Sleep-related myocardial ischemia is also called nocturnal myocardial ischemia. It is known that the risk of ischemic events is high in patients with obstructive sleep apnea. One of the reasons for this is that in patients with obstructive sleep apnea, the heart muscle, the myocardium, cannot be supplied with as much oxygen as it needs. Another reason is that the oxygen demand of the heart muscle increases more than normal during the rebreathing phase of apnea.