler sentences: Myocardial ischemia is an imbalance between myocardial oxygen supply and demand. Left untreated, it results in angina pectoris, myocardial stunning, myocardial hibernation, ischemic preconditioning, postconditioning, or under the most severe instances, acute coronary syndrome and myocardial infarction.